Dairy cows have tested positive for a strain of bird flu that had not previously been seen in the herd, the U.S. Department of Agriculture (USDA) said Wednesday, raising concerns about the spread of the virus.
The H5N1 virus has slashed milk production, driven up egg prices, killed millions of chickens and infected nearly 70 people since April as it spread across the country.
The Nevada cow milk sample identified the second strain of the virus, known as type D1.1, for the first time, the USDA said. All 957 bird flu infections in cattle herds reported since March were caused by a different strain, B3.13, according to the U.S. Department of Agriculture.
Reuters reported the discovery of the second strain on Wednesday before the agency’s announcement.
It was identified in cattle by an agency program that began testing milk for bird flu in December.
“We’re seeing that the H5N1 virus is smarter than all of us,” said Beth Thompson, South Dakota’s state veterinarian.
“The virus is modifying itself, so it’s not just confined to domestic and wild waterfowl. It’s also infecting mammals.”
Wild birds likely transmitted the second strain of the virus to cattle in Nevada, said J.J. Goicoechea, the state’s agriculture director. Farmers need to step up their safety measures to protect their animals, he said.
“We’re definitely not doing everything we can and everything we need to or the virus wouldn’t be infecting dairy cows,” he said.
The Nevada Department of Agriculture said on Jan. 31 that cattle herds in two counties had been quarantined due to the discovery of bird flu.
It is important that the federal USDA takes steps to limit the spread of the virus in the state so that it does not spread to livestock elsewhere, said veterinarian Gail Hansen.
Last year, bird flu spread across the country after infected cattle in Texas were shipped to other countries after the virus was first transmitted to cows by wild birds.
“We did not have the last case under control,” said veterinarian Hansen. “We want to avoid a repeat of the same scenario in Nevada.”
Herds that were previously infected could be at risk again from the second strain, experts said.
“Now it looks like we have new strains of the virus that can evade the immunity that has been built up against other viruses, and the situation could get worse,” said Gregory Gray, a professor of medicine at the University of Texas who studies cattle diseases.
