NATURAL AND EXPERIMENTAL BOVINE IMMUNODEFICIENCY VIRUS-INFECTION IN CATTLE

The principal diseases associated with bovine immunodeficiency virus ( BTV) infection in a production dairy were bacterial infections. The in fections were associated with histologic evidence of compromise of the immune system. The disease were most apparent after parturition and d uring early lactation. Two hundred twenty-seven different diseases wer e identified in 89 cows between 1989 and 1995. Fifty-two diseases were identified in 19 cows between 1995 and 1996. The primary lesions were encephalitis and lymphoid tissue hyperplasia followed by lymphoid tis sue, exhaustion, and laminitis. Weight loss, decreased milk production , and reproductive inefficiency were secondary to the primary lesions. Many cows responded poorly to therapy. Epidemiologic and economic res earch are needed to clarify the association between BIV and bovine dis eases and the economic impact of the infection in beef and dairy produ ction units.