Toronto The decision by Australian officials to ban bird imports from Canada because three racing pigeons were found to have antibodies to an unspecified avian flu virus was termed a “knee-jerk reaction” on Friday.
A senior Canadian official said the decision likely stemmed from high levels of anxiety surrounding the potential for spread of the deadly H5N1 virus from Southeast Asia to Australia.
But Dr. Jim Clark said there was no evidence that the birds had ever been infected with that particular avian flu strain, which has not been found in Canada.
“Due to the sensitivity concerning H5N1 in Southeast Asia, there appears to be a knee-jerk reaction that we're seeking to clarify with the Australian agricultural officials,” said Dr. Clark, acting director of the animal health and production program at the Canadian Food Inspection Agency.
“It appears to be an unfortunate set of circumstances.”
Dr. Clark said Canada expects the science-based regulations established by the international agency responsible for animal health and welfare – known by the acronym OIE – “will resolve the situation satisfactorily and will resolve any concerns Australian officials may have with respect to the (disease) status of Canada.”
He said Canada also wants Australia to clarify the unwelcome impression left by their reaction, the impression that Canada might have a problem with “bird flu” – which in the public's mind currently equates to H5N1 avian influenza.
The Australian officials will need to "make public statements to the effect that they don't have those concerns,” he said.
Blood samples from three pigeons in a shipment of 102 were found to contain antibodies to avian influenza Type A, a large family of viruses commonly found in some species of wild birds – although not generally pigeons.
Antibodies are the immune system's soldiers. Presence of antibodies suggests the birds had previously been infected with an avian-flu virus. But tests done before they left Canada and after they arrived in Australia showed the birds were not shedding virus, which would have pointed to ongoing or at least recent infection.
Viruses are infectious; antibodies are not.
Avian flu viruses are classified according to which of 16 hemagglutinin and nine neuraminidase proteins they carry on their surface. In theory, there may be as many as 144 different subsets of the viruses, thought not all combinations have been found.
The Australians did not test the antibodies to determine which subtype they corresponded to.
Most avian flu viruses would pose no human health threat. But the variant of H5N1 that Australia – and the rest of the world – is so concerned about is both highly lethal and better at infecting people than most. Since late 2003, 118 human cases of H5N1 infection have been confirmed; 61 have died. All those cases occurred in Thailand, Vietnam, Cambodia and Indonesia, where outbreaks in poultry have been widespread.
Recently the virus has been found to have spread in migratory birds to parts of Asia. But fear of it has spread farther and faster.
“I think that's what's driving the issue in Australia – the proximity to Southeast Asia, where H5N1 is a reality that they're facing every day and the opportunity for migratory birds to bring that issue into their country,” Dr. Clark said.