Feline Infectious Peritonitis (FIP)


FIP and Coronavirus interrelationship

Q: My six-month old kitten was exposed to another cat who recently passed away from FIP. Marty has tested positive for coronavirus with a titer of 1:400. (Hope I'm writing this correctly. I received the information verbally, but I know the numbers are correct.) What might I expect for Marty's future health? Is there anything I can do for him to improve his chances of not developing FIP?


A: Laura-

There is no increase in the risk for FIV for cats who have been exposed to feline coronavirus and are exposed to a cat with FIP. This is a little confusing so here goes the best explanation I can come up with:

A cat who has never been exposed to feline coronavirus won't get FIP. Probably around 50 to 60% of cats in single cat households are never exposed to this virus because they miss being exposed when kittens and then have no contact with other cats. In most households with >3 cats, cats from shelters and cats from catteries the exposure rate is much higher, probably >80%.

A cat who is exposed to feline coronavirus and becomes infected has some risk of developing FIP. At this time it appears that feline infectious peritonitis (FIP) occurs when normal feline coronavirus mutates in an individual cat into a form of the virus capable of causing FIP. The exact risk of this happening is hard to pinpoint but it is less than 5% and probably less than that.

So your kitten has a 5% or less risk of developing FIP. The 1:400 titer simply indicates exposure to feline coronavirus and does not help much at all in determining the risk that FIP will develop (except that it would be better if there were no indication of exposure at all).

I am not aware of any preventative measures that you could take to prevent the development of FIP once exposure to feline coronavirus has occurred. The good thing is that probably doesn't matter since the risk is pretty low, anyway.

I hope that luck and the odds work in your favor!

Mike Richards, DVM

FIP vaccine

Q: I am trying to decide whether I should continue getting the FIP vaccination for my four cats. I recently took one of my cats to a new vet who said that he doesn't give the FIP vaccine because a cat must have the genetic tendency toward FIP and there is a great deal of question as to how effective the
vaccine really is. I have also read your response to other various questions
about FIP.

The history of the cats in my household is:

Nine years ago, I got Callie (born to a housecat) when she was about 10 weeks
old; Two months later I got Jagger (adopted from an animal rescue group) when
he was about three months old. Callie has been basically quite healthy;
Jagger has had some odd infections over the years but has also been basically
healthy. One situation occurred when he was about two years old - to make a
long story short, he was sick and the vet ran tests for the possibility of
FIP. The tests came back with some positive results but the vet felt that
Jagger likely only had a regular corona virus rather than FIP. That was about
seven years ago, so, of course, we assume he did not have FIP.

About four years ago, I added Lily (a stray) to the household, then one year
ago I added Prince (also a stray).

Callie, Jagger and Lily have always received the FIP vaccine but it was Prince
whom the second vet said would not be vaccinated. Callie and Lily are indoor
cats while Prince and Jagger do go outside.

I guess my question is - should I consider stopping the vaccinations for
Callie, Jagger and Lily? Since Jagger likely had a corona virus when he was
about two, I assume that my other cats have been exposed. The literature I
have read says that the FIP vaccine is not effective for cats that have
already been exposed to a corona virus (as many cats have) because the vaccine
doesn't stop FIP itself but rather the corona virus which then would have to
mutate in an individual cat in order to develop into FIP. I've also read that
there is some possibility that the FIP vaccination could actually make a cat
more sensitive to a corona virus.

I admit that part of my decision comes down to money - I am more than willing
to give my cats the vaccinations that will do them good, but if they have
already been exposed to the corona virus and the FIP vaccination won't do them
much good, then it seems a waste of money to continue to get them vaccinated
for FIP.

A: Marilyn-

We do not use the FIP vaccine at all in our practice but there are a few circumstances in which it probably makes sense. You are already aware of the major issues concerning the vaccination but I want to explain our logic so I'll probably review them a little. This is the situation with feline infectious peritonitis, as we currently understand it:

1) The feline enteric coronavirus mutates randomly in cats and it can mutate into the form capable of causing FIP but this only happens in a small percentage of cats who have been exposed to coronavirus.

2) The vaccination appears to work reasonably well (but not perfectly, protecting about 75% of cats who could possibly be protected by vaccination) if it is given to cats PRIOR to the time they are exposed to feline enteric coronavirus. It does not work to prevent FIP if the cat is already infected with feline enteric coronavirus. For this reason, it is probably best to check titers for feline enteric coronavirus before starting a vaccination program for FIP and to only vaccinate cats who don't have titers.

3) You can't go back and start again, because the FIP vaccine induces titers to feline enteric coronavirus fairly often.

4) In the initial studies some cats who had been vaccinated had worse reactions when exposed to FIP virus but it is not clear if this occurs in real life situations --- and the current thinking is that it probably doesn't since there hasn't been a lot of problem with this during the years the vaccine has been used. Still, it does raise concerns about using the vaccine.

5) FIP is pretty rare in housecats who are not exposed to other cats, occurring in roughly 1 in 5000 cats in this situation. FIP is fairly common in catteries in which feline coronavirus carriers are present, occurring in about 1 in 20 cats in this situation. It is hard to figure out exactly how this relates to your situation but the risk to your cats would be lower than in a household in which there was constant movement of new cats in and out of the household and higher than a single cat living alone in a household. To put this in perspective the usual recommendation is to keep cats in groups of three or four, or less, to limit the risk of FIP. You have that situation but the inside/outside status of two of the cats compromises it a little.

6) You have at least 1 cat who may be a carrier of feline enteric coronavirus. It is likely that all the cats have been exposed given their histories (strays) and exposure to Jasper. Whether they were exposed prior to vaccination or after is not possible to determine.

7) A genetic tendency to FIP has been identified by researchers at the University of California at Davis (Dr. Pedersen and others). How strongly FIP is associated with genetic tendencies is difficult to calculate, though.

8) FIP vaccine appears to have low risk with no major risk problems identified with its use to date, unless you count the induction of titers to feline enteric coronavirus as a risk, since it can be confusing.

