Managing Corynebacterium pseudotuberculosis infection in sheep flocks to protect welfare and productivity.
CLA causes significant chronic welfare impairment in affected sheep. External abscesses — commonly seen on the prescapular, prefemoral, and parotid nodes — cause pain and discomfort, particularly as they grow, rupture, and discharge. Internal abscessation in the lungs, liver, and spleen causes progressive weight loss, respiratory compromise, and debilitation without visible external signs.
The chronic, insidious nature of CLA means welfare impacts are often underappreciated. Affected sheep may lose significant body condition over months before the cause is identified. Internal CLA is frequently only diagnosed post-mortem. The distress of chronic infection, pain, and wasting is significant.
Control requires flock testing, culling of heavily affected animals, vaccination of naïve animals, and rigorous biosecurity to prevent introduction of infected stock. The CLA vaccine reduces new case development but does not eliminate existing infections.