The Molecular Epidemiology of Malaria in Western Kenya

The Molecular Epidemiology of Malaria in Western Kenya Malaria epidemiology reflects a complex web of inter-related factors: host, parasite, vector and environment. The nature, duration and severity of malaria infection depend upon these fixed and changing factors, and are complicated by varying levels of acquired immunity in individuals. The present research used molecular biology tools to examine three distinct topics related to malaria epidemiology: 1) the distribution of TNF-α, IFN-γ, IL-6, TGF-β, and IL-10 gene polymorphisms; 2) the rate and pattern of mixed Plasmodium species infections; and 3) Plasmodium falciparum growth dynamics. The first two research topics were examined in a cohort of 248 males recruited from three highly endemic villages in western Kenya where severe malaria anemia is common. The third topic was investigated among 22 volunteers during the post-challenge phase of a malaria vaccine trial sponsored by Walter Reed Army Institute of Research. Individuals in the Kenya cohort were found to have a marked bias toward genotypes associated with low expression of IFN-γ and IL-6, cytokines that, at high plasma levels, have been previously implicated in anemia and poor malaria outcomes. By contrast, the frequency of the TNFα –238A allele, which has been associated with severe malarial anemia, was found to be similar to frequencies reported in a number of diverse populations. Over the course of three malaria transmission seasons, non-falciparum malaria was consistently seen in a minority (5-10%) of volunteers, most commonly as a dual infection with P. falciparum. In contrast to previous reports of long-term stable parasite density among