The H5N2 avian influenza virus is continuing to hopscotch through the Upper Midwest, as shown today by a report of Wisconsin's second and third outbreaks, in turkeys and backyard poultry at widely separated sites.
The two new outbreaks, combined with previous ones listed by the US Department of Agriculture (USDA), boost the count of poultry outbreaks of H5N2 in the United States since December to 43, with most of them having occurred in the Midwest since early March. Twenty-two outbreaks have been in Minnesota, where more than 1.4 million turkeys have been lost to the virus and control efforts.
In Wisconsin, the virus struck a farm with 126,000 turkeys in the northwestern county of Barron, the state Department of Agriculture, Trade and Consumer Protection reported in a statement. It also hit a flock of 40 backyard birds in Juneau County in the west-central part of the state.
Both sites are distant from Wisconsin's first outbreak, on a chicken farm in Jefferson County in the southeast, which was reported 3 days ago. That was the first commercial chicken farm to be hit by the virus, which has overwhelmingly favored turkey farms.
Wisconsin authorities said their response to the new outbreaks will follow the standard script, including quarantines of the sites, culling of the surviving birds, and testing of poultry at other sites nearby. "Officials are investigating how the virus entered the flocks and may not have answers for some time," the statement said.
Such answers have eluded investigators of all the H5N2 outbreaks so far. Officials say wild birds such as ducks can carry the virus and shed it in their feces without appearing sick, but scientists have not reported finding the virus in wild birds near any of the recent outbreak sites. The recent outbreaks have occurred in the Central and Mississippi flyways for migratory birds.
H5N2 has surfaced in Missouri, Arkansas, Kansas, Iowa, the Dakotas, and Montana since early March, as well as Minnesota and Wisconsin. Earlier in the winter it hit a few poultry flocks in Washington, Oregon, and Idaho. A few detections in wild birds have been reported as well.
Eastern poultry farmers worried
Meanwhile, poultry producers in the eastern United States are worried about the threat of an H5N2 invasion, according to an Associated Press (AP) report yesterday. It said the concern is that if the virus isn't already hiding somewhere in the Atlantic flyway, it could spread there when wild ducks fly south for the winter this fall or return north next spring.
Government scientists speculate that when ducks and other migratory waterfowl from different flyways gather on northern breeding grounds this summer, they could expose each other to the H5N2 virus, and then carry it back south this fall along several migration routes, perhaps including the Atlantic flyway, the story said. The flyway includes several of the country's top poultry producing states, such as Georgia, the Carolinas, Virginia, Delaware, and Maryland.
Hon Ip, PhD, MS, a microbiologist with the US Geological Survey's National Wildlife Health Center in Madison, Wis., told the AP that researchers believe the spread of the Eurasian H5N8 virus from Asia to Europe and North America last year resulted from the mingling of migratory birds in northeastern Russia last summer. The H5N2 virus is a product of reassortment between the Eurasian H5N8 strain and viruses from North American wild birds.
One challenge scientists have in predicting how H5N2 may spread is that they don't have enough surveillance data from wild birds to prove they're the source yet, said Tom DeLiberto, DVM, PhD, assistant director of the USDA's National Wildlife Research Center, according to the AP. He said only 56 wild birds have tested positive for H5N8, H5N2, and a few similar viruses, and most were in the Pacific Northwest. Only four or five wild birds have tested positive in the Mississippi flyway, he said.
H5N1 in Bhutan, H5N6 in Hong Kong
In other developments, Bhutan today reported its first H5N1 avian flu outbreak since April 2013. The virus killed 16 of 37 birds in a backyard poultry flock in the western province of Thimphu, an agriculture official said in a report to the World Organization for Animal Health (OIE) today.
The outbreak was first noticed Apr 3, the report said. The surviving birds were destroyed to stop the virus, and no cases were seen in nearby flocks.
Also today, Hong Kong officials reported that the H5N6 avian flu virus was found in a dead peregrine falcon, the first such detection in the territory. The carcass was found at a construction site, the Hong Kong Agriculture, Fisheries and Conservation Department said in a press release.
The H5N6 virus has caused a few poultry outbreaks in China, Vietnam, and Laos since it first cropped up in China in March 2014, and China has had three human cases, two of them fatal.
Apr 16 Wisconsin statement
USDA list of H5N2 and H5N8 outbreaks
Apr 15 AP story
Apr 16 Bhutan report to OIE
Apr 16 Hong Kong press release