Dear Dr. Pedersen,

I am reaching out to you as a concerned and confused multiple mixed breed cat owner. In December of 2012, I had four rescue cats. Jake and Joey were semi-feral siblings from a shelter (now about 4-5 years old). My oldest, Jordy, another rescue (about 8 years) and Jenks - a rescue kitten I found with herpes and in poor condition. Jenks was treated for herpes and has been healthy to date (now about 2 1/2 years old) except for a lingering chronic clear discharge from his sinuses. Jake and Joey had also developed brief minor herpes symptoms when Jenks initially arrived and also recovered. A year and a half goes by when my Jordy fell ill, not eating, high fever, retreating and hiding with weight loss. It took two different vets, and a lot of research on my own before he was diagnosed with FIP, as it is a rare disease here in the Pacific Northwest U.S. At first, Jordy presented with the “dry” form, but within a week of diagnosis it developed into the wet form and quickly progressed to the point where he had to be euthanized the following week. I was devastated - Jordy was by far my favorite and most special cat.

I began to read everything I could find on FIP, including the UC Davis and Dr. Addie’s sites.  I joined internet FIP support groups to gain more knowledge about other people’s experiences with FIP.  From these sources and communications I learned the commonly held belief that my chances were low that I would have another instance of FIP again, unless I was a breeder or a shelter.  I heeded advice to wait until the virus had cleared from my house, with the generally suggested “safe” time to be 2-3 months, and then adopted a mixed breed rescue kitten, Jerry, in May 2013.  Last month, he was neutered, after which he did not seem to be bouncing back like he should, sleeping more, scruffy coat and losing weight.  Of course I thought FIP, but dismissed it as paranoid – how could lightning strike twice at my house?  We thought it might be worms and he was treated for parasites. But then I noticed his gait was wobbly and unsteady, and I knew.  He was rushed into the vet and sure enough the blood work came back as strongly indicative of dry FIP with low A/G ratio, high WBC, high corona titer, and slight anemia.  He began having grand mal seizures and after his fourth in a 12 hour period, we had to make the decision to euthanize.  I am devastated, angry and feel responsible for Jerry’s death by bringing him into an infected house.  Now Jake has developed an upper respiratory infection, and is lethargic and sneezy with discharge from both eyes.  I am on my way to the vet tonight, which is a major stress ordeal for him being semi-feral.  It could just be a URI or relapse of the herpes virus, or could it be another case of FIP?  

I know that FIP is not thought to be contagious from cat to cat.  However, I have read countless examples of multiple instances of FIP in a single household just like mine amongst unrelated cats. When these multiple FIP clusters happen, the consensus is to discount it as just “being really unlucky” or a “probable misdiagnosis”.  It seems that there is critical misinformation being spread. My point from all this, is I am very concerned that the consensus message regarding the likely risk of FIP reoccurrence is underestimated.  I found this statement on your website:  “FIP losses occur as enzootics (disease occurs at a regular predictable rate) or epizootics (an outbreak affecting many cats at the same time at a frequency substantially greater than expected).  FIP losses are sporadic, unpredictable and infrequent in the enzootic form.  Catteries with enzootic FIP may not have any deaths for years, followed by several cases in rapid succession.  The disease may then disappear, only to reappear months or years later.  Overall mortality from enzootic disease over a 5 year or more periods is usually 1-5%.  However, epizootics of 3-49% have been observed in groups of kittens raised in one cattery over a 4 year period, and similar explosive outbreaks have been seen in several other catteries (Pedersen 1983a and Potkay et al 1974).”

