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How Terrain Affects Malaria Transmission in Western Kenya Highlands

Updated: Feb 20, 2023

Malaria is a major public health concern in sub-Saharan Africa, particularly in the highland areas where transmission is unstable and highly variable. A recent study conducted in the western Kenya highlands examined how the terrain of the area affects exposure and sensitivity to malaria. The study found that U-shaped valleys were transmission hotspots, while V-shaped valleys had lower prevalence and were considered epidemic hotspots.

The study was conducted over a period of 16 months among 6-15 year old children in five sites: two U-shaped valleys (Iguhu, Emutete), two V-shaped valleys (Marani, Fort-Ternan) and one plateau (Shikondi). Exposure to malaria was tested using circum-sporozoite protein (CSP) and merozoite surface protein (MSP) immunochromatographic antibody tests, while malaria infections were tested by microscopic examination of thick and thin smears. The children’s homes were also georeferenced using a global positioning system.

The results showed that there was a significant difference in the prevalence of antibodies and malaria infections between the two valley systems and the plateau. The U-shaped valleys had an 8.5-fold greater parasite prevalence and a 2-fold greater antibody prevalence compared to the V-shaped valleys, which had lower prevalence and were considered epidemic hotspots. The plateau ecosystem had a similar infection and immune response to the V-shaped ecosystems.

The study also found that malaria infections were clustered around flat areas in the U-shaped valleys, while they were randomly distributed in the V-shaped valleys and less clustered at the plateau. These findings suggest that the sensitivity of a site to malaria epidemics depends on the level of immunity of the human population and the terrain of the area.

In conclusion, this study highlights the importance of considering terrain when developing strategies to control and prevent malaria in highland areas. The findings suggest that U-shaped valleys are transmission hotspots, while V-shaped valleys have lower prevalence and are considered epidemic hotspots. This knowledge could inform the development of targeted interventions in the western Kenya highlands and other similar regions.

The full paper can be found here:

Parasites & Vectors 2011 Wanjala et al
Download PDF • 1.84MB

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