The Department of Agriculture announced Monday that deadly avian influenza has been confirmed in U.S. dairy cows in Texas and Kansas.
This is the first time that a cow infected with the virus has been confirmed.
According to the agency, the cattle appear to have been infected by wild birds, and dead birds have also been reported at some farms. The Texas Animal Health Commission confirmed that a subtype of influenza known as H5N1 has been identified and said the virus is similar to the type that is circulating in birds across the United States.
The findings came as multiple federal and state authorities began investigating reports of sick cattle in Texas, Kansas and New Mexico. The disease primarily affects older cows and causes symptoms such as loss of appetite, fever, and a sudden drop in milk production. So far, there have been few or no reports of deaths in affected herds, the USDA said.
In some cases, the virus was detected in unpasteurized milk samples taken from sick cows. Experts said pasteurization should inactivate the influenza virus, and authorities stressed the milk supply was safe.
“At this stage, there are no concerns about the safety of the commercial milk supply or that this situation poses a risk to the health of consumers,” the agency said in a statement.
Outside experts agreed. “So far it has only been detected in significantly abnormal milk,” said Dr. Jim Rowe, a veterinarian and influenza researcher at the University of Illinois at Urbana-Champaign's School of Veterinary Medicine.
In that case, the milk was said to be thick and syrupy and was thrown away. The agency said dairy manufacturers must divert or destroy milk from sick animals.
The cattle infections come after Minnesota officials announced last week the nation's first detection of highly pathogenic avian influenza in goats.
So far, influenza samples taken from sick cows do not contain genetic mutations that make the virus more likely to infect humans, the Agriculture Agency said, adding that the risk to the general public remains low. .
“There's no need to panic just yet,” said Stacy L. Schultz Cherry, a virologist and influenza expert at St. Jude Children's Research Hospital. “It looks like another spillover event from contact with sick wild birds.”
Still, cattle are not thought to be among the species that are particularly susceptible to avian influenza, and this case is part of the global avian influenza pandemic that has devastated wild bird populations in recent years. This is another worrying development in the epidemic, he noted.
The outbreak is caused by a new strain of avian influenza virus known as H5N1 that emerged in Europe in 2020. Wild birds can spread the virus to farmed poultry and other animals through feces and oral secretions. Epidemics often flare up in the spring and summer when migratory birds migrate.
Avian influenza viruses are primarily adapted to spread among birds, but a new version, H5N1, is circulating in wild birds and has repeatedly spread to mammals, especially carrion species such as foxes that feed on infected birds. It's infected.
Dr. Joe Armstrong, a veterinarian and livestock expert at the University of Minnesota Extension, said infected wild birds can transmit the virus to cattle by contaminating their feed and water. “When you come into the farm, especially during migration season, the geese and ducks are foraging just like everyone else,” he says. “For me, that's the most likely route.”
But free-ranging cats, which are common on farms and are known to be susceptible to the virus, may also be contributing to the spread of the pathogen, he said.
Dr Armstrong also cautioned that it was premature to conclude that avian influenza was the main cause of all reported cattle illnesses.
Andrew Bowman, a molecular epidemiologist and influenza expert at Ohio State University, said mammalian infections are always a cause for some concern as they give avian influenza viruses new evolutionary opportunities. Scientists have long worried that avian influenza viruses, which have evolved to spread more efficiently among mammals, including humans, could cause the next pandemic.
Dr Bowman said at this point it is still unclear whether all the infected cows contracted the virus directly from the birds or whether the virus is spreading from cow to cow.
“It's an issue that needs to be resolved immediately,” he said. “It's a different story if there's cow-to-cow transmission. That certainly makes me a little nervous.”
Scientists say a closer look at the viral genome should tell us more about how the virus is spreading and whether it is evolving in a way that increases the public health risk. Ta.
Richard Webby, a virologist and influenza expert at St. Jude Children's Research Hospital, said these first cases also mean that bovine influenza surveillance needs to be stepped up.
“It's clear that we now need to better understand how prevalent this is in cattle,” he says. “Historically, influenza has probably not been a major part of the workup of sick cattle, but it will certainly move forward.”
