Caseous Lymphadenitis

By Barry Whitworth

Caseous Lymphadenitis (CL) is a common disease found in sheep and goats. It is recognized when abscesses form in the external lymph nodes. This condition is found in sheep and goats worldwide. One study reported that 42.41 percent of all culled ewes and rams from the western United States had some form of CL. A Study in Canada found that 3.9 percent of goats died from CL and that 24.3 percent of the goats had CL lesions at necropsy.

There is a great economic impact associated with this disease including the cost of treatment, the loss of marketable animals, carcass condemnation and wool loss. CL is not limited to sheep and goats. Other species may be infected including humans. Unfortunately, once sheep and goats are infected, they are considered infected for life.

Corynebacterium pseudotuberculosis is the bacterium that causes CL. The organism can survive for long periods of time in the soil and for shorter periods of time on objects such as feed troughs or water buckets. When the organism is combined with organic material, the survival rate increases.

The bacteria gain entrance to the body by penetrating the skin or skin trauma. The bacteria can also be ingested or inhaled, which allows for penetration of mucous membranes. Once in the body, the bacteria travel by the lymph drainage system to a lymph node. In a few months an encapsulated abscess will usually appear. Usually the abscess eventually ruptures and drains. These active lesions serve as a source of infection for other sheep and goats.

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