Bird Flu Detected in U.S. Dairy Cows: A New Challenge for Agriculture

Agriculture officials have found the virus in cows across the country.

The U.S. Department of Agriculture verified avian flu in dairy cows in Kansas and Texas late last month. Since then, cases in Michigan, Ohio, Idaho, and New Mexico have all been confirmed.

No cases have been identified in dairy cows or humans in Wisconsin, but state officials are advising dairy farmers to take extra precautions to prevent the spread of bird flu.

To discover more about how the virus may affect Wisconsin’s dairy sector, Lake Effect interviewed Dr. Keith Poulsen, a veterinarian and head of the Wisconsin Veterinary Diagnostic Laboratory.

What Do We Know About the Latest Strain of Avian Influenza?

Poulsen notes that Wisconsin has been dealing with this specific strain of extremely dangerous avian influenza since 2022. In this situation, migratory birds spread HPAI mostly to dairy cows in their second lactation cycle. He thinks there are three critical things to know right now.

“One, pasteurized dairy products are safe, and so is meat if cooked properly,” Poulsen said. “Two, these cows will not die. It’s extremely different from what we’ve seen in our poultry flocks, which have had high mortality rates. Number three, we don’t believe this poses an exceptionally significant concern to public health at this time.”

How Does the Virus Spread Among Dairy Cows?

According to Poulsen, animal health officials first believed that the virus was only passing from migratory birds to cows and would not spread farther. However, after conducting additional study, he claims that officials have discovered the virus spreading among dairy herds moving from Texas to Ohio, Michigan, and Idaho.

“So, what causes cow-to-cow transmission? That’s up for argument,” Poulsen says. “At this point, I don’t think we have enough information.”

He claims that the virus infecting dairy cows behaves more like a low-path form of influenza. In contrast, when chicken flocks are infected with a high-path virus, they are humanely terminated.

“We’re not seeing that mortality [in dairy cows], so it’s kind of a misnomer,” Poulsen said. We’re working on communicating that this isn’t high-path influenza in cows, because the cows aren’t dying. It’s the same strain [that affects poultry flocks], but it’s causing low pathogenicity or considerably less severe clinical indications in our dairy cows during a specific stage of lactation, and they’re also older. Which offers a fresh perspective on clinical disease caused by influenza in cows.”

Should Wisconsin Dairy Producers Be Concerned About the Spread of the Avian Flu Right Now?

Poulsen notes that pasteurized dairy products are still safe to ingest, as determined by the Food and Drug Administration and the United States Department of Agriculture.

However, a major concern for producers right now is the potential of reintroducing avian influenza into their dairy herds.

“It is very, very common in the northern and the Midwestern states to send their calves to Kansas and Texas in warmer climates [during winter months],” Poulsen said. “Because it is much more efficient, cost-effective, and improves the health of their calves, and then they return when they are springing heifers. This is the most typical way cows return to Wisconsin. And of those animals, I believe many of our dairy producers are anxious about bringing influenza back into their herds.

According to Poulsen, agriculture officials and animal health leaders around the state are advising Wisconsin dairy producers to take extra care to prevent the virus from spreading by following biosecurity requirements. This involves possible diagnostic testing and thorough monitoring of animals once they are returned to the farm, under the supervision of USDA personnel.

“The strain that is currently circulating in cattle, we have no cases in Wisconsin,” Poulsen says. “All of the cases we’ve seen in Ohio, Michigan, and Idaho have included relocating nursing cows into dairy herds, which isn’t as common as what we see in Wisconsin – transporting pregnant animals. So we’re hoping that our risks there are significantly lower.”

What Level of Risk Does the Virus Represent to Humans?

Last Monday, Texas health officials announced that a human who had direct contact with sick dairy cows tested positive for the virus. According to the Texas agency, the patient’s only symptom was conjunctivitis, which is akin to pink eye, and they are being treated with the antiviral medicine oseltamivir.

According to the CDC, this is the second verified human case of H5N1 flu in the United States, and the first associated with cattle exposure.

According to Poulsen, the CDC, USDA, and FDA continue to assess the health risk to people as minimal.

“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 said.