Laboratoire de physique de l‘atmosphère Siméon Fongang, ESP\UCAD, BP 5085 Dakar‐Fann, Sénégal, <jandioneucad.sn>. Climat et santé, Centre universitaire d‘épidémiologie de population, Faculté de médecine, BP 87900, 21079 Dijon Cedex, France. Médias‐France, CNES, BPI 2102, 31401 Toulouse Cedex 4, France. Inra, Unité biomathématiques et épidémiologie, École nationale vétérinaire de Lyon, BP 83, 69280 Marcy l‘Étoile, France.
- Key words: Rift valley fever; environment; epidemiology; rain; climate; Africa, western.
- Page(s) : 176-82
- Published in: 2003
The onset and spread of epidemics of Rift Valley fever (RVF) are reported by some authors to be associated with climatic conditions and environmental changes due to priming of various irrigation systems. This article uses the example of the lower basin of the Senegal River as the basis for a critical analysis of these works. Various authors have suggested that circulation of the virus in Kenya may be linked to rainy years that follow relatively dry years. A pattern valid for southern or eastern Africa is unlikely to apply to the desert and semi‐desert (Sahelian) areas. On the other hand, two characteristics seem to have been underestimated until now in the epidemiological cycle of RVF in West Africa : the first is transhumance and commercial movements (which determine the risk of introducing or reintroducing the virus into untouched or relatively uncontaminated areas) ; the second involves the time needed to reconstitute a susceptible (that is, nonimmune) animal population ; this measurement makes it possible to assess the receptivity of cattle when the virus recirculates.