Caseous lymphadenitis (CL) is caused by a bacteria called Corynebacterium pseudotuberculosis.  It is a disease that affects goats and sheep and causes abscesses in the lymph nodes and lungs. It enters through small breaks in the skin or mucous membranes and localizes in regional lymph node. The incubation period before abscesses are noted in superficial lymph nodes is typically two to six months but could be longer. The abscess may rupture and drain spontaneously.

The animal with only external abscesses typically shows no clinical signs other than enlargement and abscessation of one or more peripheral lymph nodes. Sheep tend to have abscesses in front of the shoulder blade, in the flank region, or on the back of the thigh. This is the result of infection during the shearing process. Goats often develop abscesses of the head and neck region. The pus in these abscessed lymph nodes may be white, yellowish, or greenish, creamy, pasty, or cheesy. It typically has no odor. Internal abscesses are often associated with pneumonia or wasting.

Diagnostics include culturing pus directly from the abscess. There is also serologic testing.  This is mainly used to identify sheep and goats with early or internal forms of caseous lymphadenitis.  However, tests have not been specific enough to justify decisions for culling positive animals. It is of value in avoiding purchasing of infected animals.

Treatment of affected animals involves lancing or removing the abscessed lymph nodes. The affected animal should be isolated until the lesion is completely covered by healthy skin (20-30 days later).

Eradication of CL from a herd is very difficult. The owner must be willing to cull animals with multiple abscesses and not to purchase animals from infected herds. Infected animals that want to be kept should be isolated and their offspring removed at birth to prevent contamination of the rest of the herd mates. Needles, tattooers and surgical instruments should be sterilized between animals. During shearing, shear the youngest sheep first, as these are the most susceptible. Disinfect clippers before shearing. Also disinfect if you accidentally enter an abscess with the clippers. Animals with chronic respiratory disease or wasting should be culled or isolated.