USDA's Animal and Plant Health Inspection Service is trying to figure out how the avian influenza virus in dairy cattle is spreading within and among herds.
Cattle transported from Texas have been implicated in the spread of the H5N1 virus found in at least four of seven other states that have had infections.
State officials in North Carolina, Michigan, Ohio and Idaho detected the highly pathogenic avian influenza virus in dairy operations that had received cows from Texas. The virus also has been detected in herds in South Dakota, Kansas and New Mexico. Altogether, 20 states have imposed some type of import restriction.
Although wild and domestic mammals, such as goats and cats, have caught the virus, USDA believes many of those animals “were likely infected after consuming or coming into contact with birds that were infected with H5N1,” APHIS said in Frequently Asked Questions posted April 16. “Recent testing indicates the virus has also been spread by cattle movements between herds.”
In addition, the agency said it has evidence that the virus "also spread from dairy cattle back into nearby poultry premises through an unknown route." APHIS added that “the spread of the H5N1 virus within and among herds indicates that bovine to bovine spread occurs, likely through mechanical means.” APHIS is focusing on how the milking process may help spread the virus.
“Our field work is really kind of honing in on trying to figure out if that lateral transmission is really mechanical transmission occurring within the dairy parlors, since we are seeing predominantly these signs in the lactating dairy cattle,” Mark Lyons, director of ruminant health at APHIS, said on a heavily attended World Organization for Animal Health Zoom call earlier this month.
A spokesperson told Agri-Pulse Tuesday that the situation is "rapdily evolving" and the department is "committed to sharing updates as information becomes available. [APHIS] is maintaining resources, including a list of detections in cattle to date and biosecurity recommendations for farmers, veterinarians and farmworkers at Highly Pathogenic Avian Influenza (H5N1) Detections in Livestock."
APHIS, which has been posting information online since the first H5N1 infection in cows was announced in late March, released 239 genetic sequences April 21 from the U.S. H5N1 clade 2.3.4.4b influenza virus that were recently found in samples "associated with the ongoing highly pathogenic avian influenza (HPAI) outbreak in poultry and wild birds, and the recent H5N1 event in dairy cattle.” The service said it also is “rapidly sharing raw sequence data to the National Institute of Health’s National Library of Medicine, National Center for Biotechnology Information.”
“What we know right now is this disease appears to affect lactating dairy cows,” said Fred Gingrich, executive director of the American Association of Bovine Practitioners. “That's pretty much all we know.” He said that if the virus is transmitted within dairy herds it "would be the first time that … it's been laterally transmitted cow to cow.” But that has yet to be confirmed.
Gingrich said it could be spreading in herds by environmental contamination from urine or other animal secretions. “Is it spreading from one cow to the other via the milking machine, like contagious mastitis would?” he asks. “We don't know that right now. And hopefully we can get that figured out, because then we can put in some more specific prevention plans.”
He also emphasized, however, that wild birds could be the source. “We know for certain that birds carry this virus, and so it's just as reasonable that birds are infecting cows on other dairies, too. Both are possible.”
Jamie Jonker, chief science officer at the National Milk Producers Federation, sees “the likelihood of some transmission occurring through the transport of those animals.” Because the virus seems to have affinity for the mammary gland, it "seems to be acting much more like a mastitis,” he said. “So we see cows go off feed and off water, their rumination activity decreases, and their milk production crashes.” So far, most cows have recovered completely.
Jonker said transmission could occur through manure and urine in trucks that transport cattle or in mud on the wheels and in the fenders "and on the undercarriage of the truck and trailers.”
USDA’s response was questioned when the New York Times quoted infectious disease experts who said officials had shared only limited genetic information with scientists and with officials in other countries, which it called important to learn how the virus might be evolving as it spreads.
“We probably still have more questions than answers on some aspects of how the virus is being transmitted between herds,” Jonker said. “And that can be a frustration. Some people want answers very quickly.”
However, he said this was "the first time that high-path AI has been in dairy cattle anywhere in the world.” It may “take some time to get the full picture on all the potential routes of transmission that are occurring within our individual herds and then across herds.”
Asked whether she felt USDA has been slow to respond or share information, Amy Swinford, director of Texas A&M’s Veterinary Medical Diagnostic Laboratory, said, “I don’t share those concerns.”
Matt Herrick, senior vice president of public affairs and communications at the International Dairy Foods Association, also defended the USDA response. APHIS and FDA have "worked closely with states, they've worked closely with farmers and veterinarians and industry partners," he said.
Since H5N1 was first detected in dairy cows, Herrick said, “agency staff have worked diligently to give accurate, reliable updates of information to the public and the stakeholders.”
It’s easy to be “in the know” about what’s happening in Washington, D.C. Sign up for a FREE month of Agri-Pulse news! Simply click here.
“Not everyone is satisfied with the cadence of the updates, or the speed at which they're sharing information,” Herrick acknowledged. But he said “it seems to me right now that the federal agencies are doing a good job of responding to this crisis.”
While he did not want to minimize concerns, Herrick pointed out that it has been found in only 33 herds out of about 23,000 in the United States and that pasteurization kills the virus in milk.
“We've seen no impacts to sales, we've seen no impacts to trade,” Herrick said. “And because this disease is different than the one impacting chickens, it's not fatal in cows.”
Herrick did say USDA could provide more biosecurity education and biosecurity resources for farms so that "it wouldn't all be on the backs of farmers” to buy personal protective equipment such as gloves, hats, shoes, boots and masks.
FDA said that, "based on the information we currently have, our commercial milk supply is safe because of both the pasteurization process and that milk from sick cows is being diverted or destroyed.” Pasteurization "is very likely to effectively inactivate heat-sensitive viruses in fluid milk,” it said in a statement. On Tuesday, FDA said it had found "viral particles" in some samples of pasteurized milk, but continues to say the milk supply is safe.
The situation has some concerned about the strain on producers and people working to understand the science. "I think we need to step back and understand the significant mental duress this is putting veterinarians and dairy farmers under,” Gingrich said.
He also questioned transport practices, acknowledging that states can enact restrictions they feel are needed. “How does the dairy industry work, and the beef industry? It works via cattle movement,” he said. “And we learned during the pandemic that you can't stop pigs moving. That created just a huge strain on the system that had some unintended consequences on animals.”
“I think we need to just pause – everybody calm down and figure out what we need to do to make sure we have good commerce while protecting animal health.”
Ashley Peterson, National Chicken Council senior vice president of scientific and regulatory affairs, said there was "still much to learn about the transmission of this virus" including how it spreads to cows and between cows and if infected cows shed the virus in a way that could affect poultry. But until more is learned about transmission, she said, "out of an abundance of caution, we believe it is prudent to restrict the movement of cows from positive herds.”
Harry Snelson, executive director of the American Association of Swine Veterinarians, said “the chances of the H5N1 virus getting into pigs from a cow are low,” but “the emergence of a virus that has predominantly involved avian species in a mammalian host raises questions about what in the virus has changed and could those changes make it easier for the virus to enter a pig."
Snelson added that “Any time two different influenza viruses occupy the same animal, it increases our concern that those viruses might combine to produce a reassortant virus that could have different affinity for other animal hosts. That's what we're watching.”
For more news, go to www.Agri-Pulse.com
