diagram explanation 

Feline Infectious Peritonitis (FIP) And Your Cat

What Happened, Why It Happened and What Will Happen
Feline Enteric Coronavirus (aka FCoV=FECV=FIPV)

Ron Hines DVM PhD

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 A test is available for the dangerous mutated form of this coronavirus 

Some years ago, Dr. Niels Pedersen’s suspicions that FIP was caused by mutations in the common cat coronavirus within your cat’s body was confirmed through advances in DNA sequencing. (ref) Although the research was conducted in the Netherlands, it was paid for by the US Government through NIH grants . These discoveries were confirmed by scientists at the Veterinary School of Cornell University through research supported by the NIH, Winn Feline Foundation, the Morris Animal Foundation and the NIH. (ref) This should lead to much better ways to diagnose FIP in your cat – particularly when the “dry form” is present. Perhaps, in the future, it will also give your veterinarian real treatment options for your cat as well. 

If you chanced upon this article looking for hope for your darling cat, I am afraid I cannot offer you a cure that your veterinarian did not tell you about (other than the potential 2016 treatment breakthrough that links through the box above). But if you would be satisfied with some understanding of what has happened to your cat, why it happened, and some solace in dealing with this tragedy; I might be able to help you a bit.

Peritonitis is an inflammation of the linings of your cat’s abdomen. When it is due to a specific coronavirus of cats, we call it FIP ( = feline infectious peritonitis = FIPV). Over time, the term became used to describe all forms of lethal coronavirus disease in cats. This virus is very unpredictable. Sometimes it prefers to cause inflammation of the cat’s chest and lungs, other times it causes chronic inflammation of its other body organs, sometimes it causes a little of all of these problems and sometimes (most of the time) it causes no serious health problems at all in your cat.

FIP may be the most common infectious cause of death in cats in the developed countries of the World. (ref) It gained that number-one status because vaccines have greatly reduced both panleukopenia of cats and feline leukemia and, as importantly, because the ways that groups of cats tend to be managed in the last 60 years favor its spread.

Feline Infectious Peritonitis occurs when a normally insignificant coronavirus of cats (FCoV) goes rogue. It affects only cats, wild and domestic. In its lethal form, it is what we call a sporadic disease – striking here and there – rarely twice in the same household unless cats are grouped there in large numbers. In its non-lethal intestinal form, it is extremely common in domestic cats. In some urban areas, up to nine out of ten cats had been exposed to it at one time or another. (ref) (I do not believe the number is actually quite that high, it goes up in multiple cat situations and those are the easiest cat samples for scientists to obtain)

The majority of cats that contract FIP are young – usually between three and sixteen month of age – with over half being less than a year old. In one 2014 California study, laboratory-bred cats developed an increased resistance to FIP between 6 and 12 month of age. If genetics played any part in their susceptibility to the disease, it was not apparent in that study. (ref)That said, FIP occasionally develops in an oldster.

Some Things About The Corona Virus Group and Corona Virus of Cats

Almost every species of animal, from mice to whales, have their own form of coronavirus.
All coronavirus are RNA virus. That is, their blueprints are carried as one or two spiral strands of RNA rather than the DNA that some virus contain. Since RNA is a pretty sloppy way to code information, all RNA virus’ have a high error (mutation) rate, which makes developing vaccines against them so difficult – they keep changing and outwitting us. (ref)

Coronavirus are large, as virus go. Feline coronavirus is about three times as large as the another RNA virus of house cat, feline calicivirus. (120nm vs 35nm) . The surface of all coronavirus have a characteristic fringe of club-shaped projections (peplomers) that resemble the crown-like rays of the sun (corona=crown).

Three animal coronavirus are very similar. They are the one that causes intestinal problems in pigs, the one that causes diarrhea in puppies (ref) and the coronavirus of cats. In dogs and swine the virus is continually mutating to overcome immunity that follows infection or vaccination. Pig coronavirus is thought to occasionally combine with dog coronavirus to form new strains. (ref)

In the diagram at the top of the page, you will see that coronavirus have spikes on their outer surface. It is the distal (outer tip) ends of these spikes where many important mutations are thought to occur. (ref) Another important coronavirus is the SARS virus of humans. (ref) Many of the concepts, now being explored by veterinarians to understand FIP were developed for studying SARS. SARS first appeared in a single farmer in China in 2002. It is suspected that it leapfrogged into humans from bats – possibly through some other intermediate animal. (ref)

Feline coronavirus circulates around the world in two major varieties (serotypes), called Type I and Type II. The most common of them is Type I; but most veterinary studies are performed with Type II because it grows better in cells cultured in the laboratory. Both of these Types seem to occur in two forms, a common low to non-dangerous (= low-virulent, avirulent) form, common in cats and a much less common lethal mutant form. In their non-lethal form, both types inhabit the cells that line your cat’s lower intestinal tract (colon). (ref) Sometimes, veterinarians refer to the virus as FCoV when it is in its low-virulent form and FIPV when it has gained the ability to leave the intestine and threaten the life of the cat. Most cats that develop the mutant FIP strain of the virus are between three and sixteen months of age. Type I is thought to be the base strain of cat coronavirus while Type II is suspected to be a “hybrid” between Type I and the coronavirus of dogs. (ref)

Because of persistent research, our understanding of feline coronavirus and FIP increases (and changes) from month to month. There is a great deal of disagreement, which is reflected in the confusing array of abbreviations and terms used to describe FIP and the coronavirus that causes it. Each research groups feels compelled to use terms or abbreviations not used by the others to show their degree of independent thinking and, perhaps, in penance (feeling guilty) for our inability to offer real hope to the owners of individual, infected cats.

Where Did FIP Come From?

We are not really sure. The enlarged tummies that we see in the “wet” form of FIP are so striking that it is doubtful it would not have been mentioned long ago, had it existed. What we do know is that an inquisitive veterinarian, Jean Holtzworth first mentioned encountering this disease in 1963, based on the cases she had seen coming into Angell Memorial Hospital in Boston during the 1950s. It took another ten years for two top veterinary pathologists at Johns Hopkins, John Strandberg  and Richard Montali to sort out what was happening to these cats on a microscopic level.

Many viruses are naturally unstable in their composition. This shape-shifting ability allows them to avoid the body’s natural defenses by assuming novel, unrecognized forms. Coronavirus are notorious in this ability. So is the human influenza virus. The way they often do this is by forming a “hybrid” with a “cousin” virus that lives in some other animal species. For this to happen, the two different species must live in high numbers in close proximity. Throughout history, novel virus’ and epidemics usually appear when something new has happen in the way the two species – in this case cats and humans – interact. American and European lifestyles and pet preferences changed dramatically after World War II. Cats moved from the barn into the house, catteries proliferated to supply the cats and economical air travel allowed the animals to be shipped all over the World. The number of underfunded animal shelters, cat charity houses, and feral cat feeding stations increased dramatically – all housing large numbers of, stressed felines that were often forced to lived in crowded, unsanitary conditions.

Given this new set of circumstances, it was inevitable that new threats would emerge to take advantage of these new opportunities. In this case, it was feline leukemia and feline coronavirus that stepped to the forefront. The coronavirus of dogs, pigs and cats are all quite similar. So many veterinarians suspect that some blending of the three, along with the random mutations that so often occur in the coronavirus group, resulted in the strain of FIP virus we now face. One young California veterinarian who contemplated this emerging threat was Niels Pedersen , He published those thoughts in a 1978 article But one can never know for sure.

How Is FIP and Coronavirus Transmitted Between Cats – Where Did My Cat Catch It?

First off, most veterinarians do not believe that FIP is transmitted between cats. At least we do not believe that it is common for one cat to catch FIP from another. That assumption is based on the fact that FIP-infected cats appear to shed very little mutated virus. Remember, we think that FIP is caused only by a mutated coronavirus. Once the virus mutates, under natural home conditions, it seems to loose its ability to move from one cat to another – probably because most of the mutated virus population reside in a limited number of organs. Those places do not include the cat’s intestinal lining (enterocytes) its lungs or its blood stream – places the virus would need to reside in order to be passed through a sneeze, through the stool or through a flea bite. (ref)

That assumption had been challenged by a group of scientists at the National Cancer Institute. After collecting coronavirus from FIP positive cats in suburban Washington, DC, they came to the conclusion that there existed a strain of wild coronavirus in their area that was much more likely to cause FIP than other strains (a hot strain of virus [ref]). That was a shock to the veterinary community that studies feline infectious peritonitis. It did not take long for a second set of scientists in the Netherlands to find major flaws in the NCI study. (ref) . However, the jury is definitely still out as to whether one strain of coronavirus is more likely to cause FIP than another or more likely to result in chronic carrier cats. (ref).

Coronavirus is not a very tough or resistant virus when it is outside of the body. A little sunshine and warmth quickly destroy it and most common disinfectants readily inactivate (kill) it as do many detergents.

Experimentally, it can persist longer and be carried about when shoes, hands or clothes are contaminated with feces, but indirect environmental contamination is not how this virus usually moves about.

The spikes that cover non-mutated feline coronavirus have a predilection for compounds found on the surface of the cells that line your cat’s lower intestine (colon). Once in these cells, coronavirus multiplies and escapes back into the cat’s intestine, appearing in high concentration in its feces. It is that infected stool that is the source of infection for other cats. The more likely a cat is to come in contact with the stool of cats carrying feline coronavirus, the more likely that cat is to also become infected. The virus enters the new cat through its mouth or nose. If infected stool is present in the same environment as a susceptible cat, in a home, shelter or cattery environment, the virus will likely spread to all susceptible cats no mater what precautions are take. The greater the exposure, the quicker and more likely that is to happen. The vast majority of cats that are passing coronavirus in their stool do not appear ill in any way. Those cats can only be identified through laboratory tests that detect the virus in their stool or through the detection of antibodies against them in their blood.

How Common Is Feline Coronavirus Infection Among Cats?

Probably a bit less than half of the urban cats in Western Nations carry it or have recovered from it at one time or another in their lives. There are those that give much higher figures, but those figures are based on disturbed populations that exaggerate or over-represent the actual world situation. They rely on blood or stool samples from cattery, shelters or veterinary hospitals – places where cats congregate. And congregation and concentrated population is exactly how this virