Abstract:
Increased human population in the Western Kenya highlands has led to reclamation of natural swamps
resulting in the creation of habitats suitable for the breeding of Anopheles gambiae, the major malaria vector in the
region. Here we report on a study to restore the reclaimed swamp and reverse its suitability as a habitat for malaria
vectors. Napier grass-shaded and non-shaded water channels in reclaimed sites in Western Kenya highlands were
studied for the presence and density of mosquito larvae, mosquito species composition, and daily variation in
water temperature. Shading was associated with 75.5% and 88.4% (P < 0.0001) reduction in anopheline larvae
densities and 78.1% and 88% (P < 0.0001) reduction in Anopheles gambiae sensu lato (s.l.) densities in two sites,
respectively. Shading was associated with a 5.7°C, 5.0°C, and 4.7°C, and 1.6°C, 3.9°C, and 2.8°C (for maximum,
minimum, and average temperatures, respectively) reduction (P < 0.0001) in water temperatures in the two
locations, respectively. An. gambiae s.l. was the dominant species, constituting 83.2% and 73.1%, and 44.5% and
42.3%, of anophelines in non-shaded and shaded channels, respectively, in the two sites, respectively. An. gambiae
sensu stricto (s.s.) constituted the majority (97.4%) of An. gambiae s.l., while the rest (2.6%) comprised of
Anopheles arabiensis. Minimum water temperature decreased with increasing grass height (P = 0.0039 and
P = 0.0415 for Lunyerere and Emutete sites, respectively). The results demonstrate how simple environmental
strategies can have a strong impact on vector densities.
