Clues From Bird Flu’s Ground Zero on Dairy Farms in the Texas Panhandle

May 27, 2024

By Amy Maxmen

In early February, dairy farmers in the Texas Panhandle began to notice sick cattle. The buzz soon reached Darren Turley, executive director of the Texas Association of Dairymen: “They said there is something moving from herd to herd.”

Nearly 60 days passed before veterinarians identified the culprit: a highly pathogenic strain of the bird flu virus, H5N1. Had it been detected sooner, the outbreak might have been swiftly contained. Now it has spread to at least eight other states, and it will be hard to eliminate.

At the moment, the bird flu hasn’t adapted to spread from person to person through the air like the seasonal flu. That’s what it would take to give liftoff to another pandemic. This lucky fact could change, however, as the virus mutates within each cow it infects. Those mutations are random, but more cows provide more chances of stumbling on ones that pose a grave risk to humans.

Why did it take so long to recognize the virus on high-tech farms in the world’s richest country? Because even though H5N1 has circulated for nearly three decades, its arrival in dairy cattle was most unexpected. “People tend to think that an outbreak starts at Monday at 9 a.m. with a sign saying, ‘Outbreak has started,’” said Jeremy Farrar, chief scientist at the World Health Organization. “It’s rarely like that.”

By investigating the origins of outbreaks, researchers garner clues about how they start and spread. That information can curb the toll of an epidemic and, ideally, stop the next one. On-the-ground observations and genomic analyses point to Texas as ground zero for this outbreak in cattle. To backtrack events in Texas, KFF Health News spoke with more than a dozen people, including veterinarians, farmers, and state officials.

An early indication that something had gone awry on farms in northwestern Texas came from devices hitched to collars on dairy cows. Turley describes them as “an advanced fitness tracker.” They collect a stream of data, such as a cow’s temperature, its milk quality, and the progress of its digestion — or, rather, rumination — within its four-chambered stomach.

What farmers saw when they downloaded the data in February stopped them in their tracks. One moment a cow seemed perfectly fine, and then four hours later, rumination had halted. “Shortly after the stomach stops, you’d see a huge falloff in milk,” Turley said. “That is not normal.”

Tests for contagious diseases known to whip through herds came up negative. Some farmers wondered if the illness was related to ash from wildfires devastating land to the east.

In hindsight, Turley wished he had made more of the migrating geese that congregate in the panhandle each winter and spring. Geese and other waterfowl have carried H5N1 around the globe. They withstand enormous loads of the virus without getting sick, passing it on to local species, like blackbirds, cowbirds, and grackles, that mix with migrating flocks.

But with so many other issues facing dairy farmers, geese didn’t register. “One thing you learn in agriculture is that Mother Nature is unpredictable and can be devastating,” Turley said. “Just when you think you have figured it out, Mother Nature tells you you do not.”

Cat Clues

One dairy tried to wall itself off, careful not to share equipment with or employ the same workers as other farms, Turley recalled. Its cattle still became ill. Turley noted that the farm was downwind of another with an outbreak, “so you almost think it has to have an airborne factor.”

On March 7, Turley called the Texas Animal Health Commission. They convened a One Health group with experts in animal health, human health, and agriculture to ponder what they called the “mystery syndrome.” State veterinarians probed cow tissue for parasites, examined the animals’ blood, and tested for viruses and bacteria. But nothing explained the sickness.

They didn’t probe for H5N1. While it has jumped into mammals dozens of times, it rarely has spread between species. Most cases have been in carnivores, which likely ate infected birds. Cows are mainly vegetarian.

“If someone told me about a milk drop in cows, I wouldn’t think to test for H5N1 because, no, cattle don’t get that,” said Thomas Peacock, a virologist at the Pirbright Institute of England who studies avian influenza.

Postmortem tests of grackles, blackbirds, and other birds found dead on dairy farms detected H5N1, but that didn’t turn the tide. “We didn’t think much of it since we have seen H5N1-positive birds everywhere in the country,” said Amy Swinford, director of the Texas A&M Veterinary Medical Diagnostic Laboratory.

In the meantime, rumors swirled about a rash of illness among workers at dairy farms in the panhandle. It was flu season, however, and hospitals weren’t reporting anything out of the ordinary.

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