9) Natural immunity to FIP appears to occur based on the age distribution of affected cats. The majority of cases of FIP occur in cats less than 6 to 8 months of age and it becomes pretty uncommon when cats reach 2 years of age, making a slight comeback when cats get very old, presumably due to immune system difficulties due to aging and the presence of other illnesses.

My take on all of this is that it is doubtful that the vaccination is likely to be really helpful in your situation and I would lean away from using it --- but it is probably possible to interpret all of this information and come up with reasons to vaccinate, since some of the decision making involves guessing risks (were the others exposed prior to vaccination? how many other cats do they run across outside? how long does the vaccine confer protection? (no one seems to know this one)

I hope that is helpful. I would be glad to try to attempt to clarify anything that is confusing.

There is a pretty good site with FIP information at http://www.winnfelinehealth.org/health/FIP.html

Mike Richards, DVM

FIP- the effusive or wet form

Q: Would you know why there is an accumulation of fluid in the abdominal cavity? Thank you. What exactly is peritonitis? Jill

A: Jill-

The fluid that accumulates in cats with the effusive (or "wet") form of feline infectious peritonitis (FIP) comes from inflammation of blood vessels that allows them to leak. It is a reaction in the same family as the one that causes hives. In the case of FIP there is a severe immune system reaction to the virus that is ineffective in killing it or controlling it. If this reaction is primarily of the portion of the immune system that produces antibodies the cat will develop the effusive form of FIP. If the reaction has a stronger cell-mediated (CMI) component the virus is contained better and the cat usually develops the non-effusive form of FIP. Both forms are usually fatal so there isn't a big advantage of one over the other, unfortunately.

Peritonitis is infection of the peritoneal cavity --- or the abdomen --- as it is the area enclosed by the peritoneum. FIP is poorly named. It is a disease that affects all body systems. It is just that the effusive form was well recognized first and the fluid accumulation is most visible in the abdomen -- hence the name infectious peritonitis.

Mike Richards, DVM

FIP Exposure in a Cattery or Shelter.

Q: Hello Dr. Richards,
It's me again, Joan, I volunteer for a rescue group here in Orlando, Florida. A serious discussion arose recently when some of the volunteers suggested that we establish a cattery for the shelter cats. We currently keep our well cats in cages but since we are so small, they are in the same building with dogs. It is noisy and hard to clean thoroughly since I am an older gal and I can't move the cages as easily as the younger gals can. Our sick cats are of course kept in a separate building in quarantine and they are not a problem. Many of our cats come from Orange County Animal Services and arrive sick. Once they are thoroughly recovered from their upper respiratory conditions they are moved to the other building. We have the help of two veterinarians and so our animals are well cared for, we spare no expense, after all the money is generated by the animals in the first place, it's theirs, not ours. The heated discussion was regarding FIP. One of the volunteers had two cats she lost to FIP and she said that we would be putting our healthy cats at greater risk as FIP is very hard to diagnose and stress intensifies this fatal illness. Other volunteers argued that the occurrence was so slim that it was not that probable. One of the other volunteers lost a cat to FIP as well. We all agreed that we would find a favorite veterinarian and ask for opinions. I wrote to my sister's vet but I felt I need to take back at least two opinions since it was my idea in the first place to consider a cattery. I know nothing about FIP so I want to do the right thing. And so, my question is:

If you operated a rescue where you took in cats from various sources and didn't know that much about their background, except that they were all tested for FEV/FIV and you knew they were negative for those, and, you are such an effective rescue that your cats rarely stayed in your shelter more than thirty days before being adopted, and you provided a number of litter boxes to a multi cat group of around twenty or so cats, would you consider a cattery where they could move freely about in a large area, jump, get exercise and have the opportunity to be social with other cats? Or would you simply build a separate building (for us it would be something like a free standing shed)?

Joan, A New Beginning Pet Care & Rescue, Inc.
Orlando, Florida  http://www.anewbeginning.petfinder.org

A: Joan-

I'm going to cheat on your question. I think that you should buy a book that discusses this topic in some detail and provides strategies for dealing with multiple cat households and explains things like quarantine periods, vaccine programs, etc. It is "Feline Husbandry, Diseases and Management in the Multiple Cat Environment" by Neils Pedersen. If you read this book carefully you will find a lot of information that is useful. You do have to read the whole book because the really useful information tends to be scattered around in the text and you have to sometimes think about how it applies to your situation --- but it there and it is a good reference.
But just so you have a fast answer, this is the situation with FIP as best I can explain it in a brief format:
FIP is caused by a mutation of the intestinal corona virus of cats.

Almost all cats in group situations end up being exposed to the intestinal coronavirus. Therefore, the risk for cats living in groups of five or more is significantly greater than for single cats or two cats living in an isolated household.
The risk increases because exposure to coronavirus becomes almost totally inevitable and because there is a greater chance of a hot mutation of the virus that can spread from cat to cat in the group.

Even though the risk of FIP in the group becomes higher, it is unlikely that you would see an epidemic of FIP that would wipe out a whole group. What you are most likely to see are periodic FIP deaths of one or two cats as mutations to the corona virus occur.
It is possible to avoid FIP transmission by keeping the cats caged and practicing careful sanitation, like using paper towels instead of wash rags and throwing them out between cats, washing hands between cleaning each cage, no sharing of food bowls, etc.
The question then is, "Is living life in a cage to avoid the risk of FIP better than taking a little risk for a life that is more interesting and satisfying?" My best guess is that most cats would choose to have interaction with other cats. If you manage the introduction and maintenance of the colony carefully you can minimize the risk and maximize the benefits.
It really is worth buying Dr. Pedersen's book before you build.

Mike Richards, DVM


FIP testing, shelter situations and FIP exposure.

