Bovine Parainfluenza - 3

PI3

Pathogenesis

• Virulence varies with isolates
• Cessation of ciliary clearance and epithelial necrosis predisposes to secondary bacterial infections -> cough
• May cause rhinitis of cattle

Diagnosis

• Diseased lung tissue from dead animals or centrifuged cells from lung lavage
• Virus is too fragile for cell culture isolation (often inactivated in transport)
• Antigen detection by immunocytochemistry for intracytoplasmic viral inclusions containing labelled viral protein
• Serology: 4-fold rise in ELISA antibody in paired serum samples from several animals

Control

• Improve managemental factors
• All-in, all-out systems
• Some vaccination
  • Temperature sensitive mutant that replicates at 34^oC but not at 37^oC
  • Re-infection is common

Secondary Concerns

• With other agents causes calf pneumonia
• Associated with poor management:
  • Overcrowding
  • Poor ventilation
  • High humidity
  • Deprivation of colostrum
  • Stress caused by transport or mixing of stock

• Causative agent: parainfluenza- 3 virus (PI3)
• On its own causes rhinitis
• Often part of multi-aetiology disease complex (e.g. Enzootic pneumonia of calves), often followed by Pasteurella sp. obscuring viral origin
• Replicates in airway epithelial cells and results in an initial bronchitis -> bronchiolitis -> extension into alveoli, causing bronchointerstitial pneumonia
• Early stages may show intracytoplasmic inclusions
• The resulting exudate is predominantly neutrophilic
• Positive confirmation lies in a Fluorescent Antibody Test (FAT) to the specific virus on frozen sections of tissue