Presence of Bluetongue Virus Antibodies in Cattle and Sheep in Ogun and Osun States, Nigeria

Bluetongue is an infectious, arthropod-borne viral disease principally affecting ruminants. The occurrence of bluetongue virus (BTV) antibodies in sheep and cattle from backyard farms, cattle markets and abattoirs in Ogun and Osun states of Nigeria was investigated. Three hundred and forty (340) plasma samples comprising 205 from sheep and 135 from cattle were collected from March to September 2017, noting the sex, breed and age of the animals. The samples were screened with a commercial enzyme-linked immunosurbent assay (ELISA) kit that detects BTV antibodies in ruminant plasma or serum. All cattle tested from both states were positive for BTV antibodies giving a seroprevalence of 100% while 95% seroprevalence was obtained for sheep. In Ogun state, prevalence of 90.5% and 98% were obtained for male and female sheep respectively while 95.6% and 95% prevalence were also obtained for male and female sheep respectively in Osun state. Based on breed, 94%, 95%, 95% and 96% prevalence were obtained for Yankasa, Balami, Ouda and West African Dwarf (WAD) sheep respectively in Ogun state while 93%, 95.5%, 100% and 93% prevalence were obtained for Yankasa, Balami, Ouda and WAD sheep respectively in Osun state. Furthermore, prevalence of 92% and 96.7% were obtained for age groups of ≤ 1 year and > 1 year respectively in Ogun state, while prevalence of 96% and 94.7% were obtained for age groups of ≤ 1 year and > 1 year respectively in Osun state. Since vaccination against bluetongue disease is not practiced in Nigeria, the detection of high prevalence of BTV antibodies observed in apparently healthy animals in this study indicates natural, albeit subclinical, infection with the virus and sustained activity of the Culicoides vector. These findings suggest that bluetongue is widespread in southwestern part of Nigeria and highlight the need for continuous surveillance of the disease in the country as well as isolation, identification and characterisation of currently circulating BTV strains in Nigeria.