By Rose Hoban
In April, North Carolina’s agricultural officials received an unwelcome surprise. Cows in one of the state’s dairy herds tested positive for a strain of avian influenza that’s been appearing in herds throughout the United States since the spring.
State veterinarian Mike Martin relayed the story of how North Carolina discovered the information during a recent gathering of 150 farmers, county and state agricultural officials, and federal regulators at a panel discussion convened by N.C. Agricultural Commissioner Steve Troxler.
Martin said his office knew cows from the Texas panhandle where the outbreak was first identified had been transported to North Carolina and that routine testing for the virus, not identified symptoms, had led to the identification.
“We had already started to work on establishing a relationship with that farmer, talking with them, making sure they’re doing things in a biosecure fashion, and trying to educate them on the information that we knew as we got it,” Martin told the group gathered at the state fairgrounds in Raleigh.
Martin also told the crowd that the genetic sequence of the virus found in North Carolina-based cows was the same as the genetic fingerprint of the avian influenza virus in the Texas herd. Veterinary officials believe the Texas outbreak was the result of the cows’ contact with wild birds migrating through the center of the country in late 2023 or early 2024.
Martin said the North Carolina case was the first time cattle without symptoms of the disease had been detected in the U.S. outbreak, which now spans 14 states and 197 confirmed cases. In the past month, the disease was detected in Colorado, California, Michigan and Idaho.
Thus far, North Carolina has had just the one confirmed case.
That’s the way Troxler wants it. And his goal is for North Carolina to have no more cases going forward, despite the large number of cows that get moved around the country. That means frequent testing and providing compensation to farmers who are affected.
“It’s a numbers game. The more virus that’s out there, the more likely it is to be mutated and spread to other species,” Troxler said.
And while there’s risk to cows — and people — chickens and turkeys could be devastated if the virus got into poultry flocks. Troxler reminded the audience that agriculture, with its $111 billion in annual economic impact, is the state’s largest industry.
“And we are particularly vulnerable because of the size of our poultry industry in North Carolina,” he said. “We actually ranked No. 1 in the nation in egg and poultry receipts.”
Bird flu in cows?
Highly pathogenic avian influenza, H5N1, has been spreading around the world for decades, closely watched by both veterinary and human health officials because of its potential to cause a devastating human pandemic. In the past several years, the disease — which has caused outbreaks in countless commercial poultry flocks throughout the U.S. and the rest of the world — has jumped from birds to other species.
The disease has killed mammals on almost every continent in the past few years: red foxes in the Netherlands in 2021, thousands of sea lions and tens of thousands coastal birds in Peru in 2022, and a massive die-off of elephant seal pups in Antarctica and the Atlantic coast of Argentina in 2023. A polar bear died in Alaska last winter. Sea lions on the Pacific coast in Peru and the Atlantic coast in Uruguay have died from the disease, and the list goes on.
When “high path” avian influenza outbreak hits a farm — a thought that strikes fear in the hearts of commercial poultry farmers — Troxler said the fatal consequences can be swift. “Maybe overnight, half of the chickens are already dead,” he said.
That’s when agricultural officials jump in quickly, typically euthanizing an entire chicken house to keep the disease from spreading further.
What’s different about this outbreak in cows is that the disease, which usually affects the respiratory tract (think coughing chickens) is affecting different parts of the animals. In cattle, the virus seems to show an affinity for the cows’ mammary glands, where milk is produced. Symptoms for the cattle include reduced appetite and feeding, and reduced milk production. The milk that is produced comes out thick and yellow.
Cows tend to recover in a few weeks. But it’s not benign for all animals that come in contact. The Centers for Disease Control and Prevention issued a report of barn cats dying after drinking unpasteurized milk on a farm where the disease had been identified in cows.
Eric Deeble, a cattle veterinarian and undersecretary for marketing and regulatory programs at the U.S. Department of Agriculture, was on the panel that Troxler convened last week. He said his agency is compensating farmers for their losses while their animals are sick.
The indemnity programs were quickly implemented by the federal agriculture agency to help farmers who can’t sell milk on the market while their cows are sick. Dumping the product could be devastating for their bottom lines.
“It’s important, that message, that a farmer — if they detect this in a herd, will not lose their market,” Deeble said. “If there is somebody who suspects that they may have this on their farm, it’s really in their interest to come forward, because there are indemnity programs that can offset the losses that they will experience as this moves through the herd.”
Those incentives are there, in part, as an incentive to keep farmers from hiding cases, he added.
Managing the spread
If farmers hide cases, and health and veterinary officials don’t know about it, then the virus is sure to keep moving, agricultural officials say — in part because it’s not clear how the virus gets from cow to cow.
“We’re looking at things like mats, flooring, insects, milking equipment, individual hands, the equipment people are using for pre- and post-milking dips, dip cups, those sorts of things, towels,” Deeble said. “We know that it’s not an aerosolized infection, for which we’re very grateful.”
Several dozen cattle workers throughout the country have contracted the disease, which has largely shown up as cases of pink eye.
In recent years, more people are seeking out raw, unpasteurized milk. Credit: Rebecca Siegel, Flickr Creative Commons
The more cases that get into humans, the bigger the risk that the virus could mutate to become transmissible from person to person as a respiratory disease. That’s what health officials have been watching for in Southeast Asia, where, for instance, several children were infected after handling dead chickens last year. In Vietnam and Cambodia, several people have died, but, thus far, the disease has not shown the ability to be passed from person to person, only from animal to person.
In the spring, Martin, the state veterinarian, heard from his peers in Idaho that there had been an outbreak in a herd that had received dairy cattle from the Texas herd with the initial outbreak — the same herd that had sold cows to the North Carolina farmer.
“The Texas cows probably brought it over, cleared the virus, and now it was just our native cows that had the virus,” he said.
“The farmer, much to his credit, gave us the ability to test this herd and work forward under a time when it wasn’t even recommended to test this herd, and we developed a testing protocol,” Martin added. “We basically tested all the positive cows that came from that herd until they stopped testing positive.”
But, as Troxler noted, it’s a numbers game. The more cases there are in other species, the more chances there are for the notoriously mutable avian influenza virus to mix and match DNA and start spreading.
One easy way to contain potential spread to humans is by pasteurizing milk, all of the panelists said.
Headlines this spring proclaimed that evidence of high path avian influenza had been found in parts of the nation’s milk supply, but Troxler was quick to explain that what was found was evidence of the virus’ DNA, not the virus itself.
He noted that pasteurization — where milk is heated to high temperatures for a few seconds and then rapidly cooled — completely kills the virus, leaving behind only scraps of its DNA that pose no danger.
“Pasteurization takes care of all of it. I know that the first time that we started doing the testing for pasteurization, ‘Does it really kill it or not?’ the public had to know for sure that it killed it,” Troxler said. “There’s no mistake. Pasteurization does take care of this pathogen in the milk and other pathogens.”
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