recent literature review on malaria parasite

Advertisement

Recent Advances in Imported Malaria Pathogenesis, Diagnosis, and Management

• Published: 12 April 2023
• Volume 11 , pages 49–57, ( 2023 )

Cite this article

• Anastasia S. Weiland   ORCID: orcid.org/0009-0003-9828-0003 1  

1949 Accesses

1 Altmetric

Explore all metrics

Purpose of Review

Malaria is an important human parasitic disease affecting the population of tropical, subtropical regions as well as travelers to these areas.

The purpose of this article is to provide clinicians practicing in non-endemic areas with a comprehensive overview of the recent data on microbiologic and pathophysiologic features of five Plasmodium parasites, clinical presentation of uncomplicated and severe cases, modern diagnostic methods, and treatment of malaria.

Recent Findings

Employment of robust surveillance programs, rapid diagnostic tests, highly active artemisinin-based therapy, and the first malaria vaccine have led to decline in malaria incidence; however, emerging drug resistance, disruptions due to the COVID-19 pandemic, and other socio-economic factors have stalled the progress.

Clinicians practicing in non-endemic areas such as the United States should consider a diagnosis of malaria in returning travelers presenting with fever, utilize rapid diagnostic tests if available at their practice locations in addition to microscopy, and timely initiate guideline-directed management as delays in treatment can lead to poor clinical outcomes.

Similar content being viewed by others

A Review of Leishmaniasis: Current Knowledge and Future Directions

Sarah Mann, Katherine Frasca, … José A Suarez

Prevention Efforts for Malaria

Tinashe A. Tizifa, Alinune N. Kabaghe, … Kamija S. Phiri

Malaria Vaccines: Progress to Date

Danielle I. Stanisic & Michael F. Good

Avoid common mistakes on your manuscript.

Introduction

Malaria is a mosquito-borne disease caused by the parasites of the genus Plasmodium . Five species that infect humans include P. ovale, P. vivax. P. malariae, P. falciparum, and P. knowlesi. Transmission occurs via a bite of an infected female mosquito of Anopheles genus that serves as a vector. Human-to-human transmission, although extremely rare, may occur through a blood transfusion, organ transplantation, needlestick injuries in healthcare settings, or vertically from mother to newborn. Malaria remains an important human disease causing significant morbidity and mortality in countries within the geographic distribution of Anopheles mosquito, where disease elimination is challenged by various socio-economic factors. In the U.S., malaria remains an important diagnostic consideration in travelers returning from endemic areas who develop a febrile illness.

Epidemiology

In 2021, 247 million malaria cases occurred worldwide, an increase from 245 and 232 million cases in 2020 and 2019, respectively. This recent uptrend was attributed to disruptions in malaria control efforts during the COVID-19 pandemic. More than 90% of malaria originates in the African Region and is caused by P. falciparum . P. vivax, on the other hand, is responsible for only 2% of malaria cases around the globe. Despite lower relative numbers, the prevalence of P. vivax cases has been increasing whilst P. falciparum has been decreasing in endemic regions where both species co-exist. In 2019–2021, deaths caused by malaria were estimated to be between 568,000 and 625,000. Most lethal cases occurred in children under the age of 5 and were caused by P. falciparum [ 1 ••].

In the United States and other non-endemic countries, malaria is the most common cause of acute undifferentiated fever in returning travelers from endemic areas [ 2 •, 3 ]. In 2018, a total of 1,823 confirmed cases of malaria were reported to the Centers for Disease Control and Prevention (CDC), a 15.6% decline from the preceding year. Of these cases, 85% were acquired in Africa. P. falciparum accounted for the most infections (69.8%), followed by P. vivax (9.5%), P. ovale (5.2%), and P. malariae (2.6%). In 2018, a case of P. knowlesi was identified for the first time since 2008 [ 4 •].

Microbiology and Pathophysiology

The life cycle of Plasmodium species is completed in two hosts - mosquitoes and vertebrates. Transmission to humans occurs with Plasmodium sporozoites migrating from infected Anopheles mosquito’s salivary glands into dermis during a mosquito bite. Within minutes to hours, sporozoites migrate to liver where they mature into liver-stage schizonts. The hepatocytic schizont stage usually lasts from 2 to 10 days. Each liver schizont produces from 2,000 to 40,000 merozoites that are released into the bloodstream to invade red blood cells. In erythrocytes, merozoites mature into trophozoites and, eventually, into blood-stage schizonts. The latter continue an asexual cycle by releasing more and more merozoites, multiplying the total number of parasites in the human host. Some trophozoites, however, do not undergo asexual stages, and instead, differentiate into female and male gametocytes – the sexual stage that is infectious for a mosquito. Once ingested by another feeding mosquito during a subsequent bite, gametocytes will generate zygotes within mosquito’s gut and new parasites will migrate to its salivary glands to continue the cycle [ 5 , 6 ].

Genetic and physiologic variations between Plasmodium species are responsible for differences in geographic distribution and clinical presentation. P. falciparum , the parasite causing most severe and fatal cases of malaria, produces unique proteins that are expressed on the surface of infected erythrocytes promoting their adhesion to endothelium, platelets, and uninfected erythrocytes. Clinically, this phenomenon promotes parasite sequestration, microcirculation obstruction, tissue hypoxia, and lactic acidosis [ 7 , 8 , 9 , 10 ]. Infected red blood cell binding or sequestration allows P. falciparum to be temporarily removed from the peripheral circulation, causing low-grade parasitemia sometimes undetectable on blood smears, posing a diagnostic challenge [ 7 ].

P. vivax is the most widespread malarial parasite in tropical and subtropical regions outside of Africa [ 1 ••]. Its limited presence on the African continent is believed to be due to a lower expression of the Duffy antigen on erythrocytes of the African population, a blood group antigen, although not obligatory, but commonly used by P. vivax for erythrocyte entry [ 11 ].

Additionally, P. vivax demonstrates high affinity to reticulocytes. Due to a small number of reticulocytes in peripheral circulation, P. vivax causes a much lower degree of parasitemia than other Plasmodium species, although it triggers higher systemic inflammatory response than P. falciparum [ 12 , 13 , 14 ]. Both P. vivax and P. ovale produce dormant liver-stage hypnozoites, causing recurrent episodes of parasitemia months or even years after the initial inoculation. Malaria caused by Plasmodium malariae carries the lowest risk for severe disease of approximately 2% with a low mortality rate. Infrequent complications include severe anemia, respiratory and renal insufficiency [ 15 ].

P. knowlesi is a simian malaria parasite endemic to Southeast Asia, with the majority of human cases reported in Malaysia. Usual hosts are long-tailed and pig-tailed macaques, and humans can harbor the infection if bitten by a mosquito that has fed from a macaque. No human-to-human transmission has been reported to date. Despite continuous success in elimination of other Plasmodium species circulating in Southeast Asia, P. knowlesi’s incidence has been rising in recent years [ 16 , 17 , 18 , 19 •]. On microscopy, P. knowlesi resembles P. falciparum and P. malariae , therefore, this method cannot be used to diagnose P. knowlesi malaria [ 20 , 21 ]. A definitive diagnosis can be made using nested polymerase chain reaction (PCR); however, its use is limited in resource-poor areas. Rapid diagnostic tests (RDTs) can be used to rule out falciparum malaria in P. knowlesi -endemic areas. Therefore, it is recommended to presumably treat for P. knowlesi in cases originating from endemic areas for these parasites after ruling out falciparum malaria on RDTs [ 22 , 23 ].

Immunity and Transmission

Certain genetic factors as well as innate and adaptive immunity play an important role in illness severity. Generally, malaria severity is affected by degree of parasitemia, host’s age, immune response, chemoprophylaxis effects, and time to treatment [ 24 ]. Among important hereditary factors, as already described above, an absence of the Duffy antigen in the African population protects against P. vivax . Some hemoglobinopathies also demonstrate an advantage in combating malaria. Individuals with sickle cell trait and sickle cell disease typically do not develop significant illness in falciparum malaria despite having the same susceptibility to it as individuals without sickle cell disease. Evidence, although less compelling, also suggests protective features of ovalocytosis, thalassemias, hemoglobin E disease, and glucose-6-phosphatase (G6PD) deficiency against malaria [ 6 , 25 , 26 , 27 ]. Acquired immunity develops over time in residents of malarious areas after repeated exposure. For this reason, in endemic areas, severe disease affects mostly infants and young children, with a higher proportion of milder and asymptomatic cases in adults [ 5 , 6 ]. Traditionally, transmission and disease severity were believed to be inversely related: the risks of severe disease are lowest in populations with the highest transmission, while the highest severe disease risks are observed among populations with low-to-moderate transmission [ 28 ]. Therefore, nonimmune travelers to malarious areas are at a high risk for severe disease due to lack of preexisting immunity. However, in recent studies this relationship was found to be more complex. First, it is challenging to correctly estimate malaria prevalence in a given population due to a large number of asymptomatic or mildly symptomatic individuals with submicroscopic parasitemia [ 29 , 30 ]. Furthermore, multiple clones of parasites can be present within one host simultaneously, and sequencing methods are needed to track new genotypes acquired over time [ 31 , 32 ]. Lastly, degree of parasitemia does not always represent high infectivity. For example, a study in Ethiopia showed that only 15% of P. falciparum - and 35% of P.vivax -infected persons were infectious [ 33 ]. All of these and other factors contribute to uncertainties in establishing immunity, routes of transmission, and a true malaria burden.

Clinical Presentation of Uncomplicated Malaria

Incubation period is variable for different Plasmodium species and can last from 7 to 30 days, with shorter periods observed in P. falciparum and longer periods in P. malariae disease . About 95% of individuals develop symptoms within 6 weeks after exposure [ 6 ]. In some individuals residing in endemic areas, the disease can manifest as “asymptomatic” - with no symptoms in the setting of parasitemia. Some experts propose to favor the term “chronic” over “asymptomatic” malaria due to the long-term negative implications of untreated cases [ 34 ].

The hallmark feature of malarial illness – fever – coincides with the cyclical release of parasites during schizont rupture of erythrocytes. Once parasites are released into the bloodstream, inflammatory cytokines including tumor necrosis factor, interleukins, complement factors, prostaglandins and other pyrogenic factors trigger febrile response [ 7 , 35 ]. The classic clinical course includes febrile episodes alternating with symptom-free periods. The typical febrile malarial paroxysm includes 3 stages. The first stage, namely the cold stage, is characterized by rigors and feeling cold. It is followed by the hot stage that includes fever, sometimes reaching 40–41 °C, accompanied by malaise, nausea, vomiting, headache, myalgias, and possibly seizures, especially in the pediatric population. Finally, the paroxysm is completed by the sweating stage during which the fever subsides [ 6 , 36 ]. Although rarely observed, the duration of febrile episodes was historically associated with different species. Thus, P. falciparum , P. vivax, P. ovale cause malarial paroxysm every 48 h (“tertian” fever), and P. malariae – every 72 h (“quartan” fever) [ 35 , 37 ].

Physical examination findings are generally nonspecific and may include lethargy, anorexia, pallor, petechiae, jaundice, or mild abdominal tenderness. Children are more likely to present with hepatomegaly and splenomegaly than adults [ 38 ]. Notably, malaria does not produce lymphadenopathy [ 39 ].

Laboratory Investigations in Uncomplicated Malaria

All patients presenting with febrile illness in the setting of suspected malaria should have a complete blood count, metabolic panel, liver panel, coagulation panel, plasma lactate level, arterial blood gas analysis, urinalysis and chest imaging performed. Malaria-specific diagnostic tests are discussed separately. Laboratory abnormalities include thrombocytopenia in 60–70% of cases (although rarely significant enough to result in bleeding in uncomplicated disease), mild-to-moderate anemia, elevated liver enzymes, mild coagulopathy, elevated blood urea nitrogen and creatinine [ 38 , 39 ].

In general, obtaining blood cultures and a urine culture on admission is recommended, as invasive bacterial infections in malaria have been described. However, while the risk of concomitant bacteremia in malaria-endemic regions was shown to be of importance in children [ 40 , 41 , 42 ], in adult returning travelers it was found to be much less significant [ 43 , 44 ].

Severe Malaria

According to the World Health Organization (WHO), severe malaria is defined by the presence of one or more of the following complications occurring in the absence of an alternative cause: impaired consciousness, severe physical deconditioning, two or more seizure episodes, acidosis, hypoglycemia, severe anemia, renal impairment, hyperbilirubinemia, pulmonary edema, significant bleeding, shock, and high parasite density [ 45 ••, 46 ••]. In the US, severe malaria was diagnosed in approximately 14% of malaria patients in 2017 [ 47 ]. Risk factors for severe malaria include residence in non-endemic areas, extremes of age, pregnancy, and immunocompromise [ 5 , 6 , 39 ]. Children are more likely to develop seizures, hepatosplenomegaly, and severe anemia, while adults are at a higher risk for acute renal failure and pulmonary edema [ 41 , 46 ••]. P. falciparum is responsible for the majority of severe cases through rapid parasite biomass expansion, sequestration of infected erythrocytes, microvascular obstruction, endothelial activation, and subsequent end-organ damage [ 5 , 6 , 8 , 11 , 37 ]. It is generally accepted that P. knowlesi may cause severe disease through similar mechanisms, although cerebral malaria has not been reported to date [ 48 ]. Pathogenesis of severe malaria caused by P. vivax is poorly understood as this parasite does not tend to produce sequestration [ 5 , 7 , 49 ]. Several clinical syndromes comprise severe malaria.

Cerebral Malaria

Clinically defined as less than 11 points on Glasgow Coma Scale, cerebral malaria (CM) represents diffuse, symmetrical, potentially reversible encephalopathy caused by parasite sequestration in brain vasculature [ 50 ]. Parasites do not cross blood-brain barrier, although some degree of blood-brain barrier dysfunction may be present [ 51 ]. Brain edema is a common finding on imaging. If present, malarial retinopathy (retinal hemorrhages and patchy retinal whitening) increases diagnostic sensitivity and specificity of CM by 90% and 95%, respectively [ 52 , 53 ]. Similar clinical presentations necessitate clinicians to rule out meningitis and meningoencephalitis when considering CM, and if lumbar puncture is performed, elevated opening pressure and nonspecific cerebrospinal fluid analysis are observed in CM. Neurological sequela in survivors is common and may include epilepsy, ataxia, hemiplegia, blindness, and long-term cognitive deficits [ 54 ].

Severe Anemia

Severe anemia is characterized by hemoglobin ≤ 5 g/dL in children and ≤ 7 g/dL in adults [ 45 ••]. Pathogenesis is multifactorial and is attributed to erythrocyte lysis, immune-medicated erythrocyte destruction in spleen, and bone marrow suppression due to inflammatory state. “Blackwater fever” is a phenomenon that includes massive intravascular hemolysis, hemoglobinuria, and renal failure in patients with repeated falciparum malaria and a history of quinine chemoprophylaxis that occurs more commonly in persons with G6PD deficiency [ 46 ••]. Transfusion threshold is not well established, however it is generally indicated in severe cases.

Acute Renal Failure

Acute renal failure in severe malaria is defined by creatinine > 3 mg/dL or blood urea nitrogen > 56 mg/dL [ 45 ••]. Severe malaria promotes renal damage by affecting different structures - glomeruli, tubules, and interstitial region. Parasitized red blood cells obstruct renal vasculature causing acute tubular necrosis. Hypovolemia and shock further contribute to pre-renal kidney injury. With complement activation, immune complex deposition can trigger glomerulonephritis. Interstitial nephritis has also been described. Worsening kidney function further exacerbates acidosis [ 55 ].

Other Complications

Other life-threatening complications include pulmonary edema, acidosis, hypoglycemia, hyperbilirubinemia, distributive shock, and high-grade parasitemia. Clinicians should also be aware of possible complications such as aspiration pneumonia, gram-negative sepsis, and splenic rupture. Malaria may follow a rapidly progressive course; therefore, timely diagnosis and management are crucial.

Recrudescence

Both P. vivax and P. ovale are known to form hypnozoites, quiescent forms in liver, that can re-emerge as blood-stage forms months or even years later if initial infection was inadequately treated. Recrudescence due to P. falciparum has also been described . This parasite does not produce dedicated dormant forms but infrequently escapes treatment through drug resistance and sequestration of parasite clones [ 56 ].

Despite advances in technology in the past 20 years, microscopy (thick and thin smears) remains the gold standard for the diagnosis of malaria. Giemsa-stained thick smear is performed for identification of parasites as it examines lysed red blood cells. Thin smear allows for speciation and description of parasite stages. It is recommended to perform 2 smears of each type to increase diagnostic yield. If the initial set of smears is negative, they should be repeated 12 to 24 h apart until at least 3 sets are negative [ 57 ••]. Light microscopy is sufficient in diagnosing malaria for a parasite concentration above 5–10 parasites/µl, however, this method is interpreter-dependent [ 58 ]. Therefore, two major limitations arise with its use: availability of experienced laboratory personnel and sufficient parasite density. To aid in establishing prompt diagnosis, multiple RDTs have been developed. RDTs are designed to detect a falciparum-specific antigen and pan-malarial antigens including lactate dehydrogenase, aldolase, histidine-rich protein-2 (HRP-2), and others. Results are available within minutes [ 58 , 59 ]. In the U.S., the only Food and Drug Administration-approved RDT is BinaxNOW Malaria (Binax, Inc., Abbott Diagnostics Scarborrough, Scarborough, ME). This test detects two malarial antigens: HRP-2 ( P. falciparum- specific) and aldolase (pan-malarial). Manufacturer-reported P. falciparum sensitivity was 95.3% and specificity was 94.2%. For P. vivax , P. ovale, and P. malariae sensitivity was significantly lower – 68.9%, 50%, and 43.8%, respectively [ 60 ]. Limitations of all RDTs include inability to detect mixed infections, inability to distinguish species of Plasmodium , and limited ability to monitor response to therapy. Although some studies demonstrated RDTs’ superiority over microscopy [ 61 ], the consensus is to use both methods simultaneously [ 58 ]. Nonetheless, new RDTs are continuously being developed. As demonstrated in a recent meta-analysis, an ultrasensitive RDT outperformed conventional RDTs in sensitivity, especially in asymptomatic patients in low-grade transmission areas [ 62 ]. This ultrasensitive RDT is not yet available in the United States. Serologic tests are not recommended for the diagnosis of malaria as they cannot distinguish between acute disease and prior exposure.

General Treatment Considerations

When the diagnosis of malaria is confirmed, treatment should be initiated as soon as possible. Admission to the hospital is recommended for most malaria cases. With P. falciparum and P. knowlesi malaria, healthcare providers should be aware of possible rapid deterioration. When choosing a treatment regimen, several factors should be considered: plasmodium species, geographical area of disease acquisition, prior chemoprophylaxis, pregnancy status, and severity of the disease. Severe cases are treated with intravenous formulations while uncomplicated malaria can be treated with oral medications, if tolerated. In addition to clinical response monitoring, parasite density should be assessed via microscopy every 12–24 h. If unsuccessful chemoprophylaxis preceded the disease, a drug regimen different from the chemoprophylaxis regimen should be selected for treatment.

Uncomplicated Falciparum or Unknown Species Malaria Treatment

For uncomplicated P. falciparum malaria or unknown species malaria acquired in chloroquine-sensitive areas, chloroquine or hydroxychloroquine is recommended for children and adults by the CDC. If acquired in chloroquine-resistant area, an artemisinin-based combination therapy (ACT), atovaquone-proguanil, or quinine plus doxycycline or clindamycin is indicated [ 57 ••]. In contrary, the WHO recommends treatment of all uncomplicated malaria due to P. falciparum in adults, children including infants, pregnant women (second and third trimester) and breastfeeding women with ACT over chloroquine or hydroxychloroquine [ 45 ••]. Artemisinins as effective anti-malarial drugs were first derived from an herb in 1970s in China and since then they have gained widespread use [ 63 ]. Artemisinins are used in a two-drug combination to halt emerging resistance; they were proven to be safer and more effective than other regimens [ 64 ]. Artemether-lumefantrine, an ACT available in the U.S., is administered over a 3-day course in uncomplicated malaria and should be taken with food or fat containing drink (e.g., milk) to augment its absorption. Most common adverse events are mild and include headache, fever, and gastrointestinal disturbances. QT interval should be monitored for prolongation to avoid arrythmias [ 65 ]. ACT resistance has been increasingly reported, especially in Southeast Asia [ 66 •, 67 ]. Atovaquone-proguanil is also an effective combination in treating uncomplicated falciparum malaria, although treatment failure as high as 10% was reported in some studies [ 68 ]. Treatment duration is 3 days and the most common side effects include gastrointestinal disturbances and transaminitis. Mefloquine is an alternative treatment in falciparum malaria acquired in areas with chloroquine resistance. Treatment with mefloquine is of last resort if other agents are unavailable due to multiple undesired neuropsychiatric effects [ 69 , 70 •, 71 ].

Uncomplicated Non-falciparum Malaria Treatment

In uncomplicated malaria caused by P. malariae or P. knowlesi, either chloroquine or hydroxychloroquine is sufficient as no resistance have been reported. Both drugs are administered in 4 doses: at 0, 6, 24, 48 h. Severe adverse reactions are rare. These medications can also be used against P. vivax or P. ovale malaria acquired in areas without chloroquine resistance. For P. vivax acquired in chloroquine-resistant area, an ACT, atovaquone-proguanil, quinine plus doxycycline (preferred) or clindamycin, or mefloquine is recommended.

Most malarial drugs are effective against the erythrocytic stage of the parasite. To prevent relapses due to dormant liver hypnozoites in vivax and ovale malaria, an additional agent should be used. Primaquine can be added to any regimen, while tafenoquine can only be used in combination with chloroquine. Both medications are known to cause severe hemolytic anemia in persons with G6PD deficiency, thus testing should be obtained promptly as soon as vivax and ovale malaria is confirmed [ 45 ••, 57 ••].

Severe Malaria Treatment

Intravenous (IV) artesunate is the treatment of choice in severe malaria as it is significantly more effective than IV quinine [ 72 ]. Treatment should be initiated as soon as possible and if not available, oral artemether-lumefantrine should be given. This regimen is preferred due to the fast onset of action, and other options include atovaquone-proguanil, quinine, and mefloquine. Once available, IV artesunate should replace oral therapy for the first 24 h. If parasite density decreases to ≤ 1% and the patient can tolerate medications orally, an oral treatment, with artemether-lumefantrine preferred, should replace IV artesunate to complete a full course. Otherwise, IV artesunate should be continued for up to 7 days; parasitemia and ability to tolerate oral medications should be assessed daily. This regimen is safe and effective in adults, children, and pregnant women in the second and third trimesters. Administration in the first trimester was associated with teratogenic effects in animal models. Insufficient clinical data exist to establish safety in the first trimester of pregnancy in humans, however, the risks of untreated severe malaria in pregnant women should be compared to the hypothetical harm of the drug [ 73 •]. Additionally, clinicians should be aware of cases of post-artemisinin hemolytic anemia occurring more than 7 days after the treatment, therefore patients should be followed weekly for up to 4 weeks after the treatment [ 57 ••, 74 ].

All patients meeting the criteria for severe malaria should be admitted to an intensive care unit regardless of the causative plasmodium species. Antipyretics can be administered in pediatric patients to prevent seizures, otherwise no clear benefit has been established. IV fluids should be administered with caution to prevent pulmonary edema. Glucose should be monitored every 4 h with dextrose solutions added as maintenance fluids if indicated. Benzodiazepines are preferred for treatment of malaria-associated seizures, however, oversedation should be avoided [ 39 , 45 ••, 74 ]. Whole blood transfusion was associated with improved survival in children with cerebral malaria, however, such benefit in adults is unclear [ 75 ]. Limited evidence suggests restrictive broad-spectrum antibiotic strategy in returning travelers diagnosed with malaria as incidence of bacterial co-infections was much lower than in the population of endemic regions [ 43 , 76 ].

The following treatments were found to be harmful or of unknown benefit and therefore should be avoided: antiepileptics, mannitol, exchange transfusion, high-dose corticosteroids, albumin, and N-acetyl cysteine [ 45 ••, 77 , 78 , 79 ].

Vector control measures include the use of repellents, insecticide-treated bed nets, indoor residual spraying, larval control, and avoidance of outdoor activities from dusk to dawn. All travelers to endemic areas should be timely started on chemoprophylaxis prior to departure. Malarial chemoprophylaxis functions by targeting the liver schizont, blood schizont, or hypnozoite stages. The choice of the regimen depends on the destination, duration of travel, planned activities, comorbidities, allergies, pregnancy status, cost, and the time left to endemic country entry, as some agents should be started weeks prior [ 80 ]. Acceptable chemoprophylaxis options include doxycycline, atovaquone-proguanil, chloroquine, hydroxychloroquine, mefloquine, primaquine, and tafenoquine. The CDC Yellow Book provides extensive guidance on the use of malarial chemoprophylaxis [ 2 •].

Vaccine development is challenged by the complexity of plasmodium life cycle and ongoing mutations in key proteins of the parasite. The first and currently the only malaria vaccine approved by the WHO in 2021 for use in areas with moderate-to-high transmission in children is RTS,S/AS01, a pre-erythrocytic recombinant protein vaccine [ 45 ••]. Its development dates back to the 1980s and the results of a phase 3 clinical trial published in 2015 demonstrated 36% efficacy at 48 months follow-up in 5–17 months old children who received 4 doses [ 81 •]. However, the effect was shown to wane over the years, leading to rebound malaria cases [ 82 , 83 ]. Nevertheless, it is currently being trialed in Ghana, Kenya, and Malawi as a part of the Malaria Vaccine Implementation Programme. More vaccine candidates are underway, some of which are approaching late-stage clinical evaluation: R21/Matrix M vaccine targeting PfCSP protein, Rh5 blood-stage vaccine, attenuated whole sporozoite vaccine, and vaccine targeting sexual-stage antigens [ 84 , 85 ]. Novel technologies such as DNA and mRNA-based vaccines are also being explored.

Conclusions

Global malaria burden has decreased since the 2000s owing to local surveillance programs, robust vector control measures, new rapid diagnostic tests, and highly active artemisinin-based therapy. However, more recently, malaria elimination has plateaued and an increase in cases was seen during the COVID-19 pandemic. In addition to the socio-economic challenges disrupting local efforts in containing this parasitic disease, emerging drug resistance presents a substantial threat to malaria control.

In non-endemic countries such as the U.S., a high index of clinical suspicion in conjunction with complete history taking is needed for the diagnosis of malaria to be considered. Clinicians should familiarize themselves with the diagnostic and treatment options available at their practice locations. All travelers to endemic areas should be counseled to seek expert consultation prior to travel. Although the first malaria vaccine was approved by the WHO in 2021, it is only recommended for use in areas of endemicity in children of certain ages. There are currently no vaccines available for travelers. With novel technologies used in vaccine development, more vaccine candidates are underway.

Papers of particular interest, published recently, have been highlighted as: • Of importance •• Of major importance

•• World malaria report 2022. Geneva: World Health Organization; 2022 p. 19–21. The most recent WHO report on global and regional malaria prevalence and trends.

• Centers for Disease Control and Prevention. CDC yellow book 2020: health information for international travel, chapter 4: travel-related infectious diseases. Oxford University Press; 2017. Includes comprehensive guidelines by the CDC on chemoprophylaxis.

Wilson ME, Weld LH, Boggild A, Keystone JS, Kain KC, von Sonnenburg F, et al. Fever in returned travelers: results from the geosentinel surveillance network. Clin Infect Dis. 2007;44:1560–8.

PubMed   Google Scholar  

• Mace KE, Lucchi NW, Tan KR. Malaria surveillance - United States, 2018. MMWR Surveill Summ. Centers for Disease Control MMWR Office. 2022;71:1–35. Most recent report on malaria epidemiology in the United States.

Cowman AF, Healer J, Marapana D, Marsh K. Malaria: biology and disease. Cell. 2016;167:610–24.

CAS   PubMed   Google Scholar  

Crutcher JM, Hoffman SL. Malaria. In: Baron S, editor. Med Microbiol (Internet). 4th ed. Galveston (TX): University of Texas Medical Branch at Galveston; 1996. http://www.ncbi.nlm.nih.gov/books/NBK8584/ . Accessed 19 Jan 2023.

Milner DA. Malaria pathogenesis. Cold Spring Harb Perspect Med. 2018;8: a025569.

PubMed   PubMed Central   Google Scholar  

Grau GER, Craig AG. Cerebral malaria pathogenesis: revisiting parasite and host contributions. Future Microbiol. 2012;7:291–302.

Smith JD, Rowe JA, Higgins MK, Lavstsen T. Malaria’s deadly grip: cytoadhesion of Plasmodium falciparum-infected erythrocytes. Cell Microbiol. 2013;15:1976–83.

Fairhurst RM, Wellems TE. Modulation of malaria virulence by determinants of Plasmodium falciparum erythrocyte membrane protein-1 display. Curr Opin Hematol. 2006;13:124–30.

Lo E, Yewhalaw D, Zhong D, Zemene E, Degefa T, Tushune K, et al. Molecular epidemiology of Plasmodium vivax and Plasmodium falciparum malaria among Duffy-positive and Duffy-negative populations in Ethiopia. Malar J. 2015;14:84.

Dayananda K, Achur R, Gowda DC. Epidemiology, drug resistance, and pathophysiology of Plasmodium vivax malaria. J Vector Borne Dis. 2018;55:1.

Hemmer CJ, Holst FGE, Kern P, Chiwakata CB, Dietrich M, Reisinger EC. Stronger host response per parasitized erythrocyte in Plasmodium vivax or ovale than in Plasmodium falciparum malaria. Trop Med Int Health TM IH. 2006;11:817–23.

Moreno-Pérez DA, Ruíz JA, Patarroyo MA. Reticulocytes: Plasmodium vivax target cells. Biol Cell. 2013;105:251–60.

Kotepui M, Kotepui KU, Milanez GD, Masangkay FR. Global prevalence and mortality of severe Plasmodium malariae infection: a systematic review and meta-analysis. Malar J. 2020;19:274.

Shearer FM, Huang Z, Weiss DJ, Wiebe A, Gibson HS, Battle KE, et al. Estimating geographical variation in the risk of zoonotic Plasmodium knowlesi infection in countries eliminating malaria. PLoS Negl Trop Dis. 2016;10: e0004915.

William T, Jelip J, Menon J, Anderios F, Mohammad R, Awang Mohammad TA, et al. Changing epidemiology of malaria in Sabah, Malaysia: increasing incidence of Plasmodium knowlesi. Malar J. 2014;13:390.

Hussin N, Lim YA-L, Goh PP, William T, Jelip J, Mudin RN. Updates on malaria incidence and profile in Malaysia from 2013 to 2017. Malar J. 2020;19:55.

• Cooper DJ, Rajahram GS, William T, Jelip J, Mohammad R, Benedict J, et al. Plasmodium knowlesi malaria in Sabah, Malaysia, 2015–2017: ongoing increase in incidence despite near-elimination of the human-only plasmodium species. Clin Infect Dis Off Publ Infect Dis Soc Am. 2020;70:361–7. A review article of an emerging malarial parasite - Plasmodium knowlesi - in Malaysia.

Lee K-S, Cox-Singh J, Singh B. Morphological features and differential counts of Plasmodium knowlesi parasites in naturally acquired human infections. Malar J. 2009;8:73.

Barber BE, William T, Grigg MJ, Yeo TW, Anstey NM. Limitations of microscopy to differentiate Plasmodium species in a region co-endemic for Plasmodium falciparum, Plasmodium vivax and Plasmodium knowlesi. Malar J. 2013;12:8.

Grigg MJ, William T, Barber BE, Parameswaran U, Bird E, Piera K, et al. Combining parasite lactate dehydrogenase-based and histidine-rich protein 2-based rapid tests to improve specificity for diagnosis of malaria due to Plasmodium knowlesi and other Plasmodium species in Sabah. Malaysia J Clin Microbiol. 2014;52:2053–60.

Barber BE, William T, Grigg MJ, Piera K, Yeo TW, Anstey NM. Evaluation of the sensitivity of a pLDH-based and an aldolase-based rapid diagnostic test for diagnosis of uncomplicated and severe malaria caused by PCR-confirmed Plasmodium knowlesi, Plasmodium falciparum, and Plasmodium vivax. J Clin Microbiol. 2013;51:1118–23.

CAS   PubMed   PubMed Central   Google Scholar  

Warrell DA. Essential Malariology, 4Ed (Internet). 4th ed. CRC Press; 2017. https://www.taylorfrancis.com/books/9780203756621 . Accessed 21 Jan 2023

Aidoo M, Terlouw DJ, Kolczak MS, McElroy PD, ter Kuile FO, Kariuki S, et al. Protective effects of the sickle cell gene against malaria morbidity and mortality. Lancet Lond Engl. 2002;359:1311–2.

CAS   Google Scholar  

Leffler EM, Band G, Busby GBJ, Kivinen K, Le QS, Clarke GM, et al. Resistance to malaria through structural variation of red blood cell invasion receptors. Science. 2017;356:eaam6393.

Kariuki SN, Williams TN. Human genetics and malaria resistance. Hum Genet. 2020;139:801–11.

Snow RW, Omumbo JA, Lowe B, Molyneux CS, Obiero JO, Palmer A, et al. Relation between severe malaria morbidity in children and level of Plasmodium falciparum transmission in Africa. Lancet Lond Engl. 1997;349:1650–4.

Okell LC, Bousema T, Griffin JT, Ouédraogo AL, Ghani AC, Drakeley CJ. Factors determining the occurrence of submicroscopic malaria infections and their relevance for control. Nat Commun. 2012;3:1237.

Okell LC, Ghani AC, Lyons E, Drakeley CJ. Submicroscopic infection in Plasmodium falciparum-endemic populations: a systematic review and meta-analysis. J Infect Dis. 2009;200:1509–17.

Koepfli C, Mueller I. Malaria Epidemiology at the Clone Level. Trends Parasitol. 2017;33:974–85.

Recker M, Bull PC, Buckee CO. Recent advances in the molecular epidemiology of clinical malaria. F1000Research. 2018;7:1159.

Google Scholar  

Tadesse FG, Slater HC, Chali W, Teelen K, Lanke K, Belachew M, et al. The relative contribution of symptomatic and asymptomatic Plasmodium vivax and Plasmodium falciparum infections to the infectious reservoir in a low-endemic setting in Ethiopia. Clin Infect Dis Off Publ Infect Dis Soc Am. 2018;66:1883–91.

Chen I, Clarke SE, Gosling R, Hamainza B, Killeen G, Magill A, et al. “Asymptomatic” malaria: a chronic and debilitating infection that should be treated. PLOS Med. 2016;13: e1001942.

Oakley MS, Gerald N, McCutchan TF, Aravind L, Kumar S. Clinical and molecular aspects of malaria fever. Trends Parasitol. 2011;27:442–9.

Svenson JE, MacLean JD, Gyorkos TW, Keystone J. Imported malaria. Clinical presentation and examination of symptomatic travelers0. Arch Intern Med. 1995;155:861–8.

Price RN, Tjitra E, Guerra CA, Yeung S, White NJ, Anstey NM. Vivax malaria: neglected and not benign. Am J Trop Med Hyg. 2007;77:79–87.

Shingadia D, Shulman ST. Recognition and management of imported malaria in children. Semin Pediatr Infect Dis. 2000;11:172–7.

Fletcher TE, Beeching NJ. Malaria. J R Army Med Corps. 2013;159:158–66.

Were T, Davenport GC, Hittner JB, Ouma C, Vulule JM, Ong’echa JM, et al. Bacteremia in Kenyan children presenting with malaria. J Clin Microbiol. 2011;49:671–6.

Bassat Q, Guinovart C, Sigaúque B, Mandomando I, Aide P, Sacarlal J, et al. Severe malaria and concomitant bacteraemia in children admitted to a rural Mozambican hospital. Trop Med Int Health TM IH. 2009;14:1011–9.

Church J, Maitland K. Invasive bacterial co-infection in African children with Plasmodium falciparum malaria: a systematic review. BMC Med. 2014;12:31.

Sandlund J, Naucler P, Dashti S, Shokri A, Eriksson S, Hjertqvist M, et al. Bacterial coinfections in travelers with malaria: rationale for antibiotic therapy. J Clin Microbiol. 2013;51:15–21.

Phu NH, Day NPJ, Tuan PQ, Mai NTH, Chau TTH, Van Chuong L, et al. Concomitant Bacteremia in adults with severe falciparum malaria. Clin Infect Dis Off Publ Infect Dis Soc Am. 2020;71:e465–70.

•• World Health Organization. WHO Guidelines for malaria. Geneva; 2022. p. 105–6. The most recent WHO treatment guidelines.

•• White NJ. Severe malaria. Malar J. 2022;21:284. Comprehensive overview on pathogenesis and clinical presentation of severe malaria.

Daily JP, Minuti A, Khan N. Diagnosis, treatment, and prevention of malaria in the US: a review. JAMA. 2022;328:460–71.

Anstey NM, Grigg MJ, Rajahram GS, Cooper DJ, William T, Kho S, et al. Knowlesi malaria: human risk factors, clinical spectrum, and pathophysiology. Adv Parasitol. 2021;113:1–43.

Baird JK. Evidence and implications of mortality associated with acute Plasmodium vivax malaria. Clin Microbiol Rev. 2013;26:36–57.

Silamut K, Phu NH, Whitty C, Turner GDH, Louwrier K, Mai NTH, et al. A quantitative analysis of the microvascular sequestration of malaria parasites in the human brain. Am J Pathol. 1999;155:395–410.

