Penn Veterinary Medicine | University of Pennsylvania

Influenza in Swine

Clinical signs

• Acute febrile, respiratory disease characterized by apathy, anorexia, labored breathing (+/- coughing in later stages, also sneezing, nasal discharge and conjunctivitis may be seen less frequently).
• Morbidity can be up to 100% in a herd outbreak, mortality is low.
• Recovery is rapid – usually 5 - 7 days after onset of clinical signs.
• Secondary bacterial infections can result in pneumonia.

Epizootiology

• Swine influenza is widespread and endemic throughout the world.
• H1N1 and H3N2 infections are responsible for 50% of the cases of acute respiratory disease in pigs.
• Swine influenza is related to movement of infected pigs to susceptible herds and clinical disease appears with introduction of new pigs into a herd.
• In an infected herd, the disease persists through production of young susceptible pigs and introduction of new stock.
• Outbreaks peak in colder months.
  • Disease transmission is direct and occurs via the nasopharyngeal route (aerosols that are formed during sneezing or coughing) or indirectly after physical contact.
• Nasal secretions are laden with virus during the febrile (acute) state which will last for 5 days.
  • Severity of disease is dependent on maternal immunity, virus strain, route of inoculation and secondary bacterial infections.
  • Influenza vaccines are available for pigs.