Sequence Analysis of H5N1 Bird Flu in
Michigan
The additional testing that we're doing
would include sequencing the genetic material. What is the sequence of
the genes, and is that consistent with a North American strain or an
Asian strain? The fact that this was compatible with our North American
virus and not compatible with the Asian high path avian influenza virus
that we are able to say that this is not the incursion of that Asian
high path H5N1 virus.
There's also another test to
determine pathogenicity or really two ways to determine pathogenicity.
One is, looking at that sequence, that gene sequence. It's through that
gene sequence testing that we're able to say that from a genetic
standpoint this looks like a low pathogenic virus.
The above comments indicate that the H5N1 detected in two of twenty
mute swans on Lake Erie in southern
Michigan were LPAI (low pathogenic avian influenza. It is
likely that the full sequence will be similar top the recently releases
HA sequence of H5N1 detected on British Columbia,A/mallard/BC317/2005(H5N2), almost exactly one year ago.
However, the exact sequence can provide valuable clues about the
presence of avian HPAI version of H5N1. In wild birds, that
version is most commonly the Qinghai strain.
The Qinghai strain was first identified in May of 2005 at Qinghai
Lake. It migrated into southern Siberia for the summer and caused
outbreaks in Russia, Kazakhstan, and Siberia. The strain then
migrated to Europe, the Middle East, and Africa, as well as
China. Sequences of the H5N1 from mute
swans in Astrakhan have North
American sequences suggesting H5N1 may have already migrated to
Canada last year. However, HPAI H5N1 has not been reported in Canada.
Last year young ducks were tested as part of an expanded banding
program across southern Canada. Four H5 sero-types (H5N1, H5N2,
H5N3, H5N9) were
identified. H5N1
was in Manitoba, while H5N2 and H5N9 were in British
Columbia. In Manitoba, an alarmingly 24%
were H5 positive. In the testing in southern Michigan, 2 of the
20 tested birds were H5N1 positive, so the percentage in certain
regions of the United States may also be alarmingly high.
The high frequency6 of H5 in wild birds is a concern because H5 can
become highly pathogenic, and can acquire mammalian polymorphism.
Moreover, it can most easily recombine with H5N1 from Asia because of
regions of genetic identity.
There is already evidence for both processes. Although a large
number of H5 virus was identified last year, only one sequence has been
made public. However, that sequence has polymorphisms shared by
swine in Canada as well as H5N1 in Russia.
The tandem polymorphism from H1N1
Canadian swine were describe earlier. Today 2006 HA sequences
Russia were released. A new polymorphism found in three recent
isolates from Russia, A/cat/Dagestan/87/06(H5N1),
A/chickem/Krasnodar/199/06(H5N1),
A/chicken/Adygea/203/06(H5N1),
was also present in the H5 in British Columbia.
Analysis of the H5N1 sequence from Michigan can be used to determine of
the evolution in the 2006 isolate and can be used to evaluate new
polymorphism present in new Qinghai isolates.
Full sequences of the Michigan swans should be made public as soon as
possible.
Source: Recombimonics
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