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Avian Influenza

Fowl Pest, Fowl Plague

Highly pathogenic avian influenza (HPAI), initially known as 'fowl plague' is a complex infection of birds caused by viruses of the Influenza A genus. HPAI in poultry is characterized by a sudden onset, severe illness of a short duration, and a mortality approaching virtually 100% in vulnerable species. Due to excessive economical losses to the poultry industry, HPAI receives immense attention in the veterinary world and is globally treated as a disease immediately notifiable on suspicion to the authorities. Because of their potential to give rise to HPAIV, LPAI caused by subtypes H5 and H7 is also considered notifiable.

Recently, however, avian influenza acquired worldwide attention when a highly pathogenic strain of the subtype H5N1, which probably arose before 1997 in Southern China, gained enzootic status in poultry throughout South East Asia and unexpectedly 'traversed interclass barriers' when transmitted from birds to mammals (cats, swine, humans).

Wild aquatic birds, notably members of the orders Anseriformes (ducks and geese) and Charadriiformes (gulls and shorebirds), are carriers of the full variety of influenza virus A subtypes, and thus, most probably constitute the natural reservoir of all influenza A viruses. While all bird species are thought to be susceptible, some domestic poultry species - chickens, turkey, guinea fowl, quail and pheasants - are known to be especially vulnerable to the sequelae of infection.

Incubation Period
Following an incubation period of usually a few days (but rarely longer than 21 days).


Sneezing and/or coughing
Decreased egg production
Slight facial swelling
Difficulty breathing
Sudden death
Purple discoloration
Nasal discharge


  • History
  • Clinical signs
  • Virus isolation
  • HA, HI
  • dot-ELISA
  • PCR
  • Immunohistochemistry
  • Necropsy


MethodMethod Summary
Supportive careIsolate the bird from the flock and place in a safe, comfortable, warm location (your own duck "intensive care unit") with easy access to water and food. Limit stress. Call your veterinarian.
In mild cases, good husbandry, proper nutrition and broad spectrum antibiotics may assist in recovery.
Oseltamivir0.5 mg/kg PO q12h 3 5 days

Reported Cases

  • Case 1: Avian influenza in a Parrot A 3-month-old chick infected with Avian influenza virus hemagglutinin subtype H5N2 with low pathogenicity was experiencing severe lethargy. He was admitted to the hospital and placed in quarantine. Supportive care treatment was administered. Although detection of H5 avian influenza virus in birds in the United States typically results in euthanasia of infected birds, an alternative strategy with strict quarantine measures and repeated diagnostic testing was used. The chick recovered from the initial clinical signs after 4 days and was released from quarantine 9 weeks after initial evaluation after 2 consecutive negative virus isolation and real-time reverse transcriptase PCR assay results. Ref


  • Keep feed under cover to minimize attracting wild birds
  • Keep water fresh and free of droppings



Risk Factors

  • Poor biosecurity
  • High population of wild birds, particularly waterfowl

Also Consider