BLACKLEG - A NEW PERSPECTIVE ON AN OLD DISEASE

Two first-calf Holstein heifers with a history of anorexia, depression , decreased milk production, severe hindlimb lameness, and swelling of 18 to 24 hours in duration were examined in February of 1993. The two animals were from a herd that, within a three-week period, had four b red heifers and one first-calf heifer die suddenly after exhibiting si milar clinical signs. A pure culture of Clostridium chauvoei was isola ted from the affected legs of both examined heifers. Fluorescent antib ody examination was also positive for C. chauvoei. One heifer became r ecumbent and was euthanatized. The second heifer was treated and survi ved. None of the affected cattle in this outbreak was febrile. Despite an overwhelming infection, the two heifers had either normal or sligh tly elevated white blood cell counts and normal aspartate transaminase and creatine kinase serum chemistry values. Therefore, blood work may not be helpful in the diagnosis of clostridial myositis. Gram-stained smears or fluorescent antibody testing of the affected muscle can pro vide a rapid diagnosis of clostridial myositis. Bacterial culture can identify the species and confirm the diagnosis.