A form of avian influenza that has been very fatal in birds has been confirmed in U.S. dairy cows in Texas and Kansas, the Department of Agriculture announced Monday.
It is the first time cows infected with the virus have been identified.
The cows appeared to have been infected by wild birds, and dead birds were reported on some farms, the agency said. The findings were announced after several federal and state agencies began investigating reports of sick cows in Texas, Kansas and New Mexico.
The disease primarily affects older cows and causes symptoms such as reduced appetite, fever and a sudden drop in milk production. To date, there have been few or no reports of deaths in affected herds, according to the USDA.
In several cases, the virus was detected in unpasteurized milk samples from sick cows. Pasteurization should inactivate the flu virus, experts said, and officials stressed that the milk supply was safe.
“At this time, there are no concerns about the safety of the commercial milk supply or that this circumstance poses a risk to the health of consumers,” the agency said in a statement.
Outside experts agreed. “It was only found in severely abnormal milk,” said Dr. Jim Lowe, a veterinarian and flu researcher at the University of Illinois College of Veterinary Medicine at Urbana-Champaign.
In these cases the milk was described as thick and syrupy and was discarded. The agency said dairies are required to divert or destroy milk from sick animals.
The cattle infections follow the first nationwide detection of highly pathogenic avian influenza in goats, announced last week by authorities in Minnesota.
So far, flu samples from sick cows did not contain genetic mutations known to increase the chance of the virus infecting people, the agriculture agency said, adding that the risk to the general public remains low.
“There’s still no reason to panic,” said Stacey L. Schultz-Cherry, a virologist and flu expert at St. Jude Children’s Research Hospital. “It just looks like it’s another spillover event due to contact with sick wild birds.”
But she noted that cows were not among the species most vulnerable to bird flu and that the cases represented another worrying twist in a global bird flu outbreak that has devastated wild bird populations in recent years.
The outbreak was caused by a new form of the bird flu virus called H5N1, which emerged in Europe in 2020. Wild birds can transmit the virus to poultry and other animals through their feces and oral secretions. Outbreaks often occur in spring and summer when migratory birds are on the move.
Although bird flu viruses are designed to spread primarily among birds, the new version of H5N1 has become so widespread in wild birds that it has repeatedly spread to mammals, particularly scavenging species such as foxes that may feed on infected birds .
Infections of mammals, which give the virus new opportunities to evolve, are always a concern, said Andrew Bowman, a molecular epidemiologist and influenza expert at Ohio State University. Scientists have long feared that an avian flu virus that has evolved to spread more efficiently among mammals, including humans, could trigger the next pandemic.
At this point it is still unclear, said Dr. Bowman asked whether all infected cows picked up the virus directly from birds or whether the virus also spread from cow to cow.
“This is an issue that needs to be resolved quickly,” he said. “If there is cattle-to-cattle transmission, that’s a different story. That definitely makes me a little more nervous.”
Further testing and analysis is underway. “This is a rapidly evolving situation and USDA and federal and state partners will continue to share additional updates as information becomes available,” the agency said.
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2024-03-26 15:44:55
www.nytimes.com
