Seroprevalence of bovine leukemia virus infection in contrasting farming systems in Kenya

Enzootic bovine leukosis (EBL) is a worldwide disease of cattle caused by the bovine leukemia virus (BLV) and clinically characterised by occurrence of multiple lympho-sarcomas. In Kenya, cases of bovine lympho-sarcomas have been reported but limited information available on prevalence and distribution of BLV infection in the country. The objectives of this cross-sectional study were to estimate the seroprevalence of BLV infection in Kenya and how the seroprevalence is affected by different livestock farming systems. In 2016, 1383 bovine serum samples were randomly collected from 14 counties which were purposively selected to represent 3 livestock farming systems in the country. The sera were tested for the presence of antibodies against BLV using the IDEXX anti–BLV indirect ELISA test. An overall seroprevalence of 7.6% (95% CI: 6.3% - 9.1%) BLV infection was estimated. A multivariable mixed logistic regression model, with county as a random variable controlling for clustering, identified age and farming system as significant risk factors associated with BLV seropositivity. Zero-grazing (0.6%), ranching (4.4%) and pastoral systems (18.3%) differed in seroprevalence. Cattle under 1 year of age had a prevalence of 6.4%, while cattle over 1 year of age had a prevalence of 7.9%. BLV infection was present across the three farming systems but in only five of the fourteen counties assessed. This information contributes to designing effort on control programs of BLV infection in Kenya. Further research should be carried out to determine the frequency of clinical cases of EBL and the impact on the livestock industry in Kenya. Keywords: Bovine Leukemia Virus; Cattle, Seroprevalence; Kenya