Assessing the impact of topography on malaria exposure and malaria epidemic sensitivity in the Western Kenya highlands

Abstract

The sensitivity of a site to malaria epidemics depends on the level of immunity of human population. This study examined how terrain in the highlands affects the exposure and sensitivity of a site to malaria. The study was conducted in five sites in western Kenya, two U-shaped valleys (Iguhu, Emutete), two V-shaped valleys (Marani, Fort-Ternan) and one plateau (Shikondi) for ten months among 6-15 years old children. Exposure to malaria was tested using circum-sporozoite protein and merozoite surface protein immunochromatographic antibody test; malaria infection was tested by microscopic examination of thick and thin smears. The mean antibody prevalence was 20.5% in Iguhu, 23.6% in Emutete, 12.7% in Shikondi, 9.6% in Fort-Ternan and 10.6% in Marani. The mean malaria infection prevalence was 23.5% in Iguhu, 21.1% in Emutete, 5.1% in Shikondi, 3.1% in Fort-Ternan and 3.6% in Marani. There was a significant difference in the antibodies and malaria infection prevalence among the two valley systems and the plateau (P<0.05). There was no significant difference in the antibodies and malaria infection prevalence within the U-shaped valleys and within the V-shaped valleys (P> 0.05). There was a 5.7 fold and a 2-fold greater parasites and antibody prevalence respectively, in the U-shaped compared to the V-shaped valleys. The plateau antibody and parasite prevalence was similar to that of the V-shaped valleys. U and V-shaped valleys have similar climate therefore the observed differences in parasites and antibody prevalence are likely to be due to their drainage characteristics.