This seems to be saying what I felt all along – that lightning did not strike my house twice (or as it now seems, three times).  It appears the risk was not 10% of developing FIP in my house, but a much higher percentage.  I understand there are no absolutes with FIP, but feel that it is imperative that the common belief that FIP is not directly contagious from one cat to another cannot be trusted.   I never would have brought another cat in my home if I had known the risk was significantly higher than with the general one or two cat household.  Would you consider making this risk clearer?  It would mean so much to me.   Thanks, Ms. Jenkins

Dear Ms. Jenkins:

Your situation is not unusual, especially since your cats were obtained when young from environments and situations where FIP is common. It is also known that many of these young cats actually have the disease in a subclinical form before they come into your home and may not show clinical signs for weeks, months and sometimes years afterward. Such subclinical infections may also be activated if something happens that stresses the cats. For instance, the FIP in one of your cats became clinically apparent after he was neutered. Although it is true that FIP usually occurs in an enzootic (endemic) form with a single case now and then, there are occasions when a cluster of cases are seen. The first impulse is to blame this on cat-to-cat transmission of the FIP causing mutant form of feline enteric coronavirus. However, when we have the opportunity to examine and genetically type the viruses that attack each cat in such a household we find that every virus is unique. This means that each of the FIP viruses mutated from a common enteric coronavirus within each cat, but in a different manner. In cases where there is cat-to-cat spread, which are rare and are often associated with a more canine-like form of coronavirus, the isolates from each cat will have identical FIP-causing mutations. Therefore, without actually isolating the viruses that caused FIP in your two cats and comparing their genes, it is impossible to say whether they arose from a common enteric coronavirus exposure, or if they were indeed FIP mutants that were spread from one cat to the other. The odds are that they were unique, but that there were other common factors that increased the incidence of FIP among your cats. As you may have read, many cats are exposed to mutants of enteric coronavirus that have the potential of causing FIP, but don’t get the disease. Whether they do so or not is often dependent on a number of other risk factors. When all of these various risk factors come together at the same time and in the same place, we have the equivalent of a perfect storm. All boats (i.e., cats) in the same vicinity will be put at similar risk, but it does not mean that all boats will sink. You must also remember two facts: 1) it is a statistical truth that uncommon events often occur in clusters and this applies to all sorts of traumatic events, and 2) when a cluster of anything occurs, people will take notice and spread the news, but when a single case occurs, it does not have nearly the same impact. 

You asked me to put actual numbers on the risk of multiple cats getting FIP in the same household, but that is impossible. Many groups of cats live together happily for lifetimes without getting FIP and some households have a more or less constant problem. Others, like yours, may only have one such incident in a lifetime of cat ownership. We often average the risk at from 1-5%, but in actuality it ranges from 0 to 50%, depending on the situation. We also do not understand exactly all the factors that go into making these “perfect storms” and the relative importance of each. I can only say that at this time we only understand three of them: 

1) the level, duration, and intensity of feline enteric coronavirus exposure,
2) age at the time of exposure with younger exposure equating to increased risk (remember that infection with FIP mutants can occur as kittens and disease only appear as adults, sometimes years later), and
3) genetic susceptibility.

The other factors are not so clearly defined, but we believe that stress (physical or psychological) also plays a role, but stress levels are hard to measure and often bear no relationship to the number of cats or husbandry practices. You also seem to want to blame the one cat that has chronic rhino-sinusitis as the culprit, but there is no evidence that such cats, which are also common among cats coming from shelters, catteries, and other such dense multi-cat environments, are any more associated with FIP than healthy cats. In fact, if you were to test for fecal enteric coronavirus shedding, you might be surprised that the healthiest appearing cat may be the highest shedder. I agree that the best way to educate people is to make situations like this one more available to the public. There is much to learn about an outbreak of this type. I hope that your third cat Jake turns out not to have FIP.

