An outbreak of highly pathogenic avian influenza in both wild birds and backyard flocks has killed thousands of birds statewide, Oregon wildlife and agriculture officials say.
The disease, typically known as bird flu, has been found in nearly every county in Oregon. Its current strain is particularly deadly to wild birds, dying in greater numbers than previous outbreaks.
The number of affected backyard flocks – including chickens, ducks and other domesticated birds – was also much larger than in recent outbreaks. While turkeys are particularly susceptible to the disease, only a handful have died locally because Oregon is not a turkey-producing state, officials said.
Sick birds pretend to be drunk. You are uncoordinated and lethargic; they tremble, swim in circles and fly against building walls. Those who show symptoms usually die within 72 hours.
“It’s definitely serious,” said Ryan Scholz, a state veterinarian with the Oregon Department of Agriculture.
Avian influenza viruses occur naturally in the environment and avian influenza does not always cause death or even disease in birds. Some birds, such as mallards, have developed immunity to the disease, even to its highly pathogenic strains. They have no symptoms but spread the disease, most commonly through feces.
The virus typically comes to the US from Europe or Eurasia, carried by waterfowl flying thousands of miles. The birds spread the disease every time they rest.
Deadlier strains of bird flu have been on the rise in recent years. Highly pathogenic avian influenza has devastated wild birds and the poultry industry around the world. The virus is now endemic in Europe and Asia.
This year could prove even deadlier than usual. The virus typically attenuates in dry and hot weather as low pathogenic strains of the disease naturally outcompete it. That happened in 2014-15, the last major outbreak in the US in domestic birds.
But the birds didn’t stop getting sick this summer in the Pacific Northwest. They continued to die during the hottest months and well into the fall – an anomaly to the normal functioning of the virus.
In recent weeks, wild birds have been getting sick and dying from the Fernhill Wetlands in Forest Grove to the Tualatin River Wildlife Refuge and the Willamette Valley Wildlife Refuges. It’s impossible to know exactly how many wild birds will be affected, said Colin Gillin, state wildlife veterinarian.
“If I said it was in the thousands, that would be an underestimate,” Gillin said.
About 17 percent of the waterfowl tested have reported positive for the disease, which is “a significant number,” Gillin said. Currently the most affected species are cackling geese, but the disease is also killing scores of bald eagles, goshawks, owls and herons.
Songbirds and wild turkeys aren’t affected, Gillin said, because they don’t typically interact with waterfowl and aren’t scavengers.
There is also concern for snow geese after nearly 400 geese were found sick or dead at Wiser Lake in western Washington state a few days ago and several tested positive for bird flu. Many of the dead birds were snow geese. These birds are just beginning to arrive in Oregon, so many more could die in our state in the coming weeks, Gillin said.
In other states, avian flu has also been found in mammals like skunks, foxes and coyotes — usually younger animals.
The disease does not pose a high risk to humans, although some have been infected with avian influenza viruses. Still, it’s a mutating disease, officials said, so hunters should wear protective gear like masks and gloves to handle wild birds safely, and change clothes when they get home. Hunters should not kill birds that look sick. You should also minimize interactions between dogs and waterfowl.
Some hunters worry if the die-off will affect the duck and goose hunting season, which is now open.
“I see quite a few dead geese on Sauvie Island and quite a few sick ones too,” local hunter Eric Strand said via email.
But Brandon Reishus, Oregon’s migratory bird coordinator, said it’s too early to make a prediction. “We have no plans to stop hunting. But it is an evolving situation.”
The Oregon Department of Agriculture said 16 cases were confirmed in smaller flocks of domestic birds this year. That’s a significant increase from the two confirmed cases of the 2014-2015 outbreak, said Scholz, the Department of Agriculture’s veterinarian. More herds are being tested after a spike in calls over the past week.
About two thousand domesticated birds have been euthanized or died from bird flu in Oregon this year in reported cases, Scholz said. Some backyard flock owners only use birds or their eggs for their own needs, while others have hundreds of birds and sell their produce to the public. The state has imposed several bird flu quarantines this summer and fall to prevent the sale of meat or eggs from virus-hit areas.
No cases have been reported on commercial farms — farms with much larger herds often raised in large barns — likely because they have strict biosecurity measures, Scholz said.
The diseased herds ranged in size from 4 to 500. The larger the flocks, the more birds die quickly – so the risk of the disease is significant for larger farms. In the case of a large backyard farm with about 400 chickens, Scholz said the birds started dying on Saturday, and there were “barrels of dead birds” on Monday. Agricultural officials had to put the rest to sleep.
And it’s not just a chicken problem. In addition to hundreds of dead chickens, this year’s outbreak has killed domestic ducks, quail, pheasants and even a few emus.
As colder weather and wild bird migration peak in the coming weeks, the environment is ripe for transmission, Scholz said.
“That kind of weather… it’s a setup for a perfect storm,” he said.
Wildlife officials say it’s okay to trash and dispose of one or two dead wild birds. People may also bury birds shallowly or simply leave them where they are found in the wild. Officials said people should be careful when handling the birds and never transport them.
As with domestic birds, responsible owners can help prevent their flocks from being exposed to wild waterfowl by closing off access to farm ponds or grass fields, Scholz said.
Domestic flock owners should call the Department of Agriculture if more than one bird in their flock dies in rapid succession, officials said. Reported cases are reviewed by a veterinarian and samples are taken for testing. If the disease is confirmed, all birds will be euthanized, Scholz said.
“Avian flu is 100 percent deadly” for domestic birds that haven’t developed the immunity that some wild birds have, he added. “All the birds will die from the disease. We would much rather put them to sleep humanely than wait for them to get sick and die.”
– Gosia Wozniacka; [email protected]; @gosiawozniacka
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