Blackleg without skeletal muscle involvement as a cause of sudden death in unvaccinated calves.

Nine, 5-month-old unvaccinated black Angus calves died in less than 48 hours of each other. The calves expressed minimal or no clinical signs prior to death. On-farm post-mortem examinations were carried out on 3 of the deceased calves, and findings included: necrotizing and fibrinosuppurative myositis of the diaphragm muscle, and fibrinosuppurative pleuritis and epicarditis. Fluorescent antibody testing for pathogenic clostridia identified and a diagnosis of blackleg was made. The remainder of the herd were then vaccinated.