Q: Dear Dr. Mike,

I read with interest your previous writings on FIP (and just received your latest article). There is        so much confusion, it seems, in both the veterinary community and the general population concerning this disease.I have been involved with cat rescue work for several years and am now involved with an animal welfare organization and adoption center.  I would very much appreciate your advice regarding the following situation:

My friend Ed began fostering two stray kittens last October.  The female kitten, Jackie, was taken in as a newborn and given to Ed when she was approximately 3 weeks old.    Ed was told that her sibling had died of unknown causes (perhaps an over-the-counter flea product). Roy, the male, was between 3-4 weeks of age when he arrived at my house.  After several days Ed and I decided to assume the risk of putting the two kittens together, rather than deny the kittens the opportunity to interact with others. Aside from a 10 day stay in my home in November, when Roy and Jackie were housed with a litter of my other foster kittens, the pair never shared a litter box with other cats.  (In this less-than-perfect world, there are never enough foster homes to go around.) Ed has two older cats, but because of the health of his senior cat, who is FIV positive and in kidney failure, Ed limited the kittens' interactions with the adult cats and maintained separate litter boxes for Roy and Jackie. The kittens always appeared healthy, although Roy was on the small side, and they had chronic diarrhea.  Eventually, the diarrhea was cleared up with Flagyl after giardia was suspected.  The kittens received their first FVRCP shot on 2/12/01.   One week later, Jackie developed a fever that subsided within a day. After their second vaccination, Jackie's fever skyrocketed.  She was placed on prednisone.  The drug reduced her high fever temporarily, but it continued to return.  Within two weeks, Jackie's abdomen was clearly distended.  On March 29th, dear Jackie was euthanized due to what was clearly a full-blown case of the effusive form of FIP.

During her illness, Ed and I attempted to educate ourselves about FIP as much as possible.  I knew from an earlier experience (years ago) that there are conflicting ideas about the nature of this disease and how it should be handled. Your advice was among the most informative and useful.  But we still have some burning questions. We have wondered if prednisone hastened the progress of Jackie's disease.  Do you think that routine use of a steroid would render a cat more suspectible to FIP by compromising the animal's immune system? As an aside, since prednisone was given to relieve what was thought to be a vaccine-related fever, do you recommend that prednisone be used in that fashion, since another way of looking at the situation would be that the body was launching a response, as it should, to the vaccines?

Roy was with Jackie until she was diagnosed with FIP. He was then separated in Ed's home from both Jackie and Ed's two other cats.  For the past 2 weeks, Roy has been in another foster home as an only kitten. As he is a somewhat shy kitten, and he clearly thrives in the company of other cats, the move was a big adjustment for him. At this point in time, Roy is doing better, although his foster mom feels he is undoubtedly lonely. How concerned should we be about the impact of the stress of Roy's move on his susceptibility to FIP?  Roy is now six months old.  Should we postpone neutering him for awhile?

What would you recommend in terms of Roy's future placement? We would clearly prefer to place him with another cat. He is a very rambunctious kitten and being alone is difficult for him. Do you feel there is a reasonable period of isolation for a cat exposed to FIP, after which it is safe to place that cat with other cats?  It seems that for some individuals, including some vets, exposure to FIP marks a cat for life. Some people have stated that Roy is a carrier of FIP if only because he has been exposed to the corona virus that has the potential to mutate and develop into the FIP virus. As volunteers for a cat adoption center, we would also like to help educate our organization concerning these issues. (Our space is cageless.  Does this provide another twist to the issue of whether a cat exposed to FIP should be brought into our center?) Although you have covered this issue before, would you please confirm that you do not recommend titer testing for a cat that shows no clinical signs of disease? It seems to me there is no point in testing Roy, unless there is some reason to believe that his several months long exposure to Jackie possibly did not expose him to corona viruses.  Some people would argue for a "base-line" titer test, by which to compare future tests.  But again, isn't it true that titer levels can vary over time for a variety of reasons? Thank you in advance for responding to my questions.  A little black kitten's future is hanging in the balance.

Sincerely, Cindy

A: Cindy-

I am not aware of any studies that would help to resolve your questions about prednisone usage as a contributing factor in the development of feline infectious peritonitis (FIP). Based on the current theory of mutation of feline enteric coronavirus to become the FIP virus I think that it would

If a cat has never been exposed to feline enteric coronavirus (FECV) it won't develop FIP. So if a cat owner has a household that is free from FECV there would be an increased risk to the resident cats when a cat who is carrying feline enteric coronavirus is placed in the household. The increase in risk is not huge but it does have to be considered in decision making. If a cat in the household goes outside or if there are going to be other additions to the household, it is much harder to keep exposure to FECV from occurring. In theory, testing for FECV using the standard serology tests could at least give some hint as to whether a cat has been recently exposed to FECV or if it might be a carrier but would not be a foolproof test. So negative cats could be placed in negative cat households and positive cats in positive cat households. This is the only use of the current "FIP" tests that makes sense to me, although I guess you can make a case for testing obviously sick cats just to get some idea of the likelihood of FIP.

From a practical standpoint, if you have a no cage situation in which more than 7 to 10 cats are exposed to each other on a daily basis the odds are so high that you have FECV in your shelter, or will get it shortly, that there is very little value in screening tests.

I would adopt a cat that had been exposed to an FIP positive cat if it did not show signs of the disorder within a month or two. My cats were all strays prior to coming to our home and I pretty much assume they have been exposed to FECV, though. It would be really hard to restrict adoptions to FECV negative cats since so many cats have been exposed to FECV.

Most cats gradually stop shedding the FECV virus over time (several months) but there are cats who appear to be lifelong carriers. Despite this, there is not an FIP carrier state that I am aware of. A cat that has been exposed to a cat with FIP is very likely to have FECV exposure but is not any more likely to cause the spread of FIP than any other cat who is FECV positive and about 70% of cats from shelters are reported to have been exposed to FECV.

I can not see how a shelter would justify testing for FECV unless the testing is somehow acquired at a really low fee. There are too many other good uses for the money in a shelter when it can be presumed that it is impossible to keep FECV out of the shelter unless you are going to test all cats and refuse to handle FECV virus positive cats. That would involve turning down a big percentage of the cat population, though.

If I missed one or more of your questions, please feel free to ask them again or to ask for clarification on other points.

