Sero-surveillance of Rift Valley fever in sheep and goat flocks in high risk areas in Kenya

Abstract

The surveillance of Rift Valley Fever (RVF) was carried out in the risk areas of Kenya by monitoring free range/migratory and sedentary farm sheep and goat herds for antibodies to RVF virus (RVFV). A total of 986 serum samples were collected and analyzed from farms in Molo, (where no outbreaks has ever been previously reported), Naivasha, (an RVF-endemic area and where the first case of RVF was reported in Kenya), Kajiado, (where there had been reports of an RVF-like disease) and Shompole, (a chief transmigratory livestock-route and market on the Kenya/Tanzania border). Of the total sera tested, 16.9% (164/966), 8.4% (81/966) and 4.1% (39/966) were found to be positive by IgG-sandwich enzyme-linked immunosorbent assay (ELISA), IgM-capture ELISA and serum neutralization (SN) tests respectively. On average, the percentages of sera testing positive for antibodies from sedentary farm herds (Molo, Nakuru and Naivasha) were higher than those from the free-range herds (Kajiado, Namanga, Magadi and Shompole). Although no IgM antibodies were detected in sera from Molo, a significant percentage of the sera showed presence of IgG antibodies. This study also confirms that the RVF-like disease that had been informally reported in the pastoralist areas of Namanga and Kajiado was actually RVF.