HPAI detections decreasing in dairy herds

TOPEKA, Kan. — Highly pathogenic avian influenza is not a dairy-specific virus. It is the same virus that can infect poultry and other species.

“Our first official laboratory confirmed detection was in March 2024 in a Texas dairy herd,” said Bradley Christensen, veterinary medical officer at APHIS Veterinary Services.

“Since then we’ve had well over 1,000 confirmed detections in 19 states, with California being the most heavily impacted and accounting for probably three-quarters or more of those detections,” he said during the Secure Our Herds: Preventing Bird Flu on Dairy Farms webinar, hosted by the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service.

Dairy herd detections of HPAI peaked in late 2024.

“We believe this outbreak all started from a novel introduction of virus from wild waterfowl into dairy cattle,” Christensen said. “Once it established itself in dairy cattle, we saw it spread very swiftly from herd to herd through an animal-to-animal transmission mode.”

This is different than how it spreads with poultry.

“We get a continual reintroduction of the virus into poultry flocks from wild waterfowl,” Christensen said.

Now the outbreak of HPAI has slowed down compared to where it was last year.

“But it is not over, and the fact that we’ve seen it spill over several times from wildlife, we may never completely be out of risk from this disease in the dairy industry,” Christensen said.

The HPAI virus can cause pretty severe illness primarily in lactating dairy cows.

“We primarily find the virus in the milk, but we can find it in other secretions, as well,” Christensen said.

However, it has been proven that pasteurization is very effective in killing this virus.

“The hallmark sign with this disease is a really dramatic and sudden decrease in milk production,” the veterinary medical officer said. “We also see pretty consistently a drop in feed consumption.”

A lot of these sick cows, Christensen said, don’t really return to full health.

“They dry off early and they either don’t return to any milk production, or they just can’t regain full milk production, so they get culled earlier than they would have in a normal situation,” he said.

“So, even though we’re not necessarily seeing a lot of cows dying from this disease, we do see a very significant impact on some of these herds with the culling rate.”

Preventive Measures

“The spread of the virus between states and over large distances has been linked to cattle movements,” said Tyler McAlpin, veterinary medical officer for APHIS Veterinary Services. “The spread between farms locally has multiple factors, which may include movement of people, animals or equipment.”

Therefore, biosecurity is a key step to mitigating the risk of spreading HPAI on dairy farms.

“Biosecurity will only work if everyone on the operation follows the plan all the time,” McAlpin said. “So, your first step in protecting your herd is developing an enhanced biosecurity plan for your operation.”

This plan can include how to limit visitors to the farm, the use of dedicated boots or boot coverings for everyone visiting the farm, and disinfection of vehicles, trailers, tires and other equipment that enter the farm.

“Your plan should include methods and procedures to limit the interaction of livestock and pets with birds,” McAlpin said. “And include the frequency you need to check your livestock for signs of illness.”

Once the plan is developed, education about the different components is important for everyone at the dairy operation.

“When and where possible, have everyone enter and exit the farm from one location,” the veterinarian said. “At the entrance point, you should maintain a list of any visitor entering your farm.”

If dairymen are exhibiting their cattle at shows or fairs, McAlpin stressed the importance of cleaning and disinfecting shovels, forks or other equipment often while at the event.

“Don’t borrow someone else’s equipment,” he said. “And observe your cattle closely during, before and after they return from the show.”

For more information, go to https://tinyurl.com/Secure-Our-Herds.