For years, FIP was the diagnosis no cat owner wanted to hear. That has changed – and most people still don’t know it.
If your cat has been diagnosed with feline infectious peritonitis, or you’ve come across the term while researching symptoms, you’ve probably already read that it’s fatal. For most of the last sixty years, that was true. FIP was a near-certain death sentence, and the kindest thing a veterinarian could often offer was time and comfort.
That is no longer the case. There is now a real treatment, one that cures the majority of cats who get it.
What is FIP?
Most cats carry a common, harmless coronavirus in their gut. (Yes, “coronavirus” — it’s a whole family of viruses, and this one has nothing to do with the human kind.) In a small number of cats, that everyday virus mutates into something far more dangerous. That mutated version is FIP.
It shows up most often in younger cats, usually under two, and in cats from shelters, catteries, or busy multi-cat homes, where the original virus spreads easily.
FIP comes in two general forms:
- Wet (effusive): fluid builds up in the belly or chest, which can make breathing or moving uncomfortable.
- Dry (non-effusive): no fluid, but inflammation settles into the organs, the eyes, or the nervous system.
Early signs are frustratingly vague – a fever that won’t quit, a cat going off food, low energy, a swollen belly. That’s part of why FIP is hard to catch early.
Is FIP Contagious?
This is usually the first fear in a multi-cat home, so let’s settle it. FIP itself is not considered contagious from cat to cat. The dangerous mutation happens inside one individual cat – it isn’t something a sick cat passes to its housemates.
What spreads is the ordinary gut coronavirus, mostly through shared litter boxes. But here’s the reassuring part: in a home where one cat has it, the others have very likely already been exposed to that common virus and are carrying it harmlessly, as cats everywhere do. The odds of any one of them taking the rare turn toward FIP stay low.
If you have several cats, it’s worth a longer conversation with your vet about your specific situation. But you don’t need to brace for an outbreak.
A Breakthrough: A New Treatment for FIP
The breakthrough is an antiviral called GS-441524.
Studies beginning in 2018 showed that GS-441524 could achieve survival and long-term remission rates previously unheard of in FIP. One follow-up case even confirmed, after the fact, that the virus was gone from every tissue in the body.
The catch, for a long time, was access. The drug wasn’t available through veterinarians in the US, so desperate owners turned to unlabeled vials sold through online groups – no veterinary oversight, no quality guarantees, and a steep price tag. Not a position any pet owner should have been put in.
But in June 2024, that changed.
GS-441524 is now available in the US as a compounded oral tablet, prescribed by your veterinarian. (One honest caveat worth knowing: it isn’t formally FDA-approved. The FDA has said it doesn’t intend to enforce approval requirements when a vet prescribes it for a specific cat with FIP, which is what makes legitimate, vet-guided treatment possible.)
Published studies generally report treatment success rates in the 80–90% range, though outcomes vary depending on disease severity and the organs involved. Cats that respond often start feeling better within the first week!
How Are Cats Treated for FIP?
Treatment is usually a daily oral tablet you give at home, over a course of about twelve weeks. Your vet will check in along the way – typically with rechecks and bloodwork – to confirm the virus is retreating and your cat is tolerating things well.
Many cats start perking up within the first week, which is its own kind of relief to watch. After the course finishes, there’s usually an observation period to make sure the disease stays in remission.
It’s a commitment – daily, for several weeks, with follow-ups. But the results are worth the effort!
Start Your Cat’s FIP Treatment Today
If your cat has been diagnosed with FIP and you’re looking for a veterinary team that has experience with the treatment in your corner, you’ve come to the right place. Call our office at (850) 906-0444 or book an appointment online to get started.