Mike Richards, DVM

Feline Infectious Peritonitis (FIP)

FIP is a difficult disease to diagnose and to treat. Testing for this disease is not very accurate and the clinical signs are easily confused with a number of other diseases. The disease does not appear to affect all cats exposed to it in the same way. The only certain diagnoses are made at the time of a necropsy exam (autopsy). This makes FIP one of the most frustrating diseases for veterinarians and their clients.

FIP is caused by a coronavirus. There are other coronaviruses that affect cats but that do not produce feline infectious peritonitis. The most common of these are the feline enteric coronaviruses. The antibodies produced against these other diseases are too similar to FIP virus for current tests to be able to distinguish between them. This is the difficulty in making a definite diagnosis of FIP. To make matters worse, a negative titer (no discernible antibodies) to FIP does not rule out the disease. There are several possible explanations for this but it is not uncommon for cats to have negative FIP titers when the disease is present.

Feline infectious peritonitis is probably the most common cause of unexplained fevers in cats. It can cause a number of other signs, as well. Lethargy, weight loss, eye disease, swelling of the abdomen or fluid in the chest can all occur with FIP. Many secondary problems, such as liver or kidney disease can occur with FIP. Any cat with fevers that do not respond to antibiotics should be considered as a candidate for this disease. In any chronic illness in cats for which no other cause can be found, FIP should be considered. There are two commonly recognized syndromes associated with feline infectious peritonitis. In the "classic" FIP case, fluid accumulates in the abdomen and it can become quite distended. This is known as the effusive form of FIP. The abdominal distension does not appear to be painful. The other recognized syndrome is the "dry" form of FIP, in which the symptoms of fever, weight loss and other clinical signs develop but there is no fluid accumulation. This is the more common form of the disease.

Not all cats that are exposed to the FIP coronavirus will develop the disease. In colonies of cats in which this disease is known to be present, estimates are that 8 to 20% of cats exposed to the virus will develop clinical signs of FIP. The rest of the cats may become immune to the disease or may simply not react to it. The reason that only a relatively small number of cats exposed to the virus develop the disease is unclear. It is known that the cell mediated immune response is the primary protection for the cat's body in the case of FIP. Cats that do not have a good cell mediated response may be more susceptible to the disease. The humoral (antibody) defense system actually enhances the damage caused by FIP virus and seems to be partly the culprit in the death of affected cats.

The "war" with the FIP virus is won or lost at the places it seeks to gain access to the body. The cellular immune system consists of the white blood cells that find and destroy pathogens. If a cat has a competent cellular immune system, it has a good chance of becoming immune or of becoming a carrier of FIP with no apparent symptoms. If the white blood cells fail to find and kill the virus where it seeks to enter the body through the nasal passages and oral tissue, then the humoral (antibody) immune system takes over. Unfortunately, it appears that the complexes of antibody and virus (antigen) that develop are very harmful to the body. The immune response appears to be the cause of death in FIP cats since cats that can not mount an effective antibody response are not affected by this virus.

FIP virus itself lasts in the environment for up to 6 weeks. It is easily killed with disinfectants, so careful cleansing of a household may help prevent the spread of the disease if a cat with FIP is identified in a household with more than one cat. Due to the delay in the appearance of clinical symptoms once infection occurs, it is likely that most cats in a household have been exposed to the virus by the time it becomes evident that one of the cats is sick. Reducing stress levels by resisting overcrowding of cats in a household, providing adequate litterpans and vaccinating for other diseases may be helpful in reducing the spread of FIP as well.

Once the FIP virus gains access to the cat's body it takes about 2 weeks for the virus to become widespread. After that, the length of time to clinical symptoms is variable but probably rarely exceeds 2 months. Most cats with FIP will die within 2 to 11 months from the damage caused by the virus, the immune system and secondary problems such as kidney or liver failure. An exception to this might be cats that are able to fight off the disease at the cellular level but never completely clear it from their bodies. It is possible that these cats are carriers of the disease and that they may be affected later in life if some immunosuppressive disease or event inhibits their ability to keep the FIP virus in check.

It is possible to measure antibodies against coronaviruses in cats. This is the "FIP test" that is commonly available. Unfortunately, the cross reaction with other coronavirus antibodies makes it very likely that there will be antibodies found, sometimes in high levels, whether an FIP infection is present or not. To further complicate matters, it is not unusual for cats with FIP to have negative antibody titers because of antigen/antibody interactions, exhaustion of the ability to produce antibody, or other factors. When cats have the "effusive" form of FIP in which abdominal fluid accumulation occurs, the thick, straw colored fluid has characteristics that strongly suggest FIP. It is possible to run a more specialized lab test, a polymerase chain reaction test for FIP, on this fluid. This type of testing is more accurate than FIP antibody testing but still is not definitive. Blood tests to compare the various protein levels in the blood can be very suggestive of FIP infection, as well. High immunglobulin levels are very suggestive of FIP in the presence of clinical signs. Despite all of this, there is no clear-cut way to make a sure diagnosis of FIP prior to death. There are many instances in which the clinical signs and supportive labwork make it very likely that this disease is present and it is possible to be reasonably certain that FIP is the problem in many cats. It can be very very difficult to rule out FIP, though. Cats exhibit widely varying clinical signs of this illness and lab results can be completely inconclusive. It may be impossible for your veterinarian to tell you that FIP is definitely not the problem and it is easy for a veterinarian to overlook this disease when the clinical symptoms strongly resemble another problem.

There is no treatment that has been proven to work on a consistent basis for feline infectious peritonitis. Aggressive treatment of the secondary problems and suppression of the humoral immune system with corticosteroids or other medications may be beneficial in prolonging the lifespan of cats infected with this disease. There have been reports of recovery from FIP infection in a limited number of cats. Newer anti-viral treatments have not yet proven to be successful in cats in clinical situations but work continues and there is some hope that effective treatment will one day be possible.

