An outbreak of highly pathogenic avian influenza in both wild birds and backyard flocks has killed thousands of birds throughout the state, Oregon wildlife and agriculture officials say.
The disease, typically known as bird flu, has been detected in almost every county in Oregon. Its current strain is especially deadly for wild birds, which are dying in larger numbers than during previous outbreaks.
The number of backyard flocks – which include chickens, ducks and other domesticated birds – that have been impacted has also been much larger than in recent outbreaks. While turkeys are especially susceptible to the disease, only a handful have died locally since Oregon isn’t a turkey-producing state, officials said.
Sick birds act like they are drunk. They’re uncoordinated and lethargic; they shake, swim in circles and fly into the sides of houses. Those who show symptoms usually die within 72 hours.
“It’s definitely serious,” said Ryan Scholz, state veterinarian with the Oregon Department of Agriculture.
Bird-flu viruses occur naturally in the environment, and avian influenza does not always cause mortality or even illness in birds. Some birds, like mallard ducks, have developed immunity to the disease, even its highly pathogenic strains. They suffer no symptoms, but they spread the disease, most commonly through feces.
The virus typically arrives in the US from Europe or Eurasia, carried by waterfowl that fly thousands of miles. The birds spread the disease every time they touch down to 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 across the globe. The virus is now endemic in Europe and Asia.
This year may prove even deadlier than usual. The virus typically peters out with 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 birds did not 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 how the virus usually operates.
In recent weeks, wild birds have been getting sick and dying from the Fernhill Wetlands in Forest Grove to the Tualatin River Wildlife Refuge to the Willamette Valley Wildlife Refuges. It’s impossible to know exactly how many wild birds have been affected, said Colin Gillin, State Wildlife Veterinarian.
“If I said it was in the thousands, it would be an under-estimate,” Gillin said.
About 17 percent of waterfowl that’s been tested have registered positive for the disease, which is “a substantial number,” Gillin said. The species currently most affected is cackling geese, but the disease is also killing numerous bald eagles, hawks, owls and herons.
Songbirds and wild turkeys have not been impacted, Gillin said, because they don’t typically interact with waterfowl and aren’t a scavenger species.
There’s also concern for snow geese after nearly 400 sick or dead geese were found at Wiser Lake in western Washington state a few days ago and several tested positive for avian flu. Many of the dead birds were snow geese. Those birds are just starting to arrive in Oregon, so many more could die in coming weeks in our state, Gillin said.
In other states, avian influenza has also been detected in mammals such as skunks, foxes and coyotes — usually in younger animals.
The disease does not pose a high risk to humans, although some have been infected with bird flu viruses. Still, it’s a mutating disease, officials said, so hunters should wear protective gear like masks and gloves to safely handle wild birds, and they should change clothes when they get home. Hunters should not kill birds that look sick. They also should minimize dogs’ interactions with waterfowl.
Some hunters worry whether the die-offs will impact duck- and goose-hunting seasons, which are now open.
“I’m seeing quite a few dead geese on Sauvie Island and quite a few sick ones as well,” local hunter Eric Strand said via email.
But Brandon Reishus, Oregon’s migratory bird coordinator, said it’s too early to predict. “We have no plans to close hunting down. But it’s an evolving situation.”
The Oregon Department of Agriculture said 16 cases have been confirmed this year in smaller flocks of domesticated birds. That’s a significant increase from the two confirmed cases in 2014-2015 outbreak, said Scholz, the Department of Agriculture veterinarian. More flocks are being tested after an uptick in calls over the past week.
About two thousand domesticated birds have been euthanized or died of avian flu in Oregon this year in reported cases, said Scholz. Some backyard flock owners only use birds or their eggs for home consumption, while others have hundreds of birds and sell their products to the public. The state has imposed several avian flu quarantines this summer and fall to prevent the sale of meat or eggs from virus-impacted areas.
There have been no cases reported in commercial farms – farms with much larger flocks that are often raised in large barns — likely because they have strict biosecurity measures, Scholz said.
The sick flocks ranged from 4 to 500 in size. The bigger the flocks, the more birds die quickly – so the risk of the disease to larger farms is significant. In the case of one large backyard farm with about 400 chickens, Scholz said, the birds started dying on Saturday and by Monday there were “barrels of dead birds.” Agricultural officials had to euthanize the rest.
And it’s not just a chicken problem. In addition to hundreds of dead chickens, the outbreak this year has claimed domestic ducks, quail, pheasants, even a couple of emus.
With colder weather and wild-bird migration hitting the high point in coming weeks, the environment is ripe for transmission, Scholz said.
“This kind of weather… it’s a setup for a perfect storm,” he said.
Wildlife officials say it’s OK to double-bag and dispose of one to two dead wild birds in the trash. People can also shallowly bury birds or just leave them where they are found in the wild. Officials said people should be careful about handling the birds and should never transport them.
As for domestic birds, responsible owners can help prevent their flocks’ exposure to wild waterfowl by fencing off access to farm ponds or grassy 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 collected for testing. If the disease is confirmed, all birds are euthanized, said Scholz.
“Avian influenza is 100 percent fatal” for domestic birds, which have not developed the immunity that some wild birds have, he added. “All the birds are going to die from the disease. We would much rather humanely euthanize them then wait for them to get sick and die.”
– Gosia Wozniacka; [email protected]; @gosiawozniacka
Our journalism needs your support. Please become a subscriber today at OregonLive.com/subscribe/