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H5 Positive Geese Raise Surveillance Concerns
June 19, 2006
The delay in the release of information of the H5 detected in a dead goose on a free range backyard farm on Prince Edward Island is cause for concern. On June 4 four geese "waking funny" were observed and the next morning they were dead. Three were buried and one was brought in for testing and H5 was confirmed. However data on the pathogenicity of the isolate has been lacking, even though the birds have been dead for almost two weeks.
This delay is in marked contrast to the detection of low pathogenic H5N2 on a farm in British Columbia last November. At that time Canada had released data on H5 detected in healthy young waterfowl across southern Canada. H5 was readily detected in swabs collect in August 2005 as part of a banding program. The banded ducks were healthy and released into the wild. Detection of avian influenza in healthy waterfowl is not uncommon.
In the British Columbia incident, the duck was initially observed during processing on November 17. H5 was confirmed on Nov 18 and an OIE report was filed on Nov 20. A partial sequence of the H5 and N2 was placed on deposit at GenBank on Nov 29. Thus, within 12 days the virus was isolated, H5 was confirmed, sequence was generated, checked, and deposited at a public sequence database.
The HA cleavage site was RETR, which is markedly different that the sequence in Asian H5N1 which is RERRRKKR or GERRRKKR in the Qinghai strain. Both of the sequences have four basic amino acids inserted into the cleavage site, producing a larger gene product. This additional genetic information would produce an insert that had an additional 12 BP. Thus, the presence of the additional genetic information could be determined by just looking at the size of the insert. However, sequencing of the insert is also routine, and the added basic amino acids are diagnostic of highly pathogenic avian influenza and do not require determination of the N serotype. All H sequences with a cleavage site of RERRRKKR or GERRRKKR have been high path H5N1.
On June 16 instead of announcing the determination of the pathogenicity of the H5, there was a press release indicating that H5 had been found. There has been no OIE report filed and the H5 is said to be "low risk". The "low risk" determination seemed to be comments on the potential of the H5 causing human illness. Most countries with recent H5N1 infections in wild birds or poultry have not had human cases. The human cases were found in countries with massive outbreaks and may also be linked to further genetic changes.
However, the fact that four geese were sick and died is a hallmark of the Qinghai strain of H5N1. Most waterfowl do not get sick from low pathogenic avian influenza and many waterfowl species are resistant to H5N1 that is lethal in chickens and people. Therefore, the death of four geese was cause concern. Media reports suggested that the H5 was not highly pathogenic because the chickens on the farm were not affected. However, because the H5N1 is frequently in waterfowl that interact with domestic ducks, the first cases are frequently in domestic waterfowl.
The Qinghai strain was initially identified in waterfowl at Qinghai Lake in May of 2005. Most of the dead birds were bar headed geese. The infections at Qinghai Lake were followed by two H5N1 outbreaks in China in Xinjiang Province. Both outbreaks involved domestic waterfowl. Similarly, the initial outbreaks on farms around Chany Lake in southern Siberia were also in free range birds sharing water reservoirs with wild birds.
As H5N1 migrated to Europe, initial outbreaks were in the Volga Delta and Danube Delta. The initial isolates were from mute swans. In many countries in Europe, the H5N1 isolates have been detected in wild birds.
This year there have been no H5 OIE reports from Canada or the United States, although media reports indicated H5 had been found at a wet market in New Jersey. The failure to detect high or low pathogenic H5 this year is cause for concern.
It is likely that the H5 on a farm on PIE will be linked to wild birds, raising surveillance concerns. The failure to release additional data on the H5 isolate is also of concern. The lack of infections in chickens does not address the pathogenicity because the dead birds were removed quickly and other birds on the farm have been euthanized. The dead geese are a signal of H5N1 Qinghai infections, as is the "funny walk."
The failure to recognize the dead geese as a common scenario linked to H5N1 infections suggest education of infections via migratory birds is lacking and the delay in release of pathogenicity or sequence data is also of concern.
The owners of the dead geese have been offered anti-virals, but have been told that the H5 was not likely to be highly pathogenic. The basis of these assurances remains unclear,