Prevalence and risk factors of bluetongue in small and large ruminants maintained on Government farms in North-western Pakistan

Abstract

This study reports prevalence of antibodies against bluetongue virus (BTV) in animals kept on Government farms/research stations in North-western Pakistan and its association with different risk factors. In total, 1257 blood samples were collected, at random, from animals on 12 separate Government farms/research stations. The prevalence of antibodies against BTV was evaluated using a competitive ELISA. Mixed effects univariate and multivariate logistic regressions were applied to ascertain different risk factors associated with the prevalence of the infection using farm as random effect variable. The overall weighted seroprevalence was recorded as 52%. In univariate analysis, a significant association between sero-conversion to BTV infection and species (P < 0.0001), sex (P < 0.0001), herd size (P = 0.0295) and age of animal (P < 0.0001) was recorded. In multivariate mixed effects logistic regression analysis, prevalence of the infection was found to be 7 (95% CI =2–28) times higher in goats and buffalo than in sheep. Prevalence of the infection was found to be 2.5 (95% CI =1.7–3.3) times higher in female than male animals. However, no significant association was found between sero-conversion of BTV and herd size in multivariate mixed effects logistic regression. Age was found to be a risk factor for the sero-conversion; odds of sero-conversion to BTV increased by 1.29, 1.4, 1.32 and 1.6 times per year increase in age of sheep, goats, buffalo and cattle, respectively. Prevalence of bluetongue was found higher in animals maintained on Government owned farms than that in individual holdings, as previously reported in Pakistan.