Toll of avian influenza on Wyoming birds still unknown


WYOMING -- Wyoming’s patient zero arrived at the state’s Wildlife Health Laboratory in late March. Someone found the Canada goose dead in Bighorn County. The test came back positive for the deadly H5N1, a strain of avian influenza killing birds across the globe.

Since then, cases have popped up in magpies, great-horned owls, vultures and hawks from Jackson and Cody to Douglas and Laramie. In early April, the flu killed 11 wild turkeys near Buffalo. On Wednesday the Powell Tribune reported the Wyoming Game and Fish Department killed its broodstock of pheasants at its bird farm near Sheridan out of an “abundance of caution.” 

“This used to be mainly a domestic poultry problem,” said Dr. Samantha Allen, Wyoming Game and Fish Department’s wildlife veterinarian.

But this flu is different. The current strain is responsible for killing more than 1,000 lesser scaup ducks in Florida, scores of Canada geese in New Hampshire, and dozens of snow geese in the same fields in North Dakota.

“As we started to see large mortalities in wild bird populations, what we really don’t know is if that trend will continue or not,” Allen said.

Questions about the future of the disease loom but are hard for scientists to answer at this stage. Will it mutate into an even deadlier virus that sticks around? Will it change and more severely affect humans? Right now, humans can contract H5N1, but few have fallen ill. What impact will it eventually have on wild birds in Wyoming, the West, North America and the globe?

For now, scientists in Laramie are testing dead birds brought to them from around the state, and researchers throughout the world are trying to figure out the best ways to protect domestic poultry and wildlife, contain the virus despite its presence in migrating species, and prepare for the future.

If avian flu sounds like something you’ve heard about before, it’s because you have. Avian influenza is endemic in wild birds, and outbreaks have historically killed millions of domestic birds.

Like all influenza viruses, avian flu has the ability to mix and match with other influenza strains and then evolve and change depending on its proteins, Allen said. Each has an “H” protein, signifying hemagglutinin and an “N” protein for neuraminidase. There are 16 possible “H” proteins and nine possible “N” proteins.

“The one that we’re dealing with right now is H5N1,” she said. “We break it down based on what genetics it has picked up along the way and what it looks like.”

The virus is then further classified based loosely on its severity, essentially highly pathogenic and low pathogenic avian influenza.

“All that means is that for highly pathogenic, a lot of domestic poultry will die very quickly and at high numbers,” she said.

When high pathogenic strains hit a domestic poultry producer, the birds either die from the disease or are killed to prevent its spread.

Wild, migratory birds, on the other hand, tend to carry the low pathogenic avian influenza and general influenza strains. It’s naturally circulating in migratory birds around the world, and while it can cause occasional die offs, it rarely kills large numbers.

The difference now is that migratory birds are also carrying this deadly strain, spreading it around to other domestic and wild birds through feces, close contact and in carcasses.

The current strain likely started somewhere in Asia where it has been circulating since the 1990s, Allen said. It has changed along the way, and the recent version has caused massive die offs in places like Israel where 5,200 cranes died. Birds infected tend to have “irregular spinning body movements, uncontrolled head rolling and other abnormal neurological movements followed by sudden death,” according to the Teton Raptor Center.

It landed on the shores of North America and was first detected in December in Newfoundland and Labrador, Canada and then in February in a commercial turkey flock in Indiana. Since then, it’s spread like wildfire as birds migrate from Florida to the Midwest and Colorado north to western Canada. Tens of millions of domestic birds have either died or been killed since that first case in February. No count currently exists for the toll it has taken on wild birds.

No one knows for sure if this current strain of avian influenza will burn itself out as some have in the past or remain in our populations in some different version. Some duck species are naturally immune, but act as vectors and may continue spreading the disease.

Researchers and biologists are still studying the impact on Wyoming’s birds, though at least right now, they aren’t worried about population-level impacts on migratory game birds.

“I think states that are really big wetland and bird congregation areas, wintering grounds, staging areas, those are places that will lose big numbers,” said Noelle Smith, Game and Fish’s migratory game bird and wetland biologist. “Wyoming doesn’t have those.”

The impact on raptors is particularly concerning, especially in fragile populations, said Zack Walker, Game and Fish’s nongame section supervisor.

Hawks, eagles, owls and vultures are likely feeding on carcasses of newly dead birds and then succumbing to the disease. The second known H5N1 case in Wyoming this year was a great-horned owl found dead in Park County. 

Since then, it has killed a great-horned owl in Jackson and a red-tailed hawk near Ucross.

Hunters will see fewer pheasants stocked in western Wyoming after officials euthanized the Sheridan bird farms pheasant brood stock, reported the Powell Tribune. The captive birds were not sick, but dead turkeys had been discovered nearby that tested positive for the deadly flu strain. The birds were killed in “a preemptive action,” the Cody regional wildlife supervisor told the local newspaper.

The virus tends to thrive in cooler temperatures, which has helped its current spread, but also offers hope as the weather warms. Researchers hope as migratory birds continue their flights north the cases here will fizzle, said Hank Edwards, Game and Fish’s Wildlife Health Laboratory supervisor.

In Alberta and Saskatchewan, cases are rising, which may point to the effects of migrating birds carrying the disease with them. At the same time, cases in states like Florida and Georgia have dropped.

“The hope is we will follow that trend,” said Allen. “But right now, we just don’t know.”

If you find more than three dead waterfowl, any number of dead raptors or scavenging birds, or you see wild birds showing abnormal neurological signs, nasal discharge or diarrhea, call your local Wyoming Game and Fish office.

WyoFile is an independent nonprofit news organization focused on Wyoming people, places and policy.

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