Medana IM, Turner GDH. Human cerebral malaria and the blood-brain barrier. Int J Parasitol. 2006;36:555–68.

Beare NAV, Taylor TE, Harding SP, Lewallen S, Molyneux ME. Malarial retinopathy: a newly established diagnostic sign in severe malaria. Am J Trop Med Hyg. 2006;75:790–7.

Birbeck GL, Beare N, Lewallen S, Glover SJ, Molyneux ME, Kaplan PW, et al. Identification of malaria retinopathy improves the specificity of the clinical diagnosis of cerebral malaria: findings from a prospective cohort study. Am J Trop Med Hyg. 2010;82:231–4.

World Health Organization. Severe malaria. Trop Med Int Health. 2014;19:7–131.

da Silva GB, Pinto JR, Barros EJG, Farias GMN, Daher EDF. Kidney involvement in malaria: an update. Rev Inst Med Trop Sao Paulo. 2017;59: e53.

Malvy D, Torrentino-Madamet M, L’Ollivier C, Receveur M-C, Jeddi F, Delhaes L, et al. Plasmodium falciparum recrudescence two years after treatment of an uncomplicated infection without return to an area where malaria is endemic. Antimicrob Agents Chemother. 2018;62:e01892-e1917.

•• CDC. Treatment of malaria: guideline for clinicians (United States) (Internet). Atlanta, GA: US Department of Health and Human Services, CDC; 2022. https://www.cdc.gov/malaria/diagnosis_treatment/clinicians1.html . Accessed 4 Feb 2023. The most recent CDC treatment guidelines.

Murray CK, Gasser RA, Magill AJ, Miller RS. Update on Rapid Diagnostic Testing for Malaria. Clin Microbiol Rev. 2008;21:97–110.

Moody A. Rapid diagnostic tests for malaria parasites. Clin Microbiol Rev. 2002;15:66–78.

Abbott Diagnostics. BinaxNOW malaria test kit: product instructions (Internet). Scarborrough, ME; 2019. https://www.globalpointofcare.abbott/en/product-details/binaxnow-malaria.html . Accessed 28 Feb 2023.

Stauffer WM, Cartwright CP, Olson DA, Juni BA, Taylor CM, Bowers SH, et al. Diagnostic performance of rapid diagnostic tests versus blood smears for malaria in US clinical practice. Clin Infect Dis. 2009;49:908–13.

Yimam Y, Mohebali M, Abbaszadeh Afshar MJ. Comparison of diagnostic performance between conventional and ultrasensitive rapid diagnostic tests for diagnosis of malaria: a systematic review and meta-analysis. Gatton ML, editor. PLOS ONE 2022;17:e0263770.

Liao F. Discovery of artemisinin (Qinghaosu). Molecules. 2009;14:5362–6.

CAS   PubMed Central   Google Scholar  

Sinclair D, Zani B, Donegan S, Olliaro P, Garner P. Artemisinin-based combination therapy for treating uncomplicated malaria. Cochrane Infectious Diseases Group, editor. Cochrane Database Syst Rev (Internet). 2009.  https://doi.wiley.com/10.1002/14651858.CD007483.pub2 . Accessed 4 Feb 2023.

Abamecha A, Yilma D, Adissu W, Yewhalaw D, Abdissa A. Efficacy and safety of artemether–lumefantrine for treatment of uncomplicated Plasmodium falciparum malaria in Ethiopia: a systematic review and meta-analysis. Malar J. 2021;20:213.

• Mathenge PG, Low SK, Vuong NL, Mohamed MYF, Faraj HA, Alieldin GI, et al. Efficacy and resistance of different artemisinin-based combination therapies: a systematic review and network meta-analysis. Parasitol Int. 2020;74:101919. A systematic review and a network meta-analysis of the preferred treatment, artemisinin-based combination regimen.

Ward KE, Fidock DA, Bridgford JL. Plasmodium falciparum resistance to artemisinin-based combination therapies. Curr Opin Microbiol. 2022;69: 102193.

Blanshard A, Hine P. Atovaquone-proguanil for treating uncomplicated Plasmodium falciparum malaria. Cochrane Infectious Diseases Group, editor. Cochrane Database Syst Rev (Internet). 2021.  http://doi.wiley.com/10.1002/14651858.CD004529.pub3 . Accessed 5 Feb 2023.

McCarthy S. Malaria prevention, mefloquine neurotoxicity, neuropsychiatric illness, and risk-benefit analysis in the Australian defence force. J Parasitol Res. 2015;2015:1–23.

• Ahmad SS, Rahi M, Ranjan V, Sharma A. Mefloquine as a prophylaxis for malaria needs to be revisited. Int J Parasitol Drugs Drug Resist. 2021;17:23–6. Summarizes the findings of the most important studies on mefloquine toxicity published in the past 20 years.

Martins AC, Paoliello MMB, Docea AO, Santamaria A, Tinkov AA, Skalny AV, et al. Review of the mechanism underlying mefloquine-induced neurotoxicity. Crit Rev Toxicol. 2021;51:209–16.

Sinclair D, Donegan S, Isba R, Lalloo DG. Artesunate versus quinine for treating severe malaria. Cochrane Infectious Diseases Group, editor. Cochrane Database Syst Rev (Internet). 2012.  https://doi.wiley.com/10.1002/14651858.CD005967.pub4 . Accessed 5 Feb 2023.

• Clark RL. Safety of treating malaria with artemisinin-based combination therapy in the first trimester of pregnancy. Reprod Toxicol. 2022;111:204–10. Since scant evidence exist on artemisinin safety in first trimester of pregnancy, this article summarizes the limited data in humans.

White NJ, Pukrittayakamee S, Hien TT, Faiz MA, Mokuolu OA, Dondorp AM. Malaria. The Lancet. 2014;383:723–35.

Ackerman H, Ayestaran A, Olola CHO, Jallow M, Agbenyega T, Bojang K, et al. The effect of blood transfusion on outcomes among African children admitted to hospital with Plasmodium falciparum malaria: a prospective, multicentre observational study. Lancet Haematol. 2020;7:e789–97.

Jauréguiberry S, Thellier M, Caumes E, Buffet P. Artesunate for imported severe malaria in nonendemic countries. Clin Infect Dis. 2016;62:270–1.

Mohanty S, Mishra SK, Patnaik R, Dutt AK, Pradhan S, Das B, et al. Brain swelling and mannitol therapy in adult cerebral malaria: a randomized trial. Clin Infect Dis. 2011;53:349–55.

Namutangula B, Ndeezi G, Byarugaba JS, Tumwine JK. Mannitol as adjunct therapy for childhood cerebral malaria in Uganda: a randomized clinical trial. Malar J. 2007;6:138.

Tan KR, Wiegand RE, Arguin PM. Exchange Transfusion for severe malaria: evidence base and literature review. Clin Infect Dis. 2013;57:923–8.

DeVos E, Dunn N. Malaria prophylaxis. StatPearls (Internet). Treasure Island (FL): StatPearls Publishing; 2022. http://www.ncbi.nlm.nih.gov/books/NBK551639/ . Accessed 2023 Feb 24.

• RTS, S Clinical Trials Partnership. Efficacy and safety of RTS,S/AS01 malaria vaccine with or without a booster dose in infants and children in Africa: final results of a phase 3, individually randomised, controlled trial. Lancet Lond Engl. 2015;386:31–45. A landmark phase 3 trial of the first malaria vaccine.

Olotu A, Fegan G, Wambua J, Nyangweso G, Awuondo KO, Leach A, et al. Four-year efficacy of RTS, S/AS01E and its interaction with malaria exposure. N Engl J Med. 2013;368:1111–20.

Olotu A, Fegan G, Wambua J, Nyangweso G, Leach A, Lievens M, et al. Seven-year efficacy of RTS, S/AS01 malaria vaccine among young african children. N Engl J Med. 2016;374:2519–29.

Datoo MS, Natama MH, Somé A, Traoré O, Rouamba T, Bellamy D, et al. Efficacy of a low-dose candidate malaria vaccine, R21 in adjuvant Matrix-M, with seasonal administration to children in Burkina Faso: a randomised controlled trial. Lancet Lond Engl. 2021;397:1809–18.

Laurens MB. Novel malaria vaccines. Hum Vaccines Immunother. 2021;17:4549–52.

Download references

Author information

Authors and affiliations.

Department of Medicine, Case Western Reserve University/University Hospitals Cleveland Medical Center, Cleveland, OH, USA

Anastasia S. Weiland

You can also search for this author in PubMed   Google Scholar

Corresponding author

Correspondence to Anastasia S. Weiland .

Ethics declarations

Conflict of interest.

Anastasia S. Weiland declares that she has no conflict of interest.

Human and Animal Rights and Informed Consent

This article does not contain any studies with human or animal subjects performed by any of the authors.

Additional information

Publisher's note.

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and permissions

About this article

Weiland, A.S. Recent Advances in Imported Malaria Pathogenesis, Diagnosis, and Management. Curr Emerg Hosp Med Rep 11 , 49–57 (2023). https://doi.org/10.1007/s40138-023-00264-5

Download citation

Accepted : 28 March 2023

Published : 12 April 2023

Issue Date : June 2023

DOI : https://doi.org/10.1007/s40138-023-00264-5

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

• Imported malaria
• Severe malaria
• Malaria transmission
• Rapid diagnostic test
• Artemisinin-based therapy
• Find a journal
• Publish with us
• Track your research

Featured Clinical Reviews

• Screening for Atrial Fibrillation: US Preventive Services Task Force Recommendation Statement JAMA Recommendation Statement January 25, 2022
• Evaluating the Patient With a Pulmonary Nodule: A Review JAMA Review January 18, 2022
• Download PDF
• CME & MOC
• Share X Facebook Email LinkedIn
• Permissions

Diagnosis, Treatment, and Prevention of Malaria in the US : A Review

• 1 Department of Medicine (Infectious Diseases), Albert Einstein College of Medicine, Bronx, New York
• 2 D. Samuel Gottesman Library, Albert Einstein College of Medicine, Bronx, New York
• Medical News & Perspectives Vaccine Development Is Charting a New Path in Malaria Control Bridget M. Kuehn, MSJ JAMA
• JAMA Patient Page Patient Information: Malaria Kristin Walter, MD, MS; Chandy C. John, MD, MS JAMA
• Global Health Updated Malaria Recommendations for Children and Pregnant People Howard D. Larkin JAMA
• Medical News in Brief First Ever Malaria Vaccine to Be Distributed in Africa Emily Harris JAMA

Importance   Malaria is caused by protozoa parasites of the genus Plasmodium and is diagnosed in approximately 2000 people in the US each year who have returned from visiting regions with endemic malaria. The mortality rate from malaria is approximately 0.3% in the US and 0.26% worldwide.

Observations   In the US, most malaria is diagnosed in people who traveled to an endemic region. More than 80% of people diagnosed with malaria in the US acquired the infection in Africa. Of the approximately 2000 people diagnosed with malaria in the US in 2017, an estimated 82.4% were adults and about 78.6% were Black or African American. Among US residents diagnosed with malaria, 71.7% had not taken malaria chemoprophylaxis during travel. In 2017 in the US, P falciparum was the species diagnosed in approximately 79% of patients, whereas P vivax was diagnosed in an estimated 11.2% of patients. In 2017 in the US, severe malaria, defined as vital organ involvement including shock, pulmonary edema, significant bleeding, seizures, impaired consciousness, and laboratory abnormalities such as kidney impairment, acidosis, anemia, or high parasitemia, occurred in approximately 14% of patients, and an estimated 0.3% of those receiving a diagnosis of malaria in the US died. P falciparum has developed resistance to chloroquine in most regions of the world, including Africa. First-line therapy for P falciparum malaria in the US is combination therapy that includes artemisinin. If P falciparum was acquired in a known chloroquine-sensitive region such as Haiti, chloroquine remains an alternative option. When artemisinin-based combination therapies are not available, atovaquone-proguanil or quinine plus clindamycin is used for chloroquine-resistant malaria. P vivax, P ovale, P malariae, and P knowlesi are typically chloroquine sensitive, and treatment with either artemisinin-based combination therapy or chloroquine for regions with chloroquine-susceptible infections for uncomplicated malaria is recommended. For severe malaria, intravenous artesunate is first-line therapy. Treatment of mild malaria due to a chloroquine-resistant parasite consists of a combination therapy that includes artemisinin or chloroquine for chloroquine-sensitive malaria. P vivax and P ovale require additional therapy with an 8-aminoquinoline to eradicate the liver stage. Several options exist for chemoprophylaxis and selection should be based on patient characteristics and preferences.

Conclusions and Relevance   Approximately 2000 cases of malaria are diagnosed each year in the US, most commonly in travelers returning from visiting endemic areas. Prevention and treatment of malaria depend on the species and the drug sensitivity of parasites from the region of acquisition. Intravenous artesunate is first-line therapy for severe malaria.

Read More About

Daily JP , Minuti A , Khan N. Diagnosis, Treatment, and Prevention of Malaria in the US : A Review . JAMA. 2022;328(5):460–471. doi:10.1001/jama.2022.12366

Manage citations:

© 2024

Artificial Intelligence Resource Center

Cardiology in JAMA : Read the Latest

Browse and subscribe to JAMA Network podcasts!

Others Also Liked

Select your interests.

Customize your JAMA Network experience by selecting one or more topics from the list below.

• Academic Medicine
• Acid Base, Electrolytes, Fluids
• Allergy and Clinical Immunology
• American Indian or Alaska Natives
• Anesthesiology
• Anticoagulation
• Art and Images in Psychiatry
• Artificial Intelligence
• Assisted Reproduction
• Bleeding and Transfusion
• Caring for the Critically Ill Patient
• Challenges in Clinical Electrocardiography
• Climate and Health
• Climate Change
• Clinical Challenge
• Clinical Decision Support
• Clinical Implications of Basic Neuroscience
• Clinical Pharmacy and Pharmacology
• Complementary and Alternative Medicine
• Consensus Statements
• Coronavirus (COVID-19)
• Critical Care Medicine
• Cultural Competency
• Dental Medicine
• Dermatology
• Diabetes and Endocrinology
• Diagnostic Test Interpretation
• Drug Development
• Electronic Health Records
• Emergency Medicine
• End of Life, Hospice, Palliative Care
• Environmental Health
• Equity, Diversity, and Inclusion
• Facial Plastic Surgery
• Gastroenterology and Hepatology
• Genetics and Genomics
• Genomics and Precision Health
• Global Health
• Guide to Statistics and Methods
• Hair Disorders
• Health Care Delivery Models
• Health Care Economics, Insurance, Payment
• Health Care Quality
• Health Care Reform
• Health Care Safety
• Health Care Workforce
• Health Disparities
• Health Inequities
• Health Policy
• Health Systems Science
• History of Medicine
• Hypertension
• Images in Neurology
• Implementation Science
• Infectious Diseases
• Innovations in Health Care Delivery
• JAMA Infographic
• Law and Medicine
• Leading Change
• Less is More
• LGBTQIA Medicine
• Lifestyle Behaviors
• Medical Coding
• Medical Devices and Equipment
• Medical Education
• Medical Education and Training
• Medical Journals and Publishing
• Mobile Health and Telemedicine
• Narrative Medicine
• Neuroscience and Psychiatry
• Notable Notes
• Nutrition, Obesity, Exercise
• Obstetrics and Gynecology
• Occupational Health
• Ophthalmology
• Orthopedics
• Otolaryngology
• Pain Medicine
• Palliative Care
• Pathology and Laboratory Medicine
• Patient Care
• Patient Information
• Performance Improvement
• Performance Measures
• Perioperative Care and Consultation
• Pharmacoeconomics
• Pharmacoepidemiology
• Pharmacogenetics
• Pharmacy and Clinical Pharmacology
• Physical Medicine and Rehabilitation
• Physical Therapy
• Physician Leadership
• Population Health
• Primary Care
• Professional Well-being
• Professionalism
• Psychiatry and Behavioral Health
• Public Health
• Pulmonary Medicine
• Regulatory Agencies
• Reproductive Health
• Research, Methods, Statistics
• Resuscitation
• Rheumatology
• Risk Management
• Scientific Discovery and the Future of Medicine
• Shared Decision Making and Communication
• Sleep Medicine
• Sports Medicine
• Stem Cell Transplantation
• Substance Use and Addiction Medicine
• Surgical Innovation
• Surgical Pearls
• Teachable Moment
• Technology and Finance
• The Art of JAMA
• The Arts and Medicine
• The Rational Clinical Examination
• Tobacco and e-Cigarettes
• Translational Medicine
• Trauma and Injury
• Treatment Adherence
• Ultrasonography
• Users' Guide to the Medical Literature
• Vaccination
• Venous Thromboembolism
• Veterans Health
• Women's Health
• Workflow and Process
• Wound Care, Infection, Healing
• Register for email alerts with links to free full-text articles
• Access PDFs of free articles
• Manage your interests
• Save searches and receive search alerts

• Open access
• Published: 27 March 2018

Comparative effectiveness of malaria prevention measures: a systematic review and network meta-analysis

• Kinley Wangdi 1 ,
• Luis Furuya-Kanamori 1 , 2 ,
• Justin Clark 3 ,
• Jan J. Barendregt 4 , 5   an1 ,
• Michelle L. Gatton 6 ,
• Cathy Banwell 1 ,
• Gerard C. Kelly 1 ,
• Suhail A. R. Doi 1 , 2 &
• Archie C. A. Clements 1  

Parasites & Vectors volume  11 , Article number:  210 ( 2018 ) Cite this article

10k Accesses

34 Citations

6 Altmetric

Metrics details

Malaria causes significant morbidity and mortality worldwide. There are several preventive measures that are currently employed, including insecticide-treated nets (ITNs, including long-lasting insecticidal nets and insecticidal-treated bed nets), indoor residual spraying (IRS), prophylactic drugs (PD), and untreated nets (UN). However, it is unclear which measure is the most effective for malaria prevention. We therefore undertook a network meta-analysis to compare the efficacy of different preventive measures on incidence of malaria infection.

A systematic literature review was undertaken across four medical and life sciences databases (PubMed, Cochrane Central, Embase, and Web of Science) from their inception to July 2016 to compare the effectiveness of different preventive measures on malaria incidence. Data from the included studies were analysed for the effectiveness of several measures against no intervention (NI). This was carried out using an automated generalized pairwise modeling (GPM) framework for network meta-analysis to generate mixed treatment effects against a common comparator of no intervention (NI).

There were 30 studies that met the inclusion criteria from 1998–2016. The GPM framework led to a final ranking of effectiveness of measures in the following order from best to worst: PD, ITN, IRS and UN, in comparison with NI. However, only ITN (RR: 0.49, 95% CI: 0.32–0.74) showed precision while other methods [PD (RR: 0.24, 95% CI: 0.004–15.43), IRS (RR: 0.55, 95% CI: 0.20–1.56) and UN (RR: 0.73, 95% CI: 0.28–1.90)] demonstrating considerable uncertainty associated with their point estimates.

Current evidence is strong for the protective effect of ITN interventions in malaria prevention. Even though ITNs were found to be the only preventive measure with statistical support for their effectiveness, the role of other malaria control measures may be important adjuncts in the global drive to eliminate malaria.

Malaria imposes a great health and socio-economic burden on humanity, with an estimated 3.2 billion people at risk of being infected with malaria [ 1 ]. In 2016, there were approximately 216 million cases with 445,000 deaths, most of which were in children aged under 5 years in Africa [ 1 ]. Between 2000 and 2015, it has been estimated that there was a 37% global reduction in malaria incidence [ 2 ]. This improvement was likely made possible by economic development and urbanization in many endemic countries [ 3 ] as well as a substantial increase in investment in tackling malaria [ 4 ], leading to an increase in preventative activities, and improved diagnostics and treatment. The Global Technical Strategy for Malaria 2016–2030 (GTS) has a target to eliminate malaria in at least ten countries by 2020, 20 countries by 2025, and 30 countries by 2030 [ 2 , 5 ].

Vector control remains an essential component of malaria control and elimination. The capacity of vectors to transmit parasites and their vulnerability to vector control measures vary by mosquito species and are influenced by local environmental factors. Personal preventive measures that prevent contact between the adult mosquitoes and human beings are the main methods of prevention currently in practice. These include insecticide-treated nets (ITNs), and indoor residual spraying (IRS) [ 6 ]. ITNs are of two types: long-lasting insecticidal nets (LLINs) that have the insecticide incorporated into fibers during the manufacturing process, which leads to a longer duration of effectiveness and insecticide-treated nets (ITNs) which are impregnated with insecticides every six months. Indoor residual spraying (IRS) involves spraying insecticides on the walls of the houses. Additionally, antimalarial chemoprophylaxis is used for prevention of malaria in children and pregnant women. The commonly used prophylactic drugs (PD) are sulphadoxine-pyrimethamine (SP), mefloquine (MQ), amodiaquine (AQ), dihydroartemisinin-peperaquine (DP) and artesunate (AS). The main advantage of using PD is that they only require a single dose to achieve a full prophylactic effect [ 7 , 8 ]. However, the most common PD is SP and it is becoming less effective due to resistance [ 9 , 10 , 11 , 12 , 13 ]. As a result, other drugs such as MQ and AQ are increasingly being used as a substitute for or in combination with SP [ 12 , 14 ]. MQ provides a longer period of prophylaxis but side effects (agranulocytosis in 1 per 2000 patients) [ 15 ] are the main problem [ 16 , 17 ]. Similarly, AQ has been used in combination with SP but AQ is not well tolerated [ 14 ]. Many other less commonly utilized measures include insecticide-treated curtains (ITC), mosquito coils, insecticide-treated hammocks, and insecticide-treated tarpaulins.

There has been a decrease in malaria incidence worldwide, but what remains unclear is which of the common preventive interventions is the most effective for prevention of malaria infection. This knowledge may help prioritise resourcing of these interventions. There has been one comparative study of preventive efficacy that compares mortality across ITN, IRS and PD and this study demonstrated that the impact of IRS is equal to that of ITN on reducing malaria-attributable mortality in children [ 18 ]. There have also been several systematic reviews and meta-analyses focusing on single preventive measures. These reviews of existing data suggest that PD [ 19 , 20 , 21 , 22 ], is effective in preventing malaria infection in children when treated on a monthly basis with no protection when given three-monthly. The reviews of both ITN [ 23 , 24 , 25 ] and IRS [ 26 , 27 ] provide support for their effectiveness as malaria preventive measures, but there is no data on the effectiveness of one measure over another.

Therefore, this study aims to present an up-to-date comparison of the effectiveness of the four common malaria preventive measures (ITNs, UNs, IRS and PDs) for which data are readily available and compare these against no intervention [NI, defined as no intervention or placebo or a study group with standard care (any intervention given to all participants)]. A network meta-analysis methodology was chosen to pool the data as it allows comparisons of multiple preventive measures simultaneously and allows comparisons across preventive measures not directly tested in the included trials (indirect comparisons across a pair of studies that share a common comparator). In addition, this method allows ranking of the effectiveness of these measures for decision making.

Search strategy and eligibility criteria

A systematic literature review was undertaken using four medical and life sciences databases (PubMed, Cochrane Central, Embase and Web of Science). They were searched from their inception to March 2016 for trials that compared the effectiveness of malaria preventive measures. Search terms included were “ malaria ”, “ Plasmodium falciparum ”, “ Plasmodium vivax ”, “ bed net ”, “ mosquito control ”, “ antimalarial ”, and “insecticides” ; the specific keywords and connectors for each database are listed in the Additional file 1 : Table S1.

The inclusion of studies were restricted to (i) interventional studies; (ii) conducted in humans (with no restriction of age or sex); (iii) that compared two or more of the following malaria preventive measures: ITN, UN, IRS, PD or NI; and (iv) reported the number of new malaria cases diagnosed through microscopy or rapid diagnostic tests (RDT) after each intervention compared amongst a population at risk over time. Exclusion criteria included: (i) non-intervention studies; (ii) conference abstracts; and (iii) other less commonly utilized malaria preventive measures including ITC, mosquito coils, insecticide-treated hammocks and insecticide-treated tarpaulins. No language restrictions were imposed. Since we used a generalized pairwise modeling approach (see below), odd numbers of treatments (e.g. three treatment arms) required selection of a pair for inclusion in this study and we therefore excluded the arm that had the most available data in this synthesis [(i) arms that we excluded do not make a difference, (ii) concurrent interventions and no effect modification].

Study selection and data extraction

The citation search was developed and executed by JC, followed by selection of citations by title and abstract independently by two researchers (KW and LFK). The selected studies underwent a full-text review for all potentially relevant studies. Data from the included studies were then independently extracted in a spreadsheet by the same two researchers. The extracted data included: (i) the country of study; (ii) year(s) when the study was conducted; (iii) study design; (iv) study population characteristics; (v) preventive measures employed in the trial; and (vi) the number of new cases of malaria and person-months at risk. The extracted data were then cross-checked by the two researchers and any discrepancies during the selection of studies or data extraction were resolved through discussion and consensus following independent evaluation by another author (SARD).

Statistical analysis

The outcome of interest was the rate ratio (RR) of new malaria cases in intervention-A vs intervention-B following the implementation of different preventative measures. An automated generalized pairwise modeling (GPM) framework [ 28 ] was used to generate mixed treatment effects against a common comparator (NI). This framework is an extension of the Bucher method [ 29 ] that automates the single three-treatment loop method. This analysis starts by pooling effect sizes based on direct comparisons between any two interventions using meta-analytic methods. The indirect comparison was then performed by automated generation of all possible closed loops of three-treatments such that one of them was common to the two studies and formed the node where the loop began and ended but where the common node was never NI, while one of the other nodes was always NI. Finally, the mixed effects (multiple direct/indirect effects) were pooled using the same meta-analysis model as used for pooling direct effects. The analysis therefore led to a final mixed treatment effect estimate for different interventions versus NI. Estimates of preventive effectiveness were then ranked by their point estimates. It should be pointed out that it is common for network plots based on Bayesian methods to rank treatments by the surface under the cumulative ranking curve (SUCRA). From our frequentist perspective, treatment effects are thought of as fixed parameters and thus, strictly speaking SUCRA does not apply. A frequentist alternative called the P-score has been proposed but SUCRA or P-scores have no major advantage compared to what we have done, i.e. ranking treatments by their point estimates [ 30 ].

All direct estimates were pooled using the inverse variance heterogeneity (IVhet) model [ 31 ] as were all mixed estimates, but this synthesis process was also repeated using the random effects model for comparison (the random effects analysis was undertaken under the GPM framework as well as under the frequentist multivariate meta-analysis framework for comparison (see Additional file 1 : Tables S2 and S3 for details).

Cluster randomized controlled trials (RCT) were combined with other study types after accounting for clustering using the design effect (DEFF). The DEFF was calculated as follows:

where ρ is the intra-class correlation for the statistic in question and c is the average size of the cluster. We then divided the numbers in each 2 × 2 table of the study by the DEFF to calculate a corrected sample size, which was then utilized in the meta-analysis. Different units of clusters such as villages and households were used in different studies. The intra-class correlation coefficient ( ρ ) was provided only in one study [ 32 ], and this ( ρ = 0.048) was used for calculation of the DEFF for other cluster RCT studies.

Statistical heterogeneity across direct effects pooled in the meta-analysis were assessed by the Cochran’s Q and the H index which is the square root of H 2 , the estimated residual variance from the regression of the standardized treatment effect estimates against the inverse standard error in each direct meta-analysis. H was computed as follows:

where n is the number of study estimates pooled and Q represents the Chi squared from Cochran’s Q .

Transitivity was assessed statistically by looking at inconsistency across the network as a whole using the weighted pooled H index ( \( \overline{H} \) ) which was computed as follows from the Cochran’s Q statistic for the k final comparisons:

where n is the number of estimates pooled across each comparison and s is the number comparisons (out of k ) were n = 1. The minimum value H or \( \overline{H} \) can take is 1, it is not influenced by n , and \( \overline{H}<3 \) was taken to be minimal inconsistency based on our simulations of H in homogenous direct meta-analyses [ 28 ].

Sensitivity analyses were undertaken through limiting the network to (i) studies conducted in children or (ii) studies including only Plasmodium falciparum infection and then re-running the GPM analysis.

Publication bias was assessed using a ‘comparison adjusted’ funnel plot where on the horizontal axis the difference of each study’s observed ln(RR) from the comparison’s mean ln(RR) obtained from the pairwise fixed effect meta-analysis was plotted. In the absence of small-study effects, we expect the studies to form an inverted funnel centred at zero [ 33 ]. All the analyses involved in the generalised pairwise modelling (GPM) framework for multiple indirect and mixed effects were conducted using MetaXL v5.2 (EpiGear International, Sunrise Beach, Australia) [ 28 ]. Funnel and network plots were produced using Stata version 13 (Stata Corporation, College Station, TX, USA).

Quality assessment

The quality of the included studies was assessed using a modification of a quality checklist used in another study by one of the authors [ 34 ]. The studies were assessed on inclusion of safeguards relating to study design, selection, information, blinding of study assessors, and analytical biases. There were 12 questions with a possible maximum count of 17 safe-guards (Additional file 1 : Table S4).

Data extraction

The search strategy identified 7940 citations (Cochrane Central = 353, PubMed = 2698, Web of Science = 1534 and Embase = 3355). After deleting duplicate citations, a total of 4941 citations were retrieved for the initial screening. Of these, 4692 citations were excluded based on title only. Records of 249 citations were screened and 161 citations were excluded based on the title and abstract. Eighty eight articles were assessed for eligibility, of which 58 articles were excluded (Additional file 1 : Table S5). Thirty citations fulfilled eligibility criteria and were included in the meta-analysis (Fig. 1 ). Data from the included studies were extracted and summarized in a spreadsheet (Table 1 ).

Search flowchart. Note : details of excluded studies in Additional file 1 : Table S5

Characteristics of included studies

The literature search on malaria control and preventive measures led to the identification of the five treatment groups across the studies (ITN, UN, PD, IRS and NI). A total of 30 studies were included in the current meta-analysis. These studies were conducted from 1988 to 2015. Eighteen studies were conducted in Africa [ 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 ], 11 studies were from Asia [ 32 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 ] and one study from South America [ 63 ]. Ten studies did not restrict study participants to any age [ 36 , 41 , 51 , 55 , 57 , 58 , 60 , 61 , 62 , 63 ], four studies only included adults as study participants [ 40 , 53 , 56 , 59 ], and the rest of the studies (16) were conducted in children and adolescents (0–19 years) [ 32 , 35 , 37 , 38 , 39 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 52 , 54 ]. There were 21 studies that reported P. falciparum infection rates separately [ 32 , 35 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 45 , 46 , 47 , 48 , 50 , 51 , 52 , 54 , 55 , 58 , 60 , 62 ]. The latter two groups were used in a sensitivity analysis (see below). The most common study design was the RCT with 16 studies [ 37 , 38 , 39 , 40 , 42 , 43 , 46 , 47 , 48 , 50 , 51 , 53 , 54 , 56 , 59 , 62 ], eight studies were cluster RCT [ 32 , 36 , 44 , 49 , 52 , 57 , 58 , 60 ], and the rest (6) were quasi-experimental studies with a control group [ 35 , 41 , 45 , 55 , 61 , 63 ]. Twenty one studies had two arms [ 32 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 44 , 49 , 50 , 52 , 53 , 54 , 55 , 57 , 59 , 60 , 61 , 62 , 63 ], eight studies had three arms, [ 35 , 45 , 46 , 47 , 48 , 51 , 56 , 58 ] and one had four arms [ 43 ]. Of those with three arms we dropped the curtain arm in two studies [ 31 , 51 ] (not part of this review) and one of the PD arms in four other studies [ 43 , 46 , 48 , 56 ] that reported PD comparisons at different dosages or intervals. Microscopy was used for detection of Plasmodium parasites in 25 studies [ 32 , 35 , 37 , 38 , 39 , 40 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 ], three studies used both microscopy and RDTs [ 49 , 62 , 63 ], and one study each used RDT [ 41 ] and polymerase chain reaction (PCR) and microscopy [ 36 ] for diagnosis (Table 1 ).

Interventions utilized across studies

Twenty five studies had a NI arm [ 32 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 48 , 49 , 50 , 51 , 52 , 55 , 56 , 57 , 59 , 61 , 62 , 63 ], and seven studies had a UN arm [ 45 , 47 , 52 , 53 , 54 , 58 , 60 ]. Of the eleven studies that used a PD arms [ 37 , 38 , 40 , 42 , 43 , 46 , 47 , 48 , 50 , 56 , 59 ], the regimens were all different (Additional file 1 : Table S6). Fourteen studies reported the use of ITN in one arm [ 32 , 35 , 39 , 44 , 51 , 53 , 54 , 55 , 57 , 58 , 60 , 61 , 62 , 63 ]. In these studies, different types of nets and insecticides for treating such nets were used (Additional file 1 : Table S7). The insecticides used for IRS in the three studies of this intervention were also different and are listed in (Additional file 1 : Table S8) [ 36 , 41 , 49 ].

The quality of the studies including types of study, randomization and other characteristics was assessed through 17 safeguards against bias as outlined in the supplementary material. They were combined into a univariate overall quality score consisting of counts of safeguards ranging between 7 and 17 out of a maximum possible of 17. The ranges of the scores were 10–17, 7–14, 9–16, 10–16, and 8–11 in PD vs NI, ITN vs NI, IRS vs NI, ITN vs UN, and UN vs NI studies, respectively. The most common safeguards missing were consideration of confounders such as socio-economic status, owning LLINs, malaria prevalence and blinding of assessors in between 46.7–93.3% of studies (Additional file 1 : Table S9).

Quantitative synthesis

Seven direct estimates based on head-to-head comparison within 30 studies, which included 60 treatment groups, were available (Table 2 and Fig. 2 ). In these direct comparisons, PD (RR: 0.21, 95% confidence interval [CI] 0.13–0.33), ITN (RR: 0.57, 95% CI: 0.41–0.81), and UN (RR: 0.67, 95% CI: 0.49–0.92) were significantly better than NI. Similarly, UN (0.12, 95% CI: 0.01–0.94) was better as compared to PD, and IRS (RR: 0.55, 95% CI: 0.20–1.56) was not significantly different from NI.

Network plot showing the comparison groups. The circle size is proportional to the number of studies including that intervention while line width is proportional to the number of comparisons. Abbreviations : ITN, insecticide-treated nets; UN, untreated net; IRS, indoor residual spraying; NI, no intervention; PD, prophylactic drug

The indirect estimate for ITN (RR: 0.37, 95% CI: 0.24–0.58) was consistent with the direct estimate, while that for PD (RR: 5.70, 95% CI: 0.70–46.58) demonstrated an inconsistent and very uncertain effect as opposed to the direct estimate. UN had two indirect estimates possible and both were inconsistent with the direct effect but in opposite directions with either a grossly positive effect (RR: 0.02, 95% CI: 0.003–0.21) or a negative effect (RR: 1.03, 95% CI: 0.64–1.66) (Table 2 ).

The final estimates were based on all evidence for these interventions in comparison with NI and results showed that, PD (RR: 0.24, 95% CI: 0.004–15.43), ITN (RR: 0.49, 95% CI: 0.32–0.74), IRS (RR: 0.55, 95% CI: 0.20–1.56), and UN (RR: 0.73, 95% CI: 0.28–1.90) were all less likely to be associated with incident infection as compared to participants using no preventive measure (NI). However, only ITN demonstrated a statistically significant effect (Table 2 and Fig. 3 ).

Results of network meta-analysis of 30 studies comparing listed interventions against NI. Only the PD-NI mixed effects showed modest inconsistency and this is reflected in the marked uncertainty (wide 95% confidence intervals) of the effect estimate

There was overall minimal statistical network inconsistency ( \( \overline{H}=2.21\Big) \) over comparisons despite the inconsistent direct and indirect effects, because of the huge uncertainty associated with indirect effects possibly reflecting heterogeneity in terms of the geographical locations and population characteristics of studies. One final effect (PD-NI) demonstrated modest inconsistency ( H = 3.0) while the rest demonstrated minimal to no inconsistency (H < 3, see Table 2 ), again because of uncertainty around the individual mixed effects.

Sensitivity analysis and publication bias

Heterogeneity was evident when selection criteria were modified to include only children or only P. falciparum infections respectively (with \( \overline{H} \) at 2.35 and 2.29, respectively (Additional file 2 : Figure S1; Additional file 3 : Figure S2). However, the rank of effectiveness of different preventive measures remained unchanged in both analyses except that ITN was less effective than IRS in only P. falciparum and effects were now less precise because numbers of studies were lower.

The comparison-adjusted funnel plot demonstrated little evidence of asymmetry except for the PD-NI comparison, which was in keeping with the fact that there was both considerable heterogeneity and inconsistency across this comparison (Additional file 4 : Figure S3).

