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Avian Influenza

Other Names: Fowl Plague, Brunswick Disease, Bird Flu, Fowl Pest, Highly Pathogenic Avian Influenza, Low Pathogenic Avian Influenza, Peste Aviaire

Avian influenza (AI) is a highly contagious viral infection of birds. AI can be highly pathogenic or low pathogenic. Low pathogenicity avian influenza (LPAI) viruses cause the milder forms (mild respiratory signs) of avian influenza while highly pathogenic avian influenza (HPAI) viruses cause more severe forms (multi-systemic infections). Most birds infected with HPAI viruses do not survive, but many infected with LPAI viruses can recover.

Clinical signs can vary from a mild infection (chickens show loss of appetite, deceased egg production, mild respiratory disease, and diarrhea) for LPAI to severe respiratory, neurological, and gastrointestinal (GI) signs with HPAI (resulting in high mortality rates).

Avian influenza Diagnosis

AI is diagnosed in chickens through the use of rapid diagnostic methods, such as agar gel immunodiffusion (AGID) or rtPCR. Virus isolation is considered to be the "gold standard" in confirming that birds have been infected by the AI virus.

How Avian influenza is Transmitted

Avian influenza is transmitted through aerosol spread in the air, ingestion of influenza particles in nasal and respiratory secretions, fomites, or by direct contact with feces of infected birds. Since wild waterfowl are often carriers of the low pathogenic influenza virus, they are often a source of entry in flocks.

Avian influenza Incubation Period

The incubation period for avian influenza virus is 3-5 days and is dependent on the dose of the virus, the route of exposure, the species exposed, and the ability to detect clinical signs.

Clinical Signs

Decreased feed and water intake
Ruffled feathers
Unilateral facial swelling
Red or watery eyes
Change in voice
Open mouth breathing
Head tilt
Twisted neck
Weight loss
Sudden death
Nasal discharge
Decreased egg production
Blood-tinged discharge
Reddening skin
Dark colored feces
Pale comb or wattles
Focal ecchymosis


  • History
  • AGID
  • RT-PCR
  • Virus isolation
  • Antigen detection
  • HI


Supportive careIsolate the bird from the flock and place in a safe, comfortable, warm location (your own chicken "intensive care unit") with easy access to water and food. Limit stress. Call your veterinarian.
AmantadineAdministered orally (25 mg/kg) or in drinking water (100 mg/L) x 10 days following infectionB Speer
Oseltamivir0.5 mg/kg PO q12h x 5 days, administered prophylactically to healthy birds in the event of an outbreak.B Speer
Rimantadine (Flumadine, Forest)100 mg/L drinking water, must be used before and during exposureB Speer



  • Routinely test birds for AI
  • Biosecurity
  • Keep wild waterfowl away from chickens
  • Prevent direct contact with free-flying birds or their feces

Scientific References

Good Overviews

Risk Factors

  • Red poultry mite infestation, as mites are capable of transmitting the influenza virus
  • Exposure to high populations of wild birds, especially aquatic birds.
  • Poor sanitary conditions
  • Over-crowding
  • High Stress