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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