Epidemiology of Blackleg Disease in Ethiopia

Blackleg is an infectious bacterial disease of cattle and rarely of other ruminants. This bacteria is caused by Clostridium chauvoei which is an anaerobic, gram positive, motile, rod-shaped bacillus bacterium and persists in the soil as resistant spores. Blackleg is an acute or subacute but chronic disease may occur. It occurs most frequently in animals 6-24 months of age and the disease mainly affects none vaccinated as well as animals in good nutritional condition. It produces persistent spores when conditions are not ideal and spores are highly resistant to environmental factors and disinfectants. Infected ruminants do not directly transmit the disease to other animals. The bacteria enter the body through the alimentary mucosa after ingestion of contaminated feed. Secretion of cytolytic toxins that cause necrosis of vascular endothelia .The toxins are absorbed into the animal’s bloodstream which makes the animal acutely sick and causes rapid death. Economic importance due to blackleg is loss of animals, milk production and draft oxen, and cost for treatment and vaccination. Fatality rate of blackleg in fully susceptible populations approaches 100%. Clinical Signs include lethargy anorexia, reluctance to move lameness and recumbence. When superficial muscles are affected, swelling and crepitus are evident. Cattle found dead of blackleg are lying on the side with the affected hind limb stands out stiffly, bloating and putrefaction occur quickly and bloodstained from exudates, nostrils and anus. The disease can be diagnosed using laboratory diagnosis, Immune Fluorescent, Cell Culture and PCR. Control and prevention relies mainly on vaccination.