–Dr. Pedersen

Dear Dr. Pedersen,


I seem to have a FIP problem in my small home-based cattery. I read your excellent article “Understanding Feline Infectious Peritonitis” and I understand it better than I did before, but I still have lingering questions. My particular case may be of interest to you as there seems to be one horizontal (cat-to-cat transmission) in our case. I started my breeding program with two pure bred cats (Siberians) and bred them for 1 ½ years. The first three litters were healthy with no issues. I then acquired a second female from Russia and bred her with my male, and this is when the trouble began. I received a call with news that a kitten from this mating was diagnosed with dry FIP or intestinal lymphoma and had to be euthanized. As this was unfolding, my kitten from a different litter, (my sire and the new Russian Siberian girl), also became sickly with FIP-like symptoms. I received yet another call last night from a customer who has two kittens also from the same litter as this kitten I kept that is not well, with news that one of their kittens had developed what sounds like FIP symptoms and their vet had to euthanize. Lastly, another kitten I kept from my original sire and dam’s litter appears to be in good health except for an ulcer in the back of her mouth that is scheduled to be removed and biopsied. My cats are strictly indoors and share mutual space.

My question is if there is a test for my healthy cats to determine which cat could be the carrier and cease breeding this one, or is it necessary to start with all new cats? Any advice regarding my problem is most appreciated!

-Breeder, small home based cattery

Dear Ms xxxxxx.

It is not unusual to lose all or most of a litter from FIP. I suspect that the first kitten did not have lymphoma, but rather dry FIP involving the caecum and colon. This is a very specific form of the disease and resembles intestinal lymphoma. However one does not want to diagnose two different things when one will explain it and also GI lymphoma is not seen in young cats. The usual reason why a litter can be devastated with FIP is because they all share the same environment, genetics and history.

The virus that causes FIP is only spread from cat to cat in rare circumstances. Rather, the FIP virus is generated internally in each cat through the intermediary of feline enteric coronavirus (FECV) infection. FECV is ubiquitous among multi-cat environments and 40% or more of adult cats will shed the virus in their feces at any given time. Virtually all kittens are infected with FECV by 9 weeks of age and the infection is either unapparent or manifested by a transient diarrhea or loose stool. As you have read, the enteric virus must undergo at least three specific mutations to cause FIP, and two of these mutations are unique to each cat. When we do genetic analysis of the FIP viruses from littermates, we always find each FIP virus to be unique and therefore not spread directly from another cat. If there was direct cat-to-cat transmission the FIP viruses would be genetically identical. Although we cannot examine the viruses in each of these cats, the odds are that they each mutated to become an FIPV in different ways.

You have been subjected to what I call a “perfect storm,” where a lot of factors leading to FIP have come together at the worst possible time. Because they were littermates, they were all exposed to FECV at the same time and at the same level, they were genetically related, the exposure occurred at a similar age (the younger they are the more likely they will develop FIP as a consequence), and they are all exposed to similar external stresses that might affect their resistance. You can send feces from your older cats to IDEXX laboratories and confirm which of your cats are carrying the enteric coronavirus, but most likely a large proportion will be fecal shedders and the information will not prove helpful. This is no different than most catteries. Therefore, I suspect that other factors are also at play. The most likely is a genetic susceptibility and the recommendation in such a circumstance is not to breed these cats again, and if you do, not to each other. You also did not say how many cats and kittens you have in your cattery. The more you have, the higher the level of enteric coronavirus you will have in your cattery, and the more likely that you will periodically suffer FIP losses. I know that this is not want you want to hear, but this is my best reading of what has happened. Also, FIP is a strange disease and these perfect storms don't happen often. It is common for such outbreaks to suddenly occur and just as suddenly disappear. You then fearfully wait for the next perfect storm, which can be right around the corner or years away. I have always said that “if you breed enough cats for long enough, you will experience FIP.” You have now had your experience with the disease. Good luck, Dr. Pedersen

P.S. would you allow us to use your story and my answers in our SOCK FIP website. We would delete names and alter the story a little. Other breeders suffer similar outbreaks and it would be nice to share them. Also, you should read the "Synopsis of FIP", the updates on recent FIP research studies, and the 2008 paper on feline enteric coronavirus. - NCP