(CLA, CL, boils, abscesses, cheesy gland)
Caseous lymphadenitis is an infectious, contagious disease that primarily affects the lymphatic system, though other organs can be affected. It is caused by the bacteria Corynebacterium pseudotuberculosis. Infection results in abscess formation in the lymph nodes which when cut or ruptured, discharge pus containing the bacteria into the immediate surroundings. When the nodes spread internally, affected ewes slowly lose weight and eventually become emaciated.
CL is the third leading leading cause of carcass condemnation in the U.S.. The disease is controlled by culling visible infected animals and practicing good hygiene at shearing time. There is a vaccine licensed for sheep. It has been shown to both decrease the number of abscesses in sheep and the number of sheep that develop abscesses.