Environnement, Risques & Santé
MENUEnvironmental conditions associated with the emergence of Rift Valley fever (RVF) in the Senegal River delta in 1987 Volume 4, issue 2, Mars-Avril 2005
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- Key words: disease outbreaks, insect vectors, rain, Rift Valley fever, Senegal
- Page(s) : 10005-10
- Published in: 2005
The Rift Valley fever (RVF) epidemic that occurred in 1987 in the Senegal River delta was associated by some experts with a rainfall above normal and with the opening of the Diama dam. Our main concern in this paper is to study the hydro-climatic conditions at the time RVF emerged along the Senegal-Mauritania border. We consider the rainfall observed at Rosso, the level of the Senegal River there and at the dam, and the river flow rate at Bakel. Analysis of the 1987 rainy season shows that there was no excess rainfall associated with the emergence of RVF. The only particularity in rainfall that year was the postponement of the seasonal peak month from August to September. The first human cases were diagnosed in October, when rainfall was below normal (-35% compared to the monthly average rainfall for 1961-1990). Moreover, the opening of the dam did not upset local hydrology at that time. Hydro-climatic conditions thus do not appear to explain - certainly not alone - the emergence of RVF in the area. The pattern observed in Southern and Eastern Africa does not explain what occurred in 1987 in the Senegal River basin. Without calling into question the influence of rainfall in RVF emergence, the rainfall in especially rainy periods or during series of rains seems more important than the cumulative rainfall over the entire season, because of the importance these shorter heavy rains play in the dynamics of mosquito vector populations in West Africa.