Influenza A and Livestock in Ontario - Important Update for Veterinarians
Table of Contents
The outbreak of Highly Pathogenic Avian Influenza virus (H5N1) affecting most of East Asia since late 2003 has recently spread to areas in Eastern Europe, including Russia, Turkey, Romania and Croatia. The virus is believed to have spread via migrating waterfowl from affected regions in East Asia. At this point, the outbreak in Europe has mostly affected wild birds and small backyard operations with exposure to wild birds. No human cases have been reported in Europe. The outbreak in Asia has so far claimed more than 60 human lives, mostly in Viet Nam, Thailand and Indonesia. Those affected have usually had close contact with infected poultry. There is currently no clear evidence of human to human transmission, and properly cooked poultry is safe to eat.
It is possible that migratory birds may introduce the H5N1 virus to Canada. The Canadian Cooperative Wildlife Health Centre (CCWHC), and the federal and provincial governments are undertaking a surveillance project of wild waterfowl populations in Canada. Preliminary test results have detected the presence of Avian Influenza (AI) virus, including H5 subtypes, in migratory ducks. Further testing is being done to determine if the H5 subtype found in Canadian wild birds is the H5N1 virus circulating in East Asia. It is very unlikely that the virus found here is the same H5N1 strain.
This supports previous research showing that AI is common in wild waterfowl populations, and some of these strains can be, or can develop into, highly pathogenic strains for poultry. This underscores the importance of effective biosecurity in the poultry industry at all times to avoid introducing a potentially harmful pathogen to flocks.
H5N1 has also been detected in exotic pet birds imported to the UK. The source of the infection has not been determined, but the EU has banned all imports of live wild birds as a precaution. The global trade in exotic birds, much of it illegal, poses a significant risk for the spread of diseases such as AI. Veterinarians should also be vigilant for signs of illness in exotic pet birds and submit appropriate samples for diagnostic testing.
The incidence of the H3N2 Influenza A strain that has been circulating in Ontario since early 2005 has been dropping. However, new cases are still being reported in both swine and poultry, so veterinarians and their clients should continue to practise strict biosecurity, especially between swine and poultry holdings. Since pigs can be infected with both animal and human influenza viruses, mixing of the two viruses could occur in this species. For this reason, it is important to minimize the exposure of pigs to all influenza viruses, including human strains. In addition, pigs can transmit influenza viruses to humans, who, if infected with human influenza, may act as the "mixing vessel".
If H5N1 were introduced to Ontario through wild birds, the greatest risk would be to backyard flocks and to birds commingling with, or exposed to, wild or migratory species. Nevertheless, there are other routes by which this virus can be introduced, including people. All poultry premises should have enhanced levels of biosecurity to prevent the introduction and spread of Avian Influenza.
The risk of H5N1 notwithstanding, other influenza strains and other diseases are a constant threat to Ontario poultry. Anyone raising birds, including commercial poultry producers and owners of backyard flocks, show birds and aviaries, should be familiar with the appropriate biosecurity procedures and follow them on a permanent basis. Resources and recommendations for enhanced biosecurity are available on the OMAFRA web site listed below. With respect to controlling the introduction and spread of influenza viruses, the following recommendations are critical:
Prevent contact between domestic/commercial and wild birds, and prevent contamination of equipment, feed and water by wild birds and their droppings.
Prevent contact between all birds, domestic or wild, and swine. Swine can also be infected with avian and human influenza strains, increasing the risk to poultry and public health.
Monitor the flock for signs of disease, increased illness or mortalities, and submit appropriate samples to the Animal Health Laboratory at the University of Guelph. An early and accurate diagnosis is important. If AI is suspected, contact the CFIA immediately.
With the spread of the virus to Europe, global concerns about a human pandemic are growing. The H5N1 strain currently poses a very low human health risk, except for those in close contact with affected birds or their faeces. However, the more widespread the virus, the greater is the risk of it mixing with a human strain to form a more serious and easily transmissible influenza. For this reason, the World Health Organization and Health Canada have made several recommendations to reduce this risk, including vaccinating poultry workers with the current human influenza vaccine.
All individuals working with livestock or poultry, especially people working with birds, such as poultry producers and their employees, veterinarians, abattoir workers and those handling wild birds, should receive the annual human influenza immunization (available free to all residents who work, live or attend school in Ontario). This is not designed to protect these individuals from the H5N1 virus. The risk to Ontario from this strain of influenza is extremely low. Vaccination will reduce the possible mixing of human and avian influenza strains, which would increase the risk of a potential pandemic strain evolving.
In addition, individuals working with infected livestock and poultry should follow strict infection control measures to prevent exposure to influenza virus. These include frequent hand washing and always washing hands after handling animals, and wearing appropriate personal protective equipment such as mask, gloves, safety goggles, coveralls, shoes/boots, and hair covers. Please contact your local public health unit for more information.
If an individual develops influenza- like illness while working with infected livestock, he or she should immediately seek medical attention. Influenza is a reportable disease in Ontario and all human influenza cases must be reported to the local Medical Officer of Health.
The following resources provide more information on Avian Influenza:
Diagnostic submission information is available from the Animal Health Laboratory:
Dr. Davor Ojkic (519) 824-4120, x 54524
Dr. Jim Fairles (519) 824 4120, x 54611
For more information:
Toll Free: 1-877-424-1300