Feline Infectious Peritonitis (FIP)

By Jean Hofve, DVM

FIP is a particularly nasty disease—one that causes great confusion and distress. The name itself is misleading; the only absolutely true point about the name is the “feline,” since it is not especially infectious, nor is it always peritonitis (inflammation in the abdominal cavity). Unfortunately, the disease is virtually 100% fatal in its active form.

As a rule, FIP develops primarily in young cats under 2 years of age, or in older cats age 10 and up. It is fairly rare in the middle years. A study of more than 800 cats in Great Britain found that in homes where a cat had died of FIP, the transmission rate to other cats in the home was less than 5%. Since these other cats continued to go outside where they could also have been re-exposed to another source, it is clear that FIP does not easily pass from one cat to another.

FIP is considered to be caused by a virulent form of an otherwise harmless bug called Coronavirus. This virus causes mild diarrhea in very young puppies and kittens, but is generally self-limiting and doesn’t cause much of a problem. However, the virus is also found in cats who do ultimately contract FIP, in which it is thought to have mutated to a virulent form (though this has never been proven).

Saying that Coronavirus causes FIP might be a little like saying “flies cause garbage” just because the two are usually found together. Whether or not coronavirus is the real trigger is unknown. Many perfectly normal cats who will never develop FIP will test positive for Coronavirus; in my experience, about 40% of normal cats are positive. A positive test is only a reflection of the cat’s having been exposed to the virus at some time in its life, and doesn’t mean very much otherwise.

FIP is very difficult to diagnose correctly, at least while the cat is still alive. Most confirmed cases are recognized at necropsy (the technical term for an autopsy on a non-human animal). The early symptoms are vague, and commonly found with many other conditions, not just FIP. Symptoms include poor appetite, failure to thrive (in kittens), weight loss, ratty-looking fur, eye problems such as uveitis (inflammation), fever, anemia, lethargy, jaundice, neurological symptoms, and what vets refer to simply as “ADR”—which stands for “ain’t doin’ right.” FIP is typically diagnosed when a symptomatic cat has a positive test for Coronavirus along with other typical laboratory abnormalities that support the diagnosis.

The actual FIP disease symptoms are actually caused by the cat’s own immune system. For some reason, the immune system over-reacts and creates many patches of white blood cells that produce tons of antibodies. In some cats, this results in chronic inflammation, usually without clear symptoms; this is called “dry” FIP and is very hard to diagnose correctly. In the “wet” or “effusive” form of FIP, the body also produces large amounts of fluid—usually in the abdomen but sometimes in the chest instead. The fluid is characteristically yellow and sticky; its high protein content is diagnostic for FIP. Both forms of FIP usually cause rapid deterioration and death.

There is a vaccine for FIP, but most experts do not recommend it. The vaccine is not very effective, and it can actually cause worse problems than it purports to solve. In challenge trials, vaccinated cats got sicker and died sooner than unvaccinated cats.

There is no good treatment for FIP. Studies have shown variable results with interferon, a drug called Trental (pentoxifylline, a blood thinner), along with prednisolone (a steroid) to suppress the immune system’s over-reaction and inflammation. These drugs may reduce symptoms and prolong the cat’s life, but there is little evidence that they provide a true cure for FIP.

Since so little is really known about the true nature of FIP, it’s hard to recommend specific preventive measures. However, a nutritious diet and appropriate immune-supporting supplements are always the best bet to create optimal health for your cat. We recommend a primarily wet food diet (either canned or homemade) along with four specific supplements: digestive enzymes, probiotics, antioxidants, and omega-3 fatty acids.



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11 comments for “Feline Infectious Peritonitis (FIP)

  1. Jean Hofve DVM
    January 31, 2014 at 5:23 pm

    So sorry to hear about your little baby! One thing I’ve noticed over the years is that the kittens who go on to develop FIP are the SWEETEST kittens ever. Maybe Heaven keeps the time they are “on loan” to us short because it wants them right back, but it makes it extra hard to lose them!

  2. Monkey2boo
    January 31, 2014 at 12:49 pm

    We put our little girl, Ukulele, to sleep yesterday. We knew there was something odd about her but we’d never had kittens before… we took her to the vet when she stopped eating and drinking, and discovered that she had FIP. They gave her an appetite stimulant and some fluids but she didn’t even perk up. I’m very sad to have lost my little sweet Ukie-Boo.

  3. Evelyn
    February 8, 2012 at 2:06 pm

    Dear Jean Hofve, DVM:

    I knew I read this article before… and I am so glad to have now found your own web site. Thank you for this information which was immeasurably valuable at the time we first heard about this shocking illness. Our sweet Buddy did not suffer long because of this information. He presented with what appeared to be a collapsed lung, but the yellow fluid gave it away. He was 4 1/2 years old, which was outside the normal range, but he had always been well cared for. He died January 7, 2012 having spent a comfortable night at the Vets in the oxygen cage. His case was fast onset. We could only think later that in late Nov/ early December he got into a scuffle and got his ear nicked. The only other time he’d ever been injured was as a 9 month old kitten when he got a nasty bite.

    We found out then (January 7) that he was also FIV positive… I’ll bet it was that first bite that gave him that and the second nick pushed his immune system into overdrive. The Vet did not test for coronavirus and as you observe the correlation doesn’t shed any light on the actual immune trigger.

