An outbreak of avian cholera has killed about 500 birds at the McNary National Wildlife Refuge near Burbank in the past week.
On Thursday, a crew was out at the refuge all day collecting even more dead birds.
The disease is not unusual in cold and wet weather, said Dan Haas of the Mid-Columbia River National Wildlife Refuge Complex. But he does not remember a previous outbreak at the McNary refuge.
Birds are particularly susceptible this year because the cold and snow have left them stressed, he said.
People are not at high risk of infection by the bacteria that causes avian cholera. But they should still wear gloves when handling dead birds and wash hands thoroughly after disposing of birds, according to the National Wildlife Health Center.
Most of the birds that have died are mallard ducks, which are common at the refuge, and other ducks. U.S. Fish and Wildlife Service workers also have found a few great blue herons, belted kingfishers and northern harriers, which are a bird of prey, that have died on the refuge.
It’s a pretty virulent disease.
Dan Haas of the Mid-Columbia River National Wildlife Complex
Dead birds also have been seen on rivers and private property near the McNary refuge, but outbreaks have not been reported at other federal refuges in the Mid-Columbia River complex.
The outbreak appears to be fairly localized, said Matt Wilson, waterfowl specialist for the Washington State Department of Fish and Wildlife.
The agency has received reports of dead birds on the Snake and Columbia rivers near the refuge, he said. Outbreaks on state land have not been reported.
Refuge workers have been collecting dead birds and incinerating them to help stop the spread of the bacterial disease, Haas said.
They also have stopped knocking down corn planted to help feed waterfowl. Although birds are stressed and could use the food, congregating birds would spread the disease.
Large die-offs from avian cholera are seen primarily in wild ducks and geese where the disease affects birds very rapidly, according to the U.S. Geological Survey’s National Wildlife Health Center.
The disease is expected to continue to infect birds until the weather warms and ducks start dispersing.
Sick birds may appear lethargic or swim in circles, according to the National Wildlife Health Center of the U.S. Geological Survey. But they die so quickly after infection that it is far more common to see dead birds in an outbreak.
“It’s a pretty virulent disease,” Haas said. Birds can die in as little as six hours after infection.
Birds can be infected through contact with other birds, including dead birds harboring the bacteria, or through the droppings of infected birds. They also can pick up the bacteria from contaminated food or water, according to the National Wildlife Health Center.
Mice may also be infected with the bacteria, spreading the infection to birds of prey that eat them or eat contaminated dead birds.
Mid-Columbia residents who find a dead bird should bag it and dispose of it. They may also want to put some bleach on the carcass, Haas said.