Bird flu in cats: Study raises human transmission concerns

20/06/2024

Pet cats could be a significant vector of infection in a human avian flu pandemic, according to a review of two decades of research data.

The study, currently a preprint awaiting peer review, suggests that cat owners should be vigilant for signs of illness in their pets. This illness could also put themselves, their vets, and any other close contacts at risk.

Jumping from Species

The highly pathogenic H5N1 bird flu virus currently affecting cattle on US dairy farms has already proven itself quite capable of infecting a wide range of mammal species – around 27 at the last count, according to former CDC director Robert Redfield. But while infections in dolphins and polar bears are certainly of scientific interest, it’s the animals that share our homes that are raising the biggest concerns for epidemiologists.

This year in the US, three farm workers contracted the virus after coming into contact with infected cattle. As well as jumping from birds to cows, the disease has found its way into other farm animals – some unfortunate alpacas in Idaho, and farm cats thought to have succumbed after consuming raw milk.

While you might not necessarily think to put “bird flu” and “alpacas” in the same sentence, scientists have long been aware that cats are susceptible to avian flu. But what is the risk for our beloved pets, and for us as owners? Researchers at the University of Maryland combed through 20 years of published data on the spread of bird flu in feline species to try and find out.

Bird Flu on the Rise in Domestic Cats

Mapping the period between 2004 and 2024, the scientists noticed a sharp increase in reports of infections in domestic felines – rather than wild or zoo-kept cats – starting in 2023. The spread of highly pathogenic H5N1 coincides with this rise in domestic cat infections, as the virus infects a number of species never previously impacted by bird flu. Infections have also been reported in house mice, a favoured prey item of domestic cats everywhere, and we all know how much free-roaming cats enjoy chasing birds.

Bird Flu: Risk to Humans and Vets

The Centres for Disease Control and Prevention (CDC) says that it is unlikely for humans to catch bird flu from cats, but it is possible, “especially if there is prolonged and unprotected exposure to the animal.” Veterinarians, veterinary nurses, and other professionals who work closely with potentially infected animals may therefore also be at risk, and the CDC issues guidance about the best use of personal protective equipment (PPE) in these cases.

Protecting Your Cat

For pet owners, the study’s lead author, Professor Kristen Coleman, who researches airborne infectious diseases, had some suggestions for how to help keep your kitty safe. “Don’t feed your cat raw meat or unpasteurised milk, and limit their unsupervised time outdoors,” the author said in a statement. “Cats prey on wild birds that could be infected, and they could get into raw milk on a farm if it is not securely stored.”

Potential for Feline-to-Feline Transmission

There have also been a handful of reports of feline-to-feline transmission of avian flu. Scientists are very concerned about the possibility of a human pandemic. The more the virus adapts to mammalian immune systems, the greater the chance it could become established in the human population.

Bird Flu in Cats: Signs and Symptoms

When cats become ill with bird flu, they often show difficulty breathing or behavioural changes, so be on the lookout for these signs and seek veterinary advice promptly. Researchers have also reported that H5N1 can cause blindness in some cats.

Bird Flu: High Mortality Rate in Cats

According to Coleman, the current H5N1 strain is deadly for cats, with a mortality rate of around 67%—all the more reason to keep Felix and Fluffy indoors as much as possible.

“The virus is going to find its way into more places, just like it did in dairy farms,” she said. She said they knew cats were getting sick and they needed to be proactive to avoid a bigger issue.

Researchers have posted a study on the preprint server medRxiv.