The Effects of Climatic Factors on the Distribution and Abundance of Malaria Vectors in Kenya

Abstract

Since 1988 malaria epidemics have occurred in multiple sites in western Kenya highlands. Climatic variability has been associated with some of the recent epidemics. We examined influences of climatic factors on the distribution and abundance of three malaria vector species, Anopheles gambiae, Anopheles arabiensis, and Anopheles funestus in western Kenya and in the Great Rift Valley. Mosquito samples were collected from the lowland and highland areas with various climatic conditions. The three vector species were abundant in the lower part of western Kenya. An. arabiensis was not found in the areas above 1,400 m elevation in western Kenya Although An. gambiae and An. funestus were found in the sites above 1,700 m in western Kenya, their densities were < 1 per house. In the Great Rift Valley, An. gambiae was not recorded. An. funestus was more widely distributed than the other two species. A stepwise multiple regression analysis found that moisture index was the most important variable in shaping species composition of the An. gambiae complex. Relative abundance of An. gambiae was positively associated with moisture index, suggesting that An. gambiae is more adapted to moist climate. Seasonal differences in species composition were significant in western Kenya, and the proportion of An. funestus was higher in the dry season than the rainy season. Influence of temperature on vector density was significant for all three species. These results imply that climate changes alter the distribution and abundance of malaria vectors in future.

Spatial clustering of endemic Burkitt's lymphoma in high‐risk regions of Kenya

“…Transmission above 1,600 m is rare. 23,24 Locations included in the most likely low-risk area identified by SaTScan had minimum elevations of roughly 1,580 m or more.…”

Hot temperatures can force delayed mosquito outbreaks via sequential changes in Aedes aegypti demographic parameters in autocorrelated environments

“…Similar patterns of association between mosquito abundance and weather fluctuations have been observed in other Aedes spp. (Ho et al 1971;Makiya 1974;Sota et al 1992), culicine (Barker et al 2010;Hayes & Downs 1980;Makiya 1973) and anopheline (Minakawa et al 2002) mosquitoes, as well as other Diptera vectors of disease (Morrison et al 1995;Salomon et al 2004). One of the intriguing patterns in these associations is the emergence of relatively long delays in the association between environmental changes and the occurrence of vector outbreaks.…”

Combining Global and Local Estimates for Spatial Distribution of Mosquito Larval Habitats

“…Elevation, presented in meters, is used as a surrogate variable for climatic conditions, because temperature in general decreases, whereas precipitation increases, with elevation (Minikawa et al, 2002). Aspect is a substitute for solar radiation and associated moisture conditions (Hodgson and Gaile, 1999).…”