Exotic Diseases

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Species Infected

infects pigs

can occasionally infect humans

Clinical Signs

• sudden onset
• severe prostration
• fever and anorexia
• paroxysmal cough
• laboured, jerky respiration
• illness 2-6 days
• rapid recovery; slower recovery of weight loss
• morbidity up to 100%, mortality rare

Lesions

• hyperaemia of pharynx, larynx, trachea and bronchi
• mucoid exudate in air passages
• marked lobular atelectasis
• thoracic lymph nodes enlarged, oedematous and congested
• some fatal cases may have fibrinous exudate in airways and pleural surfaces

Pathogenesis

• precise method of transmission uncertain but thought to be direct and via nasopharyngeal route
• nasal secretions highly infectious
• carrier state may exist

Aetiology

• Influenzavirus (Orthomyxoviridae)
• same family as human, avian and equine influenza viruses
• virus undergoes antigenic drift over time, but is remarkably stable c.f. other influenza viruses

Epidemiology

• occurs late autumn, early winter
• climatic stress influences clinical expression
• high mortality only amongst piglets from non-immune sows
• some authors consider the pig lungworm (Metastrongylus spp) may involved in carrying the virus into susceptible hosts
• epidemic may be explosive

Differential Diagnoses

     1.  enzootic pneumonia - longer duration
     2.  swine fever - higher mortality
     3.  inclusion body rhinitis - longer duration, nasal deformities
     4.  pseudorabies