Changes in Rift Valley fever neutralizing antibody prevalence among small domestic ruminants following the 1987 outbreak in the Senegal River basin.

Following the Rift Valley fever (RVF) epizootic of 1987 in the Senegal River basin, 2 series of serosurveys were carried out. In 1988 and 1989, respectively, 303 and 331 randomly selected sheep and goats were investigated and sera tested for the presence of specific RVF-virus-neutralizing antibodies. In 1988, 24.4% of the sera was found to have anti-RVF neutralizing antibodies and in 1989, 19.3% was found. In 1988, we observed in the Dagana district, including the 1987 epizootic area, a significantly higher prevalence (71.1%) than in the two other more distant districts of Podor (21.5%) and Matam (9.7%). From 1988 to 1989, the antibody seroprevalence dropped significantly from 71.7 to 23.9% within the Dagana district. Young animals showed a significantly lower antibody prevalence (7.9%, N = 114) than adults (25.3%, N = 217). RVF virus circulated at a low level in 1988-89 without any epizootic manifestation. The population turnover generated an important non-immune population potentially at risk.