This meta-analysis showed that only ITNs had a significant effect in protection against malaria infection. While the effect size for PD was larger, the uncertainty was high, thus making the impact of this intervention uncertain. These findings confirm that impregnated insecticides on ITNs offers better protection than UNs in preventing mosquitoes from taking a blood meal from the host through its excito-repellency effect [ 23 , 64 , 65 , 66 , 67 , 68 , 69 , 70 ]. The insecticides on ITNs may also inhibit mosquitoes from entering a house similar to the effect of IRS. Mortality of mosquitoes in the range of 25–75% has been observed after they enter huts in search of blood meals irrespective of the various different pyrethroids used in ITNs [ 67 ]. Individual studies on efficacy of this intervention have shown that the risk of malaria infection due to ITN use can reduce by up to 39–62% and child mortality by 14–29% [ 24 , 71 ]. Interestingly, the impact of ITNs on child mortality and morbidity have been reported to extend out from areas with the actual ITN use to neighbouring areas because of the impact of the insecticidal nets on the entomological inoculation rate (EIR) of the local vector population [ 72 , 73 , 74 ]. Similarly, mathematical modelling has shown that ITNs can even protect against mosquitoes that feed outdoors [ 75 ]. ITNs have also been reported to protect women in pregnancy and in reducing placental malaria, anaemia, stillbirths and abortions [ 65 ]. Of note, the combination of IRS and ITN has been shown to offer better protection as compared to ITNs alone [ 27 , 41 , 76 , 77 , 78 , 79 ]. Only one of the latter studies was included in our synthesis which compared IRS vs NI where both arms were also given ITNs and the RR was 0.42 (95% CI: 0.34–0.52) suggesting that the effects are independent and additive on malaria prevention [ 41 ]. The other studies did not meet our inclusion criteria because these studies were cross-sectional and pre-post interventional studies but evidence from them was also supportive of this conclusion.

Despite reports of pyrethroid resistance in parts of the world including Africa [ 80 , 81 , 82 , 83 , 84 , 85 ], ITNs treated with pyrethroids continue to provide significant protection against malaria [ 69 , 71 , 86 , 87 ]. ITNs of the LLIN type have insecticides impregnated in the fibres of nets, which are wash resistant for the four- to five-year lifespan of the ITNs. ITBN types of ITNs require insecticides to be impregnated every six months. Due to reduced costs and ease of implementation, the LLINs have gained huge popularity in recent years and given their superiority to IRS in this analysis as well as in previous studies [ 27 , 88 ], this would represent a strong choice in terms of malaria prevention.

The biggest effect size was for PD. This intervention prevents or reduces the incidence of malaria primarily through clearing existing parasitaemia (or reducing it to a level below the fever threshold) and preventing new infections [ 8 , 89 , 90 ]. In our analysis however, we found the least precision for the effect estimate and the most inconsistency, suggesting that the effects varied widely across studies. Whilst the effectiveness of prophylactic drugs has been documented in children and pregnant women in sub-Saharan Africa, it has not been substantiated in other parts of the world [ 38 , 42 , 91 , 92 ], possibly because of the limited ability of drugs to prevent relapse in P. vivax infection [ 8 , 93 , 94 ]. Nevertheless, in our analysis restricted to P . falciparum, the same uncertainty was observed for PDs as in the full dataset. There are other concerns apart from preventive efficacy with the use of drugs as they can also result in impairment of natural immunity, and rebound infections of the children who received chemo-prophylaxis for 1–5 years [ 95 , 96 , 97 , 98 ]. The widespread use of chemoprophylaxis in children and pregnant women could possibly increase the rate of spread of drug resistance [ 99 ].

The preventive measure with the next highest effect estimate was IRS, a critical component of the WHO’s Global Malaria Eradication Program from 1955–1969 and the main intervention attributed to the elimination or dramatic reduction of malaria in parts of Europe, Asia and Latin America [ 27 ]. The basic principle of IRS in vector control is that IRS protects inhabitants against mosquito bites by killing the blood-fed females who rest on the walls after feeding and also protect inhabitants against mosquito bites by diverting the vector from entering a sprayed house an effect known as excito-repellency [ 100 , 101 ]. If the mosquito does enter the house, after biting, the female mosquito eventually rests on sprayed surfaces, where it picks up a lethal dose of insecticide, thus preventing transmission of the parasite to others. In a village with a high percentage coverage of houses with IRS, the mean age of the village mosquito population is expected to be reduced and very few mosquitoes will survive the approximately 12 days required for sporozoite maturation to be able to transmit the parasites [ 71 ]. Thus, IRS reduces malaria transmission at the community level by reducing mosquito longevity and abundance, but it has also been reported to provide household-level protection [ 27 ]. Studies have shown that IRS was more effective with high initial prevalence, multiple rounds of spraying and in regions with a combination of P. falciparum and P. vivax [ 26 ]. Despite all the advantages of IRS, our analysis suggested a consistently better (or at worst equivalent) efficacy for ITNs compared to IRS. Mosquito mortality has been shown to decline after the third month following IRS and by the fifth month, effectiveness reduces by 12% [ 102 ]. Efficacy might wane if walls are replastered or painted following implantation of IRS, and mosquito resistance to insecticides can emerge. In addition, there is a need for trained personnel for application of insecticides, which means IRS might not always be done effectively.

Untreated nets were the least effective in preventing malaria infection as compared to other preventive measures. UNs can offer a barrier against the bite of mosquitoes; however, mosquitoes can rest on the UNs while seeking opportunities to feed on the hosts sleeping under the nets, which can be presented when any part of a host’s body comes in contact with the nets. This happens often when hosts are in a deep sleep, especially under inadequately spaced or small nets. Untreated nets can even offer resting places to mosquitoes in an IRS-sprayed house and thus cannot be recommended given the other alternatives that exist. Finally, torn untreated nets have been shown to offer no additional protection as compared to not using nets [ 45 , 103 ].

A key strength of this analysis is the use of the GPM framework which avoids approximations and assumptions that are not stated explicitly or verified when the method is applied. On the contrary, the multivariate frequentist framework assumes that if there is no common comparator in the network, this then has to be handled by augmenting the dataset with fictional arms with high variance. This is not very objective and requires a decision as to what constitutes a sufficiently high variance [ 104 ]. Another alternative, the Bayesian framework, also has its problems such as requiring prior distributions to be specified for a number of unknown parameters and choices regarding over-dispersed starting values for a number of independent chains so that convergence can be assessed. While we have several choices for the meta-analytic framework, this choice may be less important than other choices regarding the modelling of effects [ 105 ]. Indeed, we were able to use the inverse variance heterogeneity model for direct estimates which has correct error estimation when compared with the random effects model [ 31 ]. Results from a random effects model (using both the multivariate meta-analysis framework as well as the GPM framework) differ slightly from our main results, especially regarding PD, which has spuriously precise estimates using this approach (Additional file 1 : Tables S2, S3).

There are limitations of this study worth noting. Even though clinical and statistical significance was found for ITNs, in reality the effectiveness of interventions (ITN) are dependent on a number of extrinsic factors such as population behaviour and vector aetiology. Studies have shown that ITN use is influenced by social behaviour including education, level of knowledge on malaria, and ease of use [ 106 , 107 ]. In addition, other socio-economic factors such as working and staying overnight in the forest decreases protection despite high proportion of coverage by ITNs [ 108 , 109 , 110 ]. Secondly, different insecticides being used for IRS and ITN over the study period would have impacted the findings of this study and the development of insecticide resistance would undermine the effectiveness of ITNs in preventing malaria. Thirdly, the methods of diagnosis of incident malaria were different in the studies. Since most of these studies were conducted in intense malaria transmission areas, this effect is however likely to be minimal. Fourthly, the vectors were different depending on the region of the study; for instance, the commonest malaria vectors in the Asian region including Anopheles dirus , An. baimaii and An. minimus [ 111 , 112 ], are able to avoid indoor sprayed surfaces because of their exophilic and exophagic characteristics [ 113 , 114 , 115 ] rendering most domicile-based interventions, like ITNs and IRS less effective [ 114 , 116 ]. Of the three main vectors in the African region: An. arabiensis , An. funestus and An. gambiae [ 113 , 117 ], only An. arabiensis shows feeding preferences for both indoors and outdoors while the other two are indoor-feeders [ 117 ]. Other challenges include insecticide resistance [ 118 ]. Finally, the drug types and regimens varied between studies. All of these limitations have the potential to increase heterogeneity between the included studies and make it more difficult to estimate the effects of the different interventions more precisely than what we have reported.

Conclusions

Even though ITNs were found to be the only preventive measure with statistical support for its effectiveness in this study, the role of all malaria control measures are important in the global drive to eliminate malaria. However, when a choice needs to be made for resource allocation, the results reported here tend to favour the use of ITNs.

Abbreviations

Amodiaquine

Confidence interval

Design effect

Dihydroartemisinin-peperaquine

Entomological inoculation rate

Generalized pairwise modelling

Global Technical Strategy for Malaria 2016–2030

Higher confidence interval

Indoor residual spraying

Insecticide-treated curtain

Insecticide-treated net

Inverse variance heterogeneity

Lower confidence interval

Long-lasting insecticidal nets

Malaria infection

No intervention

Prophylactic drugs

Randomized controlled trials

Rapid diagnostic tests

Sulphadoxine-pyrimethamine

Surface under the cumulative ranking curve

Untreated nets

World Health Organization

WHO. World Malaria Report, vol. 2017. Switzerland: World Health Organization, Geneva; 2017.

Google Scholar  

WHO. World Malaria Report, vol. 2015. Switzerland: World Health Organization, Geneva; 2015.

Cotter C, Sturrock HJ, Hsiang MS, Liu J, Phillips AA, Hwang J, et al. The changing epidemiology of malaria elimination: new strategies for new challenges. Lancet. 2013;382(9895):900–11.

Article   PubMed   Google Scholar  

Murray CJ, Rosenfeld LC, Lim SS, Andrews KG, Foreman KJ, Haring D, et al. Global malaria mortality between 1980 and 2010: a systematic analysis. Lancet. 2012;379(9814):413–31.

WHO. Global Technical Strategy for Malaria 2016–2030. World Health Organization, Geneva. Switzerland: WHO Library Cataloguing-in-Publication Data; 2015.

WHO. WHO recommendations for achieving universal coverage with long-lasting insecticidal nets in malaria control. World Health Organization. Switzerland: Geneva; 2014.

Greenwood B. Anti-malarial drugs and the prevention of malaria in the population of malaria endemic areas. Malar J. 2010;9(Suppl. 3):S2.

White NJ. Intermittent presumptive treatment for malaria. PLoS Med. 2005;2(1):e3.

Article   PubMed   PubMed Central   CAS   Google Scholar  

Ronn AM, Msangeni HA, Mhina J, Wernsdorfer WH, Bygbjerg IC. High level of resistance of Plasmodium falciparum to sulfadoxine-pyrimethamine in children in Tanzania. Trans R Soc Trop Med Hyg. 1996;90(2):179–81.

Article   CAS   PubMed   Google Scholar  

Mugittu K, Abdulla S, Falk N, Masanja H, Felger I, Mshinda H, et al. Efficacy of sulfadoxine-pyrimethamine in Tanzania after two years as first-line drug for uncomplicated malaria: assessment protocol and implication for treatment policy strategies. Malar J. 2005;4:55.

Roper C, Pearce R, Nair S, Sharp B, Nosten F, Anderson T. Intercontinental spread of pyrimethamine-resistant malaria. Science. 2004;305(5687):1124.

Gosling RD, Gesase S, Mosha JF, Carneiro I, Hashim R, Lemnge M, et al. Protective efficacy and safety of three antimalarial regimens for intermittent preventive treatment for malaria in infants: a randomised, double-blind, placebo-controlled trial. Lancet. 2009;374(9700):1521–32.

Tan KR, Katalenich BL, Mace KE, Nambozi M, Taylor SM, Meshnick SR, et al. Efficacy of sulphadoxine-pyrimethamine for intermittent preventive treatment of malaria in pregnancy, Mansa, Zambia. Malar J. 2014;13:227.

Clerk CA, Bruce J, Affipunguh PK, Mensah N, Hodgson A, Greenwood B, Chandramohan D. A randomized, controlled trial of intermittent preventive treatment with sulfadoxine-pyrimethamine, amodiaquine, or the combination in pregnant women in Ghana. J Infect Dis. 2008;198(8):1202–11.

Taylor WR, White NJ. Antimalarial drug toxicity: a review. Drug Saf. 2004;27(1):25–61.

Steketee RW, Wirima JJ, Hightower AW, Slutsker L, Heymann DL, Breman JG. The effect of malaria and malaria prevention in pregnancy on offspring birthweight, prematurity, and intrauterine growth retardation in rural Malawi. Am J Trop Med Hyg. 1996;55(Suppl. 1):33–41.

Briand V, Bottero J, Noel H, Masse V, Cordel H, Guerra J, et al. Intermittent treatment for the prevention of malaria during pregnancy in Benin: a randomized, open-label equivalence trial comparing sulfadoxine-pyrimethamine with mefloquine. J Infect Dis. 2009;200(6):991–1001.

Eisele TP, Larsen D, Steketee RW. Protective efficacy of interventions for preventing malaria mortality in children in Plasmodium falciparum endemic areas. Int J Epidemiol. 2010;39(Suppl. 1):i88–101.

Article   PubMed   PubMed Central   Google Scholar  

Wilson AL. A systematic review and meta-analysis of the efficacy and safety of intermittent preventive treatment of malaria in children (IPTc). PLoS One. 2011;6(2):e16976.

Article   CAS   PubMed   PubMed Central   Google Scholar  

Meremikwu MM, Donegan S, Sinclair D, Esu E, Oringanje C. Intermittent preventive treatment for malaria in children living in areas with seasonal transmission. Cochrane Database Syst Rev. 2012;2:Cd003756.

Meremikwu MM, Donegan S, Esu E. Chemoprophylaxis and intermittent treatment for preventing malaria in children. Cochrane Database Syst Rev. 2008;2:Cd003756.

Matangila JR, Mitashi P, Inocencio da Luz RA, Lutumba PT, Van Geertruyden JP. Efficacy and safety of intermittent preventive treatment for malaria in schoolchildren: a systematic review. Malar J. 2015;14:450.

Choi HW, Breman JG, Teutsch SM, Liu S, Hightower AW, Sexton JD. The effectiveness of insecticide-impregnated bed nets in reducing cases of malaria infection: a meta-analysis of published results. Am J Trop Med Hyg. 1995;52(5):377–82.

Lengeler C. Insecticide-treated bed nets and curtains for preventing malaria. Cochrane Database Syst Rev. 2004;2:Cd000363.

Van Remoortel H, De Buck E, Singhal M, Vandekerckhove P, Agarwal SP. Effectiveness of insecticide-treated and untreated nets to prevent malaria in India. Trop Med Int Health. 2015;20(8):972–82.

Kim D, Fedak K, Kramer R. Reduction of malaria prevalence by indoor residual spraying: A meta-regression analysis. Am J Trop Med Hyg. 2012;87(1):117–24.

Pluess B, Tanser FC, Lengeler C, Sharp BL. Indoor residual spraying for preventing malaria. Cochrane Database Syst Rev. 2010;4:Cd006657.

Doi SA, Barendregt JJ. A generalized pairwise modelling framework for network meta-analysis. Int J Evid Based Healthc. 2018;27 [Epub ahead of print]

Bucher HC, Guyatt GH, Griffith LE, Walter SD. The results of direct and indirect treatment comparisons in meta-analysis of randomized controlled trials. J Clin Epidemiol. 1997;50(6):683–91.

Rucker G, Schwarzer G. Ranking treatments in frequentist network meta-analysis works without resampling methods. BMC Med Res Methodol. 2015;15:58.

Doi SA, Barendregt JJ, Khan S, Thalib L, Williams GM. Advances in the meta-analysis of heterogeneous clinical trials I: The inverse variance heterogeneity model. Contemp Clin Trials. 2015;45(Pt A):130–8.

Smithuis FM, Kyaw MK, Phe UO, van der Broek I, Katterman N, Rogers C, et al. The effect of insecticide-treated bed nets on the incidence and prevalence of malaria in children in an area of unstable seasonal transmission in western Myanmar. Malar J. 2013;12:363.

Chaimani A, Salanti G. Using network meta-analysis to evaluate the existence of small-study effects in a network of interventions. Res Synth Methods. 2012;3(2):161–76.

Liu X, Clark J, Siskind D, Williams GM, Byrne G, Yang JL. SA. A systematic review and meta-analysis of the effects of Qigong and Tai Chi for depressive symptoms. Complement Ther Med. 2015;23(4):516–34.

Beach RF, Ruebush TK 2nd, Sexton JD, Bright PL, Hightower AW, Breman JG, et al. Effectiveness of permethrin-impregnated bed nets and curtains for malaria control in a holoendemic area of western Kenya. Am J Trop Med Hyg. 1993;49(3):290–300.

Charlwood JD, Qassim M, Elnsur EI, Donnelly M, Petrarca V, Billingsley PF, et al. The impact of indoor residual spraying with malathion on malaria in refugee camps in eastern Sudan. Acta Trop. 2001;80(1):1–8.

Cisse B, Sokhna C, Boulanger D, Milet J, Ba el H, Richardson K, et al. Seasonal intermittent preventive treatment with artesunate and sulfadoxine-pyrimethamine for prevention of malaria in Senegalese children: a randomised, placebo-controlled, double-blind trial. Lancet. 2006;367(9511):659–67.

Dicko A, Diallo AI, Tembine I, Dicko Y, Dara N, Sidibe Y, et al. Intermittent preventive treatment of malaria provides substantial protection against malaria in children already protected by an insecticide-treated bednet in Mali: a randomised, double-blind, placebo-controlled trial. PLoS Med. 2011;8(2):e1000407.

Fraser-Hurt N, Felger I, Edoh D, Steiger S, Mashaka M, Masanja H, et al. Effect of insecticide-treated bed nets on haemoglobin values, prevalence and multiplicity of infection with Plasmodium falciparum in a randomized controlled trial in Tanzania. Trans R Soc Trop Med Hyg. 1999;93(Suppl. 1):47–51.

Hale BR, Owusu-Agyei S, Fryauff DJ, Koram KA, Adjuik M, Oduro AR, et al. A randomized, double-blind, placebo-controlled, dose-ranging trial of tafenoquine for weekly prophylaxis against Plasmodium falciparum . Clin Infect Dis. 2003;36(5):541–9.

Hamel MJ, Otieno P, Bayoh N, Kariuki S, Were V, Marwanga D, et al. The combination of indoor residual spraying and insecticide-treated nets provides added protection against malaria compared with insecticide-treated nets alone. Am J Trop Med Hyg. 2011;85(6):1080–6.

Konate AT, Yaro JB, Ouedraogo AZ, Diarra A, Gansane A, Soulama I, et al. Intermittent preventive treatment of malaria provides substantial protection against malaria in children already protected by an insecticide-treated bednet in Burkina Faso: a randomised, double-blind, placebo-controlled trial. PLoS Med. 2011;8(2):e1000408.

Kweku M, Liu D, Adjuik M, Binka F, Seidu M, Greenwood B, Chandramohan D. Seasonal intermittent preventive treatment for the prevention of anaemia and malaria in Ghanaian children: a randomized, placebo controlled trial. PLoS One. 2008;3(12):e4000.

Marbiah NT, Petersen E, David K, Magbity E, Lines J, Bradley DJ. A controlled trial of lambda-cyhalothrin-impregnated bed nets and/or dapsone/pyrimethamine for malaria control in Sierra Leone. Am J Trop Med Hyg. 1998;58(1):1–6.

Mwangi TW, Ross A, Marsh K, Snow RW. The effects of untreated bednets on malaria infection and morbidity on the Kenyan coast. Trans R Soc Trop Med Hyg. 2003;97(4):369–72.

Nankabirwa JI, Wandera B, Amuge P, Kiwanuka N, Dorsey G, Rosenthal PJ, et al. Impact of intermittent preventive treatment with dihydroartemisinin-piperaquine on malaria in Ugandan schoolchildren: a randomized, placebo-controlled trial. Clin Infect Dis. 2014;58(10):1404–12.

Nevill CG, Watkins WM, Carter JY, Munafu CG. Comparison of mosquito nets, proguanil hydrochloride, and placebo to prevent malaria. BMJ. 1988;297(6645):401–3.

Odhiambo FO, Hamel MJ, Williamson J, Lindblade K, ter Kuile FO, Peterson E, et al. Intermittent preventive treatment in infants for the prevention of malaria in rural western Kenya: a randomized, double-blind placebo-controlled trial. PLoS One. 2010;5(4):e10016.

Pinder M, Jawara M, Jarju LB, Salami K, Jeffries D, Adiamoh M, et al. Efficacy of indoor residual spraying with dichlorodiphenyltrichloroethane against malaria in Gambian communities with high usage of long-lasting insecticidal mosquito nets: a cluster-randomised controlled trial. Lancet. 2015;385(9976):1436–46.

Sesay S, Milligan P, Touray E, Sowe M, Webb EL, Greenwood BM, Bojang KA. A trial of intermittent preventive treatment and home-based management of malaria in a rural area of The Gambia. Malar J. 2011;10:2.

Sexton JD, Ruebush TK 2nd, Brandling-Bennett AD, Breman JG, Roberts JM, Odera JS, Were JB. Permethrin-impregnated curtains and bed-nets prevent malaria in western Kenya. Am J Trop Med Hyg. 1990;43(1):11–8.

Snow RW, Rowan KM, Lindsay SW, Greenwood BM. A trial of bed nets (mosquito nets) as a malaria control strategy in a rural area of The Gambia, West Africa. Trans R Soc Trop Med Hyg. 1988;82(2):212–5.

Kamol-Ratanakul P, Prasittisuk C. The effectiveness of permethrin-impregnated bed nets against malaria for migrant workers in eastern Thailand. Am J Trop Med Hyg. 1992;47(3):305–9.

Luxemburger C, Perea WA, Delmas G, Pruja C, Pecoul B, Moren A. Permethrin-impregnated bed nets for the prevention of malaria in schoolchildren on the Thai-Burmese border. Trans R Soc Trop Med Hyg. 1994;88(2):155–9.

Rowland M, Bouma M, Ducornez D, Durrani N, Rozendaal J, Schapira A, Sondorp E. Pyrethroid-impregnated bed nets for personal protection against malaria for Afghan refugees. Trans R Soc Trop Med Hyg. 1996;90(4):357–61.

Taylor WR, Richie TL, Fryauff DJ, Picarima H, Ohrt C, Tang D, et al. Malaria prophylaxis using azithromycin: a double-blind, placebo-controlled trial in Irian Jaya, Indonesia. Clin Infect Dis. 1999;28(1):74–81.

Sahu SS, Jambulingam P, Vijayakumar T, Subramanian S, Kalyanasundaram M. Impact of alphacypermethrin treated bed nets on malaria in villages of Malkangiri District, Orissa, India. Acta Trop. 2003;89(1):55–66.

Sharma SK, Tyagi PK, Upadhyay AK, Haque MA, Mohanty SS, Raghavendra K, Dash AP. Efficacy of permethrin treated long-lasting insecticidal nets on malaria transmission and observations on the perceived side effects, collateral benefits and human safety in a hyperendemic tribal area of Orissa, India. Acta Trop. 2009;112(2):181–7.

Lwin KM, Phyo AP, Tarning J, Hanpithakpong W, Ashley EA, Lee SJ, et al. Randomized, double-blind, placebo-controlled trial of monthly versus bimonthly dihydroartemisinin-piperaquine chemoprevention in adults at high risk of malaria. Antimicrob Agents Chemother. 2012;56(3):1571–7.

Soleimani-Ahmadi M, Vatandoost H, Shaeghi M, Raeisi A, Abedi F, Eshraghian MR, et al. Field evaluation of permethrin long-lasting insecticide treated nets (Olyset(R)) for malaria control in an endemic area, southeast of Iran. Acta Trop. 2012;123(3):146–53.

Shah NK, Tyagi P, Sharma SK. The impact of artemisinin combination therapy and long-lasting insecticidal nets on forest malaria incidence in tribal villages of India, 2006–2011. PLoS One. 2013;8(2):e56740.

Hill N, Zhou HN, Wang P, Guo X, Carneiro I, Moore SJ. A household randomized, controlled trial of the efficacy of 0.03% transfluthrin coils alone and in combination with long-lasting insecticidal nets on the incidence of Plasmodium falciparum and Plasmodium vivax malaria in Western Yunnan Province, China. Malar J. 2014;13:208.

Kroeger A, Mancheno M, Alarcon J, Pesse K. Insecticide-impregnated bed nets for malaria control: varying experiences from Ecuador, Colombia, and Peru concerning acceptability and effectiveness. Am J Trop Med Hyg. 1995;53(4):313–23.

Maxwell CA, Rwegoshora RT, Magesa SM, Curtis CF. Comparison of coverage with insecticide-treated nets in a Tanzanian town and villages where nets and insecticide are either marketed or provided free of charge. Malar J. 2006;5:44.

Gamble C, Ekwaru JP, ter Kuile FO. Insecticide-treated nets for preventing malaria in pregnancy. Cochrane Database Syst Rev. 2006;2:Cd003755.

Sutanto I, Freisleben HJ, Pribadi W, Atmosoedjono S, Bandi A. Purnomo. Efficacy of permethrin-impregnated bed nets on malaria control in a hyperendemic area in Irian Java, Indonesia: influence of seasonal rainfall fluctuations. Southeast Asian J Trop Med Pub Hlth. 1999;30(3):432–9.

CAS   Google Scholar  

Maxwell CA, Myamba J, Njunwa KJ, Greenwood BM, Curtis CF. Comparison of bednets impregnated with different pyrethroids for their impact on mosquitoes and on re-infection with malaria after clearance of pre-existing infections with chlorproguanil-dapsone. Trans R Soc Trop Med Hyg. 1999;93(1):4–11.

Sharma SK, Upadhyay AK, Haque MA, Tyagi PK, Mohanty SS, Raghavendra K, Dash AP. Field evaluation of Olyset nets: a long-lasting insecticidal net against malaria vectors Anopheles culicifacies and Anopheles fluviatilis in a hyperendemic tribal area of Orissa, India. J Med Entomol. 2009;46(2):342–50.

Curtis CF, Jana-Kara B, Maxwell CA. Insecticide-treated nets: impact on vector populations and relevance of initial intensity of transmission and pyrethroid resistance. J Vector Borne Dis. 2003;40(1–2):1–8.

Wangdi K, Gatton ML, Kelly GC, Clements AC. Prevalence of asymptomatic malaria and bed net ownership and use in Bhutan, 2013: a country earmarked for malaria elimination. Malar J. 2014;13:352.

Curtis CF, Maxwell CA, Magesa SM, Rwegoshora RT, Wilkes TJ. Insecticide-treated bed-nets for malaria mosquito control. J Am Mosq Control Assoc. 2006;22(3):501–6.

Gimnig JE, Vulule JM, Lo TQ, Kamau L, Kolczak MS, Phillips-Howard PA, et al. Impact of permethrin-treated bed nets on entomologic indices in an area of intense year-round malaria transmission. Am J Trop Med Hyg. 2003;68(Suppl. 4):16–22.

PubMed   Google Scholar  

Hawley WA, Phillips-Howard PA, ter Kuile FO, Terlouw DJ, Vulule JM, Ombok M, et al. Community-wide effects of permethrin-treated bed nets on child mortality and malaria morbidity in western Kenya. Am J Trop Med Hyg. 2003;68(Suppl. 4):121–7.

Larsen DA, Hutchinson P, Bennett A, Yukich J, Anglewicz P, Keating J, Eisele TP. Community coverage with insecticide-treated mosquito nets and observed associations with all-cause child mortality and malaria parasite infections. Am J Trop Med Hyg. 2014;91(5):950–8.

Govella NJ, Okumu FO, Killeen GF. Insecticide-treated nets can reduce malaria transmission by mosquitoes which feed outdoors. Am J Trop Med Hyg. 2010;82(3):415–9.

West PA, Protopopoff N, Wright A, Kivaju Z, Tigererwa R, Mosha FW, et al. Indoor residual spraying in combination with insecticide-treated nets compared to insecticide-treated nets alone for protection against malaria: a cluster randomised trial in Tanzania. PLoS Med. 2014;11(4):e1001630.

West PA, Protopopoff N, Wright A, Kivaju Z, Tigererwa R, Mosha FW, et al. Enhanced protection against malaria by indoor residual spraying in addition to insecticide treated nets: is it dependent on transmission intensity or net usage? PLoS One. 2015;10(3):e0115661.

Fullman N, Burstein R, Lim SS, Medlin C, Gakidou E. Nets, spray or both? The effectiveness of insecticide-treated nets and indoor residual spraying in reducing malaria morbidity and child mortality in sub-Saharan Africa. Malar J. 2013;12:62.

Kleinschmidt I, Schwabe C, Shiva M, Segura JL, Sima V, Mabunda SJ, Coleman M. Combining indoor residual spraying and insecticide-treated net interventions. Am J Trop Med Hyg. 2009;81(3):519–24.

PubMed   PubMed Central   Google Scholar  

Glunt KD, Abilio AP, Bassat Q, Bulo H, Gilbert AE, Huijben S, et al. Long-lasting insecticidal nets no longer effectively kill the highly resistant Anopheles funestus of southern Mozambique. Malar J. 2015;14:298.

Chandre F, Manguin S, Brengues C, Dossou Yovo J, Darriet F, Diabate A, et al. Current distribution of a pyrethroid resistance gene ( kdr ) in Anopheles gambiae complex from west Africa and further evidence for reproductive isolation of the Mopti form. Parassitologia. 1999;41(1–3):319–22.

CAS   PubMed   Google Scholar  

Etang J, Fondjo E, Chandre F, Morlais I, Brengues C, Nwane P, et al. First report of knockdown mutations in the malaria vector Anopheles gambiae from Cameroon. Am J Trop Med Hyg. 2006;74(5):795–7.

Stump AD, Atieli FK, Vulule JM, Besansky NJ. Dynamics of the pyrethroid knockdown resistance allele in western Kenyan populations of Anopheles gambiae in response to insecticide-treated bed net trials. Am J Trop Med Hyg. 2004;70(6):591–6.

Hargreaves K, Koekemoer LL, Brooke BD, Hunt RH, Mthembu J, Coetzee M. Anopheles funestus resistant to pyrethroid insecticides in South Africa. Med Vet Entomol. 2000;14(2):181–9.

Hargreaves K, Hunt RH, Brooke BD, Mthembu J, Weeto MM, Awolola TS, Coetzee M. Anopheles arabiensis and An. quadriannulatus resistance to DDT in South Africa. Med Vet Entomol. 2003;17(4):417–22.

Wangdi K, Banwell C, Gatton ML, Kelly GC, Namgay R, Clements AC. Malaria burden and costs of intensified control in Bhutan, 2006–14: an observational study and situation analysis. Lancet Glob Health. 2016;4(5):e336–43.

Wamae PM, Githeko AK, Otieno GO, Kabiru EW, Duombia SO. Early biting of the Anopheles gambiae s.s . and its challenges to vector control using insecticide treated nets in western Kenya highlands. Acta Trop. 2015;150:136–42.

Hii JLK, Kanai L, Foligela A, Kan SKP, Burkot TR, Wirtz RA. Impact of permethrin-impregnated mosquito nets compared with DDT house-spraying against malaria transmission by Anopheles farauti and An. punctulatus in the Solomon Islands. Med Vet Entomol. 1993;7(4):333–8.

Cairns M, Carneiro I, Milligan P, Owusu-Agyei S, Awine T, Gosling R, et al. Duration of protection against malaria and anaemia provided by intermittent preventive treatment in infants in Navrongo, Ghana. PLoS One. 2008;3(5):e2227.

Menendez C, Schellenberg D, Macete E, Aide P, Kahigwa E, Sanz S, et al. Varying efficacy of intermittent preventive treatment for malaria in infants in two similar trials: public health implications. Malar J. 2007;6:132.

Mace KE, Chalwe V, Katalenich BL, Nambozi M, Mubikayi L, Mulele CK, et al. Evaluation of sulphadoxine-pyrimethamine for intermittent preventive treatment of malaria in pregnancy: a retrospective birth outcomes study in Mansa, Zambia. Malar J. 2015;14(1):576.

Article   CAS   Google Scholar  

Dicko A, Sagara I, Sissoko MS, Guindo O, Diallo AI, Kone M, et al. Impact of intermittent preventive treatment with sulphadoxine-pyrimethamine targeting the transmission season on the incidence of clinical malaria in children in Mali. Malar J. 2008;7:123.

Ranque S, Badiaga S, Delmont J, Brouqui P. Triangular test applied to the clinical trial of azithromycin against relapses in Plasmodium vivax infections. Malar J. 2002;1:13.

Pukrittayakamee S, Chantra A, Simpson JA, Vanijanonta S, Clemens R, Looareesuwan S, White NJ. Therapeutic responses to different antimalarial drugs in vivax malaria. Antimicrob Agents Chemother. 2000;44(6):1680–5.

Greenwood BM, David PH, Otoo-Forbes LN, Allen SJ, Alonso PL, Armstrong Schellenberg JR, et al. Mortality and morbidity from malaria after stopping malaria chemoprophylaxis. Trans R Soc Trop Med Hyg. 1995;89(6):629–33.

Menendez C, Kahigwa E, Hirt R, Vounatsou P, Aponte JJ, Font F, et al. Randomised placebo-controlled trial of iron supplementation and malaria chemoprophylaxis for prevention of severe anaemia and malaria in Tanzanian infants. Lancet. 1997;350(9081):844–50.

Mockenhaupt FP, Reither K, Zanger P, Roepcke F, Danquah I, Saad E, et al. Intermittent preventive treatment in infants as a means of malaria control: a randomized, double-blind, placebo-controlled trial in northern Ghana. Antimicrob Agents Chemother. 2007;51(9):3273–81.

Chandramohan D, Owusu-Agyei S, Carneiro I, Awine T, Amponsa-Achiano K, Mensah N, et al. Cluster randomised trial of intermittent preventive treatment for malaria in infants in area of high, seasonal transmission in Ghana. BMJ. 2005;331(7519):727–33.

Greenwood B. The use of anti-malarial drugs to prevent malaria in the population of malaria-endemic areas. Am J Trop Med Hyg. 2004;70(1):1–7.

Hamusse SD, Balcha TT, Belachew T. The impact of indoor residual spraying on malaria incidence in East Shoa Zone, Ethiopia. Glob Health Action. 2012;5:11619.

Indoor residual spraying WHO. Use of indoor residual spraying for scaling up global malaria control and elimination. Geneva: World Health Organization; 2006.

Bradley J, Matias A, Schwabe C, Vargas D, Monti F, Nseng G, Kleinschmidt I. Increased risks of malaria due to limited residual life of insecticide and outdoor biting versus protection by combined use of nets and indoor residual spraying on Bioko Island, Equatorial Guinea. Malar J. 2012;11:242.

Lines JD, Myamba J, Curtis CF. Experimental hut trials of permethrin-impregnated mosquito nets and eave curtains against malaria vectors in Tanzania. Med Vet Entomol. 1987;1(1):37–51.

van Valkenhoef G, Lu G, de Brock B, Hillege H, Ades AE, Welton NJ. Automating network meta-analysis. Res Synth Methods. 2012;3(4):285–99.

Senn S, Gavini F, Magrez D, Scheen A. Issues in performing a network meta-analysis. Stat Methods Med Res. 2013;22(2):169–89.

Samadoulougou S, Pearcy M, Ye Y, Kirakoya-Samadoulougou F. Progress in coverage of bed net ownership and use in Burkina Faso 2003–2014: evidence from population-based surveys. Malar J. 2017;16(1):302.

Russell CL, Sallau A, Emukah E, Graves PM, Noland GS, Ngondi JM, et al. Determinants of bed net use in southeast Nigeria following mass distribution of LLINs: implications for social behavior change interventions. PLoS One. 2015;10(10):e0139447.

Van Bortel W, Trung HD, Hoi le X, Van Ham N, Van Chut N, Luu ND, et al. Malaria transmission and vector behaviour in a forested malaria focus in central Vietnam and the implications for vector control. Malar J. 2010;9:373.

Singh N, Singh OP, Sharma VP. Dynamics of malaria transmission in forested and deforested regions of Mandla District, central India (Madhya Pradesh). J Am Mosq Control Assoc. 1996;12(2 Pt 1):225–34.

Grietens KP, Xuan XN, Ribera J, Duc TN, Bortel W, Ba NT, et al. Social determinants of long-lasting insecticidal hammock use among the Ra-glai ethnic minority in Vietnam: implications for forest malaria control. PLoS One. 2012;7(1):e29991.

Dev V, Manguin S. Biology, distribution and control of Anopheles ( Cellia ) minimus in the context of malaria transmission in northeastern India. Parasit Vectors. 2016;9:585.

Zhang S, Guo S, Feng X, Afelt A, Frutos R, Zhou S, Manguin S. Anopheles vectors in mainland China while approaching malaria elimination. Trends Parasitol. 2017;33(11):889–900.

Sinka ME, Bangs MJ, Manguin S, Rubio-Palis Y, Chareonviriyaphap T, Coetzee M, et al. A global map of dominant malaria vectors. Parasit Vectors. 2012;5:69.

Trung HD, Bortel WV, Sochantha T, Keokenchanh K, Briet OJ, Coosemans M. Behavioural heterogeneity of Anopheles species in ecologically different localities in Southeast Asia: a challenge for vector control. Trop Med Int Health. 2005;10(3):251–62.

Manh CD, Beebe NW, Van VN, Quang TL, Lein CT, Nguyen DV, et al. Vectors and malaria transmission in deforested, rural communities in north-central Vietnam. Malar J. 2010;9:259.

Somboon P, Lines J, Aramrattana A, Chitprarop U, Prajakwong S, Khamboonruang C. Entomological evaluation of community-wide use of lambdacyhalothrin-impregnated bed nets against malaria in a border area of north-west Thailand. Trans R Soc Trop Med Hyg. 1995;89(3):248–54.

