an acute infectious disease of cattle, characterized by crepitating edema, lameness, and quick death. Blackleg, which occurs in various geographical areas, is caused by the spore-forming anaerobic microbe Clostridium chauvoei. The microbe’s spores are preserved for many years in soil or water. In decomposing muscle tissue they live for as much as six months, while in the sun they die in 24 hours and in a corrosive sublimate solution (1:500) they die in ten minutes. Blackleg affects young cattle and occasionally sheep and goats. Susceptibility decreases with the animal’s age.
The source of the disease-causing microbe is an animal infected with blackleg. Factors aiding transmission of the disease are infected feeds and objects used in caring for the animals. Infection enters the body through the digestive tract with food and water or through a break in the skin. The disease is usually observed during the pasturing period. Infected animals show a sudden rise in body temperature and become lame. Painful, hot, dense swellings appear on the animals’ croup and loins. Crackling (crepitation) is observed when pressure is applied to these swellings, which contain bubbles of gas. The animals show signs of depression. They salivate excessively and stop ruminating. Their breathing becomes more frequent, and their pulse weakens. The animal dies within ten to 60 hours. The corpse is usually very bloated. A foamy liquid runs from the nose and mouth, and a bloody liquid from the anus.
Diagnosis is based on epizootic data, clinical symptoms, pathological anatomical changes, and bacteriological tests. Blackleg should be distinguished from anthrax and malignant edema by identifying the specific causative organism. Treatment, which is not always effective, involves the use of antibiotics. When the disease breaks out, the infected farm is quarantined. The affected animals are identified, isolated, and treated, as are those suspected of having the disease. The rest are vaccinated with a vaccine of concentrated aluminum hydroxide. The animal stalls are thoroughly disinfected, as are the places where sick or dead animals were kept.
It is forbidden to use the meat or skins from infected animals. After the last case of the disease is cured or the animal dies the premises are disinfected thoroughly and the quarantine is lifted in 14 days. In farms where there were previous cases of blackleg, the cattle are vaccinated two weeks before they are sent out to pasture.