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The dispersal, population dynamics, and age structure of two Rift Valley Fever Virus (Phlebovirus: Bunyaviridae) (RVFV) vectors, Aedes vexans Meigen and Culex poicilipes Theobald, were investigated in northern Senegal. The main objective was to investigate possible factors that mediate RVFV emergence and propagation at a site where humans and livestock live in proximity to temporary surface pools. In mark-release-recapture studies, recapture rates of 0.18% (156/85,500) and 3.46% (201/5,800) were obtained for Ae. vexans and Cx. poicilipes, respectively. The number of mosquitoes recaptured decreased with increasing distance from the release point and over time. The estimated daily survival rate for released females ranged from 91 to 96% for Ae. vexans and 70-79% for Cx. poicilipes. The maximum time after release when marked mosquitoes were collected was 23 and 12 d for Ae. vexans and Cx. poicilipes, respectively. The maximum distances from the release point that marked females were recaptured was 620 and 550 m for Ae vexans and Cx. poicilipes, respectively. Rainfall periodicity was a key factor controlling Ae. vexans population abundance. In contrast, rainfall had no discernible effect on the fluctuation of Cx. poicilipes numbers. The involvement of these two species in the transmission of RVFV is discussed with respect to their longevity and daily survival rate.

The aim of this study is to highlight the recent progress in mapping vector-borne diseases in West Africa using modelling and field experiments. Based on climatic indicators, methods have been developed to map Rift Valley fever (RVF) and malaria risk. Modelling results corroborate that northern Senegal and southern Mauritania appear to be critical areas for RVF outbreaks and that the malaria epidemic fringe is located at the northern edge of the Sahel. Future projections highlight that the malaria risk decreases over northern Sahel. This is related to a southward shift of the potential epidemic belt in autumn.