Sinka ME, Bangs MJ, Manguin S, Coetzee M, Mbogo CM, Hemingway J, et al. The dominant Anopheles vectors of human malaria in Africa, Europe and the Middle East: occurrence data, distribution maps and bionomic précis. Parasit Vectors. 2010;3:117.

Dhiman S, Goswami D, Rabha B, Gopalakrishnan R, Baruah I, Singh L. Malaria epidemiology along Indo-Bangladesh border in Tripura State, India. Southeast Asian J Trop Med Public Health. 2010;41(6):1279–89.

Download references

Acknowledgements

The authors pay tribute to the late Jan Barendregt of Epigear International Pty Ltd, who passed away during preparation of this work.

LFK is funded by an Endeavour Postgraduate Scholarship (#3781_2014), an Australian National University Higher Degree Scholarship, and a Fondo para la Innovación, Ciencia y Tecnología Scholarship (#095-FINCyT-BDE-2014).

Availability of data and materials

The datasets for the current study are available from the corresponding author upon request.

Author information

Authors and affiliations.

Research School of Population Health, College of Health and Medicine, The Australian National University, ACT, Canberra, Australia

Kinley Wangdi, Luis Furuya-Kanamori, Cathy Banwell, Gerard C. Kelly, Suhail A. R. Doi & Archie C. A. Clements

Department of Population Medicine, College of Medicine, Qatar University, Doha, Qatar

Luis Furuya-Kanamori & Suhail A. R. Doi

Centre for Research in Evidence-Based Practice (CREBP), Faculty of Health Sciences and Medicine, Bond University, Gold Coast, Queensland, Australia

Justin Clark

School of Public Health, The University of Queensland, Brisbane, Queensland, Australia

• Jan J. Barendregt

Epigear International Pty Ltd, Sunrise Beach, Queensland, Australia

School of Public Health & Social Work, Queensland University of Technology, Brisbane, Queensland, Australia

Michelle L. Gatton

Author notes

Jan j barendregt deceased 3rd june 2017.

You can also search for this author in PubMed   Google Scholar

Contributions

KW, LFK, SARD and ACAC conceived the idea. JC developed citation search and executed it. KW and LFK carried out the data extraction. KW, LFK, SARD and JB carried out data analysis. KW drafted the manuscript. SARD and ACAC helped in the interpretation of the findings and critical revision of manuscript. LFK, JC, JB, MLG, CB and GK were involved in revision of the manuscript. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Kinley Wangdi .

Ethics declarations

Ethics approval and consent to participate.

Not applicable.

Consent for publication

Competing interests.

Authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Additional files

Additional file 1:.

Table S1. Search Strategy. Table S2. Meta-analysis of different control measures against NI using the random effects model under the generalized pairwise modeling (GPM) framework in MetaXL. Table S3. Meta-analysis of different control measures against NI using the random effects model under the frequentist multivariate meta-analysis framework (mvmeta) in Stata. Table S4. Quality scale. Table S5. Summary of the excluded studies. Table S6. Drugs used in the included studies. Table S7. Description of ITN’s used across the studies. Table S8. Description of IRS treatments used across the included studies. Table S9. Quality assessment scores of included studies. (DOCX 56 kb)

Additional file 2:

Figure S1. Results of network meta-analysis of 21 studies with children as a study population. (TIFF 624 kb)

Additional file 3:

Figure S2. Results of network meta-analysis of 28 studies with incidence of Plasmodium falciparum . (TIFF 631 kb)

Additional file 4:

Figure S3. Funnel plot depicting asymmetry for the PD-NI comparison. (TIFF 1482 kb)

Rights and permissions

Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/ ), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/ ) applies to the data made available in this article, unless otherwise stated.

Reprints and permissions

About this article

Cite this article.

Wangdi, K., Furuya-Kanamori, L., Clark, J. et al. Comparative effectiveness of malaria prevention measures: a systematic review and network meta-analysis. Parasites Vectors 11 , 210 (2018). https://doi.org/10.1186/s13071-018-2783-y

Download citation

Received : 04 December 2017

Accepted : 06 March 2018

Published : 27 March 2018

DOI : https://doi.org/10.1186/s13071-018-2783-y

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

• Preventive measures
• Meta-analysis

Parasites & Vectors

ISSN: 1756-3305

• Submission enquiries: [email protected]

Loading metrics

Open Access

Review articles summarize the best available evidence on a topic relevant to the NTD community.

See all article types »

The application of spectroscopy techniques for diagnosis of malaria parasites and arboviruses and surveillance of mosquito vectors: A systematic review and critical appraisal of evidence

Affiliation School of Public Health, Faculty of Medicine, The University of Queensland, Brisbane, Australia

Affiliations UQ Spatial Epidemiology Laboratory, School of Veterinary Science, The University of Queensland, Brisbane, Australia, Children’s Health Research Centre, Children’s Health and Environment Program, The University of Queensland, Brisbane, Australia

Affiliations School of Public Health, Faculty of Medicine, The University of Queensland, Brisbane, Australia, UQ Spatial Epidemiology Laboratory, School of Veterinary Science, The University of Queensland, Brisbane, Australia

Affiliation Australian Defence Force, Malaria and Infectious Disease Institute, Brisbane, Australia

Affiliation Laboratório de Transmissores de Hematozoários, Instituto Oswaldo Cruz, Rio de Janeiro, Brazil

* E-mail: [email protected]

• Brendon Goh, 
• Koek Ching, 
• Ricardo J. Soares Magalhães, 
• Silvia Ciocchetta, 
• Michael D. Edstein, 
• Rafael Maciel-de-Freitas, 
• Maggy T. Sikulu-Lord

Published: April 22, 2021

• https://doi.org/10.1371/journal.pntd.0009218
• Reader Comments

Spectroscopy-based techniques are emerging diagnostic and surveillance tools for mosquito-borne diseases. This review has consolidated and summarised recent research in the application of Raman and infrared spectroscopy techniques including near- and mid-infrared spectroscopy for malaria and arboviruses, identified knowledge gaps, and recommended future research directions. Full-length peer - reviewed journal articles related to the application of Raman and infrared (near- and mid-infrared) spectroscopy for malaria and arboviruses were systematically searched in PUBMED, MEDILINE, and Web of Science databases using the PRISMA guidelines. In text review of identified studies included the methodology of spectroscopy technique used, data analysis applied, wavelengths used, and key findings for diagnosis of malaria and arboviruses and surveillance of mosquito vectors. A total of 58 studies met the inclusion criteria for our systematic literature search. Although there was an increased application of Raman and infrared spectroscopy-based techniques in the last 10 years, our review indicates that Raman spectroscopy (RS) technique has been applied exclusively for the diagnosis of malaria and arboviruses. The mid-infrared spectroscopy (MIRS) technique has been assessed for the diagnosis of malaria parasites in human blood and as a surveillance tool for malaria vectors, whereas the near-infrared spectroscopy (NIRS) technique has almost exclusively been applied as a surveillance tool for malaria and arbovirus vectors.

Conclusions/Significance

The potential of RS as a surveillance tool for malaria and arbovirus vectors and MIRS for the diagnosis and surveillance of arboviruses is yet to be assessed. NIRS capacity as a surveillance tool for malaria and arbovirus vectors should be validated under field conditions, and its potential as a diagnostic tool for malaria and arboviruses needs to be evaluated. It is recommended that all 3 techniques evaluated simultaneously using multiple machine learning techniques in multiple epidemiological settings to determine the most accurate technique for each application. Prior to their field application, a standardised protocol for spectra collection and data analysis should be developed. This will harmonise their application in multiple field settings allowing easy and faster integration into existing disease control platforms. Ultimately, development of rapid and cost-effective point-of-care diagnostic tools for malaria and arboviruses based on spectroscopy techniques may help combat current and future outbreaks of these infectious diseases.

Author summary

Malaria and many arboviruses such as Dengue virus, Zika virus, Chikungunya virus, and Ross River virus are persistent and detrimental to the global population. Rapid and accurate diagnosis of these infections in human populations and mosquito vectors is essential for understanding their epidemiology, for prompt treatment, and to improve and guide control and elimination strategies. Raman and infrared spectroscopy are rapid and cost-effective tools that have shown potential as diagnostic and surveillance tools for malaria and arboviruses. This systematic review presents up-to-date research conducted using RS, MIRS, and NIRS for the diagnosis of malaria parasite and arboviruses as well as for the surveillance of malaria and arbovirus vectors.

Citation: Goh B, Ching K, Soares Magalhães RJ, Ciocchetta S, Edstein MD, Maciel-de-Freitas R, et al. (2021) The application of spectroscopy techniques for diagnosis of malaria parasites and arboviruses and surveillance of mosquito vectors: A systematic review and critical appraisal of evidence. PLoS Negl Trop Dis 15(4): e0009218. https://doi.org/10.1371/journal.pntd.0009218

Editor: Claire Donald, University of Glasgow, UNITED KINGDOM

Copyright: © 2021 Goh et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: This work was funded by the Advanced Queensland Industry Research Fellowship scheme (AQIRF0192018) awarded to MTS-L by the Queensland State Government ( https://advance.qld.gov.au/universities-and-researchers/industry-research-fellowships ) and NHMRC project grant GNT1159384 awarded to MTS-L ( https://www.nhmrc.gov.au/ ). This work is also part of a PhD project of BG whose PhD scholarship is funded by The University of Queensland ( https://scholarships.uq.edu.au/scholarship/earmarked-scholarships-support-category-1-project-grants ). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Malaria is a mosquito-borne disease caused by the Plasmodium parasite and transmitted to humans and other animals through the bite of an infected female Anopheles mosquito [ 1 ]. In 2019, an estimated 229 million malaria cases and 409,000 malaria-related deaths were reported, highlighting malaria as a major public health concern [ 2 ]. Arboviruses such as Chikungunya (CHIKV), Dengue (DENV), and Zika (ZIKV) are transmitted to humans through bites of infected Aedes mosquitoes. CHIKV cases have been reported in Africa, Asia, Americas, and Europe causing an estimated 693,000 annual cases and an epidemic in over 50 countries [ 3 , 4 ]. The risk of death with CHIKV is approximately 1 in a 1,000 [ 5 ]. DENV infections have increased dramatically over the last 20 years, particularly in tropical countries. It is estimated that at least 390 million infections occur each year of which 96 million manifests clinically [ 6 ]. ZIKV caused an epidemic in Brazil between 2015 and 2016 resulting in approximately 1.6 million infections and 5,968 cases of microcephaly in newborns [ 7 ].

Diagnosis of malaria and arboviruses

To achieve the aims set by the World Health Organisation’s (WHO) Global Technical Strategy for Malaria 2016–2030 which aims to reduce malaria incidence and related mortality by 90% and to eradicate malaria in at least 35 countries by 2030, new strategies to address residual malaria transmission and tools to monitor the results of these strategies are urgently needed [ 8 ]. One of the cornerstones for disease control is the availability of good quality vaccines; however, malaria and some arboviruses vaccines are still under development. For example, the only approved malaria vaccine RTS,S (Mosquirix) has a relatively low efficacy and is not recommended by WHO for vaccination of babies between 6 to 12 weeks of age [ 9 ]. To achieve the WHO’s 2030 goals of reducing malaria-related mortality by 90%, diagnosis of malaria and mosquito surveillance have been pinpointed as fundamental tools [ 8 ]. In addition, to reduce the spread and unprecedented future outbreaks of mosquito-borne diseases, active surveillance of vectors and parasites within human populations is crucial.

Current diagnosis of malaria relies primarily on microscopy methods using Giemsa stained blood smears [ 10 ]. However, with a limit of detection of >5 parasites/μL of blood, it requires a well-trained microscopist [ 11 ]. Rapid diagnostic tests are also common diagnostic tools for malaria. They are very easy to use and do not require qualified personnel, but their sensitivity and specificity is low in detecting low parasitaemia [ 12 ]. Molecular based techniques such as polymerase chain reaction (PCR), quantitative PCR (qPCR), nested PCR, and enzyme-linked immunosorbent assay (ELISA) have also been developed for malaria [ 13 ] and arboviruses [ 14 , 15 ]. PCR techniques are gold standards for the diagnosis of arboviruses; however, due to time, cost inefficiencies, and technical expertise required, they are unsuited for large-scale diagnoses particularly during disease outbreaks. For example, the cost of DENV1 antibody ELISA kit is approximately $10.4 USD per sample [ 16 ], while a malaria IgG and IgM antibody ELISA kit costs are estimated at $5.5 USD per sample [ 17 ]. Additionally, basic laboratory skills are required to perform PCR or ELISA techniques efficiently and correctly.

Vector surveillance of malaria and arboviruses

Vector surveillance involves regular monitoring of mosquito populations to assess the effectiveness of vector control interventions. Surveillance assesses vector survival (age), species diversity, infection status, host preference, and insecticide resistance. These parameters are currently determined using molecular techniques including PCR and qPCR or ELISA [ 18 – 20 ]. Vector survival is the most important determinant of vectorial capacity of mosquito vectors. Mosquito age prediction can be useful in identifying potentially infectious vectors, as pathogens must incubate for a certain period of time within mosquitoes before they can be transmitted to hosts. For example, the female Anopheline mosquito can only transmit Plasmodium parasites after 10 to 12 days following ingestion of an infected blood meal due to the long incubation period required for Plasmodium parasite development within the vector [ 21 ]. Consequently, a mosquito population that survives longer that this extrinsic incubation period will be more likely to transmit malaria to susceptible hosts.

Parity dissections to determine whether a mosquito has previously laid eggs or not is the current gold standard technique to determine mosquito age [ 22 ]. A related technique which determines the number of dilatations in the ovaries indicates how many times a mosquito has laid eggs [ 23 ]. Although these techniques require minimal reagents to operate, they are time consuming and tedious allowing only a small proportion of samples to be dissected at a time which can be an accurate representation of the age composition of a mosquito population.

Raman and infrared spectroscopy

Raman spectroscopy (RS) is a technique that provides chemical fingerprints of molecules by determining their vibrational modes through inelastic scattering of photons known as Raman scattering or Raman effect [ 24 ]. During Raman scattering, molecules gain energy from an incident light source. Raman effect is therefore the difference between monochromatic incident and exit radiation. One of the important features that makes RS useful in biological applications is its ability to avoid interference by water molecules. This is due to inability of water to induce Raman scattering. RS can be used as a quantification and identification measure for biological samples. For example, RS has been used to identify molecular compositions in biological samples such as the eyes [ 25 ], teeth [ 26 ], muscles [ 27 ], and nerves [ 28 ] and quantify molecular compositions in blood [ 29 – 31 ].

Infrared spectroscopy involves the interaction of infrared radiation with biological samples to produce a diagnostic spectrum. It capitalises on the fact that molecules absorb light at specific frequencies characteristic of their chemical composition [ 32 ]. This implies that different biological samples with varying chemical profiles have unique absorption and reflectance properties characteristic of their functional groups and can therefore be quantified as peaks on an infrared spectrum. The infrared portion of the electromagnetic spectrum consist of 3 regions: near-, mid-, and far-infrared. The near-infrared region consists of frequencies that range from 14,000 to 4,000 cm −1 (800 to 2,500 nm wavelength) and is generally used to observe excitation of overtone or harmonic molecular vibrations ( Fig 1 ). The mid-infrared region consists of frequencies that range from 4,000 to 400 cm −1 (2,500 to 25,000 nm wavelength) and is used to study key rotational-vibrational structure ( Fig 2 ). Therefore, mid-infrared wavelengths provide more detailed analyses of a sample. Unlike near-infrared, mid-infrared is invasive and is unsuited for in vivo studies.

• PPT PowerPoint slide
• PNG larger image
• TIFF original image

https://doi.org/10.1371/journal.pntd.0009218.g001

Adapted from Mwanga and colleagues [ 70 ].

https://doi.org/10.1371/journal.pntd.0009218.g002

Both Raman and infrared spectroscopy techniques are rapid and inexpensive techniques compared to molecular and microscopy techniques for similar purposes. Although the initial outlay for a NIR spectrometer can be costly (approximately $40,000 USD), benefits such as minimal sample processing, large-scale applications, and minimal labour can outweigh these initial cost in the long run [ 33 ].

Chemometrics/machine learning techniques are usually coupled with spectroscopy techniques to produce diagnostic information required for sample characterisation. Following development of training models, these techniques only require basic computer and spectra collection skills. However, to date, there has not been a comprehensive review of applications of these spectroscopy techniques for mosquito-borne diseases.

We systematically reviewed published evidence from 2009 to 2021 involving the use of Raman and infrared spectroscopy techniques for the diagnosis of malaria parasites and arboviruses and for surveillance of mosquito vectors.

Search strategy

Standard systematic review and meta-analysis (PRISMA) guidelines were applied for this review [ 34 ]. We searched PUBMED, MEDILINE, and Web of Science databases for peer-reviewed journal articles published from 2009 to 2021 (January). We manually searched reference lists of included articles to capture relevant articles [ 35 ]. To identify articles on the application of RS in the field of mosquito-borne diseases, the following key terms were used: “Raman spectroscopy arboviruses,” “Raman spectroscopy malaria,” “Raman spectroscopy Chikungunya,” “Raman spectroscopy Dengue,” “Raman Spectroscopy mosquitoes,” “Raman spectroscopy Ross River,” and “Raman spectroscopy Zika.” The application of infrared techniques was searched in the same databases with the following key terms: “Infrared spectroscopy arbovirus,” “Infrared spectroscopy malaria,” “Infrared spectroscopy Chikungunya,” “Infrared spectroscopy Dengue,” “Infrared spectroscopy mosquitoes,” “Infrared spectroscopy Ross River,” and “Infrared spectroscopy Zika.” No restrictions were applied to language. EndNote software (Thompson Reuters, Philadelphia, Pennsylvania, United States of America) was used to store articles retrieved from databases which were screened for duplicates. Titles and abstracts were screened by two authors (BG and KC) to identify relevant publications that met the inclusion criteria. Full-text review was applied by one author (BG) to determine the eligibility of articles. Eligible articles were grouped into 3 categories based on the spectroscopy technique used, RS, MIRS, and NIRS.

Inclusion and exclusion criteria

Articles were eligible for inclusion if they demonstrated use of RS, MIRS, and NIRS for the diagnosis, detection, and visualisation of malaria parasites, arboviruses, or surveillance of mosquito vectors. Machine learning articles involving the same sample types were also included in this review. Articles were excluded based on the following criteria: (a) abstract or full paper was not accessible; (b) article does not mention RS, MIRS, or NIRS techniques; (c) article does not mention mosquito-borne diseases; (d) RS, MIRS, or NIRS technique was not used in the main experiments; and (e) conference proceedings, commentaries, grey literature, short communications, or review articles ( Fig 3 ). Articles excluded are indicated in S2 Table .

A total of 58 peer-reviewed articles from 2009 to 2021 (January) were reviewed.

https://doi.org/10.1371/journal.pntd.0009218.g003

Data extraction

Eligible articles were subjected to data extraction based on the following criteria: (a) type of spectroscopy technique used; (b) type of sample analysed; (c) method of sample preparation; (d) method of sample analysis; (e) method of data analysis; and (f) result of the experiment based on the spectroscopy technique used (i.e., accuracy defined as the percentage of correct predictions for a sample set, sensitivity defined as the proportion of positive samples that are correctly predicted as positive, and specificity defined as the proportion of negative samples that are predicted as negative).

Results of search strategy

Characteristics of journal articles included in this systematic review..

A total of 1,023 peer-reviewed journal articles were identified through PUBMED, MEDILINE, and Web of Science database searches. Seven peer-reviewed journal articles were identified by hand searching eligible articles. A total of 405 unique articles were retained after duplicates were removed using Endnote software. A total of 67 articles met our inclusion criteria and were subjected to full text review. After full text assessment, 58 articles met our inclusion criteria for this systematic review ( Fig 3 ).

Time trend of journal articles in this systematic review.

There has been an upward trend in the number of peer-reviewed articles published in the field of RS, NIRS, and MIRS from 2009 to 2019, with a more than 2-fold increase in 2015. In 2011, a spike in the number of NIRS and RS articles published was observed. A further increase in articles was observed in 2019 which was mainly associated with the application of MIRS in the field of malaria. A decline in studies from 2020 onwards is likely due to the ongoing COVID-19 pandemic ( Fig 4 ).

https://doi.org/10.1371/journal.pntd.0009218.g004

In this review, 27 RS, 11 MIRS, and 20 NIRS studies were included. RS, MIRS, and NIRS studies were first split into 2 groups; malaria and arbovirus studies and each of the 2 groups was further split into articles that focused on diagnostics and vector surveillance ( Table 1 ). All reviewed articles under RS were related to its application for the diagnosis of malaria or arboviruses in whole blood/red blood cells (RBCs)/serum/serum. All MIRS articles were related to its use for the diagnosis of malaria parasite in RBCs and surveillance of malaria vectors. Finally, all but one NIRS article reviewed assessed its use as a vector surveillance tool for malaria and arbovirus vectors.

https://doi.org/10.1371/journal.pntd.0009218.t001

Results and discussion

Application of rs for the diagnosis of malaria parasites.

The application of RS to differentiate ring, trophozoite, and schizont stages of the malaria parasite in human O+ RBCs has been demonstrated. Plasmodium falciparum- infected RBCs at the ring stage showed a characteristic Raman peak at 6,254 nm, while trophozoite and schizont stages had distinct peaks at 13,831 nm. The difference in the characteristic peaks were attributed to the modification of the RBC membrane during the development of the parasite [ 36 ]. Another strategy to enhance limit of detection of RS resonance utilised silver nanoparticles synthesised within P . falciparum parasites. A limit of detection of 2.5 parasites/μL for the ring stage of P . falciparum was achieved [ 37 ]. In a separate study, both malaria and DENV patient’s whole blood samples were differentiated from healthy samples with 83.3% accuracy with positive likelihood ratios of 0.9529 and 0.9584, respectively [ 31 ]. When RS was used to predict Plasmodium vivax infection in human plasma, an accuracy of 86% was achieved [ 38 ], whereas 1 parasite/μL of either P . falciparum and P . vivax infections in whole blood could be detected with surface-enhanced Raman spectroscopy (SERS) coupled with a nanostructured gold substrate [ 39 ]. A study on how pressure affects the Raman spectra was carried out on synthetic hematin anhydride equivalent to malaria pigment hemozoin. The intensity of RS peaks decreased when synthetic hematin anhydride was subjected to increasing pressure up to 27 kbar above atmospheric pressure [ 40 ]. As malaria is more prevalent in tropical countries, therefore, higher temperatures in those countries could lead to increased pressure within blood samples during long-term storage. This can influence the RS diagnostic signature obtained. Further tests using real-world malaria-infected blood samples are required to confirm this phenomenon.

RS has also been used to study both blood and tissue stages of Plasmodium berghei -infected mice. In a study reported by Hobro and colleagues [ 41 ], P . berghei infection progression was monitored with a confocal Raman microscope via infected mouse at days 1, 2, 3, 4, and 7 post inoculation. Heme-based changes were observed in mice at a parasitaemia of 0.2% in plasma, and erythrocyte membrane changes were observed on day 4 post inoculation at 3% parasitaemia [ 41 ]. In mice infected with the P . berghei ANKA strain, significantly higher heme-based Raman vibrations were observed in the tissue of mice with 5% parasitaemia compared with tissues of uninfected mice indicating possible presence of hemozoin [ 42 ].

Several other studies applied RS to visualize the hemozoin pigment produced during malaria infection. An atomic force Raman microscope was used to observe the effect of in vitro treatment procedures on P . falciparum -infected RBCs. Results showed that infected RBCs dried in phosphate buffer solution (PBS) causes localisation of hemichrome at the periphery of RBCs, formaldehyde causes diffusion of haemoglobin into the surrounding areas of the RBCs, while a mixture of formaldehyde (3%) and glutaraldehyde (0.1%) maintained the structural integrity of RBCs [ 29 ]. Other studies involving RS visualisation of malaria infection in RBCs include studies that show (a) an increase in hemozoin crystal size over time of infection [ 43 ], (b) improvement in visualization of β-hematin crystals with the use of magnetised iron oxide core and silver shell nanoparticles [ 44 ], (c) similarity in biochemical compounds found in intracellular and extracellular hemozoin [ 45 ], (d) an increase in intravascular heme solubility due to nitric oxide interaction with heme [ 46 ], (e) a reduced oxygen-affinity for intracellular haemoglobin [ 30 ], and (f) identification of five-coordinate high-spin ferric heme complex in erythrocyte digestive vacuole [ 47 ].

Structural analysis of P . falciparum -infected RBCs using RS indicated a lower number of domains arranged in transconformation, an increase in membrane protein and lipids, an increase in deoxygenated haemoglobin, and a decrease in α-helical content with an increase in undefined structures [ 48 ]. When resonance RS was used for the structural analysis of iron porphyrins and β-hematin, solid states iron porphyrin [Fe(OEP)] 2 O exhibited total symmetric mode v 4 when excited with 782 nm and 830 nm lasers. It was also observed that less supramolecular interactions were present. Based on the difference in excitation and supramolecular interactions, the authors suggested that the intensity of symmetric mode v 4 is strongly affected by C–H–X hydrogen bond interactions [ 49 ]. A summary of the studies that applied RS for diagnosis of malaria are shown in Table 2 .

https://doi.org/10.1371/journal.pntd.0009218.t002

Application of RS for the diagnosis of arboviruses

A sensitivity of 97.38% and a specificity of 86.18% were achieved when RS was used to detect DENV in blood plasma relative to ELISA testing for nonstructural protein 1, immunoglobulin M (IgM), and immunoglobulin G (IgG) [ 50 ]. However, a lower predictive accuracy of 66% and 47% was observed when RS was used to detect DENV-infected blood sera relative to IgG and IgM ELISA tests, respectively. The predictive accuracy of DENV based on IgG antibodies was lower than the accuracy based on IgM probably because IgM is generated at the onset of the infection before IgG. Overall, low accuracies were due to high false negative results [ 51 ]. Elevated lactate concentration in human blood sera was observed in DENV-infected patients possibly due to impaired function of body organs [ 52 ]. When support vector machine (SVM) learning models coupled with polynomial kernel order 1 were applied, DENV was predicted with a predictive accuracy of 85% and a sensitivity of 73% [ 53 ]. In a recent study, RS was used to differentiate between bacteria ( Salmonella Typhi ) and virus (DENV) infections in human blood serum, with 12 distinct Raman bands linked to typhoid-infected samples and 4 to DENV [ 54 ].

Multiple studies have been conducted to determine the limit of detection of RS for identifying arbovirus-related antigens, with emphasis on Rift Valley fever virus (RVFV) and West Nile virus (WNV) using SERS coupled with gold and silver nanotags [ 55 – 58 ]. When gold paramagnetic nanoparticles were used, the limit of detection for WNV-specific target DNA sequence was 10 pM [ 57 ]. The same methodology was used to identify the limit of detection of RVFV (20 nM) and WNV (100 nM) based on their RNA sequences [ 58 ]. RS and gold paramagnetic nanoparticles tags were also used to simultaneously detect WNV and RVFV where detection limits of 5 fg/mL and approximately 25 pg/mL were achieved when viruses were suspended in PBS or PBS with fetal bovine serum, respectively [ 56 ]. However, when a polyacrylic acid layer was applied, a reduction in background noise was observed and a limit of detection of 10 pg/mL for WNV, RVFV, and Yersinia pestis antigens was achieved [ 55 ].

Detection limits as low as 10 plaque-forming units (PFU)/mL were achieved for both DENV and WNV when SERS coupled with a bioconjugated gold nanoparticle was used [ 59 ]. Whereas a limit of detection of 7.67 ng/mL for DENV and 0.72 ng/mL for ZIKV was achieved by coupling RS to a lateral flow assay [ 60 ]. These detection limits are lower relative to ELISA detection limits of 120 ng/mL for ZIKV, <1 ng/mL for DENV, and 61 PFU/mL for WNV [ 61 – 63 ]. A summary of the studies that applied RS for the diagnosis of arboviruses are shown in Table 3 .

https://doi.org/10.1371/journal.pntd.0009218.t003

Application of MIRS for the diagnosis of malaria parasites

Asexual stages of P . falciparum could be differentiated with Synchrotron Fourier transform infrared microspectroscopy and artificial neural network (ANN) based on the 2,800 to 3,100 cm −1 and to 1,000 to 1,800 cm −1 MIR regions with an accuracy of 100% for all stages tested (rings, trophozoites, and schizonts) [ 64 ]. Stages of P . falciparum in human O+ RBCs were differentiated with attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy where rings, trophozoites, and gametocytes were distinct within 1,000 to 3,100 cm −1 regions. The study also identified that the limit of detection was <1 parasite/μL for the ring stage blood samples [ 65 ].

When MIRS was used for the detection of P . falciparum in human whole blood with parasitaemia ranging from 0% to 5%, a sensitivity of 70% and a specificity 98% was achieved [ 66 ]. Moreover, high-resolution infrared images of single cells infected with P . falciparum , changes in MIRS spectra region relating to increases in amide A band (consisting of N–H stretching modes of protein and C–H stretching region of lipids), and unsaturated fatty acids in infected cells could be identified [ 67 ]. Focal plane array-Fourier transform infrared (FPA-FTIR) imaging spectroscopy identified P . falciparum blood stages at a single-cell level [ 68 ] and a high-resolution FTIR could detect single malaria parasite-infected erythrocytes [ 67 ].

The effect of 3 different anticoagulants including sodium citrate, potassium ethylenediaminetetraacetic acid, and lithium heparin on plasma and whole blood in aqueous and dry phase on ATR-FTIR spectral signatures was tested. It was found that anticoagulants heavily influenced the spectra of dry blood samples compared to wet samples. Of the 3 anticoagulants tested, lithium heparin affected the mid-infrared spectra the least [ 69 ]. Findings from 2 most recent studies indicate MIRS can detect P . falciparum field-collected human blood spots on filter paper. Mwanga and colleagues identified P . falciparum with FTIR from field samples collected in Tanzania where an accuracy of 92%, sensitivity of 92.8%, and specificity of 91.7% in comparison to PCR findings was achieved [ 70 ]. The second study was done with P . falciparum samples collected in Thailand where a sensitivity of 92% and a specificity of 97% in comparison to PCR was observed [ 71 ]. A summary of the studies that applied MIR for diagnosis of malaria are indicated in Table 4 , and an example of a MIR spectra for malaria infected and uninfected red blood cells is shown in Fig 2 .

https://doi.org/10.1371/journal.pntd.0009218.t004

Application of MIRS for surveillance of malaria and arbovirus vectors

Highly variable accuracies were observed when MIRS was used to predict the age of laboratory-reared Anopheles arabiensis and Anopheles gambiae that ranged between 1 to 15 days old. Predictive accuracies of 15% to 97% and 10% to 100% were attained for An . gambiae and An . arabiensis mosquito species, respectively. Lower predictive accuracies were observed for middle age mosquitoes within 3 to 11 days old age group compared to 1 or 15 days old mosquitoes for both species [ 72 ]. The same technique also differentiated between field-collected An . arabiensis and An . gambiae with an accuracy of 82.6% [ 72 ]. A separate study used ATR-FTIR spectroscopy to predict the age of laboratory-reared w Mel-infected Ae . aegypti with an accuracy of 95% to 97% and to detect Wolbachia infections in Ae . aegypti field mosquitoes with an accuracy of 90% compared with that of PCR results. However, higher predictive accuracies of 95% to 97% were observed when mosquitoes were 2 and 10 days old. A significant difference in biochemical components between male and female was also identified by ATR-FTIR spectroscopy and the technique differentiated the 2 groups with a specificity and sensitivity of 95% to 100% [ 73 ].

Identification of the origin of a mosquito blood meal is crucial for the assessment of their host preference. Furthermore, upscaling MIRS into field studies will require models that are robust enough to accurately predict mosquitoes with various abdominal statuses including the source of their blood and blood digestion stages. MIRS has been used to successfully differentiate laboratory-reared An . arabiensis fed on goat, bovine, chicken, and human blood meals with predictive accuracies of 96%, 97%, 100%, and 100%, respectively [ 74 ]. A summary of the studies that applied MIR for surveillance of malaria and arbovirus vectors is shown in Table 5 .

https://doi.org/10.1371/journal.pntd.0009218.t005

Application of Visible-NIRS for malaria and arbovirus vector surveillance

All studies on surveillance of mosquito vectors were conducted using a Labspec NIR spectrometer (Malvern Panalytical, Malvern, United Kingdom) whose wavenumber range is 4,000 to 28,571 cm −1 . Most studies applied partial least squares (PLS) regression for data analysis to predict the age, infection, and species of mosquitoes of malaria and arbovirus-transmitting mosquitoes ( Table 6 ).

All studies on surveillance of mosquito vectors were conducted using a LabSpec NIR spectrometer (Malvern Panalytical, Malvern, UK).

https://doi.org/10.1371/journal.pntd.0009218.t006

In the past 12 years, NIRS has been used as an alternative strategy for age and species determination for malaria and arbovirus vectors in a range of studies under varying environmental conditions. Initially, NIRS’ potential for predicting the age and species was demonstrated on laboratory-reared mosquitoes where it was reported to be accurate for predicting the age of those mosquitoes into ±3 days of their actual age or into ≤ 7 days ≥ old age group and for differentiating An . gambiae from An . arabiensis with >90% accuracy [ 75 ]. Subsequent studies using An . gambiae and An . arabiensis reared in a semi-field system reported similar accuracies for age and species prediction [ 33 , 76 ]. More recent studies have indicated that the chronological age of An . gambiae and An . arabiensis can be improved using alternative machine learning techniques such as ANN as opposed to PLS regression analysis used in previous studies [ 77 , 78 ].

NIRS spectral features of laboratory-reared and wild-type An . arabiensis mosquitoes were shown to be identical regardless of the environment and diet of the mosquito (i.e., field-caught and laboratory-reared mosquitoes). Based on these findings, NIRS prediction models developed from laboratory-reared mosquitoes with known age could be possibly relied upon for predicting the age of wild mosquito populations with unknown age [ 79 ]. Two studies have demonstrated the potential of NIRS to predict the age of wild An . arabiensis and An . gambiae mosquitoes. Krajacich and colleagues [ 80 ] reported age prediction accuracy of 73.5% to 97% for wild and 69.6% for semi-field mosquitoes. This accuracy has recently been improved using an autoencoder and ANN to predict the parity status of field mosquitoes [ 78 ]. Findings from 2 other studies indicated that NIRS could differentiate field-caught An . gambiae and An . arabiensis with a predictive accuracy of 90% [ 33 , 75 ]. NIRS has also been used to predict the age of laboratory-reared Ae . aegypti [ 81 ] and Ae . albopictus [ 82 ] with or without Wolbachia with similar accuracies as those recorded for An . gambiae and An . arabiensis . However, when NIRS was used to predict Ae . albopictus mosquitoes reared from wild pupae using a model developed from laboratory-reared mosquitoes, young and old mosquitoes could not be differentiated [ 83 ]. Based on the authors’ description of their experimental design, the inability to predict the age of mosquitoes collected from wild pupae is most likely due to a weak predictive model that failed to capture the heterogeneity of the wild population including variation in the larval diet. Alternatively, the small sample size used for model development was not robust [ 83 ]. A previous study indicated that Anopheles mosquitoes reared from wild pupae could be predicted accurately if models were developed from a similar mosquito population and neither species type nor exposure to pyrethroids affected the ability of NIRS to predict their age [ 76 ]. However, larval and adult diets have been previously shown to have an influence on age-related spectral signatures [ 84 ].

Mosquitoes are commonly stored in various preservatives prior to spectral collection. Several studies have demonstrated the effect of a range of preservation techniques on the predictive accuracy of NIRS for age and species of An . gambiae and An . arabiensis . When RNAlater was used as a preservative for 1 to 3 weeks, the prediction accuracy was relatively higher (90%) for An . gambiae s.s and An . arabiensis compared to the accuracy of 83% for freshly scanned mosquitoes [ 85 ]. However, there appeared to be a decline in accuracy from 86% to 75.6% when mosquitoes were preserved for a longer period of time (50 to 62 days) [ 86 ]. Similarly, a light decrease (on average as 3.6%) in accuracy when differentiating An . arabiensis from An . gambiae were observed after 50 weeks of storage in silica gel [ 87 ]. For storage up to 4 weeks, RNAlater at 4°C, refrigeration at 4°C and silica gel are the recommended options for age and species prediction [ 86 , 87 ]. The fact that the prediction accuracy of samples stored in silica gel is comparable to the accuracy of fresh samples is encouraging as it means vector control programs would not be required to modify their current collection and storage protocols to adopt the NIRS technique. However, although silica gel is cost-effective, maintaining desiccation for a long period of time is a challenge. Due to its high cost, RNAlater is generally recommended for small-scale studies that require RNA extraction to stabilise RNA in the samples prior to analysis. Samples in RNAlater can stay at room temperature for a maximum of 2 weeks, hence RNAlater could be an alternative to silica gel for field work where access to a fridge is limited.

