Bird flu no big threat to humans, Idaho state vet says

The discovery this year of highly pathogenic avian influenza — commonly called “bird flu” or HPAI — in dairy cattle has animal scientists and livestock producers concerned, but the health threat to humans is small, they say.

Idaho State Veterinarian Scott Leibsle said the virus has been circulating among waterfowl and domestic flocks for a few years. The virus also has been detected in mink, foxes, raccoons and bears, raising fears that it could mutate and start spreading more easily among people.

It is rare for humans to become infected, but symptoms may include conjunctivitis, fever, lethargy, aches, coughing and diarrhea. Being in direct contact with domestic birds is the highest risk activity. When U.S. Department of Agriculture guidelines for cooking are followed, HPAI is not a food-borne illness.

But when some dairy cattle in Texas began showing symptoms of illness a month or two ago, producers were stumped.

“The milk was getting sicker and sicker and they couldn’t figure out what it was,” Leibsle said. Eventually it was determined that avian flu, which has been responsible for the destruction of millions of domestic chicken and duck flocks throughout the U.S. in the past few years, had jumped species and infected the cattle.

“This is the first time that we’ve seen any symptoms with cattle being infected,” Leibsle said. The disease has not been fatal to cattle, and after a recovery period of about 10 to 15 days, Leibsle said the cows were back to regular milk production.

Recently there have been two confirmed cases of avian flu in dairy herds in southern Idaho and one confirmed case of the virus in a domestic flock of birds, according to the Idaho State Department of Agriculture.

“Where this may be a significant fatal blow to a flock, this is primarily affecting the milk production of dairy cattle,” Leibsle said. “So this is more of a transient thing, not to be ignored. Our job is to try to limit the spread within the herd so few get sick.”

Avian flu is transmitted between birds through close mucous contact, fecal matter and sometimes as an aerosol. It is carried on objects such as tools, vehicles, clothes and boots, which can transfer the virus from one location to another.

It is a highly contagious virus that can cause high death loss of domestic and wild birds. Signs of HPAI in domestic poultry frequently include sudden death, decreased appetite and activity, breathing difficulty and dark combs and wattles.

Two years ago, fears of spreading the disease prompted the Washington State veterinarian to recommend suspending all poultry exhibitions, fairs and shows. In Idaho, fair organizers were requiring birds to be tested to ensure their health before being allowed to be exhibited.

So far in 2024, no cases of HPAI have been confirmed in Washington.

Leibsle said because of the pasteurization process there is no danger that the virus can be transmitted through milk to the consumer.

“Food safety has not changed,” he said. “Pasteurization works and for people buying dairy products there is no reason that people should be concerned consuming dairy.”

Although the threat to dairy cattle appears to be minimal at this point, Leibsle said he is “concerned” about the continuing danger to domestic poultry flocks.

In an effort to limit spread of the virus, the agriculture department has been stressing the importance of biosecurity on farms.

Poultry producers are encouraged to wash their boots and hands when dealing with their birds, dedicate barn clothes that are removed when leaving the barnyard, and avoid driving cars and other equipment next to the chicken coop.

“You don’t want to carry any pathogens off your facility to somewhere else,” he said. “Do all you can to maintain biosecurity. When you bring new populations onto your property, they may have pathogens, so you try to limit the spread of disease and keep new flocks separate for 30 days.

“Good biosecurity is the best way to try to prevent the spread of disease,” Leibsle said.

Anyone wishing more information about avian flu may visit these websites: idaho.gov/hpai or aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/hpai-detections/livestock.

Hedberg may be contacted at khedberg@lmtribune.com