Study identifies North American wild bird species that could transmit bird flu
25/10/2006 17:03
The US researchers from the University of Georgia reported yesterday they
have found that the common wood duck and laughing gull are very susceptible to
highly pathogenic H5N1 avian influenza viruses and have the potential to
transmit them.
Their finding, published in the November issue of the journal
Emerging Infectious Diseases, demonstrates that different species of North
American birds would respond very differently if infected with these viruses.
David Stallknecht, associate professor of the UGA College of Veterinary Medicine
and co-author of the study, said knowing which species are likely to be affected
by H5N1 viruses is a vital component of efforts to quickly detect the disease
should it arrive in North America.
"If you're looking for highly pathogenic
H5N1 in wild birds, it would really pay to investigate any wood duck deaths
because they seem to be highly susceptible, as are laughing gulls," said
Stallknecht. "It was also very interesting that in some species that you
normally think of as influenza reservoirs -- the mallard, for instance -- the
duration and extent of viral shedding is relatively low. This may be good news
since it suggests that highly pathogenic H5N1 may have a difficult time
surviving in North American wild birds even if it did arrive in
Washington."
Working under controlled conditions in an airtight bio-security
lab of Department of Agriculture, the researchers determined how much of the
virus was shed in the feces and through the respiratory system of several
species of wild birds.
"We chose birds that, because of their behavior or
habitat utilization, are most likely to transmit the virus or bring the virus
here to North America," said lead author and doctoral student Dr. Justin
Brown.
The species studied were: mallards, which are often infected with
commonly circulating, low-pathogenic avian influenza viruses in North America
and Eurasia; northern pintails and blue-winged teal, which migrate long
distances between continents; redheads, a diving species; and wood ducks, which
breed in northern and southern areas of the United States. The laughing gull is
a common coastal species ranging from the Southern Atlantic to the Gulf Coast.
Stallknecht explained that in low-pathogenic avian influenza, most of the virus
is shed in the feces of birds. The virus then spreads as other birds drink from
contaminated water. The study found that in highly pathogenic H5N1 avian
influenza, however, the birds shed most of the virus through their respiratory
tract.
Stallknecht said with this knowledge, scientists can more effectively
detect the virus in live birds by swabbing the birds' mouths and
throats.
"Doing avian influenza surveillance is pretty tricky because there
are a lot of species differences and there are also seasonal differences," he
said. "So you've got to pick the right species at the right time and you've got
to collect the right samples."
Xinhua News
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