NIRS has been used to identify mosquitoes infected with various pathogens such as P . berghei , P . falciparum , Wolbachia , CHIKV, and ZIKV. A prediction accuracy of 72% was achieved when P . berghei -infected Anopheles stephensi were differentiated from uninfected mosquitoes [ 88 ]. P . falciparum was detected in laboratory-reared An . gambiae , with accuracies of 88% for oocyst stage and 95% for sporozoite stage (14 dpi). This predictive accuracy positively correlated with the concentration of the parasite within the mosquito [ 89 ]. ZIKV in laboratory-reared Ae . aegypti mosquitoes was predicted with an overall accuracy of 97.3% in the heads/thoraces and 88.8% in abdomens in comparison to RT-qPCR [ 90 ] and w Mel-infected Ae . aegypti mosquitoes were predicted with accuracies of 92% for female and 89% for male mosquitoes [ 91 ]. Similarly, the presence of w MelPop in Ae . aegypti females and males was predicted with accuracies of 96% and 87.5%, respectively [ 91 ]. Furthermore, NIRS could differentiate between w Mel and w MelPop-transinfected mosquitoes with predictive accuracies of 96.6% for females and 84.5% for males [ 91 ]. Overall, NIRS detected Wolbachia in females more accurately than in male mosquitoes and in w MelPop more accurately than w Mel probably based on concentration levels. Lastly, a recently published article provides evidence that NIRS can also detect the presence of Wolbachia , ZIKV, and Chikungunya viruses in mosquitoes 7 days post their death [ 92 ]. A summary of the studies that applied NIRS for surveillance of malaria and arbovirus vectors is shown in Table 6 , and an example of NIRS raw spectra of ZIKV infected and uninfected female Ae . aegypti is shown in Fig 1 .

Application of Visible-NIRS for diagnosis of malaria parasites

Only one study has applied NIRS to detect P . berghei in the whole blood of mice infected with rodent malaria. The study compared NIRS spectra of 6 P . berghei -infected mice and 6 uninfected mice. A characteristic peak at 650 nm related to P . berghei infection increased in intensity with rising parasitaemia (R 2 value = 0.68) [ 93 ]. The study referenced has been added to Table 6 .

Knowledge gaps in the application of Raman and infrared spectroscopy for malaria and arboviruses

Although several studies have demonstrated the potential of RS for diagnosis of both malaria and arboviruses in laboratory settings ( Table 2 ), the validation of RS under real-world conditions is an area that has not been fully investigated. Moreover, no studies were identified that have assessed the potential of RS for surveillance and characterisation of mosquito vectors. The use of MIRS for diagnosis of malaria has been recently demonstrated in the laboratory by several studies and in the field by 2 studies [ 70 , 71 ], whereas its application as surveillance tool for malaria vectors has only been demonstrated by 3 studies in the laboratory [ 72 – 74 ]. Future research should assess the potential of MIRS for the diagnosis of arboviruses in humans and validate its feasibility under field conditions for both malaria and arboviruses. NIRS has been used in several studies for the surveillance and characterisation of mosquito vectors into age groups, species identity, and infection status. However, most of the studies were conducted on laboratory samples. Only 2 studies reported that NIRS can differentiate field-collected An . gambiae from An . arabiensis [ 33 , 75 ] and parous from nulliparous malaria vectors [ 78 , 80 ]. Further work is required to demonstrate the full potential of NIRS in the field and to validate it against gold standard techniques. Finally, only 1 study demonstrated that NIRS can detect Plasmodium in mice blood [ 93 ] opening an opportunity to investigate its diagnostic capacity for malaria and arboviruses in human tissues.

Conclusions

The objective of this systematic review was to demonstrate the various studies that have used RS, MIRS, and NIRS as diagnostic tools for malaria and arboviruses or as surveillance tools for mosquito vectors. These spectroscopy techniques are rapid, and NIRS and RS for example can be applied non-invasively without consuming reagents. Their application for the diagnosis or surveillance of malaria and arboviruses is a relatively new area of research. This review has identified opportunities which could potentially assist in the development of these techniques as future cost-effective, point-of-care diagnostics, or rapid surveillance tools for mosquito vectors. For example, the recent development of multiple infrared-based and Raman devices paired with advances in machine learning could revolutionise the application of these techniques and subsequently enable their real-time application in the field. Of importance is the standardisation and optimisation of currently available infrared and Raman spectra collection techniques to enable reproducibility between samples and instruments. Also required is a comprehensive assessment of Raman and infrared spectroscopy techniques to determine their utility in the diagnosis of infections that cause similar symptoms in humans such as arboviruses. Finally, comparative studies to determine the relationship between spectral signatures for mosquitoes infected with various pathogens including those that carry resistance genes should be investigated. Other factors that need to be investigated include how host immunity, age, gender, and blood type may all have an influence on spectral signatures collected.

The assessment of these devices in the field should be prioritised with the aim of developing point-of-care tools to support epidemiological studies of malaria and arboviruses and ultimately aide in combating current and future outbreaks of these infectious diseases. User-friendly protocols coupled with field deployable devices and cloud-based artificial intelligence platforms would improve the speed and reduce the cost of current disease surveillance programs by several magnitudes to facilitate rapid decision making by policy makers.

Key learning points

• Research in the application of RS as a potential surveillance tool for mosquito vectors is recommended.
• Research in the application of MIRS as a potential tool for diagnosis of arboviruses is recommended.
• Research in the application of NIRS for diagnosis of malaria and arboviruses is recommended.
• A protocol for standardisation of sample and spectra collection is required to harmonise the application of various spectroscopy techniques in multiple settings.

Top five papers

• Hobro AJ, Konishi A, Coban C, Smith NI. Raman spectroscopic analysis of malaria disease progression via blood and plasma samples. Analyst. 2013;138(14):3927–33.
• Mwanga EP, Minja EG, Mrimi E, Jiménez MG, Swai JK, Abbasi S, et al. Detection of malaria parasites in dried human blood spots using mid-infrared spectroscopy and logistic regression analysis. Malar J. 2019;18(1):341.
• Heraud P, Chatchawal P, Wongwattanakul M, Tippayawat P, Doerig C, Jearanaikoon P, et al. Infrared spectroscopy coupled to cloud-based data management as a tool to diagnose malaria: a pilot study in a malaria-endemic country. Malar J. 2019;18(1):348.
• Milali MP, Kiware SS, Govella NJ, Okumu F, Bansal N, Bozdag S, et al. An autoencoder and artificial neural network-based method to estimate parity status of wild mosquitoes from near-infrared spectra. PLoS ONE. 2020;15(6):e0234557.
• Santos LMB, Mutsaers M, Garcia GA, David MR, Pavan MG, Petersen MT, et al. High throughput estimates of Wolbachia , Zika and chikungunya infection in Aedes aegypti by near-infrared spectroscopy to improve arbovirus surveillance. Commun Biol. 2021;4(1):67.

Supporting information

S1 table. prisma 2009 checklist..

https://doi.org/10.1371/journal.pntd.0009218.s001

S2 Table. Summary of excluded full text articles.

https://doi.org/10.1371/journal.pntd.0009218.s002

Acknowledgments

The views expressed in this article are those of the authors and do not necessarily reflect those of the Australian Defence Force Joint Health Command or any extant Australian Defence Force policy.

• 1. Ross R. The prevention of malaria. London, United Kingdom: J Murray; 1910.
• 2. World Health Organization. World malaria report 2020. Geneva, Switzerland: WHO; 2020.
• View Article
• PubMed/NCBI
• Google Scholar
• 8. World Health Organization. Global technical strategy for malaria 2016–2030. Geneva, Switzerland: World Health Organ; 2015.
• 11. World Health Organisation. Malaria Microscopy Quality Assurance Manual—Version 2. Geneva, Switzerland: WHO; 2016.
• 16. MyBioSource. Human Dengue Virus Type 1 Antibody (Anti-DENV1) ELISA Kit 2020 [cited 2020 15/10]. Available from: https://www.mybiosource.com/human-elisa-kits/dengue-virus-type-1-antibody-anti-denv1/109524 .
• 17. abcam. Anti-Malaria ELISA Kit (ab178649) 2020 [cited 2020 15/10]. Available from: https://www.abcam.com/malaria-elisa-kit-ab178649.html .
• 20. World Health Organisation. Test procedures for insecticide resistance monitoring in malaria vector mosquitoes. 2nd ed. ed. Geneva: WHO; 2016 2016.

An official website of the United States government

The .gov means it's official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you're on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings
• Browse Titles

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.

StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-.

StatPearls [Internet].

Plasmodium falciparum malaria.

Lara Zekar ; Tariq Sharman .

Affiliations

Last Update: August 8, 2023 .

• Continuing Education Activity

Malaria is a global infectious disease that remains a leading cause of morbidity and mortality in the developing world. Severe and fatal malaria is predominantly caused by Plasmodium falciparum. Its management and prognosis depend on the awareness of a possible diagnosis in travelers returning from endemic areas, early recognition, and timely effective treatment. This activity reviews the evaluation and management of patients with falciparum malaria and explains the role of the interprofessional team in evaluating and treating patients with this condition.

• Identify the pathophysiology of P. falciparum infection.
• Summarize the findings seen in a patient with P. falciparum malaria.
• Describe common complications for patients with severe P. falciparum malaria.
• Outline the importance of communication and collaboration among the interdisciplinary team to enhance the delivery of care and improve outcomes for patients affected by P. falciparum malaria.
• Introduction

Malaria is a mosquito-borne disease caused by five protozoa: Plasmodium falciparum , P. vivax , P. malariae , P. ovale, and most recently implicated P.knowlesi . Infection with P. falciparum is being accounted for more than 90% of the world’s malaria mortality and therefore remains an important threat to public health on a global scale. [1] [2]  The World Health Organization (WHO) World Malaria report 2019 estimates 228 million cases of malaria worldwide, causing 405 000 deaths in the year 2018, many under the age of 5. Malaria is endemic in more than 90 countries, affecting approximately 40% of the world’s population. [2]  There is a significant number of cases of imported malaria and local transmission following importation occurring in non-malarial countries, including North America and Europe. [3]  Malaria is associated with travelers to the endemic areas, and increasing numbers of imported malaria necessitate an understanding of frequently non-specific symptoms, difficulties related to the malarial diagnosis, and treatment possibilities. [2]

Five species of genus Plasmodium are known to cause malaria in humans. The vector for Plasmodium spp. is a female A nopheles mosquito that inoculates sporozoites contained in her salivary glands into the puncture wound when feeding. [3]  Sporozoites enter peripheral bloodstream and are uptaken by hepatocytes, where they undergo an asexual pre-erythrocytic liver-stage as liver schizonts lasting up to 2 weeks before the onset of the blood stage. [3] [4]  As they replicate within hepatocytes, they form motile merozoites that are subsequently released into the bloodstream, where they invade red blood cells (RBC). The process continues through serial cycles of asexual replication of merozoites that go through ring, trophozoite, and schizont stages before forming and releasing new invasive daughter merozoites that consequently infect new RBC, therefore causing a rise in parasite numbers. [3] [5]   P. falciparum produces high levels of blood-stage parasites and is known to modify the surface of the infected RBC, creating an adhesive phenotype, e.g. (sticky cell) causing RBC sequestration inside small and middle-sized vessels, removing the parasite from the circulation for nearly half of the asexual cycle. [6]  Sequestration leads to splenic parasite clearance avoidance, host cell endothelial damage, and microvascular obstruction. [5] [6]  A small fraction of intra-erythrocytic parasites switch to sexual development, producing morphologically distinct male and female gametocytes that reach the host's dermis and are ingested by a mosquito, rendering it infectious to humans. [3] [4] [5]  After ingestion by a female A nopheles mosquito, the male micro-gametocytes go through a process of ex-flagellation in the mosquito's midgut, fusing with female macro-gametes to form a zygote. The zygote then reaches the stage of ookinete that migrates through a thin wall, matures into oocyst, producing and upon rupturing, releasing numerous sporozoites that are dispersed throughout mosquitos body, including salivary glands, therefore completing the lifecycle. Gametocytes are hence of vital importance to the transmission cycle of malaria. [2] [4] [7]  The clinical symptoms are, however, predominantly a result of the asexual stages of parasite replication in human blood. [5]

• Epidemiology

Worldwide 

WHO World Malaria Report 2019 states that an estimated 228 million cases of malaria occurred worldwide in 2018, and reports steadily decreasing the number of cases since 2010. In 2018, nineteen sub-Saharan African countries and India carried approximately 85% of the global malaria burden. The most prevalent and pathogenic malaria parasite, most commonly associated with severe illness and death, especially in the WHO African region, accounting for 99.7% malaria cases, is P. falciparum. [8]   P. falciparum is also highly prevalent in South-East Asia, Eastern Mediterranean, and Western Pacific regions. The most vulnerable groups affected by malaria in high-transmission areas are children younger than 5 years old, their deaths accounting for 67% of global malaria deaths, and primigravidae. In low transmission areas, all ages are at risk due to low immunity. [2]

The United States 

Most malaria cases diagnosed in the United States of America are imported from endemic countries. [9]  The risk of infection depends on the length of exposure and the intensity of malaria transmission in the geographical region. [10]  During 2015 CDC received 1517 reports of confirmed malaria in the United States of America, one of the cases was classified as congenital, 1485 were imported from endemic countries, and 31 reports had an incomplete travel history. The 12.1% decrease of imported malaria in 2015 correlates with the decrease in the number of cases imported from West Africa, possibly due to altered travel because of the Ebola epidemic. However, the overall trend shows that, on average additional 29 cases of malaria are reported every year since 1973, coinciding with an increasing number of international travel. Among the cases with species determination, the majority were P. falciparum , accounting for 86.6% cases from Africa, 70.9% from Central America, 20.8% from South America, and 4.8% from Asia . [8]  

Based on present predictions for climate change, researchers predict an increase in the geographical distribution of malaria and an increasingly suitable climate for malaria transmission in tropical regions. [11]  However, several other determinates factor in the epidemiology of malaria other than global warming: such as politics, economic development, urbanization, and population growth, migration changes, etc. [3] [11]  Additionally, there is an impending threat of artemisinin- and multidrug-resistant P. falciparum , particularly prevalent in Greater Mekong Subregion (GMS), causing high failure rates of artemisinin-combination therapies. [12] [3]

General Epidemiology and Risk Groups

Severe malaria occurs in patients with no or little effective immunity. In parts of the world with the stable and intense transmission of P. falciparum , severe malaria is mostly a disease of the pediatric population younger than 5 years, as specific acquired immunity develops with age (due to repeated infections), providing increased, although incomplete, protection in older children and adults. Severe malaria can, however, occur at any age in areas with low or/and unstable transmission rates and individuals with no-immunity (e.g., travelers to the endemic areas). [13]  Susceptibility to malarial infections increases during pregnancy. [14]  Pregnant women in the second trimester are at the greatest risk of infection, although the risk is somewhat affected by age and gravidity, with young primigravidae being at the highest risk at high transmission areas. [15]  Women living in areas with unstable and low malaria transmission rates are infected infrequently and therefore lack the immunity, which often causes a rapid progression to severe malaria and death. [14]

• Pathophysiology

The rupture of the first liver schizont and the release of motile merozoites into peripheral circulation to invade red blood cells marks the start of a possible symptomatic infection. The first rupture and invasion are usually silent in most infected patients, but as the asexual cycle repeats itself in the next 24 to 48 hours, parasitemia rises, and immune response increases accordingly. It is usually associated with an increase of TNF alpha and other inflammatory markers in the cascade, including interleukin 10 (IL-10) and interferon-gamma (IFN-gamma). [6]  Higher parasitemias are generally associated with a more severe clinical picture, but the relationship is very variable. [16]  

The most important virulence determinant in P. falciparum infection is the parasite´s ability to modify the surface of the infected red blood cell, thus creating an adhesive phenotype. The cytoadhesion is mediated through the P. falciparum erythrocyte membrane protein 1(PfEMP1) family, which is the product of var gene transcription. There is immense diversity in var genes in the parasite population, which has recently been a focus of research, due to its suggested association between increased transcription of specific var genes and the development of severe malaria. [6] [17]  The cytoadherence of mature-staged infected RBC to the endothelium, platelets, and uninfected red blood cells causes sequestration in the microvasculature of various organs, resulting in microcirculation obstruction, impaired tissues perfusion, lactic acidosis and consequently, end-organ damage. [18] [19] [20]  Prominent sequestration occurs in the placenta during pregnancy, causing low birth weight, anemia, miscarriage, and congenital malaria. [6] [19]

In essence, the key features that render a fatal disease are the sequestration of P. falciparum in tissues, in conjunction with the up-regulation of cytokines and other toxic substances and an absence or an untimely provision of effective antimalarial therapy. [6]

• History and Physical

Malaria is a complex disease with a spectrum of clinical effects that not only differ between children and adults but can range from practically none in patients with asymptomatic parasitemia, to uncomplicated malaria, through to severe and possibly lethal malaria. [20]  The mean incubation period for P. falciparum is 12 days, with most patients presenting in the first or second month after exposure in endemic areas. [21] [22]  It is key to take a detailed travel history in any patient with fever or history of fever, as malaria is a crucial diagnosis to consider in any individual who has traveled to a malaria-endemic area. [22] [21]

Uncomplicated P. falciparum  Malaria 

Malaria can be separated into two disease presentations: uncomplicated and severe.  [4]  The WHO defines the presence of symptoms without clinical or laboratory signs to indicate severity or vital organ dysfunction as uncomplicated malaria. [6]  Symptoms are generally non-specific, including fever, chills, myalgia, headache, anorexia, and cough, making clinical diagnosis unreliable. [4] [21]  Patients occasionally present with gastrointestinal symptoms, respiratory symptoms, and jaundice. [22]  The classical malarial paroxysms with spiking fever, chills, and rigors occurring at specific intervals are relatively uncommon, but if present, indicate an infection with P. ovale or P. vivax . [3]  Progression to severe or ultimately fatal disease is largely confined to P. falciparum infections, although only a small percentage, approximately 1% to 2% of infections, lead to severe malaria. [20] [13]  Features of a severe disease usually appear after 3 to 7 days of the abovementioned non-specific symptoms, although there are some reports of rapid deterioration, failure to recover consciousness after a grand-mal seizure, and non-immune patients dying within 24 hours of their first symptom. [13]

Severe P. falciparum  Malaria

The patient presenting with at least one of the clinical or laboratory features listed below, with asexual P. falciparum parasitemia (either detected in the peripheral blood smear or confirmed with rapid diagnostic test) and no other confirmed cause of his symptoms, classifies as suffering from severe malaria. [13] [23]  Although P. falciparum is responsible for the majority of the cases of severe malaria, it is also, albeit rarely, observed with P. vivax and P. knowlesi infections. [18] [13]

A shortened list of danger signs is used for rapid clinical assessment, which includes prostration, respiratory distress (acidotic breathing), and impaired consciousness. [4]  Other clinical manifestations of severe malaria include multiple convulsions, radiologically confirmed pulmonary edema (respiratory failure due to acute lung injury progressing to acute respiratory distress syndrome), abnormal bleeding (disseminated intravascular coagulation), acute kidney injury, jaundice, shock, and coma. [4] [21] [13]  Laboratory features in severe malaria can show severe anemia, hypoglycemia, acidosis, hyperlactatemia, renal impairment, and hyperparasitemia . [13]   A comprehensive list of diagnostic criteria for falciparum malaria is shown in Table 1 - Diagnostic criteria for severe P. falciparum malaria. [13] [18]

Physical Examination

Physical examination is usually unremarkable, especially of patients with uncomplicated malaria. They frequently present with irregular and erratic fever, reaching up to 41°C, sometimes accompanied by agitation or confusion. [3] [13]  Mild spontaneously resolving jaundice can sometimes be seen in patients with otherwise-uncomplicated falciparum malaria. [3] [22]  Other physical signs can include anemia and postural hypotension. [13]  In some cases, patients can present with tender hepatosplenomegaly after some days. However, a palpable spleen is particularly common in otherwise healthy populations in endemic areas, reflecting repeated infections. [3]  The comprehensive list of clinical features associated with severe malaria is shown in Table 1 - Diagnostic criteria for severe  P. falciparum  malaria. [13] [18]  

Children are more likely to present with non-specific and gastrointestinal symptoms such as fever, lethargy, malaise, nausea, vomiting, abdominal cramps, and somnolence. [22]  They are more likely to develop hepatomegaly, splenomegaly, and severe anemia without major organ dysfunction than adults. In a case of severe malaria, they present with more frequent seizures (in 60% to 80%), hypoglycemia, and concomitant sepsis but are less likely to develop pulmonary edema and renal failure than adults. [3] [22]  

Pregnant Women

The clinical features of infection in pregnancy vary from asymptomatic to severe, depending on the degree of (incomplete) immunity that a woman had acquired by the time she got pregnant. In semi-immune pregnant women, only a few infections result in fever or other symptoms. [15]  Malaria in pregnancy has a devastating effect not only on maternal health but has been associated with increased infant mortality due to low birth weight caused by either intrauterine growth restriction or preterm labor or both. [15]   P. falciparum infections are proven to be associated with complications such as maternal anemia, low birth weight, miscarriage, stillbirths, and congenital malaria. [6] [15]  It is more likely for a pregnant woman in the second or third trimester to develop severe malaria with complications such as hypoglycemia and pulmonary edema, compared to non-pregnant adults. [18]

Once malaria is considered a possible diagnosis, it is important to facilitate immediate laboratory testing. [4]  It is essential to distinguish between non-falciparum and falciparum malaria. [24]  As per the Centers for Disease Control and Prevention (CDC) guidelines, malaria should be routinely suspected in any febrile patient that has a recent history of travel to the endemic areas. The clinical features of either uncomplicated or severe malaria are non-specific, therefore requiring diagnosis by microscopy or rapid diagnostic test (RDT). [18]  The results should be communicated back to the requesting doctor as soon as possible, ideally within a few hours. [24]

A full blood count, urea, creatinine and electrolytes, blood glucose level, and liver function tests should be routinely performed. Thrombocytopenia suggests both non-falciparum and falciparum malaria infections in non-immune adults and children. In severely ill patients, additional studies such as blood gases, blood culture, lactate, and clotting studies are appropriate. In patients with fever and impaired consciousness, one should consider a lumbar puncture to exclude meningitis. [24]

The golden standard for diagnosis is a microscopic analysis of thick and thin blood smears. Thick smears allow for a sensitive parasitemia quantification, as parasitemias as low as 30-50/microL can be detected, while thin smears enable a determination of the Plasmodium species, prognostic assessment based on the staging of parasite development and estimation of the proportion of neutrophils containing malaria pigment. [13] [18]  Three sets of thick and thin blood films spaced 12 to 24 hours apart should be performed by experienced laboratory personnel before a clinician can confidently rule out malaria. [8]  

Perceived peripheral blood parasitemia varies greatly in patients with severe malaria, due to the sequestration of the infected red blood cells in tissues. [13] [18]  Although severe malaria can present with low parasite count, high counts are associated with increased risk of deterioration and subsequent treatment failure even without signs or symptoms of severity. [13]  More than 2% of parasitized RBC suggests an increased chance of developing severe disease, and parasitemia over 10% is considered as one of the diagnostic criteria for severe disease and is associated with increased mortality. [24]  Furthermore, in severe falciparum malaria, poor outcomes can be predicted by the presence of late-stage parasites in RBC and more than 5% of the neutrophils containing pigment. [18]  

Rapid diagnostic tests are commonly used in addition to blood slides and are useful alternatives in settings where a microscopic diagnosis is non-reliable or infeasible. [24] [9]  It is, however, recommended that all the RDTs should be followed by microscopy for confirmation and, if positive, quantification of parasitemia. [9]  They are immune-chromatographic tests that most commonly identify either malaria antigens (e.g., P. falciparum histidine-rich-protein 2 (PfHRP2)) or enzyme called Plasmodium lactate dehydrogenase (pLDH). Tests have several downfalls as they cannot provide quantitative results, can stay positive months after infection with P. falciparum, or are, if testing for pLDH, positive only while there are living parasites in the blood. [13]  

Polymerase chain reaction (PCR) is one of the possible diagnostic modalities but is, even if promptly available, too timely to use for initial diagnosis and prompt treatment of acute malaria. It should, however, be used for research and epidemiologic purposes in any malaria infection in the USA, to determine and confirm the infecting species. [8]  All cases should also be evaluated for evidence of drug resistance, as per CDC guidelines. [9]

• Treatment / Management

CDC recommends that the treatment of malaria should not be initiated until the diagnosis has been confirmed by laboratory testing. Treatment should be initiated immediately after the confirmation of malaria infection. Empirical treatment is, however, reserved only for extreme cases where there is a strong clinical suspicion with convincing exposure history, presence of severe disease, or an inability to diagnose malaria due to inadequate laboratory facilities.

The treatment should be guided by three main factors: the infecting Plasmodium species, the clinical status of the patient, and drug susceptibility of infecting Plasmodium , determined by the geographic region where the infection was acquired. Chloroquine sensitivity can be expected if the infection was acquired in Central America west of Panama Canal, Haiti, and the Dominican Republic. In a case when the diagnosis is strongly suspected, and it cannot be confirmed, or when there is no species determination possible, given the global spread of P. falciparum resistant to chloroquine, the clinician should opt for a treatment option effective against chloroquine-resistant P. falciparum . CDC recommends making additional blood smears in infections with P. falciparum after initiating the treatment, to confirm adequate parasitological response (decrease in density) to treatment.

Extended, evidence-based, and comprehensive guidelines for malaria management and optimal dosing of antimalarial medications can be found in the third edition of WHOs Guidelines for the treatment of malaria. Treatment and management algorithms for malaria in the USA are available on the CDC´s official website.

Uncomplicated Falciparum Malaria 

Uncomplicated falciparum malaria should be treated with one of the artemisinin-based combination therapies (ACT). Artemisinin-based combination therapy (ACT) is highly effective due to its effect on a broader range of parasite life cycles, causing faster parasite clearance and is therefore considered a drug of choice for uncomplicated malaria. [24]  The duration of ACT treatment is 3 days. ACTs are also recommended for pregnant women in the second and third trimester but should be used during the first trimester only if other treatment options are not available. During the first trimester, a combination of quinine and clindamycin should be prescribed. In low transmission areas, gametocytocidal therapy (e.g., primaquine) is added to ACTs to reduce transmission potential (except pregnant women, infants younger than 6 months and women breastfeeding infants younger than 6 months). [18]

There are some other treatment options, although not as effective as ACTs, such as atovaquone-proguanil, quinine sulfate plus doxycycline, tetracycline, or clindamycin, and mefloquine. For chloroquine-sensitive P. falciparum infections (including

pregnant women), the drug of choice is chloroquine. However, any of the drug choices listed above for chloroquine-resistant strains can be used. Treatment options are the same for the pediatric population, with doses adjusted by the patient’s weight. 

Severe Falciparum Malaria

All patients diagnosed or with a strong suspicion with signs and symptoms of severe malaria should be promptly treated with parenteral antimalarial therapy. Effective, urgent, and appropriate treatment has the greatest impact on prognosis. [24]  

Intravenous or intramuscular artesunate is the first-line treatment in all patients (including children, lactating women, and pregnant women in all trimesters) worldwide and should be used for at least 24 hours and until the oral medication is tolerated. [18]  Children should receive a higher dose (3 mg/kg BW per dose) of the artesunate to ensure the equivalent drug effect. The dose for larger children and adults is 2.4 mg/kg BW per dose. Three doses of intravenous artesunate should be given: one immediately, followed by a dose at 12 hours and 24 hours.   

If artesunate is not available, the recommended drug is artemether in preference to quinine. After the complete course of a 24 hour intravenous artesunate, a regimen of a follow-up drug should be completed. A full 3-day regimen of ACT is recommended. In returning traveler, the follow-on antimalarial medication needs to be other than the antimalarial medication taken for prophylaxis. [18]  

Intravenous artesunate is currently not approved by the Food and Drug Administration (FDA) or commercially available in the U.S. but is available from CDC under an expanded-access investigational drug (IND) protocol. It is prepositioned at distribution sites throughout the USA and readily available after contacting CDC. Since severe malaria can progress rapidly, CDC offers guidance on oral treatment that can be used while waiting for IV artesunate to be delivered. They recommend interim treatment with oral artemether-lumefantrine (preferably), atovaquone-proguanil, quinine sulfate, or mefloquine. If a patient can not tolerate oral medications, administration after an antiemetic or via nasogastric tube should be considered.

Patients with falciparum malaria should be admitted to the hospital due to the possibility of deterioration even after the effective treatment was initiated. If patients are determined to have uncomplicated malaria, they can be treated as outpatients after confirming that they can tolerate oral therapy, and the parasitemia has declined. [13]  Ideally, a patient with severe malaria should be admitted to an intensive-care unit or high dependency unit with close monitoring of clinical status, vital signs, consciousness level, and laboratory values. [13] [24]

It is important to provide supportive therapy, such as glucose to maintain euglycemia and acetaminophen for fever control, careful, individualized fluid management as patients present with variable degrees of hypovolemia, acidosis, and acute kidney failure. Blood transfusion is sometimes indicated in severe anemias; benzodiazepines should be used for seizure control. However, prophylactic antiepileptic medications are not recommended, and empiric antibiotics should be used in children with severe malaria and adults with concurrent shock. [4] [22] [18]

• Differential Diagnosis

Other travel-related infections such as typhoid, viral hemorrhagic fevers (such as Ebola, Lassa fever, etc.), hepatitis, dengue, and other arboviruses, enteric fever, avian influenza, tuberculosis, MERS-CoV infections, HIV, meningitis, and encephalitis can resemble malaria. Non-tropical infections such as bacterial pneumonia, septicemia, and influenza should be excluded. [24] [25]

Cerebral malaria can mimic bacterial meningitis, measles, (locally prevalent) viral encephalitis, toxic syndromes, and intracranial vascular or mechanical events. [13]

Patients with uncomplicated malaria, especially with timely diagnosis, treatment, and proper compliance, usually recover from malaria without consequences. The mortality rate for uncomplicated malaria is low, around 0.1%. [3] [6]   The mortality rate rises steeply once the patient develops signs and symptoms of severe falciparum malaria. Adults have higher mortality rates and more frequent multisystem involvement than children, with mortality rates being 18.5% and 9.7%, respectively. [20]  The two main determinants reflecting the outcome for both adults and children were found to be the level of consciousness assessed by coma scales and the degree of metabolic acidosis, assessed clinically by breathing pattern or more precisely with measurement of bicarbonate, base deficit, and plasma lactate. [13]   While the general mortality of treated severe malaria is between 10% to 20%, the mortality in pregnant women reaches approximately 50%. [18]

• Complications

A distinct complication of P. falciparum malaria is cerebral malaria (CM), a diffuse and symmetrical encephalopathy. [16]  It is a clinical syndrome defined as an impaired consciousness (clinically determined as stated in Table 1) that cannot be attributed to other causes such as convulsions, hypoglycemia, sedative drugs, or other non-malarial causes and is associated with an unequivocal diagnosis of malarial infection. Due to several other possible causes of altered consciousness, the presence of retinopathy has been used in an attempt to increase the specificity of diagnosis of CM and improve the classification of severe malaria. [13]

Other possible complications, predominantly caused by P. falciparum , include:

• Acute kidney injury complicates up to 40% of P. falciparum malaria. [18]
• Non-cardiogenic pulmonary edema, acute respiratory distress syndrome (ARDS), and hypoxia [13]
• Electrolyte and fluid abnormalities [13]
• Acid-base disturbances – mostly acidosis and hyperlactatemia [13]
• Hypoglycemia, often exacerbated by quinine therapy [4]
• Anemia, with the reduction in hemoglobin levels being proportional to disease severity and duration of illness before treatment [13] [16]
• Other hematological complications (delayed hemolytic anemia following artemisinin treatment, hyper-reactive malarial splenomegaly (HMS), and splenic rupture) [4]
• Blackwater fever and hemoglobinuria due to intravascular hemolysis in patients with severe clinical manifestations of falciparum malaria [13]
• Profound thrombocytopenia is often associated with P. falciparum infection, however, bleeding and disseminated intravascular coagulation (DIC) are rare. [13]
• Hepatic dysfunction [13]
• Shock and associated infections (such as Salmonella bacteriemia, aspiration pneumonia, nosocomial infections, etc.) [3] [13]
• Neurological sequelae (epilepsy, permanent focal deficits, etc.) [4]

The three most common complications occurring in children are cerebral malaria, severe anemia, and acidosis, either isolated or overlapping. [20]

• Deterrence and Patient Education

Although no intervention for preventing the infection is 100% effective, there are several different approaches available that can be used alone or in combination. Personal protective measures reduce the risk of exposure to infective mosquitoes, and chemoprophylaxis can aid in reducing the risk of a poor outcome if infected. [26]   A common approach usually applied is an “ABCD” of malaria – A standing for awareness of the risk, B for bite avoidance, C for compliance with chemoprophylaxis, and D for diagnosis in case of fever. It is essential to consider traveler´s health (especially pregnancy, age, immunosuppression) when assessing the risk for developing severe malaria and choosing an appropriate antimalarial drug. [10]

It is necessary to emphasize the importance of personal protective measures such as barrier clothing, insecticide-impregnated bed nets, application of effective mosquito repellent (higher percentage of active ingredient provides longer protection), and spraying the residence with insecticide. Products that contain 20%-40% of DEET (N, N-Diethyl-meta-toluamide), picaridin, oil of lemon eucalyptus or PMD (p-menthane-3,8-diol) and IR3535 are recommended. Behaviors to minimize exposure to mosquitos are also encouraged – for instance, staying indoors from dusk till dawn, choosing screened accommodations. [9] [26]  Indoor residual spraying and long-lasting insecticidal nets remain to be the most effective tools for malaria control and elimination, despite the emergence of insecticide-resistant Anopheles mosquitos. [27] [28]

A standard recommendation for all travelers to endemic areas is strict compliance with the antimalarial drug. There are several different drug choices, prescribed after assessing individual´s risk (level of local transmission, duration of exposure, rural vs. urban travel, type of travel and season), travelers health status, present contraindications, level of parasite drug resistance (mostly chloroquine and mefloquine resistance) and traveler’s preference based on schedule, cost and nature of possible side effects . There is an increasing problem with counterfeit and substandard medications being sold in several Sub-Saharan countries, and travelers should be advised to buy the needed medications before departure. [29] [10]   A complete list of recommendations for drug choice can be found on the CDCs website – Malaria Information by Country.

As pregnant women are at increased risk for severe malaria, the WHO and other organizations recommend not traveling to the endemic areas. [10]

Travelers to the endemic areas, former residents of malaria-endemic areas and people diagnosed with malaria should be informed, as per Food and Drug Administration (FDA) recommendations, that they may not donate blood for 1 year after travel or 3 years after departing or revisiting the country or for 3 years after treatment, respectively. [9]

Travelers should be informed that malaria can be fatal with delayed treatment, and one should, therefore, seek medical attention while abroad if symptoms of malaria develop and not fly back for treatment, as medical treatment may not be readily available on transit . [9]

• Pearls and Other Issues

Malaria vaccine would be an ideal tool to control, prevent, eliminate, and ultimately eradicate the disease. The complexity of P. falciparum infection has hindered several attempts at developing an effective vaccine, yet the acquisition of partial immunity and successful treatment of malaria with purified immunoglobulins from semi-immune adults showed that the development of a vaccine is attainable. Researchers have identified several potential targets in the parasite´s infectious cycle. Currently, 20 vaccine candidates are undergoing clinical trials. [27]   The most promising and most advanced vaccine to be developed so far is a licensed RTS, S subunit vaccine (RTS, S/ASO1), targeting the pre-erythrocytic stage of infection, thus preventing hepatocyte infection and parasite development, consequently limiting RBC invasion. It consists of a recombinant protein of the P. falciparum circumsporozoite protein (CSP) conjugated to the hepatitis B surface antigen. [27]  RTS, S/ASO1, the first malaria vaccine which has received regulatory approval for human use, was used to start the first routine malaria vaccination program in Africa – a pilot study in Malawi in April 2019, which has since expanded to Kenya and Ghana. The pilot study is planned to last about 50 months and to enroll 720 000 children in vaccination and control clusters, however several safety concerns, that are now being investigated in the pilot study, have already been identified in phase III trials:  higher risk of meningitis, cerebral malaria and doubled female mortality. If no serious safety concern is determined in the first 24 months of trial, the pilot study will run its full course before any decision will be made about its broader use in endemic countries. [30]

There has been an emergence of a (widely used) pyrethroid insecticide-resistant malaria vector population, causing extensive research with their first results suggesting a better effect of long-lasting insecticidal nets treated with PBO (piperonyl butoxide) instead of pyrethroid laced nets. [28]

• Enhancing Healthcare Team Outcomes

Most cases of malaria in the U.S. are imported and could, therefore, be avoided with appropriate personal protective measures and compliance with prescribed chemoprophylaxis. Health care providers on all levels must be educated not only on the diagnosis and treatment of malaria but especially on the importance of prevention. They should be able to provide enough information to travelers at risk. Travelers to the endemic areas should obtain appropriate clothing, insecticides, and other protective gear based on the information offered by health care providers and CDC. Collaboratively, a physician and a pharmacist, should decide on, recommend and prescribe appropriate chemoprophylaxis, considering traveler's personal preferences, time of travel, current health status, risk factors, drug-drug interactions, and possible contraindications, while emphasizing the importance of compliance with the drug-taking regimen. 

The crucial issue in the diagnosis and treatment of malaria is the consideration of the possibility of diagnosis. Expert advice from an infectious disease or travel medicine specialist should be sought once malaria is a suspected diagnosis, especially in the setting of severe disease. [24]  The execution of a microscopic analysis of a stained blood smear often depends on several factors such as laboratory equipment, quality of reagents, and laboratorian expertise. Laboratorians should, therefore, be trained in the preparation and analysis of blood-smears to diagnose a malarial infection correctly. The results need to be communicated back to the physician as soon as possible. All laboratory-confirmed cases of malaria should be reported to CDC to help with their surveillance efforts.   Healthcare providers that are a part of the interprofessional team (nurses, respiratory therapists, physicians, etc.) managing patients with severe malaria in critical or intensive care units, should be educated on early recognition of complications.

