Post by Nadica (She/Her) on Jul 4, 2024 7:49:35 GMT
Is ‘cow flu’ here to stay? Three months after it emerged, fears are growing - Published July 2, 2024
More than 3 months after the first reported H5N1 avian influenza outbreak at a U.S. dairy farm, some researchers are starting to wonder whether the virus is here to stay.
The U.S. government says it, with the help of the dairy industry, is working diligently to prevent that outcome. “We believe if we can stop the movements [of infected cattle], improve the biosecurity, and then help the producers, … we can eliminate this virus,” Rosemary Sifford, chief veterinary officer of the U.S. Department of Agriculture (USDA) said at a 25 June webinar organized by the National Academies of Science, Engineering, and Medicine.
But given the lack of cooperation from the industry and what many see as a lackluster government response, other scientists are doubtful. Sifford’s upbeat outlook “really surprised” veterinarian Michelle Kromm, another presenter at the webinar. “None of what they've done publicly from a policy standpoint would indicate that they're trying to eliminate this,” says Kromm, who was the top turkey vet at Hormel Foods during a devastating H5N1 outbreak in poultry a decade ago. “To me, all stars are aligning to say we've accepted that this is endemic.”
The H5N1 variant, a clade named 2.3.4.4b, has so far infected at least 137 dairy herds in 12 states. If it becomes endemic, farmers would have to worry about outbreaks, and concomitant losses, every year. And continuous spread in cattle also increases the risk that the virus evolves to spread more easily in humans, which could eventually trigger an H5N1 pandemic.
Kromm points out that the country is still largely flying blind: Farms and milk processing plants have resisted efforts to track the spread of 2.3.4.4b in cows, and government regulation is divided between local, state, and federal authorities, all struggling to balance the concerns of industry with those of public health. Scientists have developed workaround strategies to track the virus, including sampling milk purchased at stores and testing wastewater, but they do not pinpoint infected animals.
What’s more, the sense of urgency is muted. Although the virus quickly kills many species of birds—2.3.4.4b has devastated wild bird and poultry populations around the globe for more than 2 years—it rarely causes severe or lasting disease in cattle. Milk quality and production drop in infected cows, but the virus visibly sickens 15% of a herd at most. Pasteurization reliably inactivates the virus, and the U.S. Food and Drug Administration has stressed that only raw milk presents a risk. A mere three dairy workers are known to have become infected, with the main symptom being a temporary case of pink eye. Consumers are not shunning milk or other dairy products.
So far, USDA requires dairies test lactating cows only if they want to move them across state lines. Laboratories and state veterinarians are required to report positive tests for the virus or antibodies to it, an indication of past infections, which makes farmers reluctant to allow the sampling of their animals or milk. USDA encourages farm workers to wear goggles and other protective gear, but few do, and the U.S. Centers for Disease Control and Prevention has only run 53 tests for the virus in people.
USDA has launched a program to compensate farmers if their herds test positive. But farmers have complained that the compensation offered under the $834 million program is “less than a drop in the bucket,” says Joe Armstrong, a cow veterinarian who teaches at the University of Minnesota Twin Cities (UMTC) and hosts the podcast “The Moos Room.” “We're going to be back to square one here pretty soon of people just not testing, because there's no benefit besides sacrificing personal economics for the greater good,” he says.
“It’s time to step back and ask what would work?” says veterinarian Carol Cardona, an avian flu researcher at UMTC. She argues the dairy industry must take the lead—and government must do a better job of encouraging industry to cooperate. She suggests USDA could allow anonymous testing of cows for antibodies to the virus so that milk producers can get a clearer understanding of spread on their farms and whether their cows have immunity. “Without the cooperation of the people who actually touch the animals, you're not doing anything,” she says.
USDA has also launched pilot programs in six states that allow farmers to transport animals anywhere in the country if their tanks that hold bulk milk test negative, a sign their whole herd is disease free. This relieves farmers from having to test every animal they want to move individually, and USDA hopes it will serve as an incentive to more widespread testing, which could help identify more affected farms.
Virologist Martin Beer at Germany’s Friedrich Loeffler Institute says the virus can probably still be eliminated from U.S. dairy herds—if the response gets a lot more aggressive. "You can go back 50, 60 years: How did we get rid of tuberculosis on farms?” Beer asks. That succeeded because of what Beer calls “classic stuff”: widescale testing, removing infected animals from herds, discarding the milk. “We do not need sophisticated methods for this," Beer says.
In laboratory experiments, Beer and co-workers recently infected cows with the virus to better understand infection of the udder, which USDA has concluded is the main route of transmission as the virus moves between cows on milking equipment. If this is accurate, more aggressively disinfecting the gear between cows could have a major impact.
