Swine Influenza

Subtypes

• Avian-like H1 and human-like H3 strains vary in virulence

Pathogenesis

• Necrotising bronchiolitis with catarrhal pus
• Barking cough
• Interstitial pneumonia giving consolidation of the lungs and a 'meaty' appearance
• Often associated with bacteria, mycoplasma or immunosuppressive viruses (such as PRRS)
• The virus recycles on farms as litters outgrow maternal antibody at 12 weeks of age

Diagnosis

• Clinical pneumonia is always suspect
• Serology: retrospective diagnosis by HI

Control

• Isolation of premises
• All-in/all-out systems
• Vaccination is not licensed in the UK

• Caused by Orthomyxoviridae
• Rhinitis, may progress to pneumonia
• Clinical signs: pyrexia, lethargy, skin erythema, anorexia, severe cough and sneezing, dyspnoea, conjunctivitis, pregnant sows may abort
• Grossly:
  • Tracheobronchitis, airway obstruction -> atelectasis
  • Pleura normal or covered with serous or serofibrinous exudate
  • Pleural cavity filled with excess fluid
  • Lung lesions
    • Clear demarcation of lesions in cranial and middle lobes
    • Interstitial pneumonia
• Histologically:
  • Acute inflammation of mucosa of trachea and bronchi
• Zoonotic
• Circumstantial evidence of mutation from human strain
• Migrating ascarids thought to precipitate the disease, reservoir of infection in earthworms containing infected lungworm larvae