• Review Questions
• Access free multiple choice questions on this topic.
• Comment on this article.

Life Cycle of the Malaria Parasite Contributed by Wikimedia Commons, National Institutes of Health (NIH) (Public Domain)

Mosquito carried diseases, Zika virus, Dengue fever, West Nile Fever, Chikungunya, Yellow Fever, Malaria Contributed by National Institutes of Health (NIH)

Blood smear malaria Image courtesy S Bhimji MD

Diagnostic criteria for severe P. falciparum malaria Contributed by Lara Zekar, MD

Rings of P. falciparum in a thin blood smear. Contributed by the Center for Disease Control and Prevention (CDC)

Disclosure: Lara Zekar declares no relevant financial relationships with ineligible companies.

Disclosure: Tariq Sharman declares no relevant financial relationships with ineligible companies.

This book is distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ), which permits others to distribute the work, provided that the article is not altered or used commercially. You are not required to obtain permission to distribute this article, provided that you credit the author and journal.

• Cite this Page Zekar L, Sharman T. Plasmodium falciparum Malaria. [Updated 2023 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-.

In this Page

Bulk download.

• Bulk download StatPearls data from FTP

Related information

• PMC PubMed Central citations
• PubMed Links to PubMed

Similar articles in PubMed

• Malaria Surveillance - United States, 2017. [MMWR Surveill Summ. 2021] Malaria Surveillance - United States, 2017. Mace KE, Lucchi NW, Tan KR. MMWR Surveill Summ. 2021 Mar 19; 70(2):1-35. Epub 2021 Mar 19.
• Malaria Surveillance - United States, 2015. [MMWR Surveill Summ. 2018] Malaria Surveillance - United States, 2015. Mace KE, Arguin PM, Tan KR. MMWR Surveill Summ. 2018 May 4; 67(7):1-28. Epub 2018 May 4.
• Malaria Surveillance - United States, 2018. [MMWR Surveill Summ. 2022] Malaria Surveillance - United States, 2018. Mace KE, Lucchi NW, Tan KR. MMWR Surveill Summ. 2022 Sep 2; 71(8):1-35. Epub 2022 Sep 2.
• Review Malaria. [Clin Lab Med. 2010] Review Malaria. Garcia LS. Clin Lab Med. 2010 Mar; 30(1):93-129.
• Review Malaria vaccine can prevent millions of deaths in the world. [Hum Vaccin Immunother. 2013] Review Malaria vaccine can prevent millions of deaths in the world. Verma R, Khanna P, Chawla S. Hum Vaccin Immunother. 2013 Jun; 9(6):1268-71. Epub 2013 Feb 12.

Recent Activity

• Plasmodium falciparum Malaria - StatPearls Plasmodium falciparum Malaria - StatPearls

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

Connect with NLM

National Library of Medicine 8600 Rockville Pike Bethesda, MD 20894

Web Policies FOIA HHS Vulnerability Disclosure

Help Accessibility Careers

• Open access
• Published: 17 January 2023

Impact of insecticide resistance on malaria vector competence: a literature review

• Pierre Fongho Suh 1 , 2 ,
• Emmanuel Elanga-Ndille 3 ,
• Magellan Tchouakui 3 ,
• Maurice Marcel Sandeu 3 , 4 ,
• Darus Tagne 1 , 5 ,
• Charles Wondji 1 , 6 &
• Cyrille Ndo 1 , 7  

Malaria Journal volume  22 , Article number:  19 ( 2023 ) Cite this article

6056 Accesses

10 Citations

11 Altmetric

Metrics details

Since its first report in Anopheles mosquitoes in 1950s, insecticide resistance has spread very fast to most sub-Saharan African malaria-endemic countries, where it is predicted to seriously jeopardize the success of vector control efforts, leading to rebound of disease cases. Supported mainly by four mechanisms (metabolic resistance, target site resistance, cuticular resistance, and behavioural resistance), this phenomenon is associated with intrinsic changes in the resistant insect vectors that could influence development of invading Plasmodium parasites. A literature review was undertaken using Pubmed database to collect articles evaluating directly or indiretly the impact of insecticide resistance and the associated mechanisms on key determinants of malaria vector competence including sialome composition, anti- Plasmodium immunity, intestinal commensal microbiota, and mosquito longevity. Globally, the evidence gathered is contradictory even though the insecticide resistant vectors seem to be more permissive to Plasmodium infections. The actual body of knowledge on key factors to vectorial competence, such as the immunity and microbiota communities of the insecticide resistant vector is still very insufficient to definitively infer on the epidemiological importance of these vectors against the susceptible counterparts. More studies are needed to fill important knowledge gaps that could help predicting malaria epidemiology in a context where the selection and spread of insecticide resistant vectors is ongoing.

Malaria is the biggest killer among vector-borne diseases [ 1 ] and has claimed the lives of milllions of people over centuries [ 2 ]. In 2020, 241 million cases were reported leading to 627,000 deaths. The African region has paid the highest tributes with 96% of all deaths [ 3 ]. Malaria disease is caused by Plasmodium parasites, which are transmitted to humans by the bites of infected female mosquitoes of the genus Anopheles [ 4 ]. In Africa, Plasmodium falciparum is the most epidemiologically important of malaria parasites infecting humans [ 5 ], and Anopheles gambiae , Anopheles coluzzii , Anopheles funestus and Anopheles arabiensis are the dominant vector species [ 6 ].

Malaria control includes medical treatment of cases and protective measures against the vectors to prevent and/or limit contacts with human hosts during which transmission occurs. The control of mosquito populations on a large scale using insecticide-treated nets (ITNs) and indoor residual spraying, associated with increase case management, has led to a remarkable reduction in malaria burden from 81.1 cases per 1000 population in 2000 to 58.9 in 2015 [ 3 ]. After this period, the impact of control efforts on malaria burden have dwindled, coinciding with the spread of insecticide resistant vectors across most endemic countries [ 3 , 7 ]. Resistance of Anopheles mosquitoes to insecticides, reported for the first time in Africa in the 1950s [ 7 ], concerns four main classes of insecticides used in public health for vector control purposes, namely pyrethroids, organochlorines, organophosphates and carbamates [ 7 , 8 ]. There are four mechanisms deployed by mosquitoes to become insensitive to the insecticides, including by order of importance (1) degradation of insecticide molecules by detoxification enzymes (metabolic resistance), (2) modification of the target affinity of the insecticide (target site resistance), (3) reduced penetration of the insecticide (cuticular resistance) and, (4) avoidance of insecticide-treated surfaces (behavioural resistance). Of these four mechanisms target site and metabolic resistances are most likely to lead to control failure [ 9 ].

In target site resistance, a change (leucine changed to a phenylalanine or a serine at position 1014) occurring in the amino acid sequence of the voltage gate sodium channel (vgsc) leads to a reduced sensitivity of mosquitoes to pyrethroids and organochlorines. This phenotype is known as knock down resistance or kdr [ 10 , 11 ]. When the amino acid change (glycine replaced by serine at position 119) occurs in the neurotransmitter acetyl-cholinesterase, it occasions resistance to organophosphates and carbamates, termed ace-1 resistance [ 12 , 13 ]. About metabolic resistance, insecticide resistant mosquitoes increase the expression of detoxification enzymes, such as the cytochrome P450 monooxygenases, glutathione S-transferases (GSTs) and esterases, that eliminates xenobiotic compounds (including insecticides) before they reach their target. In another instance, an amino acid substitutions in the sequence of detoxification enzymes could modifiy its affinity with the insecticides in insect vectors [ 14 ]. For example, several cytochrome P450 genes ( CYP6P9a , CYP6P9b and CYP6M7 ) are involved in resistance to pyrethroids in the species An. funestus [ 15 , 16 ]; while a substitution of leucine by phenylalanine at position 119 in the epsilon class of GST ( GST2 - L119F) confers a cross-resistance to dichloro-diphenyl-trichloroethane (DDT) and pyrethroids in the same vector species [ 17 ].

Despite the widespread distribution of insecticide resistance, its impact on overall malaria epidemiology remains unclear and is currently a subject of intense debate. The evaluation of the potential impact of insecticide resistance on vectorial competence is therefore becoming an important and urgent research theme whose findings will help understanding whether it alters or enhances the permissiveness of malaria vectors to Plasmodium parasites, from its early stage (ookinete) to the infective form (sporozoite). In this review, the evidence of insecticide resistance impact on the infectivity of mosquitoes to Plasmodium was explored in the literature, and changes in intrinsic factors that could predict or explain the outcome of an infectious blood meal intake were broached. Finally, the knowledge gaps were pointed out.

Search strategy

A literature search was undertaken in the PubMed database to extract articles addressing the following themes: (1) Plasmodium infection in insecticide resistant malaria vectors, (2) sialome of insecticide resistant malaria vectors, (3) effect of insecticide resistance on the immunity of malaria vectors, (4) microbiota of insecticide resistant malaria vectors and infection, and (5) fitness cost of insecticide resistance in malaria vectors. The first search terms were “ Anopheles ” and “insecticide resistance” and they were associated with either “ Plasmodium infection”, “vector competence”, “salivary gland”, “sialome”, “microbiota”, “gene expression” or “longevity”. Additional articles were extracted from the references lists of the full publications. The search was done between February and August 2022 and there was no restriction regarding the date of publication of the articles. A total of 560 articles were obtained from the search. Articles that addressed insecticide resistance in Anopheles in a broad manner, and not in relation with either Plamodium infection, vector competence, sialome, or longevity were discarded. Therefore, 28 articles related to the themes mentioned above were selected and used for the review.

Malaria vector competence

Vector competence is the intrinsic ability of anopheline species or populations to allow the development of Plasmodium parasites from ookinete to infective sporozoites. When a mosquito takes an infectious blood meal from human, the gametocytes ingested begin their development in the midgut. The male gametocyte transform into eight microgametes after three rounds of mitosis, meanwhile the female gametocytes matures into macrogametes [ 4 ]. These cells fuse to form zygotes that thereafter change into ookinetes in the lumen of the intestine. The ookinetes then strive through the epithelium of the midgut and once in its basal side, transform into oocysts. The oocysts undergo several rounds of asexual multiplication (sporogony) leading to the production of thousands of haploid sporozoites in each oocyst. Mature occysts rupture and release sporozoites in the hemocoel, which immediately migrate to the salivary glands. The extrinsic incubation period of the parasite is about 14 days with the transition from ookinetes to mature oocysts having the highest duration (about 10 days) [ 18 , 19 ].

In mosquito host, Plasmodium face several immune-related bottlenecks deployed to prevent the successful transition from its early stage in the midgut to the sporozoite stage in the salivary glands [ 18 ]. The outcome of the parasite infection is reported to depend mainly on the mosquito- Plasmodium genetics adaptation [ 19 , 20 ]. Another very important factor that influences the above outcome is the compatibility of the duration of parasite development with the longevity of the mosquitoes [ 21 , 22 ]. Only species in which Plasmodium reaches infective form are referred to as competent vectors and could ensure malaria transmission. The impact of vector competence on the transmission of malaria can be estimated using Ro (Fig.  1 ), the basic reproductive number developed by McDonald in 1957. The McDonald model gives the threshold for a disease to persist or spread (Ro greater than 1) or to disappear (Ro less than 1) [ 23 ]. The Ro represents the number of individuals in a susceptible human population that are expected to get infected via a mosquito bite when a single infected individual is present in the population [ 24 , 25 ]. In the Ro equation, two parameters are related to vector competence: probability of mosquito infection (b) and mosquito longevity (p) (Fig.  1 ). Modifications of the values of components of this equation for a given vector population will cause either an augmentation or reduction in the transmission dynamics of the disease, leading probably to a change in the epidemiological profile of the locality concerned. It was established that an increase in b will increase the Ro, whereas a decrease in p will cause the opposite [ 26 ].

Basic reporductive number (Ro), Ross-MacDonald model. In bold, parameters of the vectorial competence influenced by insecticide resistance

Insecticide resistance and malaria vector infectivity to Plasmodium parasite

The rapid spread of insecticide resistance among malaria vectors accross endemic countries in the past decade have raised several questions among which that of knowing what is its impact on mosquito permissiveness to Plasmodium ? Only a limited number of studies have tried to elucidate this question [ 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. These studies compared P. falciparum infection rates in resistant Anopheline vectors with susceptible ones, either caught in the field or experimentally infected (Table 1 ).

Anopheles gambiae strain bearing kdr resistance allele ( Vgsc - L 1014S) was found naturally more infected by sporozoites than the susceptible counterpart [ 27 ]. Similar findings were experimentally observed in the same species, as well as in Anopheles coluzzii [ 30 , 32 ]. Contrary to kdr resistance, An. gambiae with ace-1 resistance allele did not differ from individuals that have the wild type allele (not conferring insecticide resistance) on infection rate despite significantly higher oocyst prevalences were observed in the resistant strain [ 32 ]. More studies using field populations are needed to ascertain whether a lower longevity suspected by the author and/or other factors are involved.

Regarding metabolic resistance, recent breakthroughs in designing simple PCR-based assays to detect glutathione S-transferase (GST)-based and cytochrome P450-mediated resistance in An. funestus sensu stricto provided a unique opportunity to assess its impact on the mosquito’s ability to develop the parasites. The L119F- GSTe2 resistant genotypes of this species showed, in an experimental infection study, higher permissiveness to oocyst infections than susceptible ones [ 31 ]. Similarly, in naturally infected populations of the same species, homozygote L119F- GSTe2 genotypes were found more infected by sporozoites though no significant difference was found at the level of oocyst prevalence [ 28 ]. In other hands, Lo and Coetzee [ 36 ], infecting experimentally two selected sub-colonies of FUMOZ displaying different degree of pyrethroid resistance by Plasmodium berghei , found that the insecticide resistant colonies were less permissive to infection than the susceptible ones. No investigation has so far explored the relationship between P450s genes implicated in insecticide resistance and P. falciparum infection in An. funestus . Moreover, because of the absence of markers of metabolic resistance in An. gambiae sensu lato such studies are still lacking in these species.

Impact of insecticide resistance on mosquito sialome

Bloodsucking arthropods, like mosquitoes, have evolved saliva containing a mixture of pharmacologically active molecules that help them counteract the hemostatis and inflammatory responses of the vertebrate host during bites, thus facilitating blood meal intake [ 37 ]. However, the activity of these molecules goes beyond the scope of ensuring blood meal success, as they possibly influence the completion of Plasmodium development in the salivary gland of malaria vectors. Proteins secreted by the salivary gland belong to several families (D7, mucin, gSG1, gSG2, gSG6 peptide, gSG7, cE5, 8.2-kDa, 6.2-kDa, etc.) [ 38 ] whose function include (1) cytoskeletal and structural activities (2) digestion, (3) circadian rythm and chemosensory, (3) immunity, (4) metabolism and other [ 39 ]. The development of insecticide resistance in malaria vectors is accompanied by physiological changes [ 26 ] that may affect the sialome composition with consequences on the vector competence. Few studies have investigated changes in the sialome in the insecticide resistant vectors [ 40 , 41 ].

The secretory protein 100 kDa, which is encoded by Saglin (a cytoskeletal and structural gene present in An. gambiae salivary gland) was considered as the binding target of P. falciparum and P. berghei on salivary gland prior to penetration into the latter [ 42 ]. This protein was found down-regulated in ace-1 bearing An. gambiae strain, suggesting an impact on the vector infectivity to Plasmodium [ 43 ]. However, a recent study showed that the 100 kDa Protein is unevenly distributed on the salivary glands lobes. Its absence on the primary site of sporozoites occupancy in the salivary glands, the distal lateral lobes, implies that this protein may instead have a secondary role in the infection of the organ [ 44 , 45 , 46 ].

The D7 salivary family has been identified in malaria vectors among the most expressed proteins involved in the antihemostatic activity and probably in digestion of blood meal [ 47 , 48 , 49 , 50 ]. Elanga et al. [ 40 ] showed that two short forms of the D7 family genes ( D7r3 and D7r4 ) are over-expressed in pyrethroid resistant An. funestus ( L119F - GSTe2 ), whereas almost all D7 genes are under-expressed in pyrethroid resistant An. gambiae ( kdr , L1014F ). A comparable observation was made in insecticide resistant Culex quinquefasciatus ( ace-1 resistance) [ 51 ] as well as in two strains of Aedes aegypti (homozygotes resistant C1534 and G1016 kdr ) [ 52 ]. These findings show that insecticide resistance mechanism may affect the sialome composition differently.

Several immune proteins such as the anti-microbial peptides cecropin and defensin were found in the saliva of mosquitoes [ 39 , 53 ]. These immune proteins underscore the role of the salivary gland in the refractoriness of the Anopheles to infections [ 39 , 53 ]. The small number of studies that evaluated the impact of insecticide resistance alleles on salivary gland gene expression in mosquito vectors have not reported significant changes related to immune genes as compared with the susceptible counterparts [ 41 , 43 , 51 , 52 ], alluding that the resistant status to insecticide does not influence noticeably the immune component of the sialome. If these factors are indeed unchanged regardless of the mosquito allelic composition, nothing is known whether under infection the expression profile of these immune proteins will vary or not according to the mosquito genotype. Das et al. [ 39 ] and Djegbe et al. [ 51 ] demonstrated that salivary gland genes expression is influenced by blood meal intake and varies towards the period coinciding with the maturation of Plasmodium parasites in mosquitoes [ 54 ]. This evidence was not previously studied and should be taken into account in subsequent research works that aims at identifying differentially expressed genes of the salivary gland and elucidating their impact on the malaria vector competence.

Impact of insecticide resistance on vector immunity

When the infectious blood meal reaches the midgut of the female Anopheles , the immune system is deployed to prevent infections [ 20 ]. In the midgut, P. falciparum faces the peritrophic membrane, a physical barrier developed to prevent infections. It also protects against the damaging effects of the human blood factors like antibodies and regulates several digestive enzymes [ 55 , 56 ]. Enzymes such as trypsin 1 and 2, chymotrypsin, carboxypeptidase, aminopeptidase and serine protease are upregulated during digestion to cleave the large content of proteins in the blood meal [ 57 , 58 , 59 , 60 ]. These proteases are apparently involved in the elimination of Plasmodium infections [ 61 ]. Three studies attempted to elucidate the effect of insecticide resistance on vectors’ immunity [ 62 , 63 , 64 ]. Mitri et al. [ 62 ], in a study evaluating genes implicated in the infectivity of An. coluzzii , demonstrated that the kdr -bearing para gene which carries mutations of the voltage-gate sodium channel (confering insecticide resistance) is not associated with infection but rather the ClipC9 gene directing the synthesis of Serine protease. This suggest that the effect of the resistant character on refractoriness to infection may be due to genes other than that involved in resistance to insecticides, and which happen to be linked to it. The Serine protease plays an important role in the activation of the three major immune signaling pathways in mosquitoes: Toll, Imd and JAK/STAT [ 20 ], which cause the release of antimicrobial peptides (AMPs) notably defensins, cecropins, attacin, gambicin and AgSTAT-A, effective against malaria parasites infections. Vontas et al. [ 63 ], using pyrethroid and organochlorine resistant An. gambiae strains, showed that defensin and cecropin are upregulated after pre-exposure to permethrin. This study sugggests that insecticide resistant mosquitoes may be better equipped than susceptible ones to combat infections, but these two immune effectors alone may not be decisive in rendering the vector completely refractory to malaria infections as many other pathways activated concomitantly during parasitic invasion are altogether implicated in the outcome of a contamination [ 20 ].

In Culex pipiens which is vector of many pathogens including arboviruses [ 65 ], filarial worms [ 66 ], and protozoa [ 67 ], immune response was stimulated in an insecticide resistant field strain by injection of Lipopolysacharide (LPS) immune elicitor. As result, no difference was found in the expression of defensin and cecropin as compared to the control group; but only an increase in gambicin was recorded [ 68 ]. One point can be drawn from these results to infer what might happen in malaria vectors: Plasmodium infections may trigger the overexpresion of some immune factors while the other may have their expression either down regulated or unchanged.

The reactive oxygen species (ROS) produced by cellular metabolism are another class of effectors of the innate immunity that can negatively affect malaria parasites [ 69 , 70 ]. They kill the parasites through both lytic and melanization pathways [ 20 ]. Ingaham et al. [ 64 ] showed that An. coluzzii VK7 colony displaying kdr resistance mechanism, CYP6M6 and CYP6P3 metabolisers, had oxidoreductase overexpressed after sub-lethal exposure to deltamethrin, suggesting that this species could be more refractory to Plasmodium infection. At this point, it is necessary to verify whether under natural conditions, insecticide-resistant Anopheles mosquitoes will display an overexpression of ROS or not.

Cellular immune responses are carried out by varous type of hemocytes that eliminate pathogens by phagocytosis, lysis and melanization [ 20 ]. Organochlorines and organophosphate were found to affect differently the hemocytes abundance including granulocytes in the insect Rhynocoris kumarii  [ 71 ]. In mosquitoes, studies are needed to ascertain the impact of insecticide resistance on cellular immunity and the resulting effect on the infectivity of resistant vector to malaria parasite. Regarding melanization of pathogens, it is lead by the phenoloxidase (PO) produced by Oenocytoids [ 72 , 73 ] and is regulated by serine protease inhibitors. In field-caught C. pipiens resistant to insecticide through an increase in detoxification (esterase) and target site mutation (ace-1), PO expression was equal to that of susceptible group [ 74 ], suggesting that some genes associated with immunity might not be affected by insecticide resistance character in mosquitoes. No studies have verified the effect of insecticide resistance on PO in malaria vectors.

Impact of insecticide resistance on commensal intestinal microbiota of malaria vectors

Bacteria, fungi and viruses colonize the gut, salivary glands and reproductive organs of the mosquitoes. These microorganisms are mainly acquired from the environnement and its composition is largely influenced by its aquatic breeding sites [ 75 , 76 ]. In addition, the microbiota composition is highly dynamic, varying greatly with localities and seasons [ 77 , 78 , 79 ]. These variations of microbiota composition within field mosquitoes may partly explain the variability in infection levels in the field [ 80 ].

Mosquito microbiota has great potential for impeding the transmission of malaria by altering vectorial capacity [ 81 ]. Also, the microbiota is capable of influencing the biology of the host such as altering its immunity, nutrition, digestion, vectorial competence, reproduction, and insecticide resistance [ 82 , 83 , 84 , 85 , 86 , 87 ]. With the growing concerns about the rapid spread of insecticide resistance in Anopheles mosquitoes, some studies have explored the functions of the mosquito's gut microbial communities in the development of resistance. For example, distinct microbita populations were found associated with organochlorine resistance in An. arabiensis [ 86 ] and Anopheles albimanus [ 88 ]. Similarly, an association between specific microbiota and intense pyrethroid resistance was reported in An. gambiae [ 89 ] and Anopheles stephensi [ 90 ], suggesting a microbiota-mediated insecticide resistance mechanism. Dieme et al. [ 91 ] suggested that changes in the feeding behaviour of insecticide resistant vectors may lead to higher microbial diversity. This diversity could modify the repertoire of protective bacteria against pathogen infections and/or that of their enhancers, with consequences on the vectorial competence [ 9 , 92 ]. Recently, Bassene et al. [ 93 ] showed that, in the species An. gambiae and An. funestus , the microbiota was signifanctly different between P. falciparum -infected and non-infected samples, although the resistance status of these mosquitoes was not evaluated. More refined studies are needed to characterize the microbial communities harboured by the insecticide resistant malaria vectors. Also the contribution of microbiota against other factors to the vectorial competence of insecticide resistant malaria vectors remains to be investigated.

Impact of insecticide resistance on the longevity of malaria vectors

Mosquito longevity is a determinant factor for parasite maturation and could influences malaria transmission [ 94 , 95 ]. In fact, the extrinsic incubation of Plasmodium in its hematophageous host is about 11–14 days. Therefore, only mosquitoes whose lifespan is long enough could allow the complete development of the malaria parasite to the sporozoite infective stage and participate in the transmission of the disease. With the emergence and spread of insecticide resistance [ 7 ], many investigations were undertaken to gain knowledge of the effect of this phenomenon on the vectors’ longevity and so on its potential epidemiological impact.

So far, studies on the impact of insecticide resistance on malaria vectors longevity have focused on four species: An. gambiae, An. arabiensis, An. coluzzii and An. funestus . Globally, the findings revealed a pleitropic effect of insecticide resistance on mosquito lifespan [ 33 , 96 , 97 , 98 , 99 , 100 , 101 , 102 , 103 , 104 , 105 , 106 , 107 , 108 ] (Table 2 ). The majority of studies (10/14) which used laboratory strains showed that pyrethroid resistant An. funestus and An. gambiae live longer than susceptible ones [ 100 , 106 ]. Of the studies including field strains, a longer life span was reported in organochlorine and pyrethroid resistant An. funestus strains [ 104 , 105 ]. In contrast, a shorter life span was observed in An. gambiae strain resistant to organochlorine. It was reported that pre-exposure to insecticide in a manner micmicing field exposure to insecticides, affects the longevity of insecticide resistant An. gambiae strain [ 97 ], and that delayed mortality observed in the vectors may be dependent on resistance intensity [ 98 ]. This later observation indicates that findings obtained with laboratory colonies are to be taken with caution given that they may not reflect exactly what is oberved on the field [ 26 ]. Nevertheless, such studies remain important as they contribute to the understanding of the potential mechanisms affecting the vectors’ longevity [ 109 , 110 ], notably resource-based trade-off and oxidative stress.

Resource based trade-off is an evolutionary ecology concept that states that when environmental constraints lead to the augmentation of resources to one biological trait, other traits will have their energy budget reduced [ 111 ]. Accordingly, when mosquitoes adopt the detoxification mechanism to prevent the effect of insecticide, an increased production of detoxifying enzymes follows and is maintained by the additional resources deployed for the function. Otali et al. [ 100 ] have demonstrated that metabolism and longevity of insecticide resistant An. gambiae are lower than that of the susceptible strain. Moreover, they showed that the resistant strain has higher Reactive Oxygen Species (ROS), which are factors determining oxydative stress. In fact, the ROS are multifunctional molecules produced by cells of all organisms during normal metabolism [ 112 , 113 ]. They have been pointed out as key aging factor in other organisms including Anopheles [ 114 ]. Therefore, mosquitoes that develop the capacity to cope with oxydative stress are likely to live longer. Oliver and Brooke [ 103 ] in an experiment evaluating the effect of oxidative stress on the longevity of both An. arabiensis and An. funestus bearing respectively kdr and Cytochrome P450 mechanisms demonstrated that these species live longer, and that Cytochrome P450 activity seems more protective against oxydative stress.

Rivero et al. [ 26 ] proposed the potential effect of different detoxifying enzymes on vector longevity. For example, Glutathion S-Transferase is considered to protect against oxydative stress. Confirming this point, a longer lifespan implicating Glutathion S-Tranferase in An. funestus was revealed with and without exposure to insecticide [ 104 , 105 ]. In contrast, monoxygenase, known to be associated with an increase in oxydative stress has not led, as expected, to reduced longevity in An. funestus [ 108 ]. More studies using field populations and micmicing field conditions are necessary to ascertain the full impact of insecticide resistance on longevity of the malaria vector.

The need for a comprehensive understanding of the impact of insecticide resistance on malaria vector competence is unquestionable. The current state of knowledge is not only insufficient but also contradictory to draw a definitive conclusion. A tendency nevertheless emerges from findings that insecticide resistance may increases the infectivity of malaria vectors to Plasmodium , thus their vector competence. This is possibly due to changes in the expression of some genes notably those involved in blood-feeding and the immunity. Additionally, microbiota communities vary in the resistant mosquitoes as compared to the susceptible counterparts. The actual effect of these changes in the course of infection and their impact on the infectivity of malaria vectors to P. falciparum is still to be investigated. Finally, the longevity of the vectors is not always affected by insecticide resistance mechanisms. It is worth noting that, studies using vectors displaying metabolic resistance were under-represented because molecular markers to diagnose this character were developped only recently, especially in An. funestus . Malaria vectors that bear metabolic resistant mechanism are, on an ecological immunology point of view, expected to have a number of biological functions impaired, including immunity. If established, this situation may cause them to become less refractory to Plasmodium infection. Taking advantage of recent advances in the genomics, transcriptomics and molecular characterization of insecticide resistance, more refined studies can now be undertaken to fill knowledge gaps regarding the effect of insectide resistance on key determinants of vectorial competence and subsequently predict changes in the epidemiology of malaria in a context of insecticide resistance escalation.

Availability of data and materials

Not applicable.

Abbreviations

Dichloro-diphenyl-trichloroethane

Glutathione S-transferases

Knock down resistance

Lipopolysacharide

Phenoloxidase

Voltage gate sodium channel

WHO. A global brief on vector-borne diseases. Geneva, World Health Organization; 2014.

Gelband H, Panosian CB, Arrow KJ. Saving lives, buying time: economics of malaria drugs in an age of resistance. 2004.

WHO. World malaria report 2021. Geneva, World Health Organization; 2021.

Phillips M, Burrows J, Manyando C. Malaria. Nat Rev Dis Primers. 2017;3:17050.

Article   Google Scholar  

Cox FE. History of the discovery of the malaria parasites and their vectors. Parasit Vectors. 2010;3:5.

Sinka ME, Bangs MJ, Manguin S, Rubio-Palis Y, Chareonviriyaphap T, Coetzee M, et al. A global map of dominant malaria vectors. Parasit Vectors. 2012;5:69.

Riveron JM, Tchouakui M, Mugenzi L, Menze BD, Chiang M-C, Wondji CS. Insecticide resistance in malaria vectors: an update at a global scale. In Towards malaria elimination-a leap forward. IntechOpen; 2018.

Elliott R, Ramakrishna V. Insecticide resistance in Anopheles gambiae Giles. Nature. 1956;177:532–3.

Article   CAS   Google Scholar  

Sheldon BC, Verhulst S. Ecological immunology: costly parasite defences and trade-offs in evolutionary ecology. Trends Ecol Evol. 1996;11:317–21.

Barnes KG, Weedall GD, Ndula M, Irving H, Mzihalowa T, Hemingway J, et al. Genomic footprints of selective sweeps from metabolic resistance to pyrethroids in African malaria vectors are driven by scale up of insecticide-based vector control. PLoS Genet. 2017;13: e1006539.

Donnelly MJ, Corbel V, Weetman D, Wilding CS, Williamson MS, Black WC. Does kdr genotype predict insecticide-resistance phenotype in mosquitoes? Trends Parasitol. 2009;25:213–9.

Weill M, Lutfalla G, Mogensen K, Chandre F, Berthomieu A, Berticat C, et al. Insecticide resistance in mosquito vectors. Nature. 2003;423:136–7.

Djogbénou L, Labbé P, Chandre F, Pasteur N, Weill M. Ace-1 duplication in Anopheles gambiae : a challenge for malaria control. Malar J. 2009;8:70.

Hemingway J, Hawkes NJ, McCarroll L, Ranson H. The molecular basis of insecticide resistance in mosquitoes. Insect Biochem Mol Biol. 2004;34:653–65.

Riveron JM, Irving H, Ndula M, Barnes KG, Ibrahim SS, Paine MJ, et al. Directionally selected cytochrome P450 alleles are driving the spread of pyrethroid resistance in the major malaria vector Anopheles funestus . Proc Natl Acad Sci USA. 2013;110:252–7.

Riveron JM, Ibrahim SS, Chanda E, Mzilahowa T, Cuamba N, Irving H, et al. The highly polymorphic CYP6M7 cytochrome P450 gene partners with the directionally selected CYP6P9a and CYP6P9b genes to expand the pyrethroid resistance front in the malaria vector Anopheles funestus in Africa. BMC Genomics. 2014;15:817.

Riveron JM, Yunta C, Ibrahim SS, Djouaka R, Irving H, Menze BD, et al. A single mutation in the GSTe2 gene allows tracking of metabolically based insecticide resistance in a major malaria vector. Genome Biol. 2014;15:R27.

Vlachou D, Schlegelmilch T, Runn E, Mendes A, Kafatos FC. The developmental migration of Plasmodium in mosquitoes. Curr Opin Genet Dev. 2006;16:384–91.

Levashina EA. Immune responses in Anopheles gambiae . Insect Biochem Mol Biol. 2004;34:673–8.

Söderhäll K. Invertebrate immunity. Springer Science & Business Media; 2011.

Cohuet A, Harris C, Robert V, Fontenille D. Evolutionary forces on Anopheles : what makes a malaria vector? Trends Parasitol. 2010;26:130–6.

Beier JC. Malaria parasite development in mosquitoes. Annu Rev Entomol. 1998;43:519–43.

Holme P, Masuda N. The basic reproduction number as a predictor for epidemic outbreaks in temporal networks. PLoS ONE. 2015;10: e0120567.

Dietz K. The estimation of the basic reproduction number for infectious diseases. Stat Methods Med Res. 1993;2:23–41.

Smith DL, McKenzie FE, Snow RW, Hay SI. Revisiting the basic reproductive number for malaria and its implications for malaria control. PLoS Biol. 2007;5: e42.

Rivero A, Vézilier J, Weill M, Read AF, Gandon S. Insecticide control of vector-borne diseases: when is insecticide resistance a problem? PLoS Pathog. 2010;6: e1001000.

Kabula B, Tungu P, Rippon EJ, Steen K, Kisinza W, Magesa S, et al. A significant association between deltamethrin resistance, Plasmodium falciparum infection and the Vgsc-1014S resistance mutation in Anopheles gambiae highlights the epidemiological importance of resistance markers. Malar J. 2016;15:289.

Tchouakui M, Chiang MC, Ndo C, Kuicheu CK, Amvongo-Adjia N, Wondji MJ, et al. A marker of glutathione S-transferase-mediated resistance to insecticides is associated with higher Plasmodium infection in the African malaria vector Anopheles funestus . Sci Rep. 2019;9:5772.

Collins E, Vaselli NM, Sylla M, Beavogui AH, Orsborne J, Lawrence G, et al. The relationship between insecticide resistance, mosquito age and malaria prevalence in Anopheles gambiae s.l. from Guinea. Sci Rep. 2019;9:8846.

Ndiath MO, Cailleau A, Diedhiou SM, Gaye A, Boudin C, Richard V, et al. Effects of the kdr resistance mutation on the susceptibility of wild Anopheles gambiae populations to Plasmodium falciparum : a hindrance for vector control. Malar J. 2014;3:340.

Ndo C, Kopya E, Irving H, Wondji C. Exploring the impact of glutathione S-transferase (GST)-based metabolic resistance to insecticide on vector competence of Anopheles funestus for Plasmodium falciparum . Wellcome Open Res. 2019;4:52.

Alout H, Ndam NT, Sandeu MM, Djégbe I, Chandre F, Dabiré RK, et al. Insecticide resistance alleles affect vector competence of Anopheles gambiae s.s. for Plasmodium falciparum field isolates. PLoS ONE. 2013;8:e63849.

Alout H, Dabiré RK, Djogbénou LS, Abate L, Corbel V, Chandre F, et al. Interactive cost of Plasmodium infection and insecticide resistance in the malaria vector Anopheles gambiae . Sci Rep. 2016;6:29755.

Alout H, Djègbè I, Chandre F, Djogbénou LS, Dabiré RK, Corbel V, et al. Insecticide exposure impacts vector-parasite interactions in insecticide-resistant malaria vectors. Proc Biol Sci. 2014;281:20140389.

Google Scholar  

Kristan M, Abeku TA, Lines J. Effect of environmental variables and kdr resistance genotype on survival probability and infection rates in Anopheles gambiae (s.s.). Parasit Vectors. 2018;11:560.

Lo TM, Coetzee M. Marked biological differences between insecticide resistant and susceptible strains of Anopheles funestus infected with the murine parasite Plasmodium berghei . Parasit Vectors. 2013;6:184.

Ribeiro JM, Francischetti IM. Role of arthropod saliva in blood feeding: sialome and post-sialome perspectives. Annu Rev Entomol. 2003;48:73–88.

Calvo E, Dao A, Pham VM, Ribeiro JM. An insight into the sialome of Anopheles funestus reveals an emerging pattern in anopheline salivary protein families. Insect Biochem Mol Biol. 2007;37:164–75.

Das S, Radtke A, Choi YJ, Mendes AM, Valenzuela JG, Dimopoulos G. Transcriptomic and functional analysis of the Anopheles gambiae salivary gland in relation to blood feeding. BMC Genomics. 2010;11:566.

Elanga-Ndille E, Nouage L, Binyang A, Assatse T, Tene-Fossog B, Tchouakui M, et al. Overexpression of two members of D7 salivary genes family is associated with pyrethroid resistance in the malaria vector Anopheles funestus s.s. but not in Anopheles gambiae in Cameroon. Genes (Basel). 2019;10:211.

Vijay S, Rawal R, Kadian K, Raghavendra K, Sharma A. Annotated differentially expressed salivary proteins of susceptible and insecticide-resistant mosquitoes of Anopheles stephensi . PLoS ONE. 2015;10: e0119666.

Ghosh AK, Devenport M, Jethwaney D, Kalume DE, Pandey A, Anderson VE, et al. Malaria parasite invasion of the mosquito salivary gland requires interaction between the Plasmodium TRAP and the Anopheles saglin proteins. PLoS Pathog. 2009;5: e1000265.

