Environmental and host factors affecting seroprevalence of bluetongue virus infections of sheep

There are several studies concerning a naturally occurring bluetongue disease, clearly indicating that factors related to both the mammalian host and the environment can influence the outcome of bluetongue virus (BTV) infection. In this study, the result of testing of 928 samples from a serologic survey of sheep with BTV infections in the Chaharmahal-Va-Bakhtiari province of Iran were analyzed for association between environmental (climate) and host (age, sex, abortion history) factors. Bivariate analysis indicated that environmental and two host factors were associated with the test result. After the chi-square test, a higher seropositive was observed in the plain region (59.94%), compared with the mountain region (24.24%) (df = 2, χ² = 104.59, P < 0.0001). An association was found between seropositivity and sex. The males (64.88%) showed a higher seropositive compared with females (31.84%) (df = 2, χ² = 106.418, P < 0.0001). An association was found between seropositivity and abortion history that abortive sheep had a higher seropositive compared with non-abortive sheep (df = 2, χ² = 6.150, P < 0.04). The investigation of bluetongue disease based on the changes in the interplay of pathogens and affecting factors including hosts and environment is very important in epidemiological survey that these changes lead to the formation of novel disease patterns.