TORONTO - A Canadian study that tested more than 12,000 live and dead wild birds for avian influenza viruses turned up no cases of the highly pathogenic Asian strain of H5N1 viruses in 2006, the Canadian Food Inspection Agency announced Friday.
In fact, initial analysis of viruses from tested birds showed no evidence of any highly pathogenic strains of avian influenza, H5 or otherwise, and none from the families of viruses found in wild birds that travel flyways through Europe and Asia, said Patrick Zimmer, director of policy and administration for the Canadian Co-operative Wildlife Health Centre.
"So far, they're just what would be expected as far as the normal kind of North American strains that are circulating in these wild birds as a reservoir," Zimmer said from Saskatoon, where the centre is headquartered. The centre conducted the study for the federal, provincial and territorial governments.
The jury is still out over whether the Asian H5N1 viruses causing poultry outbreaks and occasional human deaths through parts of Asia, the Middle East and Africa are likely to make their way to North America via wild birds.
Years of analysis of the genetic blueprints of avian flu viruses suggests there are distinct families or lineages of viruses found in birds that travel the flyways of the Americas and those that migrate through Eurasia.
The 2006 survey was the second annual effort to conduct a census of which avian flu viruses wild birds in this country carry. Wild water birds like ducks, terns, sandpipers and snow geese are infected with and shed avian flu viruses with little impact on their own health.
As in 2005, several H5 viruses were found - an H5N9 in Alberta, two H5N2s in Quebec and one British Columbia. And there was one H5N1 virus found in Prince Edward Island. All the H5 viruses were of low pathogenicity, meaning they don't kill chickens.
There were no H7 viruses found.
The initial analysis of the samples focused on H5 and H7 viruses, because these two subtypes are the only kinds of avian influenza viruses known to be able to scale up in virulence from low pathogenicity to what is known as highly pathogenic or high path viruses.
High path avian influenzas are a significant problem in poultry operations, killing large numbers of birds and forcing the culling of many more. High path outbreaks in domestic poultry birds are costly; trading partners typically shut their doors to poultry from an affected country or region in a bid to keep these highly contagious viruses out of their own bird populations.
Zimmer said additional work must now be done to subtype the other flu viruses found among the live and dead birds to see what was circulating among wild birds in Canada last summer.
In addition to details of sampling done in Canada, the survey report includes sampling done in Ecuador and Iceland. Zimmer said Environment Canada received about 400 samples from Iceland, which does bird banding, and ran tests on them at CFIA's laboratory in Winnipeg.
"Last spring when H5N1 had arrived in Europe it was thought . . . this was kind of a neat way of having a very early warning system on birds that might be travelling to Canada that stop at Iceland," Zimmer said.
"They actually had no positives whatsoever, H5 or otherwise."
The Ecuadorian sampling was done as part of a collaboration to train professionals from that country to do surveillance and testing.
The Canadian wild bird survey was designed to complement a vastly more ambitious American surveillance program, which aimed to collect samples from between 75,000 and 100,000 migratory birds. To date that program has not found any evidence of the Asian H5N1 viruses.
As the U.S. program concentrated on the large breeding grounds in Alaska -- thought to be the likely entry point if Asian H5N1 viruses were to make their way to the North American flyways -- the Canadian effort focused more attention on Eastern Canada.
The CFIA release said that Canada and the United States will continue to co-ordinate surveillance efforts in a bid to find out whether Asian H5N1 viruses are making their way to North America.
"All indications are that there will be a survey again next year," said Zimmer. "But it's still in the planning stages."