Cornelie S, Rossignol M, Seveno M, Demettre E, Mouchet F, Djègbè I, et al. Salivary gland proteome analysis reveals modulation of anopheline unique proteins in insensitive acetylcholinesterase resistant Anopheles gambiae mosquitoes. PLoS ONE. 2014;9: e103816.

Mueller AK, Kohlhepp F, Hammerschmidt C, Michel K. Invasion of mosquito salivary glands by malaria parasites: prerequisites and defense strategies. Int J Parasitol. 2010;40:1229–35.

Wells MB, Andrew DJ. Anopheles salivary gland architecture shapes Plasmodium sporozoite availability for transmission. MBio. 2019;10:e01238-e1319.

O’Brochta DA, Alford R, Harrell R, Aluvihare C, Eappen AG, Li T, et al. Is Saglin a mosquito salivary gland receptor for Plasmodium falciparum ? Malar J. 2019;18:2.

Calvo E, Mans BJ, Andersen JF, Ribeiro JM. Function and evolution of a mosquito salivary protein family. J Biol Chem. 2006;281:1935–42.

Francischetti IM, Valenzuela JG, Pham VM, Garfield MK, Ribeiro JM. Toward a catalog for the transcripts and proteins (sialome) from the salivary gland of the malaria vector Anopheles gambiae . J Exp Biol. 2002;205:2429–51.

Isaacs AT, Mawejje HD, Tomlinson S, Rigden DJ, Donnelly MJ. Genome-wide transcriptional analyses in Anopheles mosquitoes reveal an unexpected association between salivary gland gene expression and insecticide resistance. BMC Genomics. 2018;19:225.

Beerntsen BT, James AA, Christensen BM. Genetics of mosquito vector competence. Microbiol Mol Biol Rev. 2000;64:115–37.

Djegbe I, Cornelie S, Rossignol M, Demettre E, Seveno M, Remoue F, Corbel V. Differential expression of salivary proteins between susceptible and insecticide-resistant mosquitoes of Culex quinquefasciatus . PLoS ONE. 2011;6: e17496.

Mano C, Jariyapan N, Sor-Suwan S, Roytrakul S, Kittisenachai S, Tippawangkosol P, et al. Protein expression in female salivary glands of pyrethroid-susceptible and resistant strains of Aedes aegypti mosquitoes. Parasit Vectors. 2019;12:111.

Rosinski-Chupin I, Briolay J, Brouilly P, Perrot S, Gomez SM, Chertemps T, et al. SAGE analysis of mosquito salivary gland transcriptomes during Plasmodium invasion. Cell Microbiol. 2007;9:708–24.

Sor-suwan S, Jariyapan N, Roytrakul S, Paemanee A, Phumee A, Phattanawiboon B, et al. Identification of salivary gland proteins depleted after blood feeding in the malaria vector Anopheles campestris -like mosquitoes (Diptera: Culicidae). PLoS ONE. 2014;9: e90809.

Cázares-Raga FE, Chávez-Munguía B, González-Calixto C, Ochoa-Franco AP, Gawinowicz MA, Rodríguez MH, Hernández-Hernández FC. Morphological and proteomic characterization of midgut of the malaria vector Anopheles albimanus at early time after a blood feeding. J Proteomics. 2014;111:100–12.

Villalon JM, Ghosh A, Jacobs-Lorena M. The peritrophic matrix limits the rate of digestion in adult Anopheles stephensi and Aedes aegypti mosquitoes. J Insect Physiol. 2003;49:891–5.

Billingsley PF. Blood digestion in the mosquito, Anopheles stephensi Liston (Diptera: Culicidae): partial characterization and post-feeding activity of midgut aminopeptidases. Arch Insect Biochem Physiol. 1990;15:149–63.

Dana AN, Hong YS, Kern MK, Hillenmeyer ME, Harker BW, Lobo NF, et al. Gene expression patterns associated with blood-feeding in the malaria mosquito Anopheles gambiae . BMC Genomics. 2005;6:5.

Billingsley PF, Hecker H. Blood digestion in the mosquito, Anopheles stephensi Liston (Diptera: Culicidae): activity and distribution of trypsin, aminopeptidase, and alpha-glucosidase in the midgut. J Med Entomol. 1991;28:865–71.

Ribeiro JM. A catalogue of Anopheles gambiae transcripts significantly more or less expressed following a blood meal. Insect Biochem Mol Biol. 2003;33:865–82.

Vijay S, Rawal R, Kadian K, Singh J, Adak T, Sharma A. Proteome-wide analysis of Anopheles culicifacies mosquito midgut: new insights into the mechanism of refractoriness. BMC Genomics. 2018;19:337.

Mitri C, Markianos K, Guelbeogo WM, Bischoff E, Gneme A, Eiglmeier K, et al. The kdr-bearing haplotype and susceptibility to Plasmodium falciparum in Anopheles gambiae : genetic correlation and functional testing. Malar J. 2015;14:391.

Vontas J, Blass C, Koutsos AC, David JP, Kafatos FC, Louis C, et al. Gene expression in insecticide resistant and susceptible Anopheles gambiae strains constitutively or after insecticide exposure. Insect Mol Biol. 2005;14:509–21.

Ingham VA, Brown F, Ranson H. Transcriptomic analysis reveals pronounced changes in gene expression due to sub-lethal pyrethroid exposure and ageing in insecticide resistance Anopheles coluzzii . BMC Genomics. 2021;22:337.

Hamer GL, Kitron UD, Brawn JD, Loss SR, Ruiz MO, Goldberg TL, et al. Culex pipiens (Diptera: Culicidae): a bridge vector of West Nile virus to humans. J Med Entomol. 2008;45:125–8.

Morchón R, Bargues MD, Latorre JM, Melero-Alcíbar R, Pou-Barreto C, Mas-Coma S, et al. Haplotype H1 of Culex pipiens implicated as natural vector of Dirofilaria immitis in an endemic area of Western Spain. Vector Borne Zoonotic Dis. 2007;7:653–8.

Kimura M, Darbro JM, Harrington LC. Avian malaria parasites share congeneric mosquito vectors. J Parasitol. 2010;96:144–51.

Vézilier J, Nicot A, Lorgeril J, Gandon S, Rivero A. The impact of insecticide resistance on Culex pipiens immunity. Evol Appl. 2013;6:497–509.

Molina-Cruz A, DeJong RJ, Charles B, Gupta L, Kumar S, Jaramillo-Gutierrez G, et al. Reactive oxygen species modulate Anopheles gambiae immunity against bacteria and Plasmodium . J Biol Chem. 2008;283:3217–23.

Kumar S, Christophides GK, Cantera R, Charles B, Han YS, Meister S, et al. The role of reactive oxygen species on Plasmodium melanotic encapsulation in Anopheles gambiae . Proc Natl Acad Sci USA. 2003;100:14139–44.

James RR, Xu J. Mechanisms by which pesticides affect insect immunity. J Invertebr Pathol. 2012;109:175–82.

Hillyer JF, Strand MR. Mosquito hemocyte-mediated immune responses. Curr Opin Insect Sci. 2014;3:14–21.

Lavine MD, Strand MR. Insect hemocytes and their role in immunity. Insect Biochem Mol Biol. 2002;32:1295–309.

Cornet S, Gandon S, Rivero A. Patterns of phenoloxidase activity in insecticide resistant and susceptible mosquitoes differ between laboratory-selected and wild-caught individuals. Parasit Vectors. 2013;6:315.

Wang Y, Gilbreath TM 3rd, Kukutla P, Yan G, Xu J. Dynamic gut microbiome across life history of the malaria mosquito Anopheles gambiae in Kenya. PLoS ONE. 2011;6: e24767.

Gimonneau G, Tchioffo MT, Abate L, Boissière A, Awono-Ambéné PH, Nsango SE, et al. Composition of Anopheles coluzzii and Anopheles gambiae microbiota from larval to adult stages. Infect Genet Evol. 2014;28:715–24.

Akorli J, Gendrin M, Pels NA, Yeboah-Manu D, Christophides GK, Wilson MD. Seasonality and locality affect the diversity of Anopheles gambiae and Anopheles coluzzii midgut microbiota from Ghana. PLoS ONE. 2016;11: e0157529.

Krajacich BJ, Huestis DL, Dao A, Yaro AS, Diallo M, Krishna A, Xu J, Lehmann T. Investigation of the seasonal microbiome of Anopheles coluzzii mosquitoes in Mali. PLoS ONE. 2018;13: e0194899.

Sandeu MM, Maffo CGT, Dada N, Njiokou F, Hughes GL, Wondji CS. Seasonal variation of microbiota composition in Anopheles gambiae and Anopheles coluzzii in two different eco-geographical localities in Cameroon. Med Vet Entomol. 2022;36:269–82.

Rosenberg R. Malaria: some considerations regarding parasite productivity. Trends Parasitol. 2008;24:487–91.

Cansado-Utrilla C, Zhao SY, McCall PJ, Coon KL, Hughes GL. The microbiome and mosquito vectorial capacity: rich potential for discovery and translation. Microbiome. 2021;9:111.

Rodgers FH, Gendrin M, Wyer CAS, Christophides GK. Microbiota-induced peritrophic matrix regulates midgut homeostasis and prevents systemic infection of malaria vector mosquitoes. PLoS Pathog. 2017;13: e1006391.

Song X, Wang M, Dong L, Zhu H, Wang J. PGRP-LD mediates A. stephensi vector competency by regulating homeostasis of microbiota-induced peritrophic matrix synthesis. PLoS Pathog. 2018;14:e1006899.

Romoli O, Gendrin M. The tripartite interactions between the mosquito, its microbiota and Plasmodium . Parasit Vectors. 2018;11:200.

Barletta ABF, Trisnadi N, Ramirez JL, Barillas-Mury C. Mosquito midgut prostaglandin release establishes systemic immune priming. iScience. 2019;19:54–62.

Barnard K, Jeanrenaud A, Brooke BD, Oliver SV. The contribution of gut bacteria to insecticide resistance and the life histories of the major malaria vector Anopheles arabiensis (Diptera: Culicidae). Sci Rep. 2019;9:9117.

Martinson VG, Strand MR. Diet-microbiota interactions alter mosquito development. Front Microbiol. 2021;12: 650743.

Dada N, Sheth M, Liebman K, Pinto J, Lenhart A. Whole metagenome sequencing reveals links between mosquito microbiota and insecticide resistance in malaria vectors. Sci Rep. 2018;8:2084.

Omoke D, Kipsum M, Otieno S, Esalimba E, Sheth M, Lenhart A, et al. Western Kenyan Anopheles gambiae showing intense permethrin resistance harbour distinct microbiota. Malar J. 2021;20:77.

Soltani A, Vatandoost H, Oshaghi MA, Enayati AA, Chavshin AR. The role of midgut symbiotic bacteria in resistance of Anopheles stephensi (Diptera: Culicidae) to organophosphate insecticides. Pathog Glob Health. 2017;111:289–96.

Dieme C, Rotureau B, Mitri C. Microbial pre-exposure and vectorial competence of Anopheles mosquitoes. Front Cell Infect Microbiol. 2017;7:508.

Gabrieli P, Caccia S, Varotto-Boccazzi I, Arnoldi I, Barbieri G, Comandatore F, et al. Mosquito trilogy: microbiota, immunity and pathogens, and their implications for the control of disease transmission. Front Microbiol. 2021;12: 630438.

Bassene H, Niang EHA, Fenollar F, Dipankar B, Doucouré S, Ali E, et al. 6S Metagenomic comparison of Plasmodium falciparum -infected and noninfected Anopheles gambiae and Anopheles funestus microbiota from Senegal. Am J Trop Med Hyg. 2018;99:1489–98.

Garrett-Jones C, Shidrawi GR. Malaria vectorial capacity of a population of Anopheles gambiae : an exercise in epidemiological entomology. Bull World Health Organ. 1969;40:531–45.

CAS   Google Scholar  

Ferguson HM, Maire N, Takken W, Lyimo IN, Briët O, Lindsay SW, Smith TA. Selection of mosquito life-histories: a hidden weapon against malaria? Malar J. 2012;11:106.

Nkahe DL, Kopya E, Djiappi-Tchamen B, Toussile W, Sonhafouo-Chiana N, Kekeunou S, et al. Fitness cost of insecticide resistance on the life-traits of a Anopheles coluzzii population from the city of Yaoundé, Cameroon. Wellcome Open Res. 2020;5:171.

Msangi G, Olotu MI, Mahande AM, Philbert A, Kweka EJ. The impact of insecticide pre-exposure on longevity, feeding succession, and egg batch size of wild Anopheles gambiae s.l. J Trop Med. 2020;2020:8017187.

Hughes A, Lissenden N, Viana M, Toé KH, Ranson H. Anopheles gambiae populations from Burkina Faso show minimal delayed mortality after exposure to insecticide-treated nets. Parasit Vectors. 2020;13:17.

Viana M, Hughes A, Matthiopoulos J, Ranson H, Ferguson HM. Delayed mortality effects cut the malaria transmission potential of insecticide-resistant mosquitoes. Proc Natl Acad Sci USA. 2016;113:8975–80.

Otali D, Novak RJ, Wan W, Bu S, Moellering DR, De Luca M. Increased production of mitochondrial reactive oxygen species and reduced adult life span in an insecticide-resistant strain of Anopheles gambiae . Bull Entomol Res. 2014;104:323–33.

Oliver SV, Brooke BD. The effect of elevated temperatures on the life history and insecticide resistance phenotype of the major malaria vector Anopheles arabiensis (Diptera: Culicidae). Malar J. 2017;16:73.

Oliver SV, Brooke BD. The effect of multiple blood-feeding on the longevity and insecticide resistant phenotype in the major malaria vector Anopheles arabiensis (Diptera: Culicidae). Parasit Vectors. 2014;7:390.

Oliver SV, Brooke BD. The role of oxidative stress in the longevity and insecticide resistance phenotype of the major malaria vectors Anopheles arabiensis and Anopheles funestus . PLoS ONE. 2016;11: e0151049.

Tchakounte A, Tchouakui M, Mu-Chun C, Tchapga W, Kopia E, Soh PT, et al. Exposure to the insecticide-treated bednet PermaNet 2.0 reduces the longevity of the wild African malaria vector Anopheles funestus but GSTe2-resistant mosquitoes live longer. PLoS ONE. 2019;14:e0213949.

Tchouakui M, Riveron JM, Djonabaye D, Tchapga W, Irving H, Soh Takam P, et al. Fitness Costs of the glutathione S-transferase epsilon 2 (L119F-GSTe2) mediated metabolic resistance to insecticides in the major African malaria vector Anopheles funestus . Genes (Basel). 2018;9:645.

Okoye PN, Brooke BD, Hunt RH, Coetzee M. Relative developmental and reproductive fitness associated with pyrethroid resistance in the major southern African malaria vector, Anopheles funestus . Bull Entomol Res. 2007;97:599–605.

Tchouakui M, Riveron Miranda J, Mugenzi LMJ, Djonabaye D, Wondji MJ, Tchoupo M, et al. Cytochrome P450 metabolic resistance (CYP6P9a) to pyrethroids imposes a fitness cost in the major African malaria vector Anopheles funestus . Heredity (Edinb). 2020;124:621–32.

Tchouakui M, Mugenzi LMJ, Wondji MJ, Tchoupo M, Njiokou F, Wondji CS. Combined over-expression of two cytochrome P450 genes exacerbates the fitness cost of pyrethroid resistance in the major African malaria vector Anopheles funestus . Pestic Biochem Physiol. 2021;173: 104772.

Remick D. Measuring the costs of reproduction. Trends Ecol Evol. 1992;7:42–5.

Kirkwood TB, Rose MR. Evolution of senescence: late survival sacrificed for reproduction. Philos Trans R Soc Lond B Biol Sci. 1991;332:15–24.

Garland T Jr. Trade-offs. Curr Biol. 2014;24:R60–1.

Rada B, Leto TL. Oxidative innate immune defenses by Nox/Duox family NADPH oxidases. Contrib Microbiol. 2008;15:164–87.

Sumimoto H. Structure, regulation and evolution of Nox-family NADPH oxidases that produce reactive oxygen species. FEBS J. 2008;275:3249–77.

Monaghan P, Metcalfe NB, Torres R. Oxidative stress as a mediator of life history trade-offs: mechanisms, measurements and interpretation. Ecol Lett. 2009;12:75–92.

Download references

The authors acknowledge the financial support from the Wellcome Trust, UK, through the International Intermediate Fellowship (220720/Z/20/Z) granted to Cyrille NDO.

Author information

Authors and affiliations.

Department of Parasitology and Microbiology, Centre for Research in Infectious Diseases, P.O. Box 13591, Yaoundé, Cameroon

Pierre Fongho Suh, Darus Tagne, Charles Wondji & Cyrille Ndo

Faculty of Sciences, University of Yaoundé I, P.O. Box 837, Yaoundé, Cameroon

Pierre Fongho Suh

Department of Medical Entomology, Centre for Research in Infectious Diseases, P.O. Box 13591, Yaoundé, Cameroon

Emmanuel Elanga-Ndille, Magellan Tchouakui & Maurice Marcel Sandeu

Department of Microbiology and Infectious Diseases, School of Veterinary Medicine and Sciences, University of Ngaoundéré, P.O. Box 454, Ngaoundéré, Cameroon

Maurice Marcel Sandeu

Faculty of Sciences, University of Douala, P.O. Box 24157, Douala, Cameroon

Darus Tagne

Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK

Charles Wondji

Department of Biological Sciences, Faculty of Medicine and Pharmaceutical Sciences, University of Douala, P.O. Box 24157, Douala, Cameroon

Cyrille Ndo

You can also search for this author in PubMed   Google Scholar

Contributions

PFS, EEN, MT, MMS, CN wrote the manuscript. TD and PFS prepared the figures and tables. CN and CW acquiered the funding. All the authors revised the manuscript. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Cyrille Ndo .

Ethics declarations

Ethics approval and consent to participate, consent for publication, competing interests.

The authors declare no competing interests.

Additional information

Publisher's note.

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/ . The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/ ) applies to the data made available in this article, unless otherwise stated in a credit line to the data.

Reprints and permissions

About this article

Cite this article.

Suh, P.F., Elanga-Ndille, E., Tchouakui, M. et al. Impact of insecticide resistance on malaria vector competence: a literature review. Malar J 22 , 19 (2023). https://doi.org/10.1186/s12936-023-04444-2

Download citation

Received : 23 August 2022

Accepted : 04 January 2023

Published : 17 January 2023

DOI : https://doi.org/10.1186/s12936-023-04444-2

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

• Insecticide resistance
• Vector competence

Malaria Journal

ISSN: 1475-2875

• Submission enquiries: [email protected]

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

• View all journals
• My Account Login
• Explore content
• About the journal
• Publish with us
• Sign up for alerts
• Open access
• Published: 25 August 2021

Recent clinical trials inform the future for malaria vaccines

• Liriye Kurtovic 1 , 2 ,
• Linda Reiling 1 , 2 , 3 ,
• D. Herbert Opi 1 , 2 , 3 &
• James G. Beeson   ORCID: orcid.org/0000-0002-1018-7898 1 , 2 , 3 , 4  

Communications Medicine volume  1 , Article number:  26 ( 2021 ) Cite this article

8726 Accesses

10 Citations

24 Altmetric

Metrics details

This article has been updated

Malaria vaccines are urgently needed in the fight against this devastating disease that is responsible for almost half a million deaths each year. Here, we discuss recent clinical advances in vaccine development and highlight ongoing challenges for the future.

Malaria is one of the most devastating infectious diseases in humans, responsible for >200 million cases and almost half a million deaths annually. Control programs have significantly reduced disease burden since 2000, but numbers have plateaued since 2015. The disruption caused by the ongoing COVID-19 pandemic will further unwind these efforts and is predicted to increase the number of malaria deaths. New control measures are urgently needed, and lessons learned from emerging diseases such as COVID-19 highlight the enormous potential of effective vaccines. This has been recognized by the World Health Organization (WHO) and key stakeholders who recommend that, within the next decade, a vaccine should be developed that is at least 75% efficacious against malaria over 2 years (i.e., reduces disease occurrence by at least 75% in vaccinated compared to unvaccinated individuals) and also reduces malaria transmission.

This is an exciting time for malaria vaccine development, with a number of promising clinical trials recently completed and others currently underway…

Plasmodium falciparum causes the majority of malaria burden and has been the primary focus of vaccine development, and Plasmodium vivax is the second major cause of malaria. There are several vaccine strategies that target different developmental stages of the malaria-causing parasite (Fig.  1 ). This begins with the sporozoite parasite form, which is inoculated into the skin by a feeding mosquito, circulates in the blood, and infects the liver to develop into the morphologically distinct merozoite form. Merozoites then replicate within red blood cells to exponentially increase parasitemia and can cause severe disease pathology. Some merozoites will undergo development into the gametocyte form that can be taken up by the mosquito vector and subsequently be transmitted in a population. An important bottleneck in the vaccine development pipeline is the assessment of potential candidates in clinical trials. Given the limitations of malaria animal models to adequately reflect human disease, the controlled human malaria infection (CHMI) model offers a unique ability to fast-track initial evaluations of vaccine efficacy. Safe and controlled parasite infection in a clinical setting has proven more time-efficient and less variable than natural parasite exposure and can therefore rely on fewer subjects for conducting the first efficacy trial with a vaccine. CHMI has also been increasingly implemented in malaria-endemic settings, which is critically important to understand the dynamics between vaccine-induced immunity and pre-existing immunity during ongoing natural exposure to malaria.

Overview of the morphologically distinct sporozoite, merozoite, and gametocyte forms at different stages of the parasite life cycle, and the vaccine strategy for targeting each stage. Vaccines that target multiple life cycle stages are also in development. Created with BioRender.com.

Here, we discuss recent advances and insights from clinical trials of malaria vaccines and highlight ongoing challenges and priorities for the future. Table  1 lists the key trials discussed in this Comment.

Vaccines can block infection by targeting sporozoites

Vaccines can target sporozoites to prevent or impair infection of the liver, and therefore aim to induce immunity whereby an individual is protected against infection and disease. Live-attenuated sporozoite-based vaccines have the capacity to induce sterilizing immunity (no detectable parasitemia) against CHMI in malaria-naive volunteers. This includes the PfSPZ vaccine that contains radiation-attenuated sporozoites incapable of replicating. It was recently shown that an optimized PfSPZ vaccine dosage induced sterilizing immunity against CHMI in six Tanzanian adults 1 , and this dose appeared safe in African children, which supports further evaluations in younger age groups (NCT02687373) 2 . Another approach is to combine replication–intact sporozoites with antimalarial drug prophylaxis to prevent malarial illness, known as PfSPZ-CVac. PfSPZ-CVac can induce sterilizing immunity in malaria-naive volunteers, but there is no published data in malaria-endemic populations 3 . A third approach is to genetically attenuate sporozoites to prevent intrahepatic development. This includes the triple-gene knockout vaccine, GAP3KO, which recently completed an efficacy trial in malaria-naive volunteers (NCT03168854). Although sporozoite-based vaccines are promising, major obstacles include the fact that currently sporozoites cannot be cultured in vitro and are therefore isolated from infected mosquito salivary glands, and they currently require direct venous inoculation of vaccine doses and storage and transportation of vaccines using liquid nitrogen.

Subunit vaccines aim to target a key antigen, or sub-region, and have the advantage of using existing production technologies and delivery using established infrastructure and systems. The most successful is the RTS,S vaccine based on a truncated form of the major sporozoite surface antigen, circumsporozoite protein (CSP). This is expressed as a virus-like particle and administered with an adjuvant (AS01), which is used to enhance the immune response to vaccination. Promising findings from a phase 3 clinical trial in >15,000 African children led to pilot implementation of a four-dose booster regimen in children aged 5 months in Ghana, Kenya, and Malawi to further evaluate vaccine safety and efficacy, which is ongoing 4 . Additional trials are underway in African children to evaluate a modified regimen where a fraction of the third dose is administered months later, which appeared to be moderately more efficacious in malaria-naive volunteers (NCT03276962) 5 . There is also interest in whether RTS,S can synergize with seasonal malaria chemoprevention (NCT03143218).

A recent advance was the development of the R21 malaria vaccine, a virus-like particle that is similar to RTS,S, but has higher density of the CSP antigen on the particle surface and is formulated with Matrix-M adjuvant 6 . Initial results from a pediatric phase 2 clinical trial in Burkina Faso demonstrated 76% efficacy against malaria over 12 months 6 . Although this was considerably higher than vaccine efficacy achieved in previous RTS,S trials 4 , R21 was administered prior to the peak malaria season and most malaria occurred in the first 6 months 6 , making direct comparisons with RTS,S efficacy difficult to interpret. Furthermore, antibody levels had declined markedly by 12 months. Participants are still being monitored to determine vaccine efficacy over 2 years, and children are currently being enrolled in phase 3 clinical trials across multiple African sites (NCT04704830).

Vaccines targeting blood stages of malaria prevent clinical illness

Blood-stage vaccines target the merozoite form or infected red blood cells and aim to control parasitemia and prevent clinical illness. There has been considerably less progress in achieving good efficacy for blood-stage vaccines, with only a handful of candidates evaluated in phase 2 clinical trials, and none having progressed further 7 . The most recent was RH5.1 comprised of full-length RH5 protein, an indispensable merozoite invasion ligand. In a phase 1/2a clinical trial in malaria-naive volunteers, RH5.1 with AS01 adjuvant was highly immunogenic but only resulted in a 1-day delay until threshold parasitemia levels were reached following CHMI compared with that of the unvaccinated control group 8 . An upcoming phase 1 clinical trial of RH5.1 will further evaluate safety and immunogenicity in Tanzanian adults and children (NCT04318002).

Merozoites express a multitude of surface proteins and invasion ligands, including many that are polymorphic, which makes it difficult to identify candidate antigens for subunit vaccines. In addition, there are major knowledge gaps on specific mechanisms that mediate protective antimalarial immunity. Antibodies play a critical role, but the current reference growth inhibition assay (GIA) that measures antibody inhibitory activity has neither strongly nor consistently been associated with protection against malaria 7 . Several vaccines, including RH5.1, have generated substantial GIA activity but shown limited efficacy 8 . Achieving higher efficacy with merozoite vaccines may require harnessing multiple immunologic mechanisms. Recent studies found that antibodies can activate complement and mediate Fcγ-receptor effector functions against merozoites, which were associated with clinical protection in malaria-endemic population studies 9 . This creates a new opportunity to evaluate the targets of functional antibody responses and potentially identify new vaccine candidate antigens using these novel approaches 9 .

Given the lack of success in developing blood-stage subunit vaccines, there is interest in whole parasite blood-stage vaccines, which present a large antigen repertoire to the immune system and may overcome the challenge of antigen-specific polymorphisms. The first clinical study of chemically attenuated parasite-infected red blood cells promisingly induced cellular immune responses in malaria-naive volunteers, but parasite-specific antibodies were not detected 10 . Further studies are needed on this particular vaccine approach, including improvements in vaccine production and formulation to avoid immune responses to the red blood cell membrane.

Once a merozoite infects a red blood cell and matures, the host cell undergoes extensive changes and expresses parasite-derived proteins on the red blood cell surface. One such protein, VAR2CSA, facilitates the accumulation and sequestration of parasite-infected red blood cells in the placenta. Malaria during pregnancy is, therefore, a major concern and can lead to adverse outcomes such as maternal anemia, preterm delivery, stillbirth, and low birthweight babies. Two VAR2CSA-based vaccines (PAMVAC and PRIMVAC) aimed at inhibiting placental malaria have recently completed phase 1 clinical trials and were immunogenic and had acceptable safety profiles, but are yet to be evaluated for vaccine efficacy 11 , 12 .

Developing vaccines that block malaria transmission

Vaccines that target the gametocyte and gamete forms aim to prevent parasite transmission to the mosquito and thereby block malaria transmission throughout a population. Although this vaccine approach does not offer any direct clinical protection in humans, blocking malaria transmission is an essential component of effective control and elimination strategies. There has been limited progress for transmission-blocking vaccines, with one candidate based on the gametocyte surface antigen, Pfs230 (Pfs230D1M), showing promise in early clinical trials and a phase 2 clinical trial is ongoing in Mali (NCT03917654) 13 .

These vaccine approaches targeting different stages of the parasite life cycle have the ability to afford protection against infection, disease, and/or prevent parasite transmission among a population. Although each approach is of value, there may be additional benefits to developing multi-stage subunit vaccines that incorporate antigens expressed at different developmental stages.

Future directions and opportunities

This is an exciting time for malaria vaccine development, with a number of promising clinical trials recently completed and others currently underway, although there are still considerable challenges that stand in the way of achieving vaccine goals within the next decade with several priority areas for research (Fig.  2 ). Malaria exposure may drive the lower vaccine responses typically observed in malaria-exposed populations compared with malaria-naive individuals. As disease burden can be substantial among adolescents and adults in some populations, clinical trials to evaluate vaccine efficacy in these groups will also be needed. A persisting challenge for malaria vaccines is achieving sustained protective efficacy as antibody and cellular responses are often short-lived and wane within a year 6 . The immunological factors underlying these vaccine limitations remain poorly understood but will be crucial for achieving higher efficacy and wider vaccine implementation in endemic populations. Furthermore, very little progress has been made toward the development of vaccines against P. vivax , which needs to be accelerated.

The figure lists several research priorities, grouped into three main themes, for achieving malaria vaccines with high impact and have the potential to accelerate and sustain malaria elimination. Created with BioRender.com.

Recent advances in vaccine technologies, including those used in licensed COVID-19 vaccines, have opened new opportunities for malaria vaccine development. This includes mRNA-based vaccine platforms of the CSP malaria antigen, which has already shown encouraging results in animal models 14 . There has also been continued interest in heterologous prime-boost with ChAd43 and Modified Vaccinia Ankara viral vectors encoding different malaria antigens alone or in combinations (e.g., AMA1, MSP1, ME-TRAP) 15 .

Further research on these areas will greatly advance the development of effective malaria vaccines in endemic populations.

Change history

08 september 2021.

The original version of this Article was updated shortly after publication because the text selected for the pull quote ‘This is an exciting time for malaria vaccine development, with a number of promising clinical trials recently completed and others currently underway…’ was inadvertently added at the end of the main text and was not rendering as a pull quote. The error has now been correct in the HTML and PDF versions of the Article.

Jongo, S. A. et al. Increase of dose associated with decrease in protection against controlled human malaria infection by PfSPZ Vaccine in Tanzanian adults. Clin. Infect. Dis. 71 , 2849–2857 (2020).

Article   CAS   Google Scholar  

Steinhardt, L. C. et al. Safety, tolerability, and immunogenicity of Plasmodium falciparum sporozoite vaccine administered by direct venous inoculation to infants and young children: findings from an age de-escalation, dose-escalation, double-blind, randomized controlled study in Western Kenya. Clin. Infect. Dis. 71 , 1063–1071 (2020).

Mwakingwe-Omari, A. et al. Two chemoattenuated PfSPZ malaria vaccines induce sterile hepatic immunity. Nature 595 , 289–294 (2021).

RTSS Clinical Trials Partnership. First results of phase 3 trial of RTS, S/AS01 malaria vaccine in African children. N. Engl. J. Med. 365 , 1863–1875 (2011).

Article   Google Scholar  

Regules, J. A. et al. Fractional third and fourth dose of RTS, S/AS01 malaria candidate vaccine: a phase 2a controlled human malaria parasite infection and immunogenicity study. J. Infect. Dis. 214 , 762–771 (2016).

Datoo, M. S. et al. Efficacy of a low-dose candidate malaria vaccine, R21 in adjuvant Matrix-M, with seasonal administration to children in Burkina Faso: a randomised controlled trial. Lancet 397 , 1809–1818 (2021).

Beeson, J. G. et al. Merozoite surface proteins in red blood cell invasion, immunity and vaccines against malaria. FEMS Microbiol. Rev. 40 , 343–372 (2016).

Minassian, A. M. et al. Reduced blood-stage malaria growth and immune correlates in humans following RH5 vaccination. Med 2 , 701–719 (2021).

Reiling, L. et al. Targets of complement-fixing antibodies in protective immunity against malaria in children. Nat. Commun. 10 , 610 (2019).

Stanisic, D. I. et al. Vaccination with chemically attenuated Plasmodium falciparum asexual blood-stage parasites induces parasite-specific cellular immune responses in malaria-naive volunteers: a pilot study. BMC Med. 16 , 184 (2018).

Mordmüller, B. et al. First-in-human, randomized, double-blind clinical trial of differentially adjuvanted PAMVAC, a vaccine candidate to prevent pregnancy-associated malaria. Clin. Infect. Dis. 69 , 1509–1516 (2019).

Sirima, S. B. et al. PRIMVAC vaccine adjuvanted with alhydrogel or GLA-SE to prevent placental malaria: a first-in-human, randomised, double-blind, placebo-controlled study. Lancet Infect. Dis. 20 , 585–597 (2020).

Healy, S. A. et al. Pfs230 yields higher malaria transmission–blocking vaccine activity than Pfs25 in humans but not mice. J. Clin. Invest. 131 , e146221 (2021).

Mallory, K. L. et al. Messenger RNA expressing PfCSP induces functional, protective immune responses against malaria in mice. npj Vaccines 6 , 1–12 (2021).

Tiono, A. B. et al. First field efficacy trial of the ChAd63 MVA ME-TRAP vectored malaria vaccine candidate in 5-17 months old infants and children. PloS ONE 13 , e0208328 (2018).

Download references

Acknowledgements

The authors acknowledge support from the National Health and Medical Research Council of Australia (NHMRC), including Investigator Grant to J.G.B. and Ideas Grant to D.H.O. and L.R., and the Australian Centre for Research Excellence in Malaria Elimination.

Author information

Authors and affiliations.

Burnet Institute, Melbourne, VIC, Australia

Liriye Kurtovic, Linda Reiling, D. Herbert Opi & James G. Beeson

Department of Immunology and Pathology, Central Clinical School, Monash University, Melbourne, VIC, Australia

Department of Medicine, The University of Melbourne, Melbourne, VIC, Australia

Linda Reiling, D. Herbert Opi & James G. Beeson

Department of Microbiology, Monash University, Clayton, VIC, Australia

• James G. Beeson

You can also search for this author in PubMed   Google Scholar

Contributions

L.K., L.R., D.H.O. and J.G.B reviewed published literature and data and interpreted findings. L.K., L.R. and D.H.O. wrote the first draft of the manuscript with input from J.G.B. L.K., L.R., D.H.O. and J.G.B revised the manuscript and all authors approved the final version for publication.

Corresponding author

Correspondence to James G. Beeson .

Ethics declarations

Competing interests.

The authors declare no competing interests.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ .

Reprints and permissions

About this article

Cite this article.

Kurtovic, L., Reiling, L., Opi, D.H. et al. Recent clinical trials inform the future for malaria vaccines. Commun Med 1 , 26 (2021). https://doi.org/10.1038/s43856-021-00030-2

Download citation

Received : 26 July 2021

Accepted : 10 August 2021

Published : 25 August 2021

DOI : https://doi.org/10.1038/s43856-021-00030-2

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

This article is cited by

Induction, decay, and determinants of functional antibodies following vaccination with the rts,s malaria vaccine in young children.

• Gaoqian Feng
• Liriye Kurtovic

BMC Medicine (2022)

ICAM-1-binding Plasmodium falciparum erythrocyte membrane protein 1 variants elicits opsonic-phagocytosis IgG responses in Beninese children

• Jennifer Suurbaar
• Azizath Moussiliou
• Anja R. Jensen

Scientific Reports (2022)

Quick links

• Explore articles by subject
• Guide to authors
• Editorial policies

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

• Open access
• Published: 28 March 2024

Malaria infection and predictor factors among Chadian nomads’ children

• Azoukalné Moukénet 1 , 2 ,
• Kebfene Moudiné 3 ,
• Ngarkodje Ngarasta 2 ,
• Clement Kerah Hinzoumbe 4 &
• Ibrahima Seck 1  

BMC Public Health volume  24 , Article number:  918 ( 2024 ) Cite this article

59 Accesses

Metrics details

In Chad, malaria remains a significant public health concern, particularly among nomadic populations. Geographical factors and the mobility of human populations have shown to be associated with the diversity of Plasmodium species. The study aims to describe the malaria prevalence among nomadic children and to investigate its associated factors.

A cross-sectional study was conducted in February and October 2021 among nomadic communities in Chad. Blood sample were collected and tested from 187 Arab, Fulani and Dazagada nomadic children aged 3–59 months using malaria rapid diagnostic test (RDT). A structured electronic questionnaire was administered to their parents to collect information about the socio‑economic data. Malaria testing results were categorized according to the SD BIOLINE Malaria Ag Pf/Pan RDT procedures. Logistic regression analysis was used to determine key risk factors explaining the prevalence of malaria. STATA version IC 13 was used for statistical analysis.

The overall malaria prevalence in nomadic children was 24.60%, with 65.20% being Plasmodium falciparum species and 34.8% mixed species. Boys were twice as likely (COR = 1.83; 95% CI, 0.92–3.62; p  = 0.083) to have malaria than girls. Children whose parents used to seek traditional drugs were five times more likely (AOR = 5.59; 95% CI, 1.40–22.30, p  = 0.015) to have malaria than children whose parents used to seek health facilities. Children whose parents reported spending the last night under a mosquito net were one-fifth as likely (AOR = 0.17; 95% CI, 0.03–0.90, p  = 0.037) to have malaria compared to children whose parents did not used a mosquito net. Furthermore, Daza children were seventeen times (1/0.06) less likely (AOR = 0.06; 95% CI, 0.01–0.70, p  = 0.024) to have malaria than Fulani children and children from households piped water as the main source were seven times more likely (AOR = 7.05; 95% CI, 1.69–29.45; p  = 0.007) to have malaria than those using surface water.

