Spatiotemporal distribution of diurnal yellow fever vectors (Diptera: Culicidae) at two sylvan interfaces in Kenya, East Africa

Yellow fever virus (YFV) remains a significant public health threat in sub-Saharan Africa in which 90% of the estimated 200,000 cases occur annually. In East Africa, human cases of YFV are characterized by unpredictable focal periodicity, lengthy inter-epidemic periods, and a precarious potential for large epidemics. YFV had remained undetected in this region for nearly 40 years until emerging in Kenya in 1992-93 and more recently in Sudan during 2003 and 2005. From an ecological perspective the emergence and epidemiological outcomes associated with YFV, and related vector-borne diseases, are critically dependent upon the underlying vector ecology at a local scale. The study here was aimed at defining the dynamics of important vector interactions at two important sites in Kenya with previous YFV or related arbovirus activity. The temporal abundance, spatial distribution, and human host seeking behavior of diurnal man-landing mosquito species along sylvan interfaces were investigated. A number of YFV vectors were identified including their abundances for the duration of the main rainy season. Spatially, results indicated that the greatest human-mosquito interactions occurred within the forest and decreased across more domesticated biotopes. A discussion of significant differences, ecological associations, and epidemiological implications is included.