Blackleg (disease)

Blackleg, black quarter, quarter evil, or quarter ill (Latin: gangraena emphysematosa) is an infectious bacterial disease most commonly caused by Clostridium chauvoei, a Gram-positive bacterial species. It is seen in all over the world, usually affecting cattle, sheep, and goats. It has been seen occasionally in farmed bison and deer. The acute nature of the disease makes successful treatment difficult, but an effective vaccine is available to provide animals with protective immunity.

Most losses due to blackleg occur when the cattle are between the ages of six months and two years, although it can occur when they are as young as two months. Typically, cattle that have a high feed intake and are well-conditioned tend to be the most susceptible to blackleg. Furthermore, many blackleg cases occur during the hot and humid summer months or after a sudden cold period, but cases can occur at any time during the year.

Blackleg is most commonly caused by C. chauvoei, but C. feseri and other clostridial species can be isolated from some lesions. C. chauvoei is Gram-positive, rod-shaped, anaerobic, and motile, and can produce environmentally persistent spores when conditions are not ideal for growth. These spores can remain in the soil for years in an inactive state, and return to their infectious form when consumed by grazing livestock. Contaminated pasture is a predominant source of these organisms, which are also found naturally in the intestines of animals. Cases can occur over many years in areas where soil or manure is contaminated with the bacteria, and it is exceedingly difficult to remove the spores from the environment.

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