Conclusions

Malaria remains a significant public health issue in the nomadic communities of Chad. Community education and sensitization programs within nomad communities are recommended to raise awareness about malaria transmission and control methods, particularly among those living in remote rural areas. The National Malaria Control Program (NMCP) should increase both the coverage and use of long-lasting insecticidal nets (LLINs) and seasonal malaria chemoprevention (SMC) in addition to promoting treatment-seeking behaviors in nomadic communities.

Peer Review reports

Malaria is a public health disease caused by parasites belonging to the Plasmodium genus and transmitted to humans through the bites of infected female Anopheles mosquitoes that breed in aquatic habitats [ 1 , 2 ]. According to the World Health Organization (WHO), an estimated 247 million cases of malaria worldwide in 2021, resulted in 619, 000 deaths. The WHO African Region bears a disproportionately high share of the global malaria burden with 95% of malaria cases and 96% of malaria deaths. Children under 5 accounted for about 80% of all malaria deaths in the Region [ 3 ]. In Chad, malaria is endemic with areas at risk of epidemics. In 2021, the country recorded around 3.5 million cases of malaria and 11, 744 deaths [ 3 ]. Malaria has consistently been the primary health problem reported in health facilities in Chad, with around 50% of malaria cases reported in children under five years old [ 4 , 5 ]. Overall, three Plasmodium species ( falciparum, malariae and ovale ) are incriminated, but 98% of malaria cases are attributable to P. falciparum [ 6 , 7 ].

Well-explored risk factors for malaria infection include biological factors such as age (children under 5), gender [ 8 , 9 ], malnutrition status of children [ 10 ], socioeconomic factors such as poverty [ 11 ], poor awareness and knowledge about malaria prevention and control [ 12 ]. Exposure to mosquito breeding sites [ 11 , 12 , 13 ] increases the risk of malaria infection while the use of preventive interventions such as a new LLIN [ 14 , 15 , 16 , 17 ] reduces this risk. Regarding the diversity of malaria parasites, geographical proximity to areas with various Plasmodium species and the movement of human populations particularly in malaria-endemic areas for a long period have been associated with P. falciparum and P. vivax [ 18 ]..

The Chadian population consists of both mobile and settled populations with around 3.5% being nomadic [ 19 ]. Nomads mainly inhabit the areas between the Saharan and Sahelian zones. Changes in climate [ 20 ], economy [ 21 ] and politics [ 22 ] over the past decades have led to a considerable extension of pastoral mobility toward the Sudanian areas [ 23 ]. Nomads traverse various malaria transmission areas within the country Chad [ 23 ] and sometimes cross the borders in search of pasture and water for their herds. As asymptomatic carriers of malaria parasites, these populations constitute a reservoir of Plasmodium species from other countries.

Numerous malaria control interventions worldwide have been implemented and proven effective [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. The combination of some interventions such as the long-lasting insecticide-treated net (LLIN) and the seasonal malaria chemoprevention (SMC) has demonstrated increased effectiveness [ 27 ]. Chad has adopted SMC with sulphadoxine-pyrimethamine and amodiaquine (SPAQ) to prevent seasonal malaria among children aged 3–59 months in the Sahel region [ 36 ]. There is promotion of the use of LLINs distributed through mass distribution and routine basis [ 37 ]. The last mass LLIN distribution campaign in Chad occurred in 2023.

Despite deep understanding of malaria predictive factors, most studies have focused on single factors, thus not providing a holistic recognition of the factors associated with malaria among nomadic communities. Both factors at the individual/household and community levels have been omitted. In Chad, few studies related to malaria in nomadic communities are available. Some of them have focused on knowledge and attitudes toward malaria [ 38 ], and coverage of control interventions among this community [ 37 ]. To address this gap, the objective of this study is to assess the prevalence of malaria and investigate the associated factors among nomadic communities in Chad.

Participants and methods

Study area and design.

This cross-sectional study conducted in February and October 2021 among nomadic communities in the provinces of Hadjer Lamis and Chari Baguirmi in the Sahelian zone of Chad and in Moyen Chari in the Sudanian zone. In comparison to the national level (40.9%), the prevalence of malaria was moderate in Hadjer Lamis (15.9%), high in Chari Baguirmi (37.2%) and very high (68.1%) in Moyen Chari [ 39 ]. In addition to intermittent preventive treatment for pregnant women (IPTp), routine and mass LLIN distribution campaigns have been implemented in all three provinces whereas SMC is being implemented in Hadjer Lamis and Chari Baguirmi provinces targeting children aged 3–59 months.

Each year, transhumant nomads migrate in the endemic area from the Sahelian zone to the Sudanian zone and subsequently return to the northern part of the country with low or no malaria transmission, when the rainy season arrives. The structure of nomad habitat has been described elsewhere [ 38 ]. Accordingly, blood samples were taken twice a year from children aged 3–59 months, and none of these children have been sampled twice. The first samples were taken when the nomads were moving to the south (January– March) and the second set during the high malaria transmission period (July– October) when they reached the Sahelian zone.

Study population

Nomadic children, specifically Arab or Fulani or Dazagada (Daza) children aged 3–59 months at the time of the study whose parents provided consent to blood sample collection were included. To mitigate the inflation of malaria prevalence due to parents selectively designating sick children, in each randomly selected household within the camps, a blood sample was obtained from the oldest child aged 3 to 59 months. If the result from the RDT was positive for Plasmodium , the child received a dose of antimalarial in accordance with the national treatment protocol [ 40 ].

Sampling and recruitment

Within each of three nomad group a multi-stage cluster random sampling technique was employed, with the camp as first stage and the household as second-stage leading to a minimum sample of 180 study subjects. A provision of 4% was added to account for non-response. At the first level, from the list of camps provided by leaders of each three nomad groups, 51 camps were randomly selected using a random number draw. At the second stage, within each selected camp, surveyors used random number draws to select two households (four households for very large camps). For selected household, one member aged older than 18 years was requested for interviews and responded on behalf of the household to which he or she belongs. Additionally, the oldest child of the group of 3–59 months was chosen for blood sampling. Of the 187 children, 81 were blood sampled in January– March and 106 in July– October.

Data collection

After being informed, the parents of the children were required to provide written consent, they indicated their agreement by affixing their signature or fingerprint on two copies of the cards. The demographic characteristics of the child (age and sex), facial temperature by thermoflash for some children and the results of the RDT (SD BIOLINE Malaria Ag Pf/Pan, Standard Diagnostics USA) were entered on the collection sheet with a unique and anonymous identification code for each child.

To record information on the parents’ sociodemographic characteristics, their knowledge and experiences regarding malaria, and their use of mosquito nets, a structured electronic questionnaire developed based on Peto et al. [ 37 , 41 ] was administered to an adult who responded on behalf of the household during blood sample collection. The survey questionnaire was administered in February and October 2021 by three trained data collectors fluent in the local languages and experienced in collecting data for nomad immunization programs. The questionnaire included items on respondents’ socio-demographic characteristics; their knowledge and experiences regarding malaria; and their use of mosquito nets. The questionnaire was implemented in KoBoCollect v2021.2.4 [ 42 ], and was administered offline before responses were uploaded to the server once the WiFi connection was available. While data collectors were administering the questionnaire, health agents were collecting blood sample.

Response variable

The results of malaria test were categorized as either “negative” or “positive” according to the SD BIOLINE Malaria Ag Pf/Pan RDT procedures. The SD Bioline ™ Malaria Ag Pf/Pan test is a rapid, qualitative, and differential test designed to detection of the histidinerich protein 2 (HRP2) antigen of Plasmodium falciparum and the common Plasmodium lactase dehydrogenase (pLDH) of Plasmodium species in human whole blood. The reliability of RDT-based diagnosis is reported elsewhere [ 43 , 44 , 45 , 46 , 47 ].

Explanatory variables

We evaluated the association between malaria prevalence and socioeconomic and contextual factors. The questionnaire included a variety of questions related to socioeconomic and contextual factors, listed below:

characteristics of the individual households and children;

contextual characteristics;

and district and zone variables.

Characteristics of the individual households and children

The main explanatory variables were: (i) the child’s temperature; (ii) the child’s age (3–59 months); (iii) the gender of the child and household characteristics such as (iv) household wealth quintiles, categorized as “lowest”, “middle” and “highest” economic levels; (v) ethnic group (Arab, Dazagada and Fulani); (vi) marital status of the head of household categorized as, “widowed/divorced”, “monogamy” and “polygamy”; (vii) reflex in case of malaria, including seeking a “street drug seller”, “health facility”, “traditional drug”; and (viii) utilization of LLIN and knowledge of malaria.

Common principles used to measure knowledge of malaria include questions on transmission and preventive interventions [ 48 ]. This study used similar principles published elsewhere [ 37 ]. Dimensions included were related to the periods of high transmission (rainy season), the group most at risk (children and pregnant women), means of transmission (mosquito bite) and common symptoms (fever, chills, muscle pain, stomach pain, diarrhea, nausea and vomiting). The dimension of interventions related to sleeping under a LLIN as mean of protection against malaria. Each correct response to question was scored one point and zero for wrong answers. An overall knowledge score was calculated by summing the scores for each respondent across all questions. Those with scores of 2.5 (mid-point between 0 and 5) or above were considered to have good knowledge, while those with lower scores were categorized as having poor knowledge about malaria.

Contextual characteristics

These characteristics were: ix) place of residence categorized as, “urban” or “rural”. Urban residence includes townships, municipalities and cities; x) the season; xi) the malaria control intervention in place (LLINS and SMC).

District and zone variables

These included: viii) all 3 administrative provinces; and ix) all district areas.

Laboratory methods

Rapid diagnostic test

Capillary blood samples were collected by study staff using a finger prick. One drop of blood was used to perform a malaria RDT (SD BIOLINE Malaria Ag PF/Pan, Standard Diagnostics USA). Blood samples were collected by three trained health agents who had previously collected blood sample and perform RDT during the National Malaria Survey (ENIPT) [ 39 ], in addition to participating in nomad immunization programs. Health agents were responsible for collecting children’s blood samples and performing RDT, while data collectors were administered questionnaires to parents. The RDT kits used in this study were obtained from health districts as recommended by the Ministry of health (MOH) and used in public health facilities.

Statistical methods

The data collected during each period were entered into Excel files, and STATA version IC 13 was used for statistical analysis. Percentages, means and standard deviations were calculated. Differences in proportions were assessed with exact Fisher’s tests. Sample means were compared by unpaired Student’s t tests. Values of p  < 0.05 were considered significant. The parasitaemia rate was defined as the percentage of children with positive results from RDTs among the total of children surveyed. Few children had their temperature taken; therefore, the malaria prevalence rate was not processed, although children carrying Plasmodium were considered to have malaria.

Principal Component Analysis (PCA) [ 49 ] was used to develop wealth categories for the households based on access to facility including potable water and ownership of durable assets including solar kit, radio, telephone, cart tracked by animal, motorcycle/scooter, and caws/camels and sheep/goats per capita. Access and ownership were coded as 0 or 1 and missing cases were excluded. The first dimension of the PCA was taken as the household wealth score and range into tertiles; households were then placed into socioeconomic categories based on their scores.

We performed a descriptive analysis and presented participants’ social and demographic characteristics stratified by RDT results. We then employed exact Fisher’s tests to assess any difference in malaria prevalence by socioeconomic and contextual factors. Logistic regression analysis was conducted to identify the factors associated with malaria prevalence among nomads in Chad. Crude (COR) and adjusted odds ratios (AOR) were calculated to check statistical associations between the dependent and independent variables using the binary logistic regression and multivariable logistic regression models. All variables in the study were initially tested for association with malaria prevalence using a binary logistic regression model. Those showing a significant statistical association ( p  < 0.05) were added into the multivariable analysis model to assess whether the association persisted after controlling against all other variables. A 95% confidence intervals and the 5% significance level were calculated for all odds ratios.

Characteristics of the study population

Overall, 187 children aged 3–59 months were enrolled in this study, distributed across the following districts and provinces: Dourbali (17.6%) and Massenya (13.9%) in Chari Baguirmi province (31.5%); Massaguet (55.1%) in the Hadjer Lamis province (55.1%) and Niellim (13.4%) in Moyen Chari province (13.4%) were enrolled in this study (Table  1 ; Fig.  1 ). Of them, 90 (48.1%) were female, and the enrolled children belonged to Arab (36.4%), Daza (36.4%) and Fulani (27.2%) ethnic groups. Concerning malaria, 86 (46.0%) and 36 (19.2%) participants came from households using street drugs and traditional drugs respectively in case of malaria episodes. Additionally, 154 children (82.4%) were from households with poor utilization of LLINs, and 162 (86.6%) of the participants were living in SMC areas (Table  1 ).

Map of study area

Malaria prevalence according to characteristics of the study participants

Overall 46 (24.60%) children were tested positive for malaria. The malaria prevalence was 21.7% and 28.4% respectively for blood sample collected in October and February 2021 (Fig.  2 ). Fisher’s exact test revealed a notably higher prevalence of malaria in children from the southern regions of the Sahelian zone, specifically Massenya and Dourbali, as well as in Niellim located in the south of the country, compared to the northern part of Sahelian counterparts in Massaguet. Specifically malaria positivity rates were 26.9% in Massenya, 36.4% in Dourbali and 56.0% in Niellim, significantly higher than the 12.6% observed in Massaguet. A significantly higher proportion of participants were tested positive in the area not receiving SMC (56.0%). Regarding the individual characteristics of participants and that of their households, a significant proportion of positive tests were found in boys (29.9%) compared to girls (18.9%). Additionally, positive test results were significantly higher among children from the Fulani (41.2%) and Arab (22.1%) ethnic groups than among those from the Daza (14.7%) ethnic group. A significantly larger proportion of positive tests was also found among children from households seeking traditional drugs (27.8%) and health facilities (32.3%) compared to street drug sellers (17.4%) in the case of malaria episodes (Table  1 ).

Malaria prevalence by month of data collection

Malaria prevalence according to Plasmodium species

The malaria RDT results according to Plasmodium species are presented in Table  2 . Out of 46 positive malaria tests, 16 (34.8% of positive test results) exhibited mixed species ( Plasmodium falciparum, Plasmodium ovale, Plasmodium malaria and/or Plasmodium vivax ). Mixed Plasmodium species were more frequently found in Daza children (70.0%), followed by Fulani children (66.7%). Concerning the use of mosquito nets, mixed Plasmodium species were identified in children whose parents reported not spending the last night under mosquito nets.

Factors associated with a positive test for malaria prevalence

Among all variables, geographic characteristics such as province, SMC area and individual or household characteristics like gender, ethnicity, socioeconomic status and the household’s behavior during malaria episodes, were significantly associated with malaria positivity ( p  < 0.05) using the crude logistic regression (Table  3 ). Additionally, the use of mosquito nets (all types and LLINs), knowledge of malaria and the main source of water used by the household were included in the logistic regression adjusting for all other variables and only those significantly associated with malaria were retained.

After adjusting for other individual, household and geographic characteristics, Daza children were seventeen times less likely (AOR = 0.06; 95% CI, 0.01–0.79, p  = 0.024) to have malaria than Fulani children. Children whose parents used to seek traditional drugs were five times more likely (AOR = 5.48; 95% CI, 1.38–21.72, p  = 0.016) to have malaria than children whose parents used to seek health facilities. Children whose parents reported spending the last night under a mosquito net were one fifth as likely (AOR = 0.17; 95% CI, 0.03–0.93, p  = 0.041) to have malaria compared to children whose parents did not spend the last night under a mosquito net. Children from households with piped water as main source were seven times more likely (AOR = 7.05; 95% CI, 1.69–29.45; p  = 0.007) to have malaria than children from households using surface water. Children from areas not implementing SMC were twenty times more likely (AOR = 20.61; 95% CI, 2.91–145.77; p  = 0.002) to have malaria than children from areas implementing SMC.

Malaria remains a public health challenge in sub-Saharan Africa, including Chad despite ongoing efforts for control and elimination through various interventions and financial investments. It is difficult to reach mobile communities that are more exposed to malaria than the general population. This study aimed to assess the prevalence of malaria and explore individual/household and community factors associated with malaria among nomadic communities in Chad.

This study highlighted the burden of malaria in Chad, with a national prevalence in the general population of 40.9% with high variability according to the endemicity area. The prevalence of malaria is moderate in Hadjer Lamis (15.9%), high in Chari Baguirmi (37.2%) and very high (68.1%) in Moyen Chari [ 39 ]. In this study, the prevalence of malaria was 24.6% which is low compared to the aforementioned study conducted in the general population without specificity for nomad considerations. However, this result is consistent with other studies conducted in the nomadic setting of Chad reporting a malaria prevalence of up to 30% [ 50 ]. The high prevalence documented in this study is also in line with studies in other African countries among nomadic populations such as Fulani pastoralists in southwestern Nigeria, recording a prevalence of 33.6% [ 51 ]. Additionally, in the general population of Ghana, a prevalence of 20.9% was reported [ 9 ].

Among malaria positive tests, 34.8% were found to be a mix of malaria parasites. This result underscores the necessity for further analysis to assess the malaria parasite species in Chad. Studies forming the basis for malaria management protocols in Chad tend to be out dated, reporting 98% of species as Plasmodium falciparum and only 2% as other malaria parasite species [ 6 ]. Furthermore, the results from this study indicate a high percentage of mixed Plasmodium species in Daza children, followed by Fulani children and children whose parents are not accurate users of mosquito nets. This result can be explained by the trajectory followed by both the Daza and Fulani groups during transhumance, with Daza group crossing the country in the east and the Fulani group in the south.

The current study revealed significant variation in the odds of malaria prevalence across provinces. In Chad, approximately 53% of the total land has climatic conditions favorable for malaria transmission (sahelian and sudanian area), covering 98% of the population. Malaria transmission in the Sahelian area spans between 3 and 4 months seasonally, while the Sudanian exhibits high endemicity throughout the year. Other factors, including altitude, temperature, humidity, rainfall, presence of breeding sites, and agricultural activities within provinces may explain variation in the prevalence of malaria between provinces. In this study, the higher malaria prevalence in Moyen Chari (Sudanian area) compared to Chari Baguirmi (Sahelian area) can also be attributed to the impact of malaria intervention in the Sahelian area (SMC) in contrast to the Sudanian area. Therefore, the SMC area was found to be associated with a lower prevalence of malaria.

In the current study, male participants were more likely to test positive for malaria than female. This finding aligns with the results of a study from Ghana and Cameroon establishing a significant association between gender and malaria prevalence, with males having a higher prevalence than females [ 8 , 9 , 12 ]. This could be explained by nomadic boys assisting parents with herds in the early evenings and, therefore, exposing them more to mosquito vectors. Additionally, other studies have suggested that boys tend to play outdoors in the early evenings more frequently than girls, resulting in increased exposure to mosquito vectors [ 8 ].

The study’s findings indicated a higher risk for malaria prevalence for Fulani children compared to Daza children. This result can be attributed to the area of exposure visited by these nomad groups. Fulani nomads ventured further into the Sudanian Chad than Daza who mostly stayed in the Sahelian zone. Furthermore, in recent decades, due to climatic, economic and political changes, a significant increase in pastoral mobility has been recorded in the Sudanian zone [ 23 , 38 ]. Moreover, some nomadic groups, such as the Fulani, have started transitioning to a more sedentary lifestyle in the Sudanese area [ 38 ].

Children whose parents sought traditional drugs for malaria treatment were more likely to have malaria than those whose parents sought health facilities. This finding can be explained by the low efficacy of traditional drugs against malaria and the lack of awareness regarding malaria prevention and treatment. Since these drugs often lack active principles to cure malaria, children may continue to harbor malaria parasites. As indicated elsewhere [ 38 ], traditional drugs in nomadic communities sometimes include ‘koulkul tree leaves’, ‘camel urine’ and ‘beef urine’ or ‘milk butter’. However, these results underscore the imperative need to enhance the availability and accessibility of health services. It has been mentioned elsewhere that the cost of health care and the severity of illness were the primary reasons for selecting health services in nomadic communities [ 38 ]. Furthermore, such interventions should be complemented by health promotion activities, as these factors influence community treatment-seeking patterns and contribute to ongoing malaria transmission.

Among all participants in the study, four to five mentioned spending the last night under a mosquito net of various types. While some may use the mosquito nets to protect themselves from other insect bites [ 38 ], the use of mosquito nets has proven effective in protecting children from malaria. Children whose parents reported spending the last night under a mosquito net were less likely to have malaria than those whose parents had not used a mosquito net. This result underscores the high potential for preventing malaria within this community by utilizing mosquito nets. This impact might have been more significant if nomads had access to LLINs; however, as mentioned elsewhere [ 37 , 38 ], this community has limited access to LLINs.

Children from households with piped water as main source of water were more likely to have malaria than those from households relying on surface water. Typically, piped water and wells are in proximity to nomad camps, enabling women and children to fetch water late at night. In contrast, surface water is far from camps, requiring women and children to seek water during the day with less exposure to mosquito bites. Additionally, queuing for other water sources may be longer than for surface water; resulting in a shorter duration of exposure to mosquito bites. This result appears contrary to findings in Tanzania [ 11 ], which considered piped water as free from stagnant water. However, in the nomad camps, all water sources are used by both humans and animals, meaning stagnant water surrounds all water sources. These stagnant waters serve as breeding ground mosquitoes, facilitating the development of the larvae into adult mosquitoes.

Strengths and limitations

This study has some limitations, including a small size of enrolled children, which may affect its representativeness for the entire nomadic child population. Nevertheless, the results provide insights into the overall descriptive situation of nomadic children. There may be potential bias in measuring LLIN use among children tested for malaria as only member per household responds on behalf of the household without specifying if children were under the mosquito net. Another limitation of this study was the reliance on a cross-sectional survey conducted at the end of the rainy season and the dry season when mosquito density and malaria transmission may be lower than in the rainy season. The study could not delve into parasite typology research through polymerase chain reaction (PCR) analysis due to funding. In terms of recommendations, interventions would be more cost-effective if tailored to the district level rather than at the provincial or national level. However, the study can be valuable for understanding factors associated with an increased likelihood of malaria positivity, guiding stakeholders in the implementation of malaria prevention, control and elimination strategies in nomadic communities, and the entire population in Chad. Furthermore, the study suggests the need for additional research to assess the typology of malaria parasites.

The study findings revealed a malaria prevalence of 24.6% with 34.8% of positive test indicating a mix of malaria parasites. This prevalence is relatively lower as compared to other studies conducted in other settings. Factors influencing malaria infection in nomad communities include the participants’ ethnic group, the reflex of households in malaria cases, the utilization of mosquito nets regardless of type, the main water source used by households and the participants’ living area. The findings underscore that malaria remains a public health concern in Chad, particularly in nomadic communities. The gathered information can guide the implementation of malaria prevention, control and elimination strategies benefiting the entire population in Chad.

The study recommends that the MOH and the NMCP organize community education and sensitization programs within nomadic communities, especially those in remote rural areas, emphasizing the effects of malaria. The NMCP should also enhance both the coverage and use of LLINs and SMC, along with promoting of treatment-seeking behaviors in nomadic communities.

Data availability

The datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request.

Abbreviations

Antenatal care

Adjusted odd ratio

Crude odd ratio

Deoxyribonucleic acid

Intermittent preventive treatment for pregnant women

Long-lasting insecticide-treated net

Ministry of Public Health

National Malaria Control Program ( Programme National de Lutte contre le Paludisme )

Polymerase chain reaction

• Seasonal malaria chemoprevention

Sulphadoxine-pyrimethamine and amodiaquine

United Nations Children’s Fund

World Health Organization

Akpodiete NO, Diabate A, Tripet F. Effect of water source and feed regime on development and phenotypic quality in Anopheles gambiae (s.l.): prospects for improved mass-rearing techniques towards release programmes. Parasit Vectors. 2019;12:210.

Article   PubMed   PubMed Central   Google Scholar  

Talapko J, Škrlec I, Alebić T, Jukić M, Včev A. Malaria: the past and the Present. Microorganisms. 2019;7:179.

Article   CAS   PubMed   PubMed Central   Google Scholar  

WHO. World malaria report 2022. Global Malaria Programme. Geneva: WHO; 2022.

Google Scholar  

Ministere de la Sante Publique. Annuaire Des statistiques sanitaires 2017 [Health statistics yearbook 2017]. N’Djamena: Ministry of Health Chad; 2018.

Ministère de la Santé Publique. Annuaire De Statistique sanitaire. Ndjamena: Ministère de la Santé Publique; 2019.

Programme National de Lutte contre le Paludisme. Plan stratégique National de lutte contre le paludisme 2014–2018. 2013.

Traoré B. Epidémiologie moléculaire de la résistance de plasmodium falciparum aux médicaments antipaludiques en République du Tchad. Thesis. USTTB; 2020.

Nyasa RB, Fotabe EL, Ndip RN. Trends in malaria prevalence and risk factors associated with the disease in Nkongho-mbeng; a typical rural setting in the equatorial rainforest of the South West Region of Cameroon. PLoS ONE. 2021;16:e0251380.

Tetteh JA, Djissem PE, Manyeh AK. Prevalence, trends and associated factors of malaria in the Shai-Osudoku District Hospital, Ghana. Malar J. 2023;22:131.

Folarin OF, Kuti BP, Oyelami AO. Prevalence, density and predictors of malaria parasitaemia among ill young Nigerian infants. Pan Afr Med J. 2021;40:25.

Shayo FK, Nakamura K, Al-Sobaihi S, Seino K. Is the source of domestic water associated with the risk of malaria infection? Spatial variability and a mixed-effects multilevel analysis. Int J Infect Dis. 2021;104:224–31.

Article   PubMed   Google Scholar  

Tarekegn M, Tekie H, Dugassa S, Wolde-Hawariat Y. Malaria prevalence and associated risk factors in Dembiya district, North-western Ethiopia. Malar J. 2021;20:372.

Ahmed A, Mulatu K, Elfu B. Prevalence of malaria and associated factors among under-five children in Sherkole refugee camp, Benishangul-Gumuz region, Ethiopia. A cross-sectional study. PLoS ONE. 2021;16:e0246895.

Mkali HR, Reaves EJ, Lalji SM, Al-mafazy A-W, Joseph JJ, Ali AS, et al. Risk factors associated with malaria infection identified through reactive case detection in Zanzibar, 2012–2019. Malar J. 2021;20:485.

Woday A, Mohammed A, Gebre A, Urmale K. Prevalence and Associated Factors of Malaria among Febrile Children in Afar Region, Ethiopia: A Health Facility based study. Ethiop J Health Sci. 2019;29:613–22.

Andronescu LR, Buchwald AG, Coalson JE, Cohee L, Bauleni A, Walldorf JA, et al. Net age, but not integrity, may be associated with decreased protection against Plasmodium falciparum infection in southern Malawi. Malar J. 2019;18:329.

Amare A, Eshetu T, Lemma W. Dry-season transmission and determinants of Plasmodium infections in Jawi district, northwest Ethiopia. Malar J. 2022;21:45.

Khaireh BA, Briolant S, Pascual A, Mokrane M, Machault V, Travaillé C, et al. Plasmodium Vivax and Plasmodium Falciparum infections in the Republic of Djibouti: evaluation of their prevalence and potential determinants. Malar J. 2012;11:395.

INSEED. Deuxième Récensement Général De La Population et de l’Habitat 2009 [Second General Population Census and Habitat 2009]. Rapport De récensement. Ndjamena: Institut National de Statistique, des Etudes Economique et Démographique; 2012.

CTA. Atlas d’élevage Du Bassin Du Lac Tchad. Wageningen. Pays-Bas; 1996.

Clanet J. Géographie Pastorale Au Sahel central. Thèse d’Etat en Géographie Humaine. Paris IV Sorbone; 1994.

Fuchs P. Nomadic society, civil war, and the state in Chad. Nomadic Peoples. 1996;:151–62.

Wiese M. Health-vulnerability in a complex crisis situation. Implications for providing health care to nomadic people in Chad. Verlag für Entwicklungspolitik. Saarbrûcken; 2004.

Bojang K, Akor F, Bittaye O, Conway D, Bottomley C, Milligan P, et al. A randomised trial to compare the safety, tolerability and efficacy of three drug combinations for intermittent preventive treatment in children. PLoS ONE. 2010;5:e11225.

Chatio S, Ansah NA, Awuni DA, Oduro A, Ansah PO. Community acceptability of Seasonal Malaria Chemoprevention of morbidity and mortality in young children: a qualitative study in the Upper West Region of Ghana. PLoS ONE. 2019;14.

Cissé B, Sokhna C, Boulanger D, Milet J, Bâ EH, Richardson K, et al. Seasonal intermittent preventive treatment with artesunate and sulfadoxine-pyrimethamine for prevention of malaria in Senegalese children: a randomised, placebo-controlled, double-blind trial. Lancet. 2006;367:659–67.

Dicko A, Diallo AI, Tembine I, Dicko Y, Dara N, Sidibe Y et al. Intermittent preventive treatment of Malaria provides Substantial Protection against Malaria in Children already protected by an insecticide-treated Bednet in Mali: a Randomised, Double-Blind, placebo-controlled trial. PLoS Med. 2011;8.

Druetz T, Corneau-Tremblay N, Millogo T, Kouanda S, Ly A, Bicaba A, et al. Impact Evaluation of Seasonal Malaria Chemoprevention under Routine Program implementation: a quasi-experimental study in Burkina Faso. Am J Trop Med Hyg. 2018;98:524–33.

Konaté AT, Yaro JB, Ouédraogo AZ, Diarra A, Gansané A, Soulama I, et al. Intermittent preventive treatment of Malaria provides Substantial Protection against Malaria in Children already protected by an insecticide-treated Bednet in Burkina Faso: a Randomised, Double-Blind, placebo-controlled trial. PLoS Med. 2011;8:e1000408.

Sesay S, Milligan P, Touray E, Sowe M, Webb EL, Greenwood BM, et al. A trial of intermittent preventive treatment and home-based management of malaria in a rural area of the Gambia. Malar J. 2011;10:2.

Tagbor H, Antwi GD, Acheampong PR, Bart Plange C, Chandramohan D, Cairns M. Seasonal malaria chemoprevention in an area of extended seasonal transmission in Ashanti, Ghana: an individually randomised clinical trial. Trop Med Int Health. 2016;21:224–35.

Plucinski MM, Chicuecue S, Macete E, Colborn J, Yoon SS, Kachur SP, et al. Evaluation of a universal coverage bed net distribution campaign in four districts in Sofala Province, Mozambique. Malar J. 2014;13:427.

Secrétariat de l’Organisation Mondiale de la Santé. Paludisme: projet de stratégie technique mondiale pour l’après-2015. Rapport Du Secrétariat. Génève: Organisation Mondiale de la Santé; 2015.

Lengeler C. Insecticide-treated bed nets and curtains for preventing malaria. The Cochrane Collaboration; 2004.

Gamble CL, Ekwaru JP, ter Kuile FO. Insecticide-treated nets for preventing malaria in pregnancy. Cochrane Database Syst Rev. 2006;2006.

Programme National de Lutte contre le Paludisme. Plan stratégique national de lutte contre le paludisme 2019–2023 [National strategic plan to fight against malaria 2019–2023]. N’Djamena; 2019.

Moukénet A, Richardson S, Moundiné K, Laoukolé J, Ngarasta N, Seck I. Knowledge and practices surrounding malaria and LLIN use among arab, Dazagada and Fulani pastoral nomads in Chad. PLoS ONE. 2022;17:e0266900.

Moukénet A, Honoré B, Smith H, Moundiné K, Djonkamla W-M, Richardson S, et al. Knowledge and social beliefs of malaria and prevention strategies among itinerant nomadic arabs, fulanis and Dagazada groups in Chad: a mixed method study. Malar J. 2022;21:56.

National Malaria Control Program, National Institute of Statistics. Enquête Nationale sur les Indicateurs Du Paludisme Au Tchad De 2017: ENIPT-2017. Ndjamena: National Malaria Control Program Chad; 2018.

Programme National de Lutte contre le Paludisme. Politique Nationale De Lutte Contre Le Paludisme. Politique Nationale. Ndjamena: Ministère de la Santé Publique et de la Solidarité Nationale; 2014.

Peto TJ, Tripura R, Sanann N, Adhikari B, Callery J, Droogleever M, et al. The feasibility and acceptability of mass drug administration for malaria in Cambodia: a mixed-methods study. Trans R Soc Trop Med Hyg. 2018;112:264–71.

The Harvard Humanitarian Initiative. KoBoToolbox. 2021.

Tadesse E, Workalemahu B, Shimelis T. Diagnostic performance evaluation of the SD bioline, malaria antigen AG PF/PAN test. (05FK60) In a malaria endemic area of southern Ethiopia. Rev Inst Med Trop São Paulo. 2016;58:59.

PubMed   PubMed Central   Google Scholar  

Pujo JM, Houcke S, Lemmonier S, Portecop P, Frémery A, Blanchet D, et al. Accuracy of SD Malaria Ag P.f/Pan® as a rapid diagnostic test in French Amazonia. Malar J. 2021;20:369.

Kashosi TM, Mutuga JM, Byadunia DS, Mutendela JK, Mulenda B, Mubagwa K. Performance of SD Bioline Malaria Ag Pf/Pan rapid test in the diagnosis of malaria in South-Kivu, DR Congo. Pan Afr Med J. 2017;27:216.

Malaria rapid diagnostic test performance. Results of WHO product testing of malaria RDTs: Round 8 (2016–2018). https://www.who.int/publications-detail-redirect/9789241514965 . Accessed 12 Mar 2023.

Mfueni E, Devleesschauwer B, Rosas-Aguirre A, Van Malderen C, Brandt PT, Ogutu B, et al. True malaria prevalence in children under five: bayesian estimation using data of malaria household surveys from three sub-saharan countries. Malar J. 2018;17:65.

Fuge TG, Ayanto SY, Gurmamo FL. Assessment of knowledge, attitude and practice about malaria and ITNs utilization among pregnant women in Shashogo District, Southern Ethiopia. Malar J. 2015;14:235.

Vyas S, Kumaranayake L. Constructing socio-economic status indices: how to use principal components analysis. Health Policy Plan. 2006;21:459–68.

Moto DD, Daoud S, Tanner M, Zinsstag J, Schelling E. Répartition de la morbidité dans trois communautés nomades du Chari-Baguirmi and Kanem, Chad. Med Trop (Mars). 2004;64:469–73.

Ekpo UF, Omotayo AM, Dipeolu MA. Sendentarization and the prevalence of malaria and anaemia among settled Fulani pastoralists in south-western Nigeria. Niger J Parasitol. 2008;29.

Download references

Acknowledgements

We gratefully thank the nomadic pastoralists of the Arab, Dazagada and Fulani for their hospitality and participation in this study. We acknowledge the medical officers of Massakory, Massaguet, Massenya, Korbol and their teams for their diligent help during this study. This study would not have been possible without the field workers Kabo Karadjom, Bianzoumbé Jonas, Annour Kanika and Issa Younous who helped with the sample and data collection, and performed the rapid diagnostic test. We are thankful to Tsakeu Elyonore Leponkouo for revising the manuscript.

The authors received no specific funding for this work.

Author information

Authors and affiliations.

Cheikh Anta Diop University, Dakar, Senegal

Azoukalné Moukénet & Ibrahima Seck

University of Ndjamena, Ndjamena, Chad

Azoukalné Moukénet & Ngarkodje Ngarasta

Abomey-Calavi University, Abomey-Calavi, Benin

Kebfene Moudiné

UNDP, Ndjamena, Chad

Clement Kerah Hinzoumbe

You can also search for this author in PubMed   Google Scholar

Contributions

AM, KM, CKH, NN, and IS conceived the project; KM and AM oversaw the data collection; KM, CKH, and AM analyzed and interpreted the quantitative data, and KK, BJ, AK and IY processed the RDT. AM drafted the manuscript and all authors reviewed subsequent versions and approved the final version for submission.

Corresponding author

Correspondence to Azoukalné Moukénet .

Ethics declarations

Ethics approval and consent to participate.

The aim and objectives of the research were explained to caregivers’ prior consent. Written informed consent was obtained from all participants or their guardians prior to their enrollment. The study protocol was approved by the National Ethics Committee of Chad (Approval No 0193/PR/MESRI/SG/CNBT/2020, 21 September 2020). All experiments were performed in accordance with relevant guidelines and regulations.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note.

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Supplementary Material 1

Supplementary material 2, supplementary material 3, rights and permissions.

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/ . The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/ ) applies to the data made available in this article, unless otherwise stated in a credit line to the data.

Reprints and permissions

About this article

Cite this article.

Moukénet, A., Moudiné, K., Ngarasta, N. et al. Malaria infection and predictor factors among Chadian nomads’ children. BMC Public Health 24 , 918 (2024). https://doi.org/10.1186/s12889-024-18454-5

Download citation

Received : 23 July 2023

Accepted : 26 March 2024

Published : 28 March 2024

DOI : https://doi.org/10.1186/s12889-024-18454-5

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

• Long-lasting insecticidal nets

BMC Public Health

ISSN: 1471-2458

• Submission enquiries: [email protected]
• General enquiries: [email protected]