Avian Influenza (AI)

AI is a viral disease that can affect the respiratory, enteric (digestive) or nervous system of many kinds of poultry and other birds. Clinical signs of AI are variable and depend on factors such as strain of the virus, the pathogenicity (disease-producing capability) of the virus, host species, age, sex, environmental conditions (poor environmental conditions worsen the disease) and presence of concurrent infections. Clinical signs of High Pathogenicity Avian Influenza (HPAI) in chickens and turkeys depend on the organs and tissues affected by the virus. Please note that not all clinical signs are seen in every bird.

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Clinical signs of HPAI may include:

  • Sudden increase in mortality (death rate) - up to 100%, without any prior clinical signs
  • Severe drop in egg production - production may completely stop within six days; eggs frequently lack shells
  • Severe depression - flock is very quiet and inactive; feathers are ruffled
  • Severe decrease in feed consumption
  • Water consumption can be significantly increased (birds with a fever may be very thirsty) or decreased (birds may feel too sick to drink)
  • Watery diarrhea -may be bright green or white
  • Swollen combs and wattles, swelling around the eyes; combs may develop blisters and dark spots (sometimes at the tips)
  • Red patches (hemorrhages) may occur on legs between feet and hocks
  • Respiratory signs are less common, but can include coughing and sneezing
  • Nervous signs such as tremors of head and neck, inability to stand and paralysis can occur in individual birds 

Some of the more common signs in the currently (2021/22) circulating strain of AI are sudden death and nervous signs.

Sources of AI Virus

All avian (bird) species are susceptible to infection by the AI virus. However, most shorebirds, gulls, geese, terns, etc. and especially wild ducks are considered to be crucial to the spread of the virus. Wild ducks carry the virus without any signs of illness and are considered the major reservoir for AI infections in domestic poultry. Small flocks in Atlantic Canada that have been infected with this virus have commonly had watercourses on their property. It is essential that you do not allow your domestic birds to co-mingle with wild waterfowl.

Co-mingling of birds from different sources, fecal material of crates and vehicles and purchase of birds with unknown AI status all contribute to the chance that the virus will be carried to the home farm.

Spread Between Birds

Contact with infected fecal material is the most important mode of bird-to-bird transmission. Birds commonly shed virus for seven to 14 days after infection, but shedding has been documented for up to four weeks after infection. Wild ducks often introduce the virus through fecal contamination into domestic flocks raised outdoors.Many other species of wild birds have been shown to carry this current (2021/22) strain without appearing sick themselves. Within a poultry barn, transfer of the virus between birds can also occur via airborne secretions.

Spread Between Premises

AI virus can survive in manure for up to 105 days, especially in high moisture and low temperature conditions. Mechanical transmission by anything that can walk, crawl or fly from farm to farm can occur. Vectors are agents of disease spread. Rodents, insects including flies, and wild birds like sparrows, can act as vectors for AI by carrying the virus on their bodies from place to place. AI virus can also be found on the outer and inner surfaces of eggshells. Airborne transmission of virus from farm to farm probably does not occur under usual circumstances.

The spread of AI from one poultry premises to another between poultry premises almost always follows the movement of contaminated people (farm personnel, egg collectors, chicken catchers, etc.) and equipment., but so far, 2021-22 infections in North America appear to be happening mainly due to interactions with wild birds. This seems to indicate we are doing well at protecting one another with good biosecurity practices between farms.  We must remain vigilant about this and increase our awareness of how wild birds might gain access to our domestic birds and put preventative measures in place.

While the risk to humans of this current strain appears low, Avian influenza can be transmitted to humans.  Do not handle dead wild birds and report any disease suspicion in your flock to a veterinarian without delay.

For more information:

Please refer to the Canadian Food Inspection Agency's  Factsheet: Avian Influenza 


October 11: 


Published date: 
October 11, 2022
Agriculture and Land

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