What is Avian Influenza?
Avian Influenza (AI) or bird flu is a highly contagious viral disease that affects several species of birds including; chickens, turkeys, quails, guinea fowl and many species of wild and pet birds.
There are two groups of avian influenza viruses; the Highly Pathogenic Avian Influenza (HPAI) and the Low Pathogenic Avian Influenza (LPAI). Wild birds generally carry the LPAI strain, which rarely causes death of the bird and may be present in birds presenting no symptoms.
The HPAI viruses are causing an epidemic in many counties, killing large numbers of birds. Several HPAI strains exist, of which the H5 and H7 types are currently the most pathogenic and are listed as a Notifiable Disease by the World Health Organization for Animal Health. In Canada, presence of avian influenza disease must be reported to the Canadian Food Inspection Agency. A major concern at this time is the virus strain H5N1 which originated in Southeast Asia. It has been incriminated as the cause of severe disease in humans and over half of the people infected perish within 9 to 10 days.
How is the virus spread?
The AI virus is spread between birds through direct contact with secretions of an infected bird, particularly feces and respiratory secretions. The virus can also be passed through contaminated feed, water, and equipment or through humans cross contaminating the bird’s environment.
Species other than birds can be infected by the avian influenza virus but usually the virus is species specific meaning it cannot be passed to humans.
In humans, the avian influenza virus, particularly the HPAI H5N1 type, has been linked to causing human infections. The AI virus can be passed to humans via inhalation or ingestion of the virus present in fecal material or respiratory secretions of an infected bird. The HPAI virus can also be present in the skeletal muscle (meat), the heart, the blood vessels, the liver, and the nerves of infected birds. The risk of humans contracting the virus through consumption of an infected animal has not been proven and the chance of spread between humans is rare.
What are the symptoms of an infection?
Birds: Birds that are infected with HPAI usually die within 2 to 3 days with symptoms including: depression, decreased egg production often with a soft shell or shell-less egg, coughing, sneezing, nervous behavior, ruffled feathers, and swollen wattles, combs and eyes.
Humans: Symptoms of Avian Influenza in humans range from influenza-like symptoms (fever, cough, and sore throat) to eye infections, pneumonia and respiratory distress with breathing difficulty and chest pain. Over 50% of individuals with an infection die in 9 to 10 days.
What is the food risk?
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There have been no confirmed cases of AI virus infection in humans acquired from the ingestion of properly cooked, prepared and handled meat from fowl.
The avian influenza virus is destroyed during adequate cooking of chicken and other fowl. Recommended internal temperatures in all areas on the food of 85oC for a whole bird or 74oC for pieces are more than adequate to destroy this virus. Eggs should also be thoroughly cooked eggs (no runny yolk or egg white).
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Following proper handling and cooking techniques is especially important in countries where the disease is prevalent or when handling wild game, because the transmission of the virus through food has not been ruled out.
An infected bird is unlikely to be offered for consumer consumption because of the rapid death rate of birds infected with the virus. Also all commercially sold meat must pass inspection; most birds infected with the HPAI virus show lesions in multiple organs and tissues and would therefore, not pass inspection.
What kind of environmental conditions can the virus survive?
The avian influenza virus can remain infective for long periods of time in tissues and water. It can remain in bird feces for 6 days and survive at temperature below 4oC for 35 days and above 37oC for 6 days. It is inactivated by 56oC for 3 hours or 60oC for 30 minutes.
Is a vaccine available?
A vaccine is available that has proven to protect healthy birds from developing symptoms of the disease and reduce the shedding of viruses in birds that are infected.
What is the prevalence of Avian Influenza in Canada?
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In Canada there has not been a human case of avian influenza virus infection. There have been only two outbreaks in our poultry industry of highly pathogenic avian influenza. The latest incident involving type H7N3 was reported in Saskatchewan in September of 2007 and an outbreak of type H5N2 was reported in British Columbia in 2005.
Although the disease has an extremely low incidence in Canada, persons such as poultry farmers and workers in slaughter facilities who are routinely exposed to poultry and other fowl should use extreme caution.
Hunters should follow the recommendations for cleaning wild game provided by Public Health Agency of Canada at http://www.phac-aspc.gc.ca/influenza/fs-hwb-fr-mos_e.html
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Information Sources:
Das, A., Spackman, E., Thomas, C., Swayne, D., and Suarez, D. (2008). Detection of H5N1 High-Pathogenicity Avian Influenza Virus in Meat and Tracheal Samples from Experimentaly Infected Chickens. Avian Diseases, 52, 40-48.
Doyle, M., and Erickson, M. (2006). Emerging microbiological food safety issues related to meat. Meat Science, 74, 98-112.
Jones, Y., and Swayne, D. (2004). Comparative Pathobiology of Low and High Pathogenicity H7N3 Chilean Avian Influenza Viruses in Chickens. Avian Diseases, 48, 119–128.
Kelly, T., Hawkins, M., Sandrock, C., and Boyce, W. (2008). A Review of Highly Pathogenic Avian Influenza in Birds, With an Emphasis on Asian H5N1 and Recommendations for Prevention and Control. Journal of Avian Medicine and Surgery, 22(1), 1-16.