    So glad this menace is rare. It is heartbreaking all around. Grateful to have awesome Vets for our animals… and your excellent information. I found your own site today by looking up constipation for our new foundling Niels.

  4. jhofve77
    December 7, 2011 at 10:04 pm

    Hi, sorry I do not know of any reliable treatment for FIP. If you wish to consult a holistic veterinarian, please visit the directory at http://www.holisticvetlist.com

    You had also asked about the sodium ascorbate (referred to above by another reader). This is just another name for Ester C, you can get it at any grocery store, health food store, or pharmacy.

  5. Maria Machado
    December 7, 2011 at 9:18 am

    Hi, My cat has lost 3lb and yesterday they run test and my vet says that FIP is on the top of the diagnostics, but we are waiting until tomorrow for the test to come. She has most of the simptoms, but she is still eating which gives me hope. Please let me know of all the things that you have use, so that I can tell my vet, in the case that tomorrow the test shows that it is actually FIP. I want to start as soon as I can doing something. I don’t want to loose her. Thanks.

  6. jhofve77
    November 10, 2011 at 8:36 am

    This advice came from another commenter, we at Little Big Cat have no knowledge of this protocol, nor do we endorse it. I’m re-posting your enquiry in case the original poster comes back and can respond.

  7. Cheri Baird
    November 9, 2011 at 4:48 pm

    Please tell me where, how do I obtain these supplements? My 6 mo. old female has just been given this “death sentence” and I feel desperate as to what to do or where to begin. Any info would be so appreciated.


  8. Cheri Baird
    October 22, 2011 at 6:16 pm

    Please tell me where, how do I obtain these supplements? My 6 mo. old female has just been given this “death sentence” and I feel desperate as to what to do or where to begin. Any info would be so appreciated.


  9. Nikki
    October 20, 2011 at 3:43 pm

    We have turned around advanced-stage, effusive FIP kittens with viamin C and another supplement blend (with probiotics, enzymes, etc). High doses of sodium ascorbate (started gradually), and Wysong F-biotic were all I used to arrest the disease and produce gradual improvement in a mixed batch of FIP kittens. These 7 kittens were of three different litters from a breeder’s cattery. The two youngest kittens (littermates) filled with fluid and died. It was just about that time I read about Sodium Ascorbate for FIP and found one person who saved his cat’s life. The other 5 were at the point where each one was extremely bloated, had severe diarrhea, depression, and wasting. We were just waiting for them to die, but they had other plans. All 5 of the older kittens were given a clean bill of health after several weeks on the supplements. I recently spoke with the president of the rescue that owned these kittens. She said she had 16 more FIP kittens come around to a healthy state. If I hadn’t been the one who helped her with the first batch of kittens, I wouldn’t have believed her. I would love to see more people try these affordable and safe options. If these supplements save even 1% of cats with FIP, it would be worth it to try it with all of them.

  10. L.H.
    June 11, 2011 at 8:47 am

    I have lost 2 kittens to, what is thought to have been, FIP. Both had the dry form which caused neurological problems. My first kitten suffered from severe seizures. She was put on an anti-seizure medication which stopped the seizures for about a month. But she was also very groggy and not herself at all since her first hospitalization. My second kitten slowly developed paralysis in her legs. It began with a loss of balance, and toward the end, she could not walk at all. We put her on a steroid which brought back the use of her limbs for a few weeks, then she began to decline again. Once she developed seizures and was clearly beginning to suffer, we decided to put her down. Both kittens were female, and very petite in size. Both kittens also developed a bad respiratory infection shortly after bringing them home for the first time. I also have a male cat, about 2 years, that is perfectly healthy, and very intelligent and spunky. We have tried twice to have another cat in the house as a companion for our male cat. He gets along very well with other cats, and really has enjoyed the company of the female cats while we had them. It is very sad and frustrating to loose two cats to the same disease. The female cats were adopted from two different animal rescue organizations located in completely different states. The research available on FIP, and the conflicting Vet’s opinions is also a bit frustrating.

  11. Lee
    January 14, 2011 at 6:40 pm

    My 13 year old cat was diagnosed with Dry FIP in October 2010. He was given a conservative prognosis of 2 to 6 weeks. He’s still kickin’. We (My vet anmd I) decided to treat with cortisone, antibiotics, fluids and appetite stimmulants (actually a human anti-depresant. He did well for about 6 or 7 weeks, (although very finicky), so right before Christmas we gave another prednisone and antibiotic shot. He is still on appetite stimmulant and now subcutaneous fluids (lactated ringers) In the meantime, I have researched and am trying an elixir of fish oil, rescue remedy, liquid b-complex and C. I have supplemented with some of the more commonly named homeopathic remedies (please research- your cats symptoms may be different from mine). Today I started a non-vegetable liquid probiotic supplement- we’ll see. Am researching digestiv enzyme supps too. Aware of the controversy around steroids, I did ask vet about aspirin for inflammation. He said it could be done, (and absolutely consult your vet for dosage and okays- it is VERRRRRY easy to kill a cat by misdosing) but it is imperative for the coricosteroids to be out of his system before trying. As it is, with lots of wet and dry food rotations he is still interested in food, and clearly in no pain. He also loves my heating blanket (on low with a layer or two between it and him) or the heating vents for extra warmth. Today he even ventured outside- for about 5 seconds until he realized it is really cold! I hope this helps a bit, and that your baby is still going strong

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