Caseous lymphadenitis (CLA) caused by Corynebacterium pseudotuberculosis is a chronic bacterial disease of sheep and goats causing abscesses in superficial and internal lymph nodes, with significant welfare and production consequences.
Sheep with CLA experience varying welfare impact depending on whether disease is external or internal. External abscesses are largely painless until they rupture, releasing infectious material. Internal abscesses, however, cause progressive physiological compromise — respiratory difficulty from lung involvement, and weight loss from reduced absorption in heavily affected animals. The chronic nature of the disease means affected sheep may carry impaired quality of life for months or years. Vaccination before first shearing significantly reduces flock prevalence and protects individual animals from developing disease. Culling animals with ruptured or multiple external abscesses prevents flock contamination and removes chronically affected animals from a welfare perspective.