Sheep Pulmonary Adenomatosis

Antigenicity

• The virus cannot be grown in culture, although it can be seen by EM on tumor cells of infected sheep

Pathogenesis

• Causes a proliferation of alveolar lining cells, producing massive amounts of fluid
• Proliferative foci project into alveoli and bronchi and from slow-growing tumors
• Death occurs between 3-4 years of age

Clinical signs:

• Low exercise tolerance
• Gradual weight loss
• Dyspnoea
• Coughing
• Nasal fluid discharges during wheelbarrow test
• Secondary bacterial infection by Pasteurella hemolytica often precipitates death
• PM reveals fawn-gray tumor (for more see here)

Epidemiology

• Found in 25% of pneumonia cases in Scotland
• Absent in USA, common in UK

Diagnosis

• Electron microscopy on lung biopsy

Control

• Cull clinically affected animals

• Also called pulmonary carcinomatosis
• Infectious bronchiolar-alveolar carcinoma caused by a retrovirus
• Commonest under intensive management systems which favour aerosol transmission and close contact of disease
• Behaves like chronic pneumonia
• Takes months to years to express itself clinically as coughing and exercise intolerance
• Gross pathology:
  • Heavy lungs which fail to collapse
  • The lesions progress from small firm grey/white nodular lesions to extensive confluent areas with replacement by neoplastic tissue
  • Cut surface oozes fluid
  • There is often coexistent infection present
  • Occasional metastases to bronchial and mediastinal lymph nodes can occur
• Histopathology:
  • Widespread proliferation of alveolar (Type 2) and terminal bronchiolar epithelium, lining the alveoli and lower airways
  • Multiple neoplastic foci of cuboidal/columnar cells forming papillary projections into the lumen
  • Metastases of the same in the bronchial and mediastinal lymph nodes
• There is no serological test, and diagnosis depends upon raising the animal by the hind limbs whereupon a clear fluid issues from the nose = "Wheelbarrow test"
• More information