There are two ways to prevent FIP infection. Strict sanitation and isolation of infected cats and all susceptible kittens from each other is one approach. Vaccination is the other. Sanitation appears to be a major factor in preventing the spread of this virus. In catteries with known FIP exposure, it is possible to severely limit the spread of the disease by keeping kittens isolated from adult cats after the age of 6 weeks and following good sanitary practices. As noted previously, this virus is susceptible to most disinfectants. If kittens are not exposed to other cats in the household after six weeks of age, there is a very good chance that they can avoid infection. Once they go to a home where they are the only cat, there is little chance that they will be exposed to the virus. Vaccination for FIP is a controversial subject. Studies done at Cornell University with the new vaccine seemed to show that it was not very effective and that it may even sensitize some cats to the disease. The manufacturer of the vaccine, Pfizer, believes that the study was flawed by the severity of the viral challenge used. The increased sensitivity to FIP does not appear to occur in clinical situations, at present. The decision on whether or not to vaccinate is a difficult one. The best approach is to assess the risk of infection with FIP for an individual patient and make the decision accordingly. It is unlikely that an individual housecat will be exposed to the disease and vaccination probably does not make sense for these cats. It is much more likely that cats in a large cattery will be exposed and vaccination makes more sense in this situation. Even in this case, strict isolation of kittens from infected cats would be necessary until the entire course of the vaccine is administered, to allow the vaccine time to work effectively prior to exposure to FIP virus.

Feline infectious peritonitis must always be considered in cats with persistent fevers or vague histories of "not doing right". In multiple cat households, it is worthwhile to confirm the presence of this problem through post-mortem examination (autopsy, necropsy) of cats that have died. Knowing for sure that it is a problem will help a great deal when mapping out a plan to eliminate it from a cattery or household. If other problems are the cause of death, knowing that will help as well.

FIP is among the most complex of diseases to understand. There will continue to be controversy surrounding the prevention, treatment and diagnosis of this disease.

Michael Richards, DVM

DNA - PCR test for FIP, vaccination for FIP

Q: Dear Dr. Mike,

I spoke with my vet tonight about my Siamese cat, Prissy, and her positive DNA test.   He said the test was not the ELISA test but it was the DNA-PCR test.  (This whole mess is starting to drive me crazy!) Anyway, he told me that THAT test does indeed pick up the FIP virus and that Prissy does have FIP.  Then he told me that it is not until Prissy gets sick that she will begin to shed the virus and thus endanger my other three cats.  With that said, he then recommended my other three cats get the FIP vaccine with a booster three weeks afterwards.  That way, he said, if she gets sick, and he admitted she may not because FIP is not a death warrant necessarily, but if she should get sick the others will be protected.  (He even offered a multiple cat discount of 50%!).  I told him that I had read where the vaccine isn't all that good and he said although the subject of FIP is very controversial, the vaccine itself is very good.  I forgot to ask him if he thought her positive test result could be from her having had the vaccination.  I will call him Monday about that.  Right now, I just really don't know what to do.  Will I be jeopardizing my other cats if I have them vaccinated or will I be jeopardizing them by NOT having them vaccinated?

Thank you for your time in helping me with this matter. Donna

A: Donna-

There will always be disagreements among vets but I think that I can tell you these things based on the literature and information available online either on the Veterinary Information Network or the NOAH database:

There is not a specific test for FIP at this time. Just about everyone thought that the FIP-PCR test was going to be the answer to FIP testing but it is apparent after field use that it does not distinguish between feline enteric coronavirus and feline infectious peritonitis virus. The reason that this test should have worked, in theory, is that it can be done on fluids in the abdomen and on virus that is in the blood stream. It tests directly for the virus, so it seemed logical that it would pick up only virus that was in the systemic circulation (or in fluid in the abdomen outside the intestines) if the sample came from the blood (or body fluids). Since the difference between feline enteric coronavirus and FIP virus was thought to be the ability to pass from the intestines into the body, it seemed like this test would be conclusive for FIP. The fault in the logic was simple -- there had never been a test that was this sensitive so no one ever realized before that feline enteric coronavirus does sometimes get carried into the systemic circulation in the white blood cells. This is enough to make the PCR test positive. So we are back to square one.  All we have are tests that can tell us that cats have been exposed to feline corona virus.

The second thing that is hard to understand is that almost all cases of FIP appear to start out with feline enteric coronavirus infections. This virus usually causes no harm and many cats are infected with it. The feline enteric coronavirus is prone to mutating, though. Some of the mutations become capable of living in white blood cells and thus getting into the general circulation (systemic circulation) and other body tissues. These mutant feline coronaviruses are referred to as FIP viruses.  In a small number of cases one of these viruses will be contagious to other cats, based on very high instances of FIP occurring in small outbreaks in some catteries or multiple cat households. In most cases, the FIP virus is not directly contagious. Most cats have feline corona virus and then make their own mutations. So the fact that your cats have been exposed to feline coronavirus means that they have a very small chance of developing FIP. Statistically, though, their chances of getting it are not much higher than a random sampling of cats.

FIP vaccination is not helpful at all in cats that already have feline enteric coronavirus. It can protect cats that have never been exposed to the virus and/or do not currently have the virus from becoming infected with feline corona virus but once cats are infected, there is no advantage to the vaccine. So it is not likely to help in a situation in which cats have been exposed already to feline corona virus.  That is very likely to be the case for your other cats.

There is no way to diagnose FIP with certainty without histopathologic examination of tissues, either from an biopsy or from a post mortem examination. There are cats who are diagnosed with FIP based on clinical exams, positive serology and other lab work, such as protein electrophoresis which can be helpful in pinning the diagnosis down, but it is never certain that these cats have FIP until tissues can be obtained for examination by a pathologist. I honestly think that the cats who are reported to live through FIP infections probably do not have it, although it is possible that your vet is right and we simply don't know enough about the infection to be able to figure out that some cats live through the infections.

I know that this is confusing for you. FIP is a very confusing disease and it is not completely understood by anyone that I know. I think that you will probably find that Prissy does not have FIP but that can't be guaranteed.  The odds are just in your favor.

Mike Richards, DVM


Feline infectious peritonitis (FIP) and feline coronavirus (FeCoV)  in multi cat household - isolation and waiting to check other cats

Q: Dear Dr. Richards,

Thank you so much for your reply to my questions re:FIP. Your
information was very thorough and very helpful to us. I have a couple of follow-
up questions that I am hoping that you may be able to clarify.

You had said that th FeCoV virus is usually passed by contact with the stools of infected cats. We were told to wash out the cat bowls (ceramic) with bleach and water and to throw out everything of Huckleberry's that we could (carrier, pillow, toys, etc.). That made me think that the virus was transmitted from infected cats by other body fluids as well. Is that correct? Huckleberry had a very bad respiratory infection and was sneezing alot. They did do a cytology culture of his nasal mucas (when they were considering a feeding tube) and found it to be only a normal respiratory infection. Does that mean that his sneezing was probaly not speading the FeCoV virus?  We have a cat who has Cerebellar Hyperplasia and can not use her back legs. Although she spends most of her day in the same room/s as our other cats (with Huckleberry before he was isolated), she does not use the litter boxes (can't get to them or in them). She is feed seperately and sleeps by herself in large metal crate. Does that mean that her risk of exposure to FeCoV from Huckleberry was minimal?

You had mentioned that the most dangerous period for our current cats was during the first 2-4 months after exposure. We isolated Huckleberry in a room by himself (we wore hospital gowns and used disposable gloves) the second week in Nov. I know that you can't tell for sure, but is that when you would start counting from? We did not throw out all the liter boxes (ones that he had used prior to his isolation), although they were cleaned 2X daily and the litter is completely changed ever 2 weeks, until after Huckleberry's autopsy report (first week in Dec.) came back. Does that mean that most likely we would start counting at the end of the first week in Dec.?

As I read your answer I think that you were saying that there were two threats to our remaining cats; having been exposed to FeCoV from Huckleberry and continued contact to other of our cats that may have become FeCoV carriers. Is that correct? Is there any way to test to see if a cat is a FeCoV carrier? Do all FeCoV carriers eventually develop FIP themselves? Am I correct in understanding your message to me that if we don't have another outbreak within a year then probably none of the cats (even if they had only suppressed the virus and had become carriers) will come down with FIP from exposure to Huckleberry?

We have been thinking about how to monitor our other cats (since the FIP symptoms are so vague until the cat gets very sick). When we first brought Huckleberry to the vet (he had lost some weight) all of his blood work was normal except that his globulin level was very elevated. I was thinking that I might have blood work done at our cats annual exams or if I have particular concerns about any of them (one of other our cats has lost some weight--however, she had put on weight while on elavil, which she has come off, and is now on a high fiber diet (OM) --her energy level seems fine, but I wanted to be sure that the weight loss wasn't from FIP) and check to see if the globulin level was high. That of course didn't give us a differential diagnosis with Huckleberry, but since I know that they have been exposed to FeCoV a high globulin level might suggest that I have another sick cat. Do you think this might be useful?

Finally, we had been told that we should consider not adopting any other cats since our house has had an incidence of FIP (we have no current plans to add any animals, but I am sure that at some point, especially as we lose some of our current cats, it is something that we would consider). In your answer to me you talked about the risk of reinfecting our current cats by adopting new ones. I think that the vet who suggested this to us meant that our house was not safe for other animals and was a risk to them. Is this your understanding?

Thank you again so much for your help with information re: FIP, and for all the excellant work that you do!!

Sincerely, Karen
A: Karen-

I think that there is still a lot to be learned about feline infectious peritonitis (FIP) and feline coronavirus (FeCoV). So there is some chance that what I think I know about these viruses at this time may be wrong. However, this is my current understanding:

Approximately 30% of housecats in "few" cat households have titers to feline coronavirus, indicating that they have been exposed to it and may be carrying it.  About 70 to 80% of cats in multiple cat households (more then five cats) have titers to feline corona virus, indicating that they have been exposed to the virus. So feline corona virus is very common.

Cats who develop feline infectious peritonitis have a mutant form of the feline corona virus which has developed the ability to penetrate the body's defenses and enter the tissues outside the intestine. This happens because the FeCo virus mutates within a cat and develops the ability to cause FIP.  It is though that this mutation process produces almost all the cases of FIP, although there are a few exceptions that seem to have been proven to occur, in which already developed FIP virus has been passed from one cat to another.

It is very easy to test for exposure to feline corona virus. The standard serology testing will pick up antibodies against feline coronavirus, measured as a titer. A positive titer indicates exposure to feline coronavirus and high titers may occur in infected cats. All of the currently available tests for FIP are actually FeCoV tests -- they can not discern an FIP infection from a feline enteric coronavirus infection. So if you were to test all your cats and all were negative for coronavirus titers and you kept them all separate from other cats forever, in theory it would be really unlikely that they would ever develop a positive titer. On the other hand, if one or more of them has a positive titer all that it means is that cat has been exposed to feline coronavirus.

Based on the history and the fact that many cats have had exposure to feline coronavirus, it seems to me that testing your cats is very likely to show that at least some of them have antibodies to feline corona virus. Since you can't tell from that if any of them will ever actually develop FIP it doesn't seem to be worth doing the testing, to me.

Even though it is likely that one or more of your cats were exposed to coronavirus from Huckleberry, it is highly likely that none of them will develop FIP.  The virus they picked up would be feline coronavirus and the virus would still have to mutant again in the next cat for FIP to develop. While this actually happens (two or more cats in one household get FIP), it isn't a common problem. I also think that this makes it unlikely that a new cat exposed to your present cats would be at a higher than average risk of developing FIP, either.

My best advice would be to maintain a high degree of suspicion for FIP among your cats but not to try to test for it on a routine basis. There just isn't any test procedure that is specific enough for this virus to make it worthwhile, at this time.

Feline corona virus can be transmitted from oral or nasal secretions as well as passed through the feces. The virus lives longer in the environment when it is passed in the stool, though. It was an oversight not to include the oral to oral and nasal to oral transmission possibilities, as they are probably about equal to fecal to oral spread of the feline corona virus.

If I have just confused the issue more, please feel free to ask for clarifications again.

Mike Richards, DVM


DNA test for FIP, PCR test for FIP

Q: I need to ask about the DNA test for FIP and it's accuracy and it is urgent!

A: Donna-

If you are referring to the PCR  (polymerase chain reaction) test for FIP,it is not considered to be more accurate than standard testing in diagnosing FIP at this time. It is probably more sensitive for picking up exposure to feline cornoaviruses, ONE of which is the FIP virus. This is the problem with all tests for FIP. The feline enteric coronavirus is very common and it is estimated that about 80% of cats in multiple cat households will test positive for exposure to coronaviruses. The FIP virus, which is thought to be a mutant of the feline enteric coronavirus, will also cause a positive test but since so many cats test positive, it is hard to figure out the value of a positive test.

A negative PCR test is pretty good evidence that a cat has not been exposed to either feline enteric coronavirus or feline infectious peritonitis virus. This may be a helpful finding in a very sick cat, because the standard serology tests were sometimes negative even when a cat had FIP because they would get so sick they couldn't mount a titer even though they had been exposed.

At the present time, the best way to diagnose FIP with certainty is to test either biopsy or post-mortem tissue samples for the virus.

If this doesn't answer your question, or if  you need clarification of anything in this note, please feel free to ask for more details.

Mike Richards, DVM

Feline infectious peritonitis (FIP) and Feline coronavirus

(FeCoV)- finding a case in a multi cat household

Q: Dear Dr. Richards,

Thanks for your wonderful web site. It has been helpful to us a number of times to get more information about a condition one of our cats has. I am a new subscriber to your service and had a question that I wanted to ask.

We have a multiple cat (and 1 dog) household with a number of special needs cats. About two and a half years ago we adopted Huckleberry through a rescue group. He had lived with a family in an apartment complex and they left him outside when they moved. He kept trying to get back in as he knew it was his home, unfortunately the new owners didn't like cats and kept trying to drive him off. This happened in a town where the local pound does not accept cats (they leave them out to fend for themselves). We don't know how long he was out for before someone got him to a rescue group, but when we adopted him he was exhausted and very thin. His health seemed fine otherwise and he quickly put back on his weight. Huckleberry was healthy during the rest of the time that we had him.         

Late in October (2000) I happened to pick Huckleberry up and he  seemed thinner. Checking with our vet he had lost 1 1/2 lbs since his yearly check in May (2000). We have a phenomenal 24hr specialty/emergency center where we live. We brought Huckleberry there. His blood work was all normal except for an extremely elevated globulin level (9). We did the corona titer which was high (1:1500) but not necessarily conclusive. All other tests came back normal. Huckleberry developed a serious respiratory infection and at that point (about 1 week after testing) we isolated him in a room by himself. Huckleberry continued to rapidly get sicker. We brought him to the vets to have a feeding tube put in and he never made it home again. He started to develop respiratory difficulty, then his blood pressure and temperature collapsed (over a 5 day span from going in for the feeding tube). Huckleberry died about 4 weeks from the time we noticed that he had lost some weight (http://kspope.com/huckleberry/).

We had an autopsy done which confirmed that Huckleberry had FIP.

Our concern now is for our other cats. We realize that they have all been exposed to the FIP virus. We have spoken to a number of vets (all of whom concurred in their advice not to give the FIP vaccine) regarding the clean up in our home and have gotten very different information about how long the FIP virus is likely to remain active. We have heard everything from 6 weeks, to it will always be in the house and that we should not adopt other cats. Can you tell us what information you have about how long the virus may be active? One other question, I know that there is no certain answer regarding when our other cats might develop FIP (that it could be years). But is there is usual time period where we might expect to see it in our other cats?? That is if they were going to develop right away in response toexposure to the virus, how long before we would see symptoms?

Thanks again for your wonderful service and for any help that you can
give us with this.

Sincerely, Karen

A: Karen-

Feline infectious peritonitis (FIP) is caused by feline coronavirus (FeCoV), which also causes transient diarrhea and inapparent infection in many cats.  For many years it was assumed that there were two distinct strains of FeCoV, the one that caused minor disease and the one that caused FIP. At the present time, the prevailing theory is that the  FeCoV mutates in some cats, allowing it to live and even reproduce inside the white blood cells (in this case macrophages) of some cats. This gives it two advantages, it can sometimes survive despite the immune system's efforts to get rid of it and it can be transported out of the intestinal tract and into the rest of the body by wandering white blood cells. These allow it to cause severe systemic disease which is almost always fatal.  It seems clear that the presence of infection with FeCoV eventually leads to mutation of the virus in some cats, so they are not originally infected with a strain of virus that normally causes FIP, they just don't fight off the FeCoV virus fast enough to prevent a mutation from occurring that makes it become the FIP causing form of the virus. It is also apparent that the strains of FeCoV that can cause FIP can sometimes be spread from one cat to another, since severe outbreaks of FIP virus sometimes occur. How frequently the cause of an individual cat's FIP is a mutant from FeCoV the cat had or from FeCoV already mutated to an FIP producing form is hard to say. However, when there is a "pre-mutated" FeCoV virus infection, there are usually a number of cases in one household over the course of a couple of months, if there are more than four or five cats in the household.

Most cats that develop FIP are less than two years of age or over thirteen years of age. This is probably due to the fact that cats who live to be two years of age probably have immune systems that function well and are therefore able to control the mutant virus. The return of susceptibility after cats age is probably due to the development of immunosupressive disorders, such as diabetes, kidney failure, liver disease and cancers as cats mature, which weakens immune systems that were formerly functioning well. This brings out the first point that it is necessary to make regarding control of FIP.  Cats can be exposed to this virus and have sufficient immune competence to either eliminate it from their body or keep it suppressed to the point that they can live with it.  Cats that merely suppress the FeCoV viruses may be long term carriers. It is known that cats can carry the virus for long periods, at least a year and probably longer.

The coronavirus itself is not especially hardy in the environment but it can survive for as long as seven weeks in some situations. It is usually passed by contact with the stools of infected cats. If there were not carriers of the virus, who keep it alive in their body and spread it for long periods of time, you would be home free after a couple of months.

Since chronic carriers do exist, it can be very hard to eliminate this virus from a household once it has found its way in. Approximately 25% of cats living in one cat or two cat households have FeCoV when studies are done looking for it. In catteries, the rate is closer to 75% and approaches 100% if there are more than 10 cats at one location.  This brings up the next point that you have to consider in your situation. If you intend to continue adopting cats in rescue efforts it is going to be really hard to prevent reinfection of your household and eventually you will have to deal with FIP again. This is sort of a lifestyle choice. The only really good way to limit exposure is simply to quit bringing new cats into the household. This only works for as long as your present cats live, unless you decide not to replace them.  So for most people who have several cats, this choice is too restrictive and is essentially not an option. You have to live with the possibility that this virus will occur in your household, if you wish to continue to house multiple cats and to bring new cat into the household on occasion.

The risk from the exposure to Huckleberry will lessen over the course of about a year. If you have not seen an outbreak in your household by that time, it is safe to assume that new outbreaks are probably from new mutations of the FeCo virus in your group of cats. The greatest risk is in the first two to four months after exposure to a cat with FIP, so you are already getting out of the really high risk period, now.

There are some things that you can do to lessen the probability of an FIP outbreak in a multiple cat home.  Try to keep stress to a minimum. Keep an adequate number of litter pans, striving for 1 per cat + one spare, which isn't always possible. Feed a good quality food and try to stick to a regular schedule for feeding. Making sure that food aggressive cats don't bully the less aggressive ones during mealtimes by keeping them separate can be helpful. For most houses, keeping five or less cats will greatly reduce the stress levels. In households with more then eight to ten cats, the stress levels are high enough to consistently cause stress related behavioral and medical problems in most cases. Regular veterinary care is a good way to ensure maximum immune competence. Oddly, for this particular disease, isolation of new additions to the household probably isn't helpful, because the carrier state lasts long enough that practical isolation periods are not long enough to prevent infection.

Vaccination for FIP is still controversial among veterinarians.  The vaccine caused some problems in clinical studies that do not seem to occur in the "real world" but are very worrisome. The most severe of these problems being sensitization of the cat's immune system leading to a more severe infestation with FIP in some cats in lab studies. This has made veterinarians wary of the vaccine. The effectiveness of vaccination is hard to measure in clinical situations, too, primarily due to the fact that it doesn't do much for cats that are already exposed to the FeCo virus which we know to be the case in most group housing situations. However, there is some justification for vaccinating cats who have no titer to FeCo when they are going to be placed into a home known to have had FeCoV exposure, since these cats have probably not been exposed and therefore may gain protection from the vaccine. They do have to be isolated until the vaccination series is complete, too.  This is such a small group of cats who might actually benefit from vaccination that they are often overlooked.  However, it is something to consider if you are going to continue to do rescue work with cats and are willing to pay for FeCoV testing and to isolate cats for a while prior to introducing them to the other cats.

I know that was a complicated and probably confusing answer, so please feel free to ask for any clarifications that are necessary.

Mike Richards, DVM


Q: Hello,  Thank you for helping me.  Our family suffered a crushing blow when we lost the best cat we have ever had.  We are truly devastated and desperate to experience that love again.  We have three other Persians but they are not very responsive and loving the way our deceased cat was.  We were hoping to adopt a ragdoll cat as that personality is what we need.  However,  our beloved cat died of FIP at 13 after a very long struggle with renal failure.  All our cats are indoor so this disease was unexpected.   One of our cats had an "unexplained" fever a few years ago but the rather extensive tests showed no cause and her recovery was dramatic and complete.  Another cat had a fever, vomiting, and lack of appetite.  He was tested for everything and showed a FIP titer of 400. He was tested again and the titer remained exactly the same.  He also made a very complete recovery.  Do we have a hope of adopting a kitten if we wait several months and engage in other precautions?  Is the punch (DNA) FIP reliable enough to make it worthwhile?  Is is likely our other cats will get FIP?  Thank you or dealing with such a lengthy  letter, but we are so very concerned.

A: Simone-

Feline infectious peritonitis is caused by a mutation of the feline enteric coronavirus and probably also requires immune susceptibility on the part of the affected cat. Approximately 30% of "housecats" and approximately 80% of cats in catteries (from breeding establishments) are infected with feline coronavirus. The great majority of these cats never develop FIP, so the susceptibility to this infection is low. Therefore, it is likely that you can bring a kitten into your household with very little risk of it developing FIP,  but if the remaining cats have coronavirus there will be a small risk at any time that you chose to add a cat to the household.  This is a small enough risk that it is reasonable to take, in my opinion.

None of the current tests for FIP accurately differentiate the FIP mutant from the normal enteric coronavirus. Therefore, these are tests for coronavirus, not for FIP. Since we know that very many cats have positive coronavirus titers, this test has limited value as a diagnostic tool for FIP. If the diagnosis of FIP in your older cat was not made based on histopathologic examination of tissues from a post-mortem exam there is a reasonable chance that the diagnosis is wrong. However, your vet may have very good reasons to suspect it or the diagnosis may have been confirmed by histopathologic examination.

To summarize all of this, it is unlikely that your other cats will developFIP and it is also unlikely that a kitten you might adopt in the futurewill develop FIP by being brought into your household but it would haveslightly more risk of this than if it was brought into a household in which the cats are negative on serologic tests for feline coronavirus.  Not enough more risk that it would deter me from adopting a kitten, though.

Mike Richards, DVM


Michael Richards, D.V.M. co-owns a small animal general veterinary practice in rural tidewater Virginia. Dr. Richards graduated from Iowa State University's College of Veterinary Medicine in 1979, and has been in private practice ever since. Dr. Richards has been the director of the PetCare Forum...