Genetic host factors play a substantial role in susceptibility to and severity of malaria, which continues to cause at least one million deaths per year. Recently, members of the toll-like receptor (TLR) family have been shown to be involved in recognition of the etiologic organism Plasmodium falciparum: The glycosylphosphatidylinositol anchor induces signaling in host cells via TLR-2 and -4, whereas hemozoin-induced immune activation involves TLR-9. Binding of microbial ligands to the respective TLRs triggers the release of proinflammatory cytokines via the TLR͞IL-1 receptor (TIR) domain and may contribute to the host response in malaria, including cytokine induction and fever. In a case-control study among 870 Ghanaian children, we examined the influence of TLR-2, -4, and -9 polymorphisms in susceptibility to severe malaria. TLR-2 variants common in Caucasians and Asians were completely absent. However, we found a rare previously undescribed mutation (Leu658Pro), which impairs signaling via TLR-2. We failed to detect any polymorphisms within the TLR-9 Toll͞IL-1 receptor domain. Two frequent TLR-9 promoter polymorphisms did not show a clear association with malaria severity. In contrast, the TLR-4-Asp299Gly variant occurred at a high rate of 17.6% in healthy controls and was even more frequent in severe malaria patients (24.1%, P < 0.05). Likewise, TLR-4-Thr399Ile was seen in 2.4% of healthy children and in 6.2% of patients (P ‫؍‬ 0.02). TLR-4-Asp299Gly and TLR-4-Thr399Ile conferred 1.5-and 2.6-fold increased risks of severe malaria, respectively. These findings suggest TLR4-mediated responses to malaria in vivo and TLR-4 polymorphisms to be associated with disease manifestation.single-nucleotide polymorphisms ͉ innate immunity ͉ Plasmodium falciparum

Concerns about the tolerability of mefloquine highlight the need for new drugs to prevent malaria. Atovaquone-proguanil (Malarone; GlaxoSmithKline) was safe and effective for prevention of falciparum malaria in lifelong residents of malaria-endemic countries, but experience in nonimmune people is limited. In a randomized, double-blind study, nonimmune travelers received malaria prophylaxis with atovaquone-proguanil (493 subjects) or mefloquine (483 subjects). Information about adverse events (AEs) and potential episodes of malaria was obtained 7, 28, and 60 days after travel. AEs were reported by an equivalent proportion of subjects who had received atovaquone-proguanil or mefloquine (71.4% versus 67.3%; difference, 4.1%; 95% confidence interval, -1.71 to 9.9). Subjects who received atovaquone-proguanil had fewer treatment-related neuropsychiatric AEs (14% versus 29%; P=.001), fewer AEs of moderate or severe intensity (10% versus 19%; P=.001), and fewer AEs that caused prophylaxis to be discontinued (1.2% versus 5.0%; P=.001), compared with subjects who received melfoquine. No confirmed diagnoses of malaria occurred in either group. Atovaquone-proguanil was better tolerated than was mefloquine, and it was similarly effective for malaria prophylaxis in nonimmune travelers.

Malnutrition is a fundamental factor contributing to malaria-associated morbidity and anemia, even if the latter exhibits multifactorial patterns. Our data demonstrate that malaria-control programs alone may not have the desired impact on childhood morbidity on a large scale without concomitant nutrition programs.

The symptoms of severe malaria and their contribution to mortality were assessed in 290 children in northern Ghana. Common symptoms were severe anemia (55%), prostration (33%), respiratory distress (23%), convulsions (20%), and impaired consciousness (19%). Age influenced this pattern. The fatality rate was 11.2%. In multivariate analysis, circulatory collapse, impaired consciousness, hypoglycemia, and malnutrition independently predicted death. Children with severe malaria by the current World Health Organization (WHO) classification, but not by the previous one (1990), showed relatively mild clinical manifestations and a low case fatality rate (3.2%). In hospitalized children with severe malaria in northern Ghana, severe anemia is the leading manifestation, but itself does not contribute to mortality. In this region, malnutrition and circulatory collapse were important predictors of fatal malaria. The current WHO criteria serve well in identifying life-threatening disease, but also include rather mild cases that may complicate the allocation of immediate care in settings with limited resources.