Caseous Lymphadenitis (CL) in Sheep and Goats

Etiology and Pathogenesis

• Causative Agent: Corynebacterium pseudotuberculosis

• Transmission: Through skin wounds, environmental contamination, and respiratory secretions

• Pathogenesis: Bacteria enter through skin or mucous membranes, travel to lymph nodes, and form encapsulated abscesses.

Clinical Findings

• External Form: Abscesses in peripheral lymph nodes (e.g., submandibular, prescapular, prefemoral)

• Internal Form: Chronic weight loss, respiratory signs (cough, nasal discharge)

Diagnosis

• Definitive Diagnosis: Culture of purulent material

• Serologic Tests: Detect antibodies, but interpretation requires caution

Treatment

• Management: Culling, antimicrobial therapy (intralesional and systemic), abscess drainage and isolation

• Antibiotics: Penicillin, rifampin, tulathromycin, oxytetracycline

Control and Prevention

• Biosecurity: Strict hygiene, disinfection, and isolation of affected animals

• Vaccination: Species-specific vaccines

• Quarantine: New animals should be tested and isolated before introduction to the herd

For more detailed information, visit the Merck Veterinary Manual.