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Commentary
Did H5N8 Fly Into Fraser Valley Canada?
Recombinomics Commentary
December 3, 2014 14:00
In 2005, 60,000 birds were killed after a mild version of H5 was found at a Yarrow farm. In 2009, 41 farms were placed in quarantine and 72,000 birds were slaughtered after an H5 version was found on two farms in Abbotsford. That version of the flu was determined to be “of low pathogenicity.”
The above comments describe the detection of H5 at two farms in the Fraser Valley in British Columbia (see map). The high death rate at both locations indicates the H5 will be high path (HPAI), in contrast to prior H5 outbreaks in this area.
The previously reported high path outbreak in Fraser Valley involved H7N3, which began as low path and then evolved to high path in 2004. Canada also reported high path H7N3 in 2007 in Saskatchewan.
The repeated outbreaks in this region are likely related to wild birds. In late 2005 an extensive survey was done in Canada, largely because of the spread of the Qinghai strain (clade 2.2) from China to Russia, Kazakhstan, and Mongolia in the summer, and onward transmission to Europe in the fall. The Canada survey found widespread H5 in healthy wild birds. Sequence analysis showed that these various wild bird H5 serotypes involved North American sequences which did not have a polybasic cleavage site.
The most likely example of high path H5 in Canada centered on a farm on Prince Edward Island in the following year. Goslings on a farm developed neurological symptoms and died. PCR testing was H5 positive leading to the culling of all birds and offering Tamiflu to the farm owners. A necropsy of one of the dead birds was “inconclusive”, in contrast to prior necropsies on birds infected with low path H5 which determined that the H5 infection was not responsible for the bird death.
The neurological symptoms, coupled with the death of the goslings raised concerns that the H5 was HPAI, but shipping of the sample to the National Labs in Winnipeg was delayed. When the degraded sample finally arived in Winnipeg the H5 PCR result was not confirmed and efforts to isolate virus failed, so Canada never filed an OIE report, which was mandatory for H5 and H7, regardless of pathology.
Thus, Canada has never reported a high path H5 case, which raises concerns that the H5 in the Fraser Valley is an Asian strain. Recent reports from Japan have described H5N8 in wild birds (Tundra swans, ducks, white necked crane), which are closely related to wild bird (wigeon) sequences identified in The Netherlands, as well as an Eurasian Teal in Germany.
In addition to H5N8 (which is clade 2.3.4), other clades have been reported in wild birds in Asia, including the Qinghai strain (clade 2.2), as well as two Fujian strains (clade 2.3.2 and 2.3.4), with the Fujian strains being more common in eastern Asia.
Thus, while Asian H5 HPAI has not been reported in Canada previously, they have never reported any HPAI H5, and the mortality cited above indicates the current Fraser Valley outbreaks will represent the first reported H5 HPAI outbreak in Canada.
Release of sequence data from the H5 PCR insert would be useful.
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