More Than Half of Cats on Farm Where Bird Flu Infected Cows Died After Drinking Milk

WEDNESDAY, May 1, 2024 (HealthDay News) -- In yet another sign that bird flu is spreading widely among mammals, a new report finds more than half of cats at the first Texas dairy farm to have cows test positive for bird flu this spring died after drinking raw milk.

Published Tuesday in the Emerging Infectious Diseases journal, the report details the early stages of the investigation into the spread of bird flu among the country's dairy farms.

Cats at the Texas farm had been fed raw milk from cows that turned out to be infected with avian influenza, also known as H5N1. A day after the farm noticed cows were getting sick, the cats started getting sick. In the end, more than half of the cats perished.

"The cats were found dead with no apparent signs of injury and were from a resident population of [approximately] 24 domestic cats that had been fed milk from sick cows," the scientists wrote in their report.

Tests of the samples collected from the brains and lungs of dead cats yielded results suggesting "high amounts of virus," and autopsies revealed "microscopic lesions consistent with severe systemic virus infection," in the eyes and brain, they said

"Although the U.S. Food and Drug Administration has indicated the commercial milk supply remains safe, the detection of influenza virus in unpasteurized bovine milk is a concern because of potential cross-species transmission," they added.

Roughly 1 in 5 samples of pasteurized milk the FDA has checked from retailers has tested positive for H5N1, although the agency said last week that pasteurization is killing off the virus in milk because only harmless viral fragments have been discovered so far. Still, officials have repeatedly urged Americans not to drink raw milk.

While the spread of the virus from cows to cats through raw milk is new, cats have long been known as one of the species that is especially vulnerable to severe disease from H5N1, CBS News reported. 

The U.S. Department of Agriculture has said that deaths and neurological disease in cats have been widely reported around farms with outbreaks of the virus.

Conversely, only 15% of cows developed signs of illness in herds with the infection, scientists added. The virus has been devastating for poultry flocks that faced widespread deaths or had to be culled after catching the virus from wild birds, CBS News reported. 

The recent cat infections on dairy farms prompted the U.S. Centers for Disease Control and Prevention to issue new guidance this month for veterinarians treating suspected H5N1 cases in cats, urging the use of respirators and goggles to avoid contracting the virus.

"While it's unlikely that people would become infected with bird flu viruses through contact with an infected wild, stray, feral or domestic cat, it is possible -- especially if there is prolonged and unprotected exposure to the animal," the agency said in its guidance.

Meanwhile, health authorities have been racing to curb further spread of the virus in dairy cattle. 

The USDA said Monday it would test ground beef sold at retailers for H5N1 and would study how cooking beef could keep the virus in check. Last week, the agency ramped up testing on dairy cattle being shipped over state lines.

"As of April 30, 34 dairy herds have been impacted by H5N1. For context, there are more than 26,000 dairy herds nationwide," an spokesperson told CBS News.

More information

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

SOURCES: Emerging Infectious Diseases, April 29, 2024; CBS News