Agriculture officials have detected avian influenza in dairy herds across the country.
The U.S. Department of Agriculture first confirmed avian flu in dairy herds in Kansas and Texas late last month. Since then, cases in Michigan, Ohio, Idaho and New Mexico have also been confirmed.
No cases have been detected in dairy cows or humans in Wisconsin, but state leaders are urging dairy farmers to take extra precautions against the spread of avian flu.
To learn more about how the virus could impact Wisconsin’s dairy industry, Lake Effect spoke with Dr. Keith Poulsen, a veterinarian and director of theWisconsin Veterinary Diagnostic Laboratory.
This interview has been edited and condensed for length and clarity.
What do we know about this current strain of avian flu?
Poulsen explains that Wisconsin has been dealing with this particular strain of highly pathogenic avian influenza since 2022. In this case, migratory birds are spreading HPAI mostly to dairy cows in their second lactation cycle. He says there’s three important points to know right now:
“One, pasteurized dairy products are safe, and so is meat if cooked properly," Poulsen says. “Two, these cows are not dying. It’s very different than what we've seen in our poultry flocks where we've seen high mortality. Number three, is that we don't really consider this an extremely high threat to public health at this time.”
How is the virus spreading to dairy cows?
Poulsen says animal health officials first thought that the virus was primarily spreading from migratory birds to cows and not going beyond that. But after further research, he says officials have noticed a spread of the virus among dairy herds moving from Texas into other states like Ohio, Michigan and Idaho.
“Now, what exactly is causing cow-to-cow transmission? That's a kind of up for debate,” Poulsen explains. “At this point, I don't think we have enough information.”
He says that the virus affecting dairy cows is acting more like a low-path strain of influenza. Whereas, when poultry flocks are affected by a high-path strain, they’re humanely euthanized.
“We're not seeing that mortality [in dairy cows], so it's kind of a misnomer,” Poulsen says. We're working on that messaging of this really isn't high-path influenza in cows, because the cows are not dying. It's more of the same strain [affecting poultry flocks], but it's causing low pathogenicity or much less severe clinical signs in our dairy cows of a very particular part of their lactation and they’re older [too]. Which is a novel way of seeing clinical disease due to influenza in cows.”
Should the spread of avian flu be of concern to Wisconsin dairy farmers right now?
Poulsen emphasizes that pasteurized dairy products are still safe to be consumed, and is deemed safe by the Food and Drug Administration and the U.S. Department of Agriculture.
However, a main concern that farmers are facing right now is the risk of bringing back avian influenza into their dairy herds.
“It is very, very common in the northern and the Midwestern states to actually send their calves to Kansas and Texas in warmer climates [during winter months]," Poulsen explains. “Because it's much more efficient, it's more cost effective, and the health of their calves are better, and then they come back when they're springing heifers. That's the most common way that we see cows coming back into the state of Wisconsin. And of those animals, that's where I think a lot of our dairy producers are concerned about ‘Well, am I bringing influenza back into my herds?’”
Poulsen says agriculture officials and animal health leaders across the state are urging Wisconsin dairy producers to take extra precautions against the spread of the virus by following biosecurity guidelines. That includes possible diagnostic testing and closely monitoring animals, with the guidance of USDA officials, once they are transported back to the farm.
“The strain that we're seeing circulating in cattle right now, we don't have any cases in Wisconsin, Poulsen says. “All the cases that we've seen in Ohio, Michigan, and Idaho, have been from transporting lactating cows into dairy herds, which is really not as common as what we see in Wisconsin — transporting pregnant animals. So we're really hoping that our risks there are much lower.”
How much of a risk does the virus pose to humans?
Last week, Texas health officials reported that a person in direct contact with infected dairy cows tested positive for the virus. The Texas agency stated that the patient experienced conjunctivitis, similar to pink eye, as their only symptom and is being treated with the antiviral drug oseltamivir.
It’s the second confirmed human case of H5N1 flu in the U.S. and the first linked to exposure to cattle, according to the CDC.
Poulsen says the CDC, USDA and FDA continue to deem thehealth risk to humans as low.
“What we can do on [dairy] farms is make sure we have personal protective equipment available [such as] safety glasses with shields, or just having the face shield in front, wearing gloves and dedicated clothing," he says.
