Bird flu (avian influenza, H5N1) has gotten a lot of headlines over the last year. If you’re a subscriber to our free monthly newsletter, you’ve read a lot about it. [And if you’re not… go here to sign up right now!  littlebigcat.substack.com]

Bird Flu Basics

Cats (domestic, wild, exotic, and big cats) are unusually susceptible to this bird flu. But it’s not just cats–carnivores in general seem more vulnerable to this flu. Foxes, bears, skunks, raccoons, dolphins, and sea lions have all been affected. (Only a handful of cases in domestic dogs have been documented.)

Viruses are classified in “clades” (a strain or version). Last year, a bird flu virus that had already been circulating around the globe since 2021 developed a new clade, a mutation known as 2.3.4.4b within the B3.13 genotype (sorry if that’s “TMI”!), which gave it the ability to jump from birds to mammals. The B3.13 virus suddenly turned up in dairy cows. Not a lot of viruses can cross species (rabies being a notable exception), so this was worrisome.

The other unusual ability of this new clade is transmission by ingestion. Most viruses move around via secretions like eye and nose discharges, saliva, urine, or feces. But cats were getting this virus by eating it. Specifically, they were getting sick from drinking milk from infected cows. This lovely virus has an affinity for mammary tissue, and collects in large quantities in milk. Cats drinking that milk were getting a massive viral load. The first clue, in fact, that there was a problem, was a lot of dead cats on dairy farms.

Bird flu, of course, primarily affects birds, and has run rampant among wild birds (especially ducks, geese, and gulls–the major transmitters across the world) as well as chickens,  turkeys, ducks, and geese–both large commercial operations and backyard flocks. Raptors and scavenging birds, like hawks, vultures, and crows, can also be infected. Songbirds, jays, cardinals, and robins can get avian flu, but in this outbreak have been less likely to get ill. But they can still carry the more deadly virus varieties.

Signs of Bird Flu in Cats

The symptoms of bird flu can look like many other diseases, and can present with a wide variety of symptoms, including:

  • Lethargy/depression
  • Poor or no appetite
  • Fever
  • Conjunctivitis (red, puffy, or inflamed eyes)
  • Discharge from the eyes or nose
  • Sneezing
  • Coughing
  • Difficulty breathing/dyspnea
  • Neurologic signs like tremors, seizures, unsteadiness, wobbly gait, weakness, or blindness

Bird flu usually starts with loss of appetite, lethargy, and/or upper respiratory signs (red or irritated eyes, nasal discharge. It can progress very fast to neurological signs. Cats can die within 24 hours of developing symptoms. If you see these signs, and your cat has any possibility of exposure, seek veterinary care immediately.

Bird Flu Transmission

As mentioned, bird flu is easily to cats transmitted via raw milk. There have been no documented cases of milk transmitting bird flu in any other species, including humans–but if you’re in a state where raw milk is legal, just don’t give it to cats. More than 1,000 dairies in the U.S. have documented bird flu cases. (Raw milk can transmit a whole lot of other disease-causing bugs, too, so do use caution for all species.) Fortunately for the cows, most of them don’t get very sick, and the vast majority recover.

There have also been cases where cats and other animals have gotten bird flu from raw meat. Now, before anyone gets on their high horse about “it could have gotten into the meat from the air!” let me assure you that the science is very solid. The genetic fingerprint of the virus from the meat and the dead eaters of that meat was specific down right to a particular molecular trigger. It is a hot, smoking gun.

In the first well-publicized case, it wasn’t just two housecats, it was 17 animals, including 15 exotic and big cats and one fox. The virus was tracked to the exact farm where the infected turkeys were raised and the same meat was consumed in all cases.

Two other batches of infected raw cat food from other companies were subsequently recalled after deaths were reported. Fortunately one cat did survive.

Whether bird flu can be transmitted between mammals is controversial. The evidence suggests that it can be, but it’s not common. Fomites (inanimate objects like buckets, boots, or shovels) seem to be the likely culprit in dairies. But nobody is entirely certain exactly how the cows got it in the first place, though wild birds are sure to be involved.

While research is still in its early stages and not nearly enough testing has been done, we also know that mice, rats, and squirrels can also get–and likely transmit–bird flu. Therefore it’s very important to prevent cat predation on rodents as well as birds.

It’s also important to know that the bird flu in cats is very unlikely to mutate into a form that will cause a giant pandemic. It is most likely going to be a dead-end infection in cats. (Infections in other animals, like birds and pigs, who are essentially mutation factories, are a far bigger concern!)

Testing

There is a good test for bird flu, and every state diagnostic lab in the U.S. has it, because H5N1 has been found in all 50 states.

Unlike rabies, which requires the cat to be dead for testing, living cat samples (blood, urine, saliva, eye or nasal discharges) are totally acceptable and accurate for testing.

If you have a cat with signs of bird flu and a history of possible exposure (for example, my cat Perry Christmas was very good at catching mice inside the house), your veterinarian can submit samples. USDA has even been paying for testing at the state lab (but it’s only $50 if they don’t). We really need the data!

The Big Conundrum

A lot of media and even some reputable research institutions have been very alarmist about bird flu. No doubt it’s a serious disease, and it can be fatal to many species besides cats, including humans.

Some headlines have trumpeted a supposed 90% fatality rate in cats. This is absolutely false and I don’t want you to worry about that! There have been many cases of exposure where the cats didn’t get bird flu at all, and many cases where cats have had milder cases and recovered.

The 90% comes from cases where the cat gets sick and progresses to neurological disease. This can happen very quickly. And 90% of neuro cases will in fact die.

But I suspect that there is a lot more bird flu going around in cats than anyone thinks. The symptoms mimic several other viruses, including the very common feline herpesvirus and calicivirus, which almost all cats carry, and veterinarians see every single day. Vets are not going to send samples from every weepy-eyed, snotty-nosed cat to the diagnostic lab. If symptoms progress, that’s the time to consider avian flu and to take more serious steps to diagnose (and, of course, provide major supportive treatment!).

But more testing of symptomatic/exposed cats can only increase our database and help us understand the scope of the problem. Then we can do a reality-based assessment and not go around fear-mongering like some are fond of doing!

Preventing Bird Flu

So now that you know more about bird flu than you should ever need, let’s talk about how to prevent it. Even if most infections are mild, you don’t want your cat to get it!

I’ve been contemplating and refining my recommendations for six months. They are based on the latest science, my own knowledge base, and many conversations with scientists, diagnosticians, and colleagues. I am more cautious than others, especially about raw meat. Perhaps I know more than is good for me about how meat is grown and processed, and about the pet food industry, that makes me much less trusting. But I’ve been directly involved in the pet food industry for over 20 years and this is where I’ve landed.

My biggest concern is for cats who go outdoors or hunt (Perry Christmas was adept at indoor hunting). Preventing access to wild birds and rodents is key. For new readers (and anyone who wasn’t paying attention), here are my current tips for keeping your cat safe:

  1. Keep cats away from backyard chickens, wild birds,  mice, rats, shrews, voles, squirrels. Put fine mesh screens on all outdoor catios and habicats.
  2. Do not feed cats raw milk or cheese made from raw milk.
  3. Do not feed commercial raw food without HPP (high pressure pasteurization) or cooking to 140oF.
  4. Cook grocery store poultry and non-HPP raw cat food to 140oF.
  5. If you are cooking commercial raw food, add a small amount of B vitamins and extra water or broth to make up for what’s lost in heating.
  6. Whole beef cuts, rabbit and other meats (except pork and seafood) are probably safe to feed raw.