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As bird flu spreads to dairy cows, Minnesota's raptors show signs of building remarkable immunity

Greg Stanley, Star Tribune on

Published in Health & Fitness

A little barred owl looked up from the crux of Dana Franzen-Klein's elbow, stared the veterinarian in the eye and, in as tough and menacing of a posture as he could muster, clicked his beak. The injured bird was a baby, maybe a month old. His click was a warning, that despite being a puffball barely bigger than Franzen-Klein's palm, he would bite the medical director of the Minnesota Raptor Center if he had to.

"You're not going to get me," Franzen-Klein said, as she checked the way the baby owl moved for a sign of where he was hurting.

"It's your leg," she said. "It's your right leg."

Then before Franzen-Klein could do anything else, before she could take an x-ray to see if the broken bone could be mended or if the owl had to be put down, she stuck a needle into his elbow at the base of his wing and took a blood sample to find out if he had built up or inherited any antibodies over the course of his short life to the dreaded avian flu.

The worst strain of bird flu to ever hit North America continues to spread. It's spilled over and infected far more types mammals than previously thought possible since first arriving to the continent in late 2021. This spring, for the first time, it infected dairy cows in nine states, including North Dakota and Michigan. The virus has been found in milk from those infected cows.

But, in a promising sign, blood samples from the Minnesota Raptor Center and other rehabilitation facilities across the United States show that high numbers of animals are building up immunity to the deadly virus in the woods, swamps and other wild places that harbor it.

 

For the last year and a half, Franzen-Klein and other veterinarians at the Raptor Center have been taking blood samples from each of the 1,000-plus injured and sick birds that come through their doors to test for the antibodies, for signs that the birds had, at some point, beaten the H5N1 strain of high pathogenic avian influenza. The results have been overwhelmingly positive.

More than half of the hundreds of bald eagles treated at the center have gotten this strain of bird flu and recovered from it, said Victoria Hall, the center's executive director. High numbers of barred and great horned owls have, too, as well as red tailed hawks, peregrine falcons, and just about every other kind of bird the center treats.

And it's not just in Minnesota. Florida's black vultures, California's condors, cormarants and blue teal ducks that span the Mississippi Flyway from Ontario to the Gulf of Mexico are showing much higher than expected levels of antibodies and signs of recovery, said David Stallknecht, a professor emeritus at the University of Georgia who has been testing blood samples from rehabilitation centers across the country.

It's too early to say if the virus is actually waning in the wild, Stallknecht said. But the more immunity that wild birds build up, the less opportunity there will be for the virus to cause widespread deaths. And the fewer infected dead birds for scavengers to eat, the less opportunity the virus will have to keep infecting mammals.

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