Bluetongue in cattle: a serologic survey of slaughter cattle in the United States.

Serologic tests for bluetongue virus (BTV) were done on 19,758 blood serum samples systematically collected at brucellosis laboratories throughout the United States from Nov 28, 1977 to Feb 20, 1978. Prevalence of BTV antibody varied from 0 to 79% of the samples collected in various states, with a national prevalence of 18.2%. The prevalence was generally low in the northern states and high in the southwestern states. The highest prevalence rates were found in Puerto Rico and the Virgin Islands.