CVMA | Documents | Avian Influenza

Avian Influenza

October 24, 2012

Avian influenza (AI) is a contagious viral infection caused by the influenza virus Type "A", which can affect several species of food producing birds (chickens, turkeys, quails, guinea fowl, etc.), as well as pet birds and wild birds.

AI viruses can be classified into two categories: low pathogenic (LPAI) and high pathogenic (HPAI) forms based on the severity of the illness caused in birds, with AI causing the greatest number of deaths in birds. Most AI viruses are low pathogenic and typically cause little or no clinical signs in infected birds. However, some low pathogenic viruses are capable of mutating into high pathogenic viruses. There are many influenza subtypes, two of which include H5 and H7. Historically, only the H5 and H7 subtypes are known to have become high pathogenic in avian species.

What are the signs of disease?

Some or all of the following clinical signs are evident in infected birds:

  • quietness and extreme depression
  • sudden drop in production of eggs, many of which are soft-shelled or shell-less
  • wattles and combs become swollen and congested; swelling of the skin under the eyes; coughing, sneezing and nervous signs
  • diarrhea; oedema (swelling) and congestion of the combs; hemorrhages on the hock;

A few deaths may occur over several days, but an outbreak may follow, killing hundreds or thousands of birds each day.

Diagnosis of avian influenza may be made on the basis of clinical signs and events leading to the disease. However, since the signs and course of avian influenza are similar to other diseases, laboratory diagnosis is essential.

How is the disease transmitted to birds?

Wild birds, especially waterfowl, are natural reservoirs for the influenza viruses - yet show no clinical signs - and can be responsible for the primary introduction of infection into domestic poultry.

The disease can also spread to birds through contact with infected poultry and poultry products, and through manure and litter containing high concentrations of the virus, for example through contaminated clothing and footwear, vehicles and equipment, and feed and water.

Is avian influenza transmissible to humans?

Avian influenza viruses, such as the H5 virus present in Asia, may, on rare occasions, cause disease in humans. Human transmission has occurred to people having prolonged contact with heavily contaminated environments. Human to human transmission of avian influenza is extremely limited.

Due to the potential for human infection, it is recommended that those people working with or in contact with poultry suspected of being infected with avian influenza wear protective clothing, including face masks, goggles, gloves and boots.

For more information, visit the Public Health Agency of Canada Web site at:

Does avian influenza occur in Canada?

In the sixties, when turkeys were often raised in ranges (outdoors), cases of low pathogenic avian influenza were often reported in the autumn. One of the viruses isolated in 1966 was later found to meet the modern criteria of a high pathogenic influenza virus. Since the sixties, the majority of turkeys have been raised in closed poultry houses to control other diseases and are managed under more stringent bio-security conditions. As a result, the cases of low pathogenic avian influenza have been rare. Canada has had a number of cases of low pathogenic H5 and H7 since 1975, the latest of which was reported in 2005. H7N3 and H5N2 outbreaks have occurred in the Fraser Valley of British Columbia in 2004 and 2005 respectively.

In February 2004, the Canadian Food Inspection Agency (CFIA) identified the presence of a low pathogenic H7 avian influenza in the Fraser Valley area of southern British Columbia. Subsequent tests revealed the presence of highly pathogenic H7 avian influenza in British Columbia in March 2004. The CFIA depopulated all infected premises (42 commercial and 11 backyard premises) on which highly pathogenic avian influenza was found and pre-emptively destroyed all birds in the surrounding three kilometre areas. In September 2007, a highly pathogenic H7N3 outbreak occurred in Saskatchewan.

Source: Canadian Food Inspection Agency

What can travellers do to avoid bringing the disease into the country?

While out of the country:

Avoid visiting areas where you may come into contact with live birds, such as poultry farms, live bird markets or any other area where birds congregate. This is most important in countries experiencing an outbreak of high pathogenic avian influenza. (An updated list of countries affected by AI can be found at the World Organisation for Animal Health Web site at If you are in contact with live birds infected with the AI virus, the virus may persist on clothing, footwear and in hair. Take appropriate personal hygiene measures including thorough hand washing and showering, wash clothing, and clean and disinfect footwear.

On returning home:

Ensure all birds and poultry products you wish to bring into Canada are eligible for entry and declare all animal products upon arrival.

If you visit an area where you have been in contact with live birds while abroad and/or you plan to go onto a live bird premises shortly after your return to Canada, make sure that any clothing and footwear you wear are free from soil and manure before entering Canada. Also, take appropriate personal hygiene measures including thorough hand washing and showering, wash clothing, and clean and disinfect footwear after arrival.

For more travel information, visit Public Health Agency of Canada Travel Medicine Program Web site at

What can livestock producers do to prevent infection on their farm?

Wild bird populations are the natural reservoir for the influenza viruses. Therefore, it is essential for commercial poultry producers to maintain strict bio-security practices.

On the farm:

  • Keep away from areas frequented by wild fowl; Keep strict control over access to your poultry houses by people and equipment
  • Keep equipment cleaned and disinfected before taking it into poultry houses
  • Do not keep bird feeders and duck ponds on your farm. This will discourage wild birds
  • Maintain high sanitation standards.

If clinical signs are noticed or suspected in poultry, contact your veterinarian or the CFIA office in your area. Producers are obligated to report any suspicion of AI because it is a reportable disease under the Health of Animals Act.

There are reports of H5N1 infections in domestic cats.

Is it possible for household pets to contract avian flu?

Avian influenza typically affects species of food producing birds (chickens, turkeys, quails, guinea fowl, etc.), as well as pet birds and wild birds. Studies have shown that a small number of mammalian species, including pigs, seals, whales, mink, and ferrets, are susceptible to natural infection with avian influenza viruses. However, of these species, the pig is the only one that has significance for human health. While there have been recent reports of avian influenza infection in domestic cats in Thailand and Europe, this is a rare event. The World Health Organization continues to investigate the case in Thailand but reports that is unlikely that H5N1 infection in cats presents a risk to human health.

How to get more information?

Contact the Canadian Food Inspection Agency Area Offices:

Atlantic Area: (506) 851-7400
Quebec Area: (514) 283-8888
Ontario Area: (519) 837-9400
Western Area: (403) 292-4301

You can also find the telephone number of your local Canadian Food Inspection Agency District Office by consulting the blue pages of your local phone directory.

Health Canada Website links: