An outbreak of highly pathogenic avian flu in both wild birds and backyard flocks has killed thousands of birds across the state, Oregon wildlife and agriculture officials say.
The disease, commonly known as avian flu, has been found in nearly every Oregon county. The current species is especially deadly to wild birds, which are dying in greater numbers than during previous outbreaks.
The number of backyard flocks — including chickens, ducks and other domestic birds — that have been affected is also far greater than in recent outbreaks. While turkeys are particularly susceptible to the disease, only a handful have died locally since Oregon is not a turkey-producing state, officials said.
Sick birds pretend to be drunk. They are 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, a state veterinarian with the Oregon Department of Agriculture.
Bird flu viruses occur naturally in the environment and bird flu does not always cause death or even disease in birds. Some birds, such as mallard ducks, have developed immunity to the disease, even against the highly pathogenic strains. They have no symptoms, but they spread the disease, usually through feces.
The virus usually arrives in the US from Europe or Eurasia, carried by the waterfowl that fly thousands of miles. The birds spread the disease every time they perch to rest.
Deadlier forms of bird flu have been on the rise in recent years. The highly pathogenic avian flu has devastated wild birds and the poultry industry around the world. The virus is now endemic in Europe and Asia.
This year could be even deadlier than usual. The virus usually dies out in dry and warm weather, as low-pathogenic strains of the disease naturally outcompete it. That happened in 2014-2015, the last major outbreak in the US in domestic birds.
But birds continued to get sick in the Pacific Northwest this summer. They continued to die during the warmest months and well into autumn – a departure from the way the virus usually works.
In recent weeks, wild birds have been sickened 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, says Colin Gillin, state veterinarian.
“To say it was in the thousands would be an underestimation,” Gillin said.
About 17 percent of waterfowl tested have registered positive for the disease, which is “a significant number,” Gillin said. The species most affected today are cackling geese, but the disease is also killing numerous bald eagles, hawks, owls and herons.
Songbirds and wild turkeys aren’t affected, Gillin said, because they typically don’t interact with waterfowl and aren’t scavengers.
There is also concern about snow geese after nearly 400 sick or dead geese were found a few days ago at Wiser Lake in western Washington state 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 our state in the coming weeks, Gillin said.
In other states, bird flu has also been seen in mammals such as skunks, foxes and coyotes, usually in younger animals.
The disease does not pose a high risk to humans, although some are infected with bird flu viruses. Still, it’s a mutating disease, officials said, so hunters should wear protective gear such as masks and gloves to safely handle wild birds, and they should change when they get home. Hunters should not kill birds that look sick. They should also minimize dogs’ interaction with waterfowl.
Some hunters worry whether the extinctions will affect duck and geese hunting seasons, which have now opened.
“I see quite a few dead geese on Sauvie Island and quite a few sick ones as well,” said local hunter Eric Strand via email.
But Brandon Reishus, Oregon’s migratory bird coordinator, said it’s too early to predict. “We have no plans to lock up the hunt. But it is an evolving situation.”
The Oregon Department of Agriculture said 16 cases have been confirmed this year in smaller flocks of domestic birds. That’s a significant increase from the two confirmed cases in the 2014-2015 outbreak, said Scholz, a veterinarian for the Department of Agriculture. More couples are being tested after an increase in calls over the past week.
About 2,000 domesticated birds have been euthanized or died from avian flu in Oregon this year in reported cases, Scholz said. 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 bird flu quarantines this summer and fall to prevent the sale of meat or eggs from virus-affected areas.
No cases have been reported on commercial farms — farms with much larger flocks 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 larger the flocks, the more birds die quickly – so the risk of the disease for larger farms is significant. In the case of a large backyard farm with about 400 chickens, Scholz said, the birds started dying on Saturday and by Monday there were “barrels of dead birds.” Agriculture officials had to euthanize the rest.
And it’s not just a chicken problem. In addition to hundreds of dead chickens, this year’s outbreak has claimed domesticated ducks, quail, pheasants and even a few emus.
With colder weather and wild bird migration peaking in the coming weeks, the environment is ripe for transmission, Scholz said.
“This kind of weather… it’s a setup for a perfect storm,” he said.
Conservationists say it’s OK to double bag one or two dead wild birds and toss them in the trash. Humans may also bury birds shallowly or simply leave them where they are found in the wild. Officials said people should be careful handling the birds and never transport them.
As for domestic birds, responsible owners can help prevent their flocks from being exposed to wild waterfowl by fencing off access to farm ponds or lawns, Scholz said.
Domestic flock owners should call the Department of Agriculture if more than one bird in their flock dies in quick succession, officials said. Reported cases are reviewed by a veterinarian and samples are collected for testing. If the disease is confirmed, all birds will be euthanized, Scholz said.
“Avian influenza is 100 percent lethal” to domestic birds, which have not developed the immunity that some wild birds have, he added. “All the birds die of the disease. We would much rather humanely euthanize them than wait for them to get sick and die.”
– Gosia Wozniacki; [email protected]; @gosiawozniacka
Our journalism needs your support. Become a subscriber today OregonLive.com/subscribe/