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Bird flu worries heighten with the fall migration

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Nick Fewings
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This year’s outbreak of highly pathogenic avian influenza across the country has been primarily spread through wild birds that can carry the virus in their intestinal tract and shed it through their excrement or saliva. Experts are watching the fall migration closely.

On a hot day in September, hundreds of Ty Rinner’s turkeys suddenly died.

The Washington County turkey producer called his veterinarian, who was already scheduled to visit his farm to check on another flock. When the veterinarian arrived, they noticed many turkeys couldn’t breathe very well.

“Immediately we were on high alert,” said Rinner, who wondered then if highly pathogenic avian influenza — a highly contagious and deadly disease to poultry — could be in his flock.

As Rinner waited for test results, he put up barricades around the entrance to his farm and called his neighbors to alert them.

The test for bird flu came back negative, to his relief. He lost just shy of 1,500 turkeys to a respiratory problem that was exacerbated by the heat.

“But it was bad enough, having the scare,” Rinner said. “It was kind of a sleepless night, to say the least.”

Across the Midwest, highly pathogenic avian influenza is recirculating, coinciding with the fall migration of wild birds. States to the north of Iowa, such as Minnesota, North Dakota, South Dakota and Wisconsin, which typically see migrating birds earlier in the season, have all seen new cases in September and October. Iowa hasn’t seen a new case of bird flu since early May, but agriculture officials and scientists are cautioning producers about the disease as the fall migration intensifies and wild birds head south to their wintering grounds.

Iowa Agriculture Secretary Mike Naig said his department has been aware of the recent bird flu cases in nearby states and has been cautioning commercial producers and backyard flock owners to watch their flocks, minimize contact with wild birds, and double down on their biosecurity efforts to keep diseases off of their farm.

“It has served as an early warning system for us,” Naig said. “We’re certainly on a heightened alert.”

Iowa has been hit harder by bird flu this year than any other state. From March to early May, more than 13 million commercial and backyard birds in Iowa died from the disease or were killed to stop it from spreading. Iowa is the top egg-producing state in the country and ranks seventh for turkey production.

New cases of bird flu didn’t show up in fall 2015 after Iowa’s spring bird flu outbreak that year. But this year’s outbreak of highly pathogenic avian influenza across the country has been primarily spread through wild birds that can carry the virus in their intestinal tract and shed it through their excrement or saliva. Waterfowl, like ducks and geese, seem to be the primary source of introduction. And experts are watching the fall migration closely.

During spring migration, wild birds are generally in a rush to return to their breeding grounds in the North, said Adam Janke, an extension wildlife specialist with Iowa State University. But fall migration to their wintering grounds is a lot slower.

“We see the species themselves spread out a little more,” Janke said. “They don’t all come through roughly at the same time like they do in the spring. You’ll start to see a few ducks, and then they’ll sort of start to build as the ice comes.”

Smaller birds, such as warblers and songbirds, have largely moved through Iowa already, Janke said. Meanwhile, waterfowl, like ducks, geese and swans are starting their migration.

“The big congregations of waterfowl, ducks, geese and swans are going to occur largely in November here,” Janke said.

Rachel Ruden, the state wildlife veterinarian with the Iowa Department of Natural Resources, said congregation — birds flocking together in large groups — is a “principle of infectious diseases,” increasing the odds of birds getting infected.

“Oftentimes it’s around artificial points of congregation,” Ruden said. “Sometimes it happens at bird feeders and where birds have a certain bacteria or a protozoa infection, and they're contaminating that common feeding source, and so they all pick it up.”

Waterfowl and shorebirds have been known to carry the virus in a less severe form, which can mutate to more severe in poultry. But this year, Ruden said, highly pathogenic avian influenza has been circulating in wild birds. It’s been sickening them and causing seizure-like activity and death. And the strain has hung around.

Scientists point out in a 2021 research paper published in the Journal of Wildlife Management that highly pathogenic avian influenza outbreaks were long restricted to poultry, but as it has evolved from transmission between bird species, it’s been seen more and more in wild birds.

“It’s been able to persist in that highly pathogenic form,” Ruden said. “We can expect that as birds pass through Iowa and head south, that they may still be harboring the virus.”

Ruden has been surveying hunter-harvested birds with the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service Wildlife Services. In September, they found three detections of highly pathogenic avian flu in healthy hunter-harvested teal, in western Iowa. As the fall migration intensifies in Iowa, Ruden said it’s unclear what impacts the virus may have.

Ty Rinner, the turkey producer in Washington County, said bird flu is a top concern of his.

There hasn’t been a case of bird flu confirmed in Washington County, he said, but his farm employs biosecurity practices year-round. For example, he said, farmers wear different boots into the turkey barns and step through disinfectant before they enter and after they leave a barn.

“We’re on top of it just as much as we can be,” Rinner said.

Katie Peikes is IPR's agriculture reporter