Caseous lymphadenitis (CL) is a chronic, contagious bacterial disease that manifests clinically as abscesses of peripheral and/or internal lymph nodes and organs. The characteristic purulent material is very thick and nonodorous. Whereas the peripheral form presents as abscesses of single or multiple peripheral palpable lymph nodes, internal CL typically manifests as chronic weight loss and ill thrift. Culture of active lesions for Corynebacterium pseudotuberculosis is diagnostically definitive. When eliminating animals from the herd/flock is undesirable, treatment consists of consistent, sustained antimicrobial therapy to reduce the numbers of active draining lesions and isolation from other herd mates until lesions are dry and/or resolved. Economic losses from CL include death, condemnation and trim of infected carcasses, hide and wool loss, loss of sales for breeding animals, and premature culling of affected animals from the herd or flock. Once established on a farm or region (endemic), it is primarily maintained by contamination of the environment with active draining lesions, animals with the internal form of the disease that contaminate the environment through nasal discharge or coughing, the ability of the bacteria to survive harsh environmental conditions, and lack of strict biosecurity necessary to reduce the number and prevent introduction of new cases.