Caseous lymphadenitis (CLA) is a chronic bacterial disease of sheep and goats caused by the highly infectious bacterium Corynebacterium pseudotuberculosis. The disease is characterised by abscess development in the lymph nodes and other tissues, and is increasing in prevalence in the UK.
CLA results in welfare issues and economic losses due to ill thrift and carcase trimming or (in severe cases) carcass condemnation at abattoir. CLA may also increase susceptibility to other infections.
Affected animals often have visible lumps in the superficial lymph nodes i.e. those lymph nodes which can be accessed from the outside of the animal. Most frequently in the UK, lymph node abscesses tend to be associated with the head and neck region. Abscesses in this area can press on the oesophagus preventing normal rumination, leading to weigh loss. It is generally held that infected animals remain infected for their entire lives, and as such sheep and goat producers must apply strict biosecurity measures to help prevent and control the disease.
CLA is found in most parts of the world where small ruminants are farmed, including Europe, Australasia, North and South America, Africa, and the Middle East. Prevalence of infection increases with age and is more common in sheep kept under intensive management conditions.
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