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H5 Testing of Farm Duck from Abottsford British Columbia
Recombinomics Commentary
November 19, 2005
Two weeks ago, the B.C. government announced it had discovered H5 avian flu in wild birds in surveillance in Merritt that was conducted in August.
Tests have determined about 174 ducks were positive for the H5 virus from more than 700 samples that were taken from young ducks.
A sample from the infected duck has been flown to the Canadian Science Centre for Human and Animal Health in Winnipeg, which contains one of the world's most secure laboratories for the testing of deadly diseases.
It will take at least a day before the scientists can grow the virus and start to characterize it. And it could take up to a week for the lab to get definitive results. It's also possible the scientists might never be able to get a clear reading from the sample to determine what strain of the virus it is, said Clark.
The infected duck was pulled off the processing line for inspection, but for reasons unrelated to avian flu. As a result of increased surveillance, the duck was also tested for the flu virus.
The above comments are curious and confusing. The initial H5 positive wild bird samples were sent to Winnipeg over two weeks ago, yet there has been no announcement on the HPAI status of the birds, even though such determinations are routine and can be done in hours. Although statements on dual infections have been issued along with cautions that typing may never be completed, the determination of HPAI is very straightforward, even in samples that contain mixtures of viruses. H5 HPAI is also a reportable disease in animals.
H5 HPAI isolates, especially those related to H5N1 in Asia have multi-basic amino acids at the HA cleavage site. These additional amino acids create a larger insert in a PCR test and the larger insert can be molecularly separated from LPAI inserts. Thus, sequencing does not require cloning. Since 174 have been identified, generating data on the HPAI status of these isolates should be rapid and straight forward.
The same can be said for the commercial bird because the extracts can be made from multiple organs to ensure a positive result. Moreover, if the bird was identified via random sampling, then more positive birds should be present at the processing plant as well as the farm of origin. Positives at the farm of origin is very likely because the birds had been kept outdoors and earlier reports indicated 24% of the wild birds in the area were H5 positive.
An update on the sequencing results from the H5 positive samples from British Columbia, Quebec, and Manitoba are long overdue, as is an update on the H5 status of wild birds in the other provinces in Canada as well as other birds on or near Abbotsford's Fraser Valley Duck and Goose.
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