USDA scientists confirmed the bird flu virus in a dairy herd in Idaho on Tuesday — the 12th herd in five states — with Ohio appearing for the first time on the list of states with “presumptive positive” results that will be double-checked. Meanwhile, officials said a Texas egg farm suffered the largest U.S. outbreak of bird flu in four months.
Authorities said the risk of transmission to people of the H5N1 strain of highly pathogenic avian influenza (HPAI) remained low. The Texas state Agriculture Department said a “dairy worker who had direct contact with cattle” was being treated for bird flu. The CDC said on Monday the patient’s only symptom was eye redness, consistent with conjunctivitis.
USDA’s National Veterinary Services Laboratories (NVSL) in Ames, Iowa, conducted the confirmatory tests on the Idaho herd and was conducting the same tests on presumptive positive results from Kansas, New Mexico, Ohio, and Texas, said the Animal and Plant Health Inspection Service.
“It is important to note that while these samples are from cattle with at least some clinical signs in common with other cattle diagnosed with HPAI, the presence of HPAI should not be considered confirmed until the NVSL analysis is complete,” said the agency.
To date, HPAI was confirmed in seven herds in Texas, two in Kansas, and one each in Idaho, Michigan, and New Mexico.
Cal-Maine Foods, the largest egg producer in the country, said it would cull 1.6 million egg-laying hens and 337,000 pullets — females less than a year old — at its farm near Farwell, Texas, after tests confirmed HPAI was present. Farwell is in the Texas Panhandle near the border with New Mexico. As a matter of course, animal health officials kill all the birds in an infected flock to try to stop the virus from spreading.
“Production at the facility has temporarily ceased,” said Cal-Maine. “The company remains dedicated to robust biosecurity programs across all its locations; however, no farm is immune from HPAI.”
Losses at the Farwell facility amount to 3.6 percent of Cal-Maine’s 42.2 million laying hens. It was the largest HPAI outbreak in the United States since 2.6 million laying hens in Hardin County, in west-central Ohio, last Dec. 7, according to USDA data. Nearly 84 million birds in domestic flocks have died from bird flu since outbreaks began in February 2022.
“Given this latest development, all producers must practice heightened biosecurity measures,” said Texas Agriculture Commissioner Sid Miller. “The rapid spread of this virus means we must act quickly.”
The discovery of bird flu in cattle, and the possibility of cattle spreading the disease among themselves, has highlighted questions of further adaptations that could threaten humans. There are two known U.S. cases of HPAI in humans. The USDA says its tests of the H5N1 virus found in dairy cattle have not found changes that would make the virus more transmissible to people.
The H5N1 strain of HPAI has circulated widely around the world for years. Since 2003, more than 23 countries have reported more than 880 human infections with the H5N1 bird flu virus to the World Health Organization. Illnesses have ranged from mild, such as the U.S. cases, to severe, such as pneumonia and even death, in other countries.