Bird flu found in dairy cows in Texas and Kansas

The USDA announced Monday that unpasteurized milk samples from sick cattle at two dairy farms in Kansas and one in Texas, as well as an oropharyngeal swab from another dairy in Texas, tested positive for highly pathogenic avian influenza (HPAI).

USDA stressed that the commercial milk supply is not at risk. “Initial testing by the National Veterinary Services Laboratories has not found changes to the virus that would make it more transmissible to humans, which would indicate that the current risk to the public remains low,” the agency said.

Wild, migratory birds are believed to be the source of the infection, and bird flu has primarily affected domestic poultry flocks. But in late 2022 and early 2023, reported infections of mink, otters, and sea lions raised the risk of a spillover into humans.

Martin Beer, head of the Institute of Diagnostic Virology in Germany, told the medical journal JAMA in Feb. 2023 that an outbreak on a mink farm in Spain deserved special attention. “Spread between mammals might allow for further adaptations to the mammalian host,” he said. Fewer than 900 human cases of H5N1 avian influenza, the type now circulating, have been reported in two decades.

The dairy cow tests were made as part of an investigation by the USDA, the Food and Drug Administration, and the Centers for Disease Control and Prevention, as well as state veterinary and public health officials, “into an illness among primarily older dairy cows in Texas, Kansas, and New Mexico that is causing decreased lactation, low appetite, and other symptoms.”

In a statement, the USDA said, “At this stage, there is no concern about the safety of the commercial milk supply or that this circumstance poses a risk to consumer health. Dairies are required to send only milk from healthy animals into processing for human consumption; milk from impacted animals is being diverted or destroyed so that it does not enter the food supply. In addition, pasteurization has continually proven to inactivate bacteria and viruses, like influenza, in milk. Pasteurization is required for any milk entering interstate commerce.

“For the dairies whose herds are exhibiting symptoms, on average about ten percent of each affected herd appears to be impacted, with little to no associated mortality reported among the animals. Milk loss resulting from symptomatic cattle to date is too limited to have a major impact on supply and there should be no impact on the price of milk or other dairy products.”

A total of 79.7 million domestic birds, mostly egg-laying hens and turkeys being raised for human consumption, have died from HPAI or in eradication efforts since the first confirmed outbreak on Feb. 8, 2022. Since then, the disease has been confirmed in 1,059 flocks in 47 states.

The ongoing HPAI outbreak is the worst U.S. animal disease event ever and is far larger than the 2014-15 outbreak that killed 50 million birds in commercial flocks.