Special Veterinary Pathology

CONTAGIOUS BOVINE PLEUROPNEUMONIA

Definition

• Characterized by subacute or chronic disease of cattle produced diffuse pneumonia, “marbling of lung” and sequestration caused by Mycoplasma mycoides

Aetiology

• The organism classified under the pleuropneumonia like organism (PPLO)

Incidence

• Calves are less susceptible than adults

Pathogenesis

• Infection is spread through droplet infection and sets up inflammation of bronchioles
• Thickening of interlobular septa and reaches alveoli
• Thrombosis and well demarcated circumscribed necrosed areas called sequestrum are produced
• During violent coughing, the fibrous capsule of the sequestrum rupture releasing the organisms causing spread of infection
• In a herd about a quarter of the affected animals become carrier
• The carrier are also known as lungers

Clinical signs

• Acute – dry painful cough with laboured respiration
• Latter – mucopurulent discharge from the nose and swelling of joints (polyarthritis)

Gross and microscopic Lesions

• Usually limited to one lung
• Pleural cavity contained excess pleural fluid with adhesion of thoracic wall
• Lung parenchyma cut surface showed 'marbled appearance' due to the infiltration of the interlobular septa by yellowish exudate
• Later, zone of necrosis with sequestration surrounded by dense connective tissue
• Abscess formation with infiltration of lymphocytes and plasma cells
• Separation of the lobules into distinct compartments by the heavily thickened interlobular septa
• Infiltration of lymphocytes and plasma cells is seen around blood vessels and bronchi
• History, clinical symptoms, gross and microscopic lesions and recovery of organisms.