Mycoplasma bovis associated with decubital abscesses in Holstein calves

California Veterinary Diagnostic Laboratory System, University of California, Davis, CVDLS San Bernardino Branch 92412.

Between April of 1990 and March of 1992, calves on a Holstein calf ranch experienced subcutaneous decubital abscesses involving the brisket region, dorsal aspect of the carpus, and lateral aspect of the stifle joints. Fifty out of 2,500 (2%) Holstein calves between the ages of 3 and 12 weeks were affected. Needle aspirates of brisket abscesses from 8 calves and 6 live or dead calves with 1 or more decubital abscesses were submitted for examination. Two of the 6 calves in addition had bronchopneumonia. Mycoplasma bovis was isolated from all abscesses and 1 lung. Formalin fixed tissues taken from the affected areas also revealed M. bovis by immunoperoxidase staining. No evidence of joint involvement was apparent, and no mycoplasma was isolated from the joints adjacent to affected areas. Attempts to isolate mycoplasma from milk and environmental samples were unsuccessful.