Study Warns That Cats Might Be Bird Flu Carriers

THURSDAY, Dec. 12, 2024 (HealthDay News) -- Picture this: a beloved cat, playful and healthy one day, falls mysteriously ill the next. Soon after, the shocking culprit is revealed -- bird flu, a virus that most people associate with poultry and wild birds.

Now, scientists are warning that domestic cats could potentially prompt a public health crisis.

According to a new study published Dec. 9 in the journal Emerging Microbes & Infections, domestic cats could become an unexpected player in the evolution and transmission of the H5N1 bird flu virus, potentially creating opportunities for it to become more dangerous.

The virus, which began circulating in dairy cattle earlier this year, has killed many cats, mainly on farms where herds were infected. It has also sickened at least 60 people, most of whom had direct contact with infected dairy cows or poultry.

H5N1 does not currently spread easily among humans, but studies suggest just one or two key mutations could allow it to jump between people more readily.

While there is no evidence that cats have transmitted H5N1 to humans, researchers caution that these pets may still present a risk.

If a cat were infected with both H5N1 and a seasonal flu virus at the same time, the bird flu virus could potentially acquire the mutations needed to spread widely among humans.

Cats frequently mingle with both wild animals and people, which could turn them into a bridge for the virus to evolve.

For months, the focus has been on testing cows and people for H5N1, with no single government agency taking responsibility for tracking other animals like cats, the New York Times reported.

But the U.S. Department of Agriculture (USDA) recently announced plans to test the national milk supply to identify infected dairy herds.

The cat study emphasizes the need for public health officials to ramp up surveillance for bird flu in cats, study author Dr. Suresh Kuchipudi, a veterinary microbiologist at the University of Pittsburgh, told the Times.

“In the process of addressing the immediate problem -- which is dairy farms and the milk as a food safety problem, and then human surveillance -- we might be missing a much bigger, evolving story,” Kuchipudi said. “It may already have been happening in plain sight.”

Meanwhile, the Biden administration has stated it has no immediate plans to authorise a bird flu vaccine for humans, NBC News reported, leaving that decision to the incoming Trump administration. The delay raises concerns about the government's preparedness in addressing a potential outbreak.

This milk testing ordered by the USDA, set to begin next week in six states, is designed to reassure farmworkers about the safety of their animals and their ability to protect themselves from infection. It should also help officials track the virus’s spread among herds.

In the latest study, researchers investigated a case in South Dakota where 10 outdoor cats that were considered pets died after showing respiratory and neurological symptoms.

The virus isolated from the cats closely resembled the strain found in cattle on a nearby dairy farm. Researchers believe the cats were infected after eating wild birds that had carried the virus from the farm.

In the past, scientists typically have worried most about pigs, considered the ideal “mixing vessels” in which two flu viruses -- seasonal and H5N1 -- might swap genes.

But many other animals may also host bird flu and seasonal flu viruses at the same time, Richard Webby, an influenza expert at St. Jude Children’s Research Hospital, told the Times.

“Cats seem to be a pretty good candidate,” Webby added.

Since late 2022, at least 53 domestic cats in the United States have been infected with H5N1, according to the USDA.

What's more, the current H5N1 strain has already infected an unusually wide range of species, including 90 types of birds and more than 20 mammal species, Tom Peacock, a virologist at the Pirbright Institute in Britain, told the Times.

“This virus is doing all sorts of wonky things that we haven’t really thought of flu viruses doing," he added.

More information

The American Veterinary Medical Association (AVMA) has more on keeping pets safe from bird flu.

SOURCE: Emerging Microbes & Infections, Dec. 9, 2024