Abstract
IntroductionDynamics of most of vector-borne diseases are strongly linked to global and local environmental changes. Landscape changes are indicators of human activities or natural processes that are likely to modify the ecology of the diseases. Here, a landscape approach developed at a local scale is proposed for extracting mosquito favourable biotopes, and for testing ecological parameters when identifying risk areas of Rift Valley fever (RVF) transmission. The study was carried out around Barkedji village, Ferlo region, Senegal.MethodsIn order to test whether pond characteristics may influence the density and the dispersal behaviour of RVF vectors, and thus the spatial variation in RVFV transmission, we used a very high spatial resolution remote sensing image (2.4 m resolution) provided by the Quickbird sensor to produce a detailed land-cover map of the study area. Based on knowledge of vector and disease ecology, seven landscape attributes were defined at the pond level and computed from the land-cover map. Then, the relationships between landscape attributes and RVF serologic incidence rates in small ruminants were analyzed through a beta-binomial regression. Finally, the best statistical model according to the Akaike Information Criterion corrected for small samples (AICC), was used to map areas at risk for RVF.ResultsAmong the derived landscape variables, the vegetation density index (VDI) computed within a 500 m buffer around ponds was positively correlated with serologic incidence (p<0.001), suggesting that the risk of RVF transmission was higher in the vicinity of ponds surrounded by a dense vegetation cover. The final risk map of RVF transmission displays a heterogeneous spatial distribution, corroborating previous findings from the same area.ConclusionsOur results highlight the potential of very high spatial resolution remote sensing data for identifying environmental risk factors and mapping RVF risk areas at a local scale.
Highlights
Dynamics of most of vector-borne diseases are strongly linked to global and local environmental changes
In order to test whether pond characteristics may influence the density and the dispersal behaviour of Rift Valley fever (RVF) vectors, and the spatial variation in RVF virus (RVFV) transmission, we used a very high spatial resolution remote sensing image (2.4 m resolution) provided by the Quickbird sensor to produce a detailed land-cover map of the study area
Among the derived landscape variables, the vegetation density index (VDI) computed within a 500 m buffer around ponds was positively correlated with serologic incidence (p
Summary
Dynamics of most of vector-borne diseases are strongly linked to global and local environmental changes. A landscape approach developed at a local scale is proposed for extracting mosquito favourable biotopes, and for testing ecological parameters when identifying risk areas of Rift Valley fever (RVF) transmission. The RVF virus (RVFV) is a member of the Phlebovirus genus (Bunyaviridae family). It is transmitted by mosquito bites, and through contact with viremic fluids from infected ruminants to healthy ruminants or humans [5]. In its most severe form, the illness can progress to hemorrhagic fever, encephalitis, or ocular disease with significant death rate. Animals such as sheep, goats, and cattle are primarily affected. RVF causes abortions in pregnant females (80-100%), and high mortality of newborns, inducing important direct and indirect economic losses [6,7]
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