Prevalence of Influenza A viruses in wild migratory birds in Alaska: Patterns of variation in detection at a crossroads of intercontinental flyways

[Shiloh]

Source: http://7thspace.com/headlines/283467...l_flyways.html

Prevalence of Influenza A viruses in wild migratory birds in Alaska: Patterns of variation in detection at a crossroads of intercontinental flyways

The global spread of the highly pathogenic avian influenza H5N1 virus has stimulated interest in a better understanding of the mechanisms of H5N1 dispersal, including the potential role of migratory birds as carriers. Although wild birds have been found dead during H5N1 outbreaks, evidence suggests that others have survived natural infections, and recent studies have shown several species of ducks capable of surviving experimental inoculations of H5N1 and shedding virus.

To investigate the possibility of migratory birds as a means of H5N1 dispersal into North America, we monitored for the virus in a surveillance program based on the risk that wild birds may carry the virus from Asia.

Results: Of 16,797 birds sampled in Alaska between May 2006 and March 2007, low pathogenic avian influenza viruses were detected in 1.7% by rRT-PCR but no highly pathogenic viruses were found.

Our data suggest that prevalence varied among sampling locations, species (highest in waterfowl, lowest in passerines), ages (juveniles higher than adults), sexes (males higher than females), date (highest in autumn), and analytical technique (rRT-PCR prevalence = 1.7%; virus isolation prevalence = 1.5%).

Conclusion: The prevalence of low pathogenic avian influenza viruses isolated from wild birds depends on biological, temporal, and geographical factors, as well as testing methods.

Future studies should control for, or sample across, these sources of variation to allow direct comparison of prevalence rates.
Author: Hon S Ip, Paul L Flint, J CHRISTIAN Franson, Robert J Dusek, Dirk V Derksen, Robert E Gill, Craig R Ely, John M Pierce, Richard B Lanctot, Steven M Matsuoka, David B Irons, Julian B Fischer, Russell M Oates, Margaret R Petersen, Thomas F Fondell,

Published on: 2008-06-04

[Oracle]

Re: Prevalence of Influenza A viruses in wild migratory birds in Alaska: Patterns of variation in detection at a crossroads of intercontinental flyway

Open Access Paper: BioMed Central, Virology Journal, current issue.

http://www.virologyj.com/content/5/1/71

6.2 MB

Prevalence of Influenza A viruses in wild migratory birds in Alaska: Patterns of variation in detection at a crossroads of intercontinental flyways. Virology Journal 2008, 5:71doi:10.1186/1743-422X-5-71 4 June 2008 (Provisional paper).

[gsgs]

Re: Prevalence of Influenza A viruses in wild migratory birds in Alaska: Patterns of variation in detection at a crossroads of intercontinental flyway

no serotypes, no sequences ?
low-path refers to H5,H7 only ?
did viruses from different continents mix,reassort - were Eurasian
viruses found in Alaska ?

[Gert van der Hoek]

Re: Prevalence of Influenza A viruses in wild migratory birds in Alaska: Patterns of variation in detection at a crossroads of intercontinental flyway

More details on methods etc. here:

http://www.virologyj.com/content/pdf/1743-422x-5-71.pdf

[Shiloh]

Re: Prevalence of Influenza A viruses in wild migratory birds in Alaska: Patterns of variation in detection at a crossroads of intercontinental flyway

Source: http://www.reuters.com/article/middl.../idUSN05338427

Bird flu search finds none yet coming to N.America
Thu Jun 5, 2008 5:25pm EDT

By Maggie Fox, Health and Science Editor

WASHINGTON, June 5 (Reuters) - The feared H5N1 avian influenza has yet to make it to North America in the bodies of migrating birds, researchers said on Thursday.

Testing of more than 16,000 migratory birds between May 2006 and March 2007 showed no evidence of the H5N1 bird flu virus, which has become entrenched in many parts of Asia and which regularly pops up in flocks in Europe, the Middle East and Africa.

The birds are infected with virtually every other known strain of influenza, said Hon Ip of the U.S. Geological Survey, National Wildlife Health Center in Madison, Wisconsin. But not the highly pathogenic H5N1 virus.

"Maybe the Pacific Ocean is a nice, big biological barrier, for which I am forever grateful," Ip said.

"The general avian influenza infection rate is not really different in Alaska or North America than pretty much anywhere else. In spite of H5N1's spread through most of Asia and into Africa and Europe, that spread has not come into North America," Ip added in a telephone interview

About 1.7 percent of the birds were infected, but all with low-pathogenic strains of influenza viruses, which typically do not cause disease, Ip's team reported in the Virology Journal.

Highly pathogenic H5N1 avian influenza has forced the death or destruction of an estimated 300 million birds, according to the world animal health organization OIE.

SOURCE OF VIRUS

Birds are considered the original source of all influenza viruses. While H5N1 rarely infects people, it has killed 241 out of 383 infected in 15 countries.

Experts say the danger is that the virus will evolve just slightly into a form that people can easily catch and pass to one another, in which case the transmission rate could soar, causing a pandemic in which millions of people could die.

U.S. government officials have said it is inevitable that migratory birds will carry H5N1 to the Americas at some time.

An estimated that 1.5 million to 2.3 million birds migrate from Asia to Alaska each year.

But Ip, who worked with teams at the U.S. Department of Agriculture, the Fish and Wildlife Service and the Alaska Department of Fish and Game, says it has not happened yet.

The researchers are sampling birds that ornithologists say are the most likely to have migrated recently from Asia.

"Some of these viruses contain a mix of genes from both North American and Asian viruses," Ip said.

"We have direct evidence that the birds are carrying back at least a relative or descendant of viruses from Asia," he added. "This confirms we are sampling from those birds that are most likely to bring H5N1 back if H5N1 was to be brought back from Asia."

It also confirms that the viruses swap genes inside the birds -- a process that scientists believe gives rise to new and sometimes more dangerous strains.

The researchers have been testing birds since 2005 for H5N1, concentrating on Alaska but looking in all regions.

The birds most likely to be infected with any kind of flu virus are the dabbling ducks -- species such as mallards, Ip said. This reinforces the theory that the virus spreads as birds feed in the same water in which they are defecating.

Just this week U.S. chicken producer Tyson Foods Inc (TSN.N: Quote, Profile, Research) said it would eradicate about 15,000 chickens in Arkansas that carried antibodies to a mild H7N3 strain of bird flu, even though the birds were never sick and there was no risk to human health.

An outbreak this week of H7N7 flu forced the slaughter of all the chickens at a farm in Oxfordshire in Britain.

(Editing by Will Dunham and Cynthia Osterman)

[gsgs]

Re: Prevalence of Influenza A viruses in wild migratory birds in Alaska: Patterns of variation in detection at a crossroads of intercontinental flyway

they found Asian viruses/segments in Alaska ?
But apparantly those don't survive , don't enter or mix
with the American virus-population for long.

Few Asian viruses or segments were found previously in normal American
samples, the lineages evolved separately.
At least in PB2,PB1,NP - not so sure about PA

So Asian PB2 doesn't survive in America or rarely enters it
and American PB2 is rarely in other continents

[Giuseppe]

Re: Prevalence of Influenza A viruses in wild migratory birds in Alaska: Patterns of variation in detection at a crossroads of intercontinental flyway

Open Access Paper: BioMed Central, Virology Journal, current issue.

http://www.virologyj.com/content/5/1/71

6.2 MB

Prevalence of Influenza A viruses in wild migratory birds in Alaska: Patterns of variation in detection at a crossroads of intercontinental flyways. Virology Journal 2008, 5:71doi:10.1186/1743-422X-5-71 4 June 2008 (Provisional paper).

I provide a shot of a document map.
[LEGEND:

Figure 1. Geographical location of sampling sites in Alaska in 2006 and 2007. Hunter-harvest
sampling locations are noted in red. Live bird surveillance sampling locations are marked

in green. Habitat classifications based on Bird Conservation Regions [36,37]. ]

[AlaskaDenise]

Re: Prevalence of Influenza A viruses in wild migratory birds in Alaska: Patterns of variation in detection at a crossroads of intercontinental flyway

they found Asian viruses/segments in Alaska ?
But apparantly those don't survive , don't enter or mix
with the American virus-population for long.

Few Asian viruses or segments were found previously in normal American
samples, the lineages evolved separately.
At least in PB2,PB1,NP - not so sure about PA

So Asian PB2 doesn't survive in America or rarely enters it
and American PB2 is rarely in other continents

see Niman's travel logs showing Eurasian and NA mixing at

http://www.flutrackers.com/forum/showthread.php?t=10744&highlight=alaska+sequences

.