The other day, I said that finding H5N1 avian flu in dogs was unsurprising. That also applies (probably even more so) to cats. We’ve known for years that cats are susceptible to H5N1, and since some cats spend a lot of time unsupervised outside and interact with (and eat) birds, they have lots of chances for (sometimes quite high) exposure.
The Wyoming State Veterinary Laboratory recently identified H5N1 in a barn cat from central Wyoming. It is suspected the cat was infected by eating infected waterfowl. Whether or not the cat was sick isn’t mentioned, but since it was a barn cat and testing for this virus isn’t common in cats, I’d guess that the cat was either very sick or died, and that’s why they tested it.
This follows a report from February 2023 of H5N1 in two cats in Nebraska. The first cat was an outdoor cat that died from severe and rapidly progressive neurological disease. Another outdoor cat in the same household also developed neurological disease shortly thereafter and was euthanized. The H5N1 virus was found in the brain tissue in both cases. Whether the two cats were infected from the same source or whether there was cat-to-cat transmission would be pretty hard or impossible to differentiate. The other two cats in the household were healthy and tested negative on nasal swabs.
Reports of this virus in cats aren’t overly surprising, and reflect rare spillover during a period when there’s an unprecedented amount of virus circulating in birds internationally. However, these rare cases still highlight the animal health risks from spillover infections, and the potential for domestic animals to act as a bridge between wildlife and humans.
So what should we do now?
Not really anything different from what we’ve already been recommending.
Keep domestic animals away from wildlife as much as possible. That’s tough with outdoor cats, but keeping cats indoors whenever possible (especially with avian flu is in the area) would be a good start. Some cats can’t stay indoors and there’s less we can do about them. Making sure outdoor cats are well fed helps but won’t stop them from hunting altogether, so we can’t eliminate the risk of exposure. Considering influenza infection in cats that have outdoor access and develop severe neurological or respiratory disease is important for surveillance purposes.
Can cats infect other cats or people with H5N1?
It’s hard to say. We generally assume that spillover infections are lower risk for transmission since the virus isn’t infecting its typical host. However, the first Nebraska cat had a really high viral burden in the brain, based on the PCR test results. It’s hard to say how much virus a cat with a central nervous system infection would shed in its respiratory secretions, but it’s still fair to assume there’s some degree of risk.
Should we take extra precautions when handling sick cats with outdoor access?
Sure. Based on what’s been reported to date, neurological disease is probably a big component of these infections, so we should already be taking precautions with these animals because rabies would be another possible cause of acute neurological signs. The same precautions will help prevent transmission of flu from such a cat. Outdoor cats with severe respiratory disease probably don’t have flu (since there are other more likely causes), but taking added precautions in veterinary clinics (e.g. keeping the cat isolated from other animals, use of PPE) and households (e.g. limiting close contact, attention to hand hygiene) are certainly reasonable.