Swine Sequences In H5 Wild
Birds In British Columbia

By Dr. Henry L. Niman, PhD

The HA sequence of A/mallard/BC/317/2005(H5N2) has been released. This isolate was obtained via an expanded banding project by the Canadian Cooperative Wildlife Health Centre. Last year the agency reported that H5 had been found in live healthy wild birds throughout southern Canada. A remarkable 24% of the birds tested in British Columbia were H5 positive. The latest breakdown by species indicates bird flu was detected in 1165/2657 of the mallards tested and H5 was detected in 187/811. The update report by region indicates H5 was detected in 167/380 birds tested in British Columbia.
Analysis of the above sequence indicates it has a HA cleavage site consistent with low path H5. However, analysis of individual polymorphisms indicates the H5 has acquired two tandem polymorphisms, C1367T and C1377T.
Other isolates in the Los Alamos flu database having these two polymorphisms are listed below. The only H5 or avian isolate in the list is the H5N1 sequence from British Columbia. All other isolates are mammalian H1 isolates, including recent isolates from Canadian swine as well as a fatal human case in Maryland
The most extensive homology is identified with a 25 bp probe which identifies the recent isolate A/swine/Ontario/11112/2004(H1N2), which was among a group of Canadian swine showing both extensive recombination as well as extreme conservation of sequences. As noted below, the 25 bp probe identifies A/Wilson-Smith/33 and A/WSN/33, the first human flu isolate as well as its neurotropic derivative.
The acquisition of these polymorphisms in a health wild bird population is cause for concern. Recent data from Prince Edward Island suggests the Qinghai strain of H5N1 has already entered North America. Recombination between low path H5 and high path H5N1 is common and provides a mechanism for acquisition of these mammalian polymorphisms by the Qinghai strain of H5N1 bird flu.
The initial H5N1 human isolates from Vietnam and Thailand had acquired a number of mammalian polymorphisms that were not found in other H5N1,s. The acquisition of swine polymorphisms in H5 in wild birds in Canada, and presumably the United States, is cause for concern.



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