Cardona, Kromm, and others, however, think eliminating the virus is no longer a realistic goal. Instead, they argue, launching a vaccination scheme for cows could limit the illness in infected animals and possibly slow spread. But USDA has yet to endorse the idea, even though vaccinemakers have begun to make and test potential products. One concern is that other countries may become reluctant to import dairy products from vaccinated cows. Another hurdle is psychological: Launching a vaccination program means “admitting that this is now endemic in a domestic animal population,” Kromm says.
Some scientists have looked for clues about H5N1’s spread and evolution that don’t rely on cooperation from farmers and dairy processing plants. Stanford University environmental engineer Alexandria Boehm, for example, is principal investigator of WastewaterSCAN, which looks for the virus at 190 treatment plants across the country. “You don't have to reach out to lots of individuals and get them to cooperate and convince them of the utility of this,” Boehm explains.
Early results suggest such testing could be prescient. As Boehm and colleagues reported in a preprint posted on 29 April on bioRxiv, a retrospective analysis of samples from a county in Texas found relatively high levels of the virus on 1 March, 3 weeks before that area had the country’s first detection of the virus in cows. Wastewater testing could have caught the cattle outbreak as early as November 2023, when genetic analyses suggest the virus first jumped from birds to cows, says Marc Johnson, a molecular virologist at the University of Missouri who does wastewater sampling in the state.
To act on such information, however, authorities would need to pinpoint the cows that spilled the virus into the sewer system. That rarely happens. Boehm’s group identified a processing plant in Amarillo, Texas, that had contaminated milk, but she doesn’t know whether the infected herd was ever identified. “It would be great to have some sort of nimble task force to rapidly bring these pieces of the puzzle together,” she says.
Microbiologist David O’Connor at the University of Wisconsin-Madison has found a workaround for another bottleneck: the dearth of genetic sequences from the virus, which makes it hard for evolutionary biologists to detect the emergence of new variants or mutations that could ease spread in humans. O’Connor developed a technique that allows his team to pull entire viral sequences from milk bought at stores and has made four of them public to date. “It's going to become really easy for a lot of people to be generating this data,” O’Connor says.
But O’Connor is only fishing in milk cartons for viral sequences because so few are available from the primary source: farms and processing plants. “Whatever time we have, we're squandering that by not acting more aggressively,” O’Connor says. “It seems like we're staring at the Titanic and the iceberg, and we're just waiting to see if the ship turns at the last minute. That's not a great strategy.”
More than 3 months after the first reported H5N1 avian influenza outbreak at a U.S. dairy farm, some researchers are starting to wonder whether the virus is here to stay.
The U.S. government says it, with the help of the dairy industry, is working diligently to prevent that outcome. “We believe if we can stop the movements [of infected cattle], improve the biosecurity, and then help the producers, … we can eliminate this virus,” Rosemary Sifford, chief veterinary officer of the U.S. Department of Agriculture (USDA) said at a 25 June webinar organized by the National Academies of Science, Engineering, and Medicine.
But given the lack of cooperation from the industry and what many see as a lackluster government response, other scientists are doubtful. Sifford’s upbeat outlook “really surprised” veterinarian Michelle Kromm, another presenter at the webinar. “None of what they've done publicly from a policy standpoint would indicate that they're trying to eliminate this,” says Kromm, who was the top turkey vet at Hormel Foods during a devastating H5N1 outbreak in poultry a decade ago. “To me, all stars are aligning to say we've accepted that this is endemic.”
The H5N1 variant, a clade named 2.3.4.4b, has so far infected at least 137 dairy herds in 12 states. If it becomes endemic, farmers would have to worry about outbreaks, and concomitant losses, every year. And continuous spread in cattle also increases the risk that the virus evolves to spread more easily in humans, which could eventually trigger an H5N1 pandemic.
Kromm points out that the country is still largely flying blind: Farms and milk processing plants have resisted efforts to track the spread of 2.3.4.4b in cows, and government regulation is divided between local, state, and federal authorities, all struggling to balance the concerns of industry with those of public health. Scientists have developed workaround strategies to track the virus, including sampling milk purchased at stores and testing wastewater, but they do not pinpoint infected animals.
What’s more, the sense of urgency is muted. Although the virus quickly kills many species of birds—2.3.4.4b has devastated wild bird and poultry populations around the globe for more than 2 years—it rarely causes severe or lasting disease in cattle. Milk quality and production drop in infected cows, but the virus visibly sickens 15% of a herd at most. Pasteurization reliably inactivates the virus, and the U.S. Food and Drug Administration has stressed that only raw milk presents a risk. A mere three dairy workers are known to have become infected, with the main symptom being a temporary case of pink eye. Consumers are not shunning milk or other dairy products.
