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Bird flu in raw cow’s milk has killed farm cats in a worrying first: ScienceAlert

In mid-March, a mysterious disease began spreading among cows on a North Texas dairy farm. Just a few days later, cats on the farm started acting strangely.

Their eyes and noses leaked profusely, they walked incessantly in circles, their bodies became stiff, and they lost their vision and coordination. Then they started dying.

According to officials with the U.S. Centers for Disease Control and Prevention (CDC), a dozen domestic cats at this one farm have fallen victim to a highly contagious bird flu. They appear to have contracted the virus by drinking raw, unpasteurized milk from cows on the property.

The cats are just the latest victims of an ongoing outbreak of bird flu, which first entered the US in late 2021 and has since moved from birds to mammals, including foxes, raccoons, opossums, skunks, seals, leopards, bears, mountain animals, lions and bobcats.

On March 25, the U.S. Department of Agriculture reported the first confirmed case of bird flu ever identified in cows.

Several dairy farms in Kansas and Texas were affected, and their cows later carried the virus to Michigan, Idaho and Ohio when transported interstate.

Although one farm worker became ill with the virus through contact with the cows, this outcome has so far been extremely rare. Few more than a handful of cases of this avian flu strain have infected humans worldwide, and only one of these cases is likely to have involved mammal-to-human transmission, not bird-to-human transmission.

Officials have assured the public that drinking pasteurized dairy milk will not expose them to the virus. The Food and Drug Agency is conducting extensive testing on milk products and has so far found no signs of the virus.

Unfortunately, the dozens of domestic cats that died on North Texas dairy farms contracted the virus before farmers knew what pathogen they were dealing with. Unknowingly, they fed their cats contaminated milk.

Cows in the US that are sick with bird flu produce thick and syrupy milk, but perhaps this symptom is not so obvious in the first days of the disease.

The first cat to show signs of illness at the North Texas dairy farm was recorded just a day after the first cow became ill.

On March 21, samples of cow’s milk from the affected dairy farms and two deceased cats from these farms were donated to an Iowa State University (ISU) diagnostic laboratory. The cats tested positive for the influenza A virus (IAV).

Cases of bird flu among cats have been well documented worldwide. Our cats are especially susceptible to the virus when they come into contact with sick birds, but transmission from cows has never been reported before.

ISU researchers say the cow and cat samples they analyzed contained signs of IAV with “a remarkable degree of similarity”, suggesting a “shared origin” for the strain.

Although exposure to and consumption of dead wild birds cannot be completely ruled out for the cats described in this report, the known consumption of unpasteurized milk and colostrum from infected cows and the high amount of viral nucleic acid in the milk ensure that the milk and colostrum consumption is a likely route of exposure,” writes the team of researchers led by pathologist Eric Burrough.

The findings suggest that bird flu can jump from mammal to mammal, making the infection more difficult to control. Even among cows, experts still don’t know how the virus is transmitted.

While the public waits for more answers, one thing is clear: pasteurized milk is the safest option of all. For both people and cats.