DECREASE IN THE NATURAL IMMUNITY OF RIFT- VALLEY FEVER NEUTRALIZING ANTIBODIES FROM DOMESTIC RUMINANTS IN THE SENEGAL RIVER BASIN 3 YEARS AFTER THE 1987 EPIZOOTIC

A domestic ruminants serosurvey of Rift valley fever (RVF) neutralizin g antibodies has been carried out during three years after the 1987 ep idemic in the Senegal River Basin. Authors present results from the 19 90 serosurvey that are matched with the preview surveys. Out of 1,225 ongulate tested, 17.2 % had RVF virus antibodies. There is a global de crease in the herds immunity since the epizootic manifestation associa ted with the 1987 epidemic. Significant differences in seroprevalence are observed from the delta (28.5 %) to the lower (17.9 %) and middle valley (6.1 %) of the Senegal river. Cattle are more likely to be with an higher seroprevalence than goat and sheep.