So far, USDA requires dairies test lactating cows only if they want to move them across state lines. Laboratories and state veterinarians are required to report positive tests for the virus or antibodies to it, an indication of past infections, which makes farmers reluctant to allow the sampling of their animals or milk. USDA encourages farm workers to wear goggles and other protective gear, but few do, and the U.S. Centers for Disease Control and Prevention has only run 53 tests for the virus in people.
USDA has launched a program to compensate farmers if their herds test positive. But farmers have complained that the compensation offered under the $834 million program is “less than a drop in the bucket,” says Joe Armstrong, a cow veterinarian who teaches at the University of Minnesota Twin Cities (UMTC) and hosts the podcast “The Moos Room.” “We're going to be back to square one here pretty soon of people just not testing, because there's no benefit besides sacrificing personal economics for the greater good,” he says.
“It’s time to step back and ask what would work?” says veterinarian Carol Cardona, an avian flu researcher at UMTC. She argues the dairy industry must take the lead—and government must do a better job of encouraging industry to cooperate. She suggests USDA could allow anonymous testing of cows for antibodies to the virus so that milk producers can get a clearer understanding of spread on their farms and whether their cows have immunity. “Without the cooperation of the people who actually touch the animals, you're not doing anything,” she says.
USDA has also launched pilot programs in six states that allow farmers to transport animals anywhere in the country if their tanks that hold bulk milk test negative, a sign their whole herd is disease free. This relieves farmers from having to test every animal they want to move individually, and USDA hopes it will serve as an incentive to more widespread testing, which could help identify more affected farms.
Virologist Martin Beer at Germany’s Friedrich Loeffler Institute says the virus can probably still be eliminated from U.S. dairy herds—if the response gets a lot more aggressive. "You can go back 50, 60 years: How did we get rid of tuberculosis on farms?” Beer asks. That succeeded because of what Beer calls “classic stuff”: widescale testing, removing infected animals from herds, discarding the milk. “We do not need sophisticated methods for this," Beer says.
In laboratory experiments, Beer and co-workers recently infected cows with the virus to better understand infection of the udder, which USDA has concluded is the main route of transmission as the virus moves between cows on milking equipment. If this is accurate, more aggressively disinfecting the gear between cows could have a major impact.
Cardona, Kromm, and others, however, think eliminating the virus is no longer a realistic goal. Instead, they argue, launching a vaccination scheme for cows could limit the illness in infected animals and possibly slow spread. But USDA has yet to endorse the idea, even though vaccinemakers have begun to make and test potential products. One concern is that other countries may become reluctant to import dairy products from vaccinated cows. Another hurdle is psychological: Launching a vaccination program means “admitting that this is now endemic in a domestic animal population,” Kromm says.
Some scientists have looked for clues about H5N1’s spread and evolution that don’t rely on cooperation from farmers and dairy processing plants. Stanford University environmental engineer Alexandria Boehm, for example, is principal investigator of WastewaterSCAN, which looks for the virus at 190 treatment plants across the country. “You don't have to reach out to lots of individuals and get them to cooperate and convince them of the utility of this,” Boehm explains.
Early results suggest such testing could be prescient. As Boehm and colleagues reported in a preprint posted on 29 April on bioRxiv, a retrospective analysis of samples from a county in Texas found relatively high levels of the virus on 1 March, 3 weeks before that area had the country’s first detection of the virus in cows. Wastewater testing could have caught the cattle outbreak as early as November 2023, when genetic analyses suggest the virus first jumped from birds to cows, says Marc Johnson, a molecular virologist at the University of Missouri who does wastewater sampling in the state.
To act on such information, however, authorities would need to pinpoint the cows that spilled the virus into the sewer system. That rarely happens. Boehm’s group identified a processing plant in Amarillo, Texas, that had contaminated milk, but she doesn’t know whether the infected herd was ever identified. “It would be great to have some sort of nimble task force to rapidly bring these pieces of the puzzle together,” she says.
Microbiologist David O’Connor at the University of Wisconsin-Madison has found a workaround for another bottleneck: the dearth of genetic sequences from the virus, which makes it hard for evolutionary biologists to detect the emergence of new variants or mutations that could ease spread in humans. O’Connor developed a technique that allows his team to pull entire viral sequences from milk bought at stores and has made four of them public to date. “It's going to become really easy for a lot of people to be generating this data,” O’Connor says.
But O’Connor is only fishing in milk cartons for viral sequences because so few are available from the primary source: farms and processing plants. “Whatever time we have, we're squandering that by not acting more aggressively,” O’Connor says. “It seems like we're staring at the Titanic and the iceberg, and we're just waiting to see if the ship turns at the last minute. That's not a great strategy.”