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H5 and H7 Wild Bird Flu Detected in Canada's Maritimes
Recombinomics Commentary
November 25, 2005
Thirty-six healthy, wild ducks from the Maritime provinces have tested positive for H5 and H7 strains of avian influenza viruses.
Of 710 birds tested as part of a national wild bird surveillance program, 35 in the Maritime provinces were found to be carrying H5 viruses and one carried an H7 viruses.
The above comments extend the H5 surveillance program in Canada. As part of a banding program in August, captured birds were swabbed and test results are being released. 700-800 birds were captured in each of 6 regions/provinces in Canada. These were predominantly healthy young wild birds that were banded, swabbed, and released. Thus far H5 has been detected in all reporting provinces including 5 birds in Manitoba, 28 in Quebec, and 174 in British Columbia. Further sero-typing of 11 birds yielded 2 H5N3's in Quebec, 2 H5N1's in Manitoba, 2 H5N2's and 5 H5N9's in British Columbia.
The 11 isolates that were fully sero-typed were all LPAI and most closely related to prior H5 isolates from North America. It remains unclear if the 196 other positive birds match the first 11 or contain additional sero-types. The high frequency of H5 in health wild birds was unexpected. There are over 100 GenBank deposits from Canada and only two were H5 (H5N2 in 1980 and H5N9 in 1966).
The high frequency of H5 in healthy wild birds in Canada is cause for concern because the virus can be transmitted from wild birds to domestic birds. Moreover, H5 and H7 low path viruses can convert to HPAI. The most recent example of this type of conversion was seen in British Columbia last year when H7N3 LPAI converted into HPAI resulting in the culling of 17 million birds.
This season H5 has been detected on two farms in the same region of Fraser Valley. One of the farms was characterized as be "rife" with H5 infected ducks and geese. Waterfowl typically do not show symptoms of influenza infection, even when infected with HPAI. The designation of HPAI is base of the sequence of the HA cleavage site and/or the pathogenicity in experimental chickens. The pathogenicity data on the H5 on the farms has not been released nor have full sero-types of the various isolates.
The detection of H5 in wild birds in four of four reporting regions in Canada is cause for concern. Since the released results have been incomplete, it is not know if some of the H5 isolates are HPAI or related to the dangerous H5N1 found in Asia and more recently in Europe and the Middle East. This H5N1 wild bird flu has been found in asymptomatic, long range migratory birds which migrate to Alaska and northeaster Canada. Transfer of H5N1 to Canadian birds that migrate south in the winter is cause for concern and has led to pledges of increased surveillance.
However, the finding of H5 in all reporting provinces that collected samples in August would indicate that H5 has transferred to more farms in Canada and to farms and nature reserves in the US. However, these infections have not been reported, suggestion major flaws in the surveillance network.
Similar flaws are evident in Europe where OIE reports have been limited to Turkey, Romania, Croatia, and Russia. The widespread detection of H5N1 in migratory birds in these countries indicate H5N1 is widespread. Kuwait has acknowledged H5N1 infections, but has not file OIE reports. Other countries have cited negative data in surveillance efforts. However, the data from Canada indicates that the negative test results for H5N1 lacks credibility unless other less virulent sero-types are detected in view of the widespread infections of migratory birds by various influenza sero-types.
Moreover, reports from Israel suggest an H5N1 infection in a worker exposed to migratory birds.
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