A seroepidemiologic survey of antibody to bluetongue virus in Alabama cattle.

Bluetongue (BT) is an insect transmitted viral disease of sheep that often causes mild or inapparent disease but rarely causes severe disease in cattle. Until recently, bluetongue viral infection was believed to be more prevalent in the Western United States, as compared with other regions of the country. However, a national survey for bluetongue antibody and clinical evidence of the disease in the Southeastern United States prompted the present investigation that was designed to determine the serological prevalence of BT virus in Alabama cattle. Results of the study demonstrated that 16% of the samples collected from 1,500 cattle in 64 of the 67 counties were positive. The prevalence of positive cattle in the western part of the State was significantly higher (P less than .001) than the prevalence in the eastern half of the State. On a herd basis, 52% of all herds tested had positive animals. Results of this study suggest that bluetongue infection is more common in the Southeastern United States than previously suspected.