Monday, 15 July 2024

Die-off appears to be caused by avian cholera

LUCERNE – California Department of Fish & Game officials working to collect thousands of dead ducks and waterfowl along the Northshore believe that the animals have perished due to avian cholera. 

DFG veterinarian Pam Swift said a number of dead ducks collected for testing arrived at the DFG's lab in Rancho Cordova Tuesday morning.

Andy Atkinson, a senior wildlife biologist supervisor in Lake County this week to lead DFG efforts in addressing the die-off, said additional samples were sent to the California Animal Health & Food Safety Lab at UC Davis.

Final test results are expected Wednesday afternoon, Swift said, but officials are already venturing an educated guess based on initial tests on the animals.

“We've already made a presumptive diagnosis of avian cholera,” said Swift.

That diagnosis, she said, is based on the discovery during necropsies of white spots or lesions, caused by bacteria that causes avian cholera, on the birds' livers.

Swift said the DFG lab coordinates disease testing for animals, and also has been conducting tests for an avian cholera outbreak that occurred at the Sacramento National Wildlife Refuge's Butte Sink section earlier this month.

DFG set up its staging center for dead bird collection this week at Lucerne's Harbor Park.

On Tuesday afternoon, Atkinson worked with other staff to collect the dead animals and take samples from some of them.

Atkinson said a total of 11 DFG staffers from different agency divisions were on scene to collect the birds

For this die-off event, Atkinson said, they had already picked up more than 1,500 dead birds, with an estimated 700 picked up on Tuesday alone.

“We covered the entire lake today,” said Atkinson.

He added that they know where the concentrations of dead birds are and they're working to clean them up.

Atkinson said avian cholera can affect any avian species. A DFG manual he follows for avian influenza and cholera outbreaks explains that avian cholera is caused by the bacteria Pasteurella multocida, which commonly affects waterfowl, coots, gulls and crows.

The vast majority of the die-off victims appear to be ruddy ducks, a migratory bird that winters on Clear Lake, said Atkinson.

However, one of the bags of dead birds collected Tuesday included numerous grebes, thousands of which make the lake their home.

“We're really hoping it doesn't get into the grebe colony in the lower part of the lake,” said DFG Game Warden Lynette Shimek, who was among the first to respond to the die-off which began this past weekend.

Shimek spent Tuesday morning on the lake collecting dead ducks and later hauling them to the landfill. She said DFG has four boats it's using to aid collection.

The birds appear to be dying in the same portion of the lake where the massive 2004 avian cholera die-off occurred, said Shimek, which is in the lake's main arm.

She said the ruddy ducks, which are a smaller species of duck, are apparently dying in the lake center and the wind is blowing them toward shore, where they're being found in areas stretching from Nice to Glenhaven.

The birds are flying in with the disease, Shimek said. Once in the lake, they like to stay out more in the open water, where they congregate in close, tight-knit groups.

Atkinson said avian cholera is transmitted in a number of ways, including through direct contact and bacteria transmitted through the air.

With the ruddy ducks staying so close together, the disease can easily among them, said Shimek. “That's why they're affected so much more than other species.”

Collecting the dead bodies helps stop the spread of the disease, said Atkinson.

Sandie Elliott of SpiritWild, Lake County's wildlife rescue group, said she received her first call from an area resident Friday reporting dead birds.

Shimek, Elliott and some volunteers began collecting the dead animals along a 12-mile stretch of shoreline over the weekend until the other DFG staffers arrived.

Elliott said at that time they spotted nearly 1,000 more sick or dead ducks in a small stretch of water. “It's going to be big,” she said of the die-off.

Avian cholera is commonly seen in winter, said Elliott.

The National Wildlife Health Center's (NWHC) Field Manual of Wildlife Diseases notes that waterfowl in California that often are hit with the disease during the migration period that starts in fall and ends in the spring.

DFG urges people not to touch the animals at all until they have an official diagnosis for the die-off's cause.

Shimek said people can call her home office, 275-8862, to report dead animals for pick up.

She asked for the community's patience while the main collection goes on, and said she will respond to pick up the animals as quickly as she can.

For now, she said, “We have to focus on the hot spot areas.”

Atkinson said he expects to have a better idea by Wednesday of how much more collection will be required and what other resources he'll need to finish the job.


E-mail Elizabeth Larson at This email address is being protected from spambots. You need JavaScript enabled to view it.

 

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