H5N1 Bird Flu Detection in North America
Recombinomics Commentary
September 24, 2006
A Colorado State University laboratory tested 66 samples taken from Northern pintail ducks in Montana, the U.S. Department of Agriculture and the Interior Department said in a news release. Sixteen of the 66 were sent to the National Veterinary Services Laboratory in Iowa for more tests. Some tested positive for H5, some were positive for N1 and one sample was positive for both.
The Montana Department of Fish, Wildlife and Parks collected the samples last Friday at Benton Lake, near Great Falls, during routine work in which bands are placed on migratory birds to help track their movement.
The above comments provide additional information on the screening program in the United States and help explain the differences between reports from Canada, which reported multiple H5 subtypes in 2005, and the United States, which reported only H5N1 in 2006.
In August, 2005, Canada collected swabs as an adjunct to a banding experiment. A few months later they announced the finding of widespread detection of H5 serotypes across southern Canada. H5N1 was detected in Manitoba, but most positives were in British Columbia, where H5N2 and H5N9 was detected. H5N3 was detected in Quebec. Sequences from one of the British Columbia H5N2 isolate were recently released, and although it was most closely related to prior North American low path isolates, it did have some polymorphism found in H5N1 high path isolates from Asia, indicating there had been prior dual infections leading to the acquisition of these sequences via recombination,
This year Canada has said results mirrored last year’s results, but specific breakdown of serotypes has not been released. One report from Quebec describes an H5N2 and H5N6 isolate, bit there have been no details on the frequency of detection of H5N1.
This year however, the United States has reported H5N1 in Michigan, Maryland, Pennsylvania, and Montana recently. Thus, it seems likely that the H5 in southern Canada and northern United States would be similar, and the reports from the US may indicate limited sero-typing, as opposed to limited serotypes.
Although each initial announcement from the US warns that the H5 and N1 discoveries may be originating from two different serotypes, cloning of isolates has indicated that H5N1 was present, which has also been characterized as low path North American strain, but no 2006 sequences have been released from Canada or the United States.
However, the failure to find the Qinghai strain of H5N1 in live wild birds does not indicate the absence of H5N1 in North America. Detection of H5N1 in live wild birds is rare. The first reports of the Qinghai strain were from dead bar headed geese at Qinghai Lake in May of 2005. The strain was subsequently detected in Russia, Mongolia, and Kazakhstan, but the detection was again primarily in dead wild birds. Although Russia subsequently detected H5N1 in birds shot by hunters, these detections followed detection in dead birds.
This pattern has held up world-wide. When H5N1 migrated west and was found in the Volga Delta and the Danube Delta, the initial reports were from dead birds. As H5N1 became more widespread, the detection was in dead wild birds or poultry and reports were significantly delayed. Turkey and Romania reported H5N1 in October, but neighboring countries did not acknowledge H5N1 outbreaks until people began to die in Turkey in early 2006. However, the announcement by neighbors and most European countries were linked to H5N1 in dead wild birds.
This detection scheme extended into the Middle East and Africa, were H5N1 was found in dead birds, primarily on farms. Conservation groups failed to find H5N1 in wild birds in Africa, even though the sequences from isolates in Eastern and western Africa indicated infections were due to independent introductions of various versions of the Qinghai strain, as had been seen earlier in Europe and the Middle East.
In North America, the only reports of H5 in dead birds on a farm were reported in June on Prince Edward `Island. Four geese suddenly died with bird flu symptoms. One was tested and H5 was confirmed in a PCR test. However, by the time the sample was sent to Winnipeg for virus isolation and sequencing, the sample had degraded and H5 was not recovered. The PCR test on PEI however would generate an insert, and the size of the insert would have indicated if the H5 was high or low path, because high path has 4 additional amino acids, which would have created an insert 12 base pairs larger than low path. Canada declined to comment on the size of the insert.
Thus. although the H5N1 detected in live birds has been characterized as low path and North American, the details on the H5 from dead birds in North America has been withheld. More information on the sequences of H5N1 in both the United States and Canada would be useful.
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