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• Posted April 25, 2024

Dairy Cows Moved Across State Lines Must Now Be Tested for Bird Flu

As bird flu continues to spread among dairy cows in the United States, the U.S. Department of Agriculture said Wednesday it will start requiring testing of the animals if they are moved across state lines.

The "USDA has identified [bird flu] spread between cows within the same herd, spread from cows to poultry, spread between dairies associated with cattle movements and cows without clinical signs that have tested positive," the agency said in a news release announcing the moves to mandate both testing and the reporting of positive results.

"To further protect the U.S. livestock industry from the threat posed by highly pathogenic H5N1 avian influenza, [the] USDA is sharing a number of actions that we are taking with our federal partners to help us get ahead of this disease and limit its spread," the agency noted.

Lactating cows must now test negative for influenza A viruses, a class that includes bird flu, before they are transported to another state, according to the new order. If those tests come back positive, herd owners will need to provide data on the movements of those cattle so investigators can trace the disease.

That should help stem the spread of the virus and help officials “better understand this disease,” Mike Watson, administrator of the USDA's Animal and Plant Health Inspection Service, said during a media briefing, the New York Times reported.

Ever since a highly contagious form of bird flu was detected in the United States back in 2022, federal officials have reassured Americans that the threat to the public remained low. But the U.S. Food and Drug Administration announced Tuesday that inactive viral fragments had been found in pasteurized milk, which suggests the virus has been spreading much more widely among cattle than thought. The results of tests to determine whether any live virus is in the milk supply are expected in the coming days, FDA officials added.

So far, no changes have been seen in the virus that would help it spread easily among people, Dr. Nirav Shah, principal deputy director of the U.S. Centers for Disease Control and Prevention, said Wednesday, the Times reported. States have been monitoring 44 people who were exposed to the virus, Shah added.

As of Wednesday, the outbreak had spread to 33 herds in nine states, according to the USDA. But just one human infection has been reported, in a dairy worker in Texas who had direct contact with sick cows. The case was mild.

Shah said the federal government was relying on local officials and health workers to communicate with dairy producers and their workers, including veterinarians who have close relationships with people who might be hesitant to open up to strangers.

“There may be owners that are reluctant to work with public health, to say nothing of individual workers who may be reluctant to sit down with somebody who identifies themselves as being from the government in some way,” Shah explained.

While it isn't clear when the bird flu outbreak among cows began, an analysis of genetic data suggests wild birds may have passed the virus to cows as early as last December. Cows were not believed to be vulnerable to bird flu, and it was late March before federal officials first announced the virus had been detected in sick cows in Texas and Kansas.

While testing more cows is critical, reducing the risk of infection among dairy workers exposed to raw cow milk is paramount, said Seema Lakdawala, a virologist at Emory University in Atlanta.

If a worker were splashed with raw, infected milk in the nose or eyes and become sick, that would give the virus new chances to start spreading among people, she explained.

Although federal health officials said Wednesday they had reminded states that they could request protective worker equipment from the national stockpile, Lakdawala said the risks of worker infections were already serious enough that farms should mandate the use of face shields.

She said other steps, like two-week ‘stay-at-home’ orders for infected cows, could also lower the need for more drastic measures.

More information

The U.S. Centers for Disease Control and Prevention has more on bird flu.

SOURCES: U.S. Department of Agriculture, news release, April 24, 2024; New York Times