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Avian Influenza Virus

Background

In 2005, Canada initiated a national inter-agency survey for influenza A viruses in healthy live wild ducks. This survey was stimulated, in the first instance, by a major outbreak of influenza in the Canadian poultry industry in 2004, and subsequently by the spread of the Asian H5N1 highly pathogenic strain from SE Asia to Europe and Africa in 2004-05. The Survey objectives were to identify strains of influenza viruses present in Canada's wild bird reservoir, to acquire information needed to assess the bio-security of Canada's poultry industry, and to monitor viral genes of concern to human and animal health.

From 2006 to 2010, the wild bird influenza survey was continued, with both live bird and dead bird components. The objective of the survey based on birds found dead was vigilance for highly pathogenic virus strains and careful assessment regarding whether or not influenza viruses had caused the death of the birds. The objectives of the live bird survey were to monitor year-to-year variation in viruses present in the wild duck population, to sample in the eastern Canadian arctic to which trans-Atlantic migrant birds might carry the virus from European or African wintering grounds, to sample species that migrate seasonally deeply into Central and South America, and to sample additional species of aquatic birds to better understand the wildlife reservoirs of influenza A viruses.

These Surveys have been highly successful. The importance of wild duck populations as reservoirs for avian influenza viruses, particularly compared with other related bird species, was clarified. The probable precursor virus of Canada's 2004 and 2005 influenza outbreaks in poultry, a low-pathogenicity H7N3 strain, was discovered in wild duck populations. Canada's national Avian Influenza Virus Laboratory Network was greatly strengthened through the conduct of the Surveys. New communications challenges associated with responses to important epidemic diseases were identified and protocols were established to overcome them. Collaborations among federal, provincial and territorial agencies responsible for animal health, public health and wildlife, and with Canada's veterinary college wildlife health expertise, were greatly advanced through the planning and conduct of the Surveys, and new tools and methods for complex data management on a national scale were developed, tested and improved. The entire genetic composition of over 100 avian influenza viruses has been sequenced and is now being analysed for evidence of intercontinental virus movement, among other parameters. Through this Survey, Canada participates in Canada-USA-Mexico Tri-lateral collaborations for continental surveillance for avian influenza, and in analysis of the risks posed to commercial poultry by avian influenza viruses in wild birds, collaboratively with the US Department of Agriculture.