More avian flu in US birds; Asian H9N2 found in Alaska

The highly pathogenic avian influenza (HPAI) viruses H5N2 and H5N8 are continuing to turn up in US birds, with the latest detections in Montana and California, while an Asian H9N2 virus was found in wild birds in western Alaska, according to recent reports.

In Montana, the HPAI H5N2 virus was found in a captive gyrfalcon in Columbia Falls in the northwestern part of the state, the Montana Department of Livestock reported in a statement yesterday. The report apparently is the first discovery of the strain in the state.

The agency said the falcon died of unknown causes and was sent to a state wildlife lab in Bozeman for analysis. The H5N2 finding was later confirmed by a US Department of Agriculture (USDA) lab in Ames, Iowa.

The bird was owned by a falconer who has about 50 other captive birds, according to a story today in the newspaper The Missoulian. Martin Zaluski, DVM, state veterinarian, said the rest of the birds would be tested for the virus. It appears that the dead falcon was exposed to the disease through contact with a harvested wild duck, he reported.

The H5N2 virus caused outbreaks in March on several commercial turkey farms in Minnesota, Missouri, and Arkansas, as well as a backyard flock in Kansas.

H5N8 in wild California ducks

Meanwhile in California, the HPAI H5N8 virus was found in wild wigeons in two counties, Colusa and Solano, says a report that the USDA filed yesterday with the World Organization for Animal Health (OIE). The report did not specify how many wigeons were infected. Colusa is in the Central Valley northwest of Sacramento, while Solano is in the San Francisco region.

The H5N8 strain, which originated in Asia, made its first known US appearance in a captive gyrfalcon in Washington state last December. It has since been found in a number of wild birds in California, Oregon, Washington, Idaho, and Nevada, in commercial turkeys and chickens in California, and in backyard poultry in Oregon.

H9N2 in Alaska

In other news, researchers with the US Geological Survey reported that they found H9N2 viruses in two wild birds in Alaska that match strains from China and South Korea.

The viruses were found in testing of samples from 2,924 wild birds at the Izembek National Wildlife Refuge in western Alaska, the researchers reported on Mar 30 in Virology. A fecal sample from an emperor goose and a cloacal sample from a northern pintail duck, both collected in September 2011, yielded the isolates.

All eight gene segments of the two viruses were more than 99.4% the same as recent H9N2 isolates from Lake Dongting, China, and Cheon-su Bay, South Korea, the researchers wrote.

The Izembek refuge provides staging habitat for hundreds of thousands of migratory birds in the fall, including several species with intercontinental migratory tendencies, such as emperor geese and northern pintails, the authors said.

"The novel finding of nearly identical viruses in Alaska, China, and South Korea provides direct evidence for the dispersal of influenza A viruses between East Asia and North America by wild birds," they wrote. It's unlikely that the finding is related to commercial poultry, they added, because western Alaska has no poultry production, and very similar H9N2 strains have not been reported in poultry in East Asia or North America.

H9N2 infections have occasionally been reported in humans, but they have typically caused only mild illness. No human H5N2 or H5N8 infections have been reported.

Minnesota investigation

Elsewhere, the first round of testing of backyard poultry flocks near the site of last week's turkey-farm H5N2 outbreak in western Minnesota's Lac Qui Parle County has been completed without finding any infected birds, the Minnesota Board of Animal Health (MBAH) reported yesterday. The board said 13 flocks were tested, and a second round of tests in planned.

In addition, the MBAH said 60 backyard flocks near the site of the more recent H5N2 outbreak in Stearns County in central Minnesota are being tested. The control zone around the outbreak also contains 15 to 20 commercial poultry farms, all of which have been routinely tested for years.

A USDA report posted by the OIE yesterday said the Lac Qui Parle County outbreak killed 1,600 of 65,800 turkeys on the farm, prompting the destruction of the rest to stop the virus. The same report said all 45,140 turkeys on the Stearns County farm were culled, but it did not list any cases or deaths caused by the virus.

See also:

Mar 31 Montana Department of Livestock press release

Apr 1 Missoulian story

Mar 31 OIE report on H5N8 in California wigeons

Mar 30 Virology report

Mar 31 OIE report on Minnesota outbreaks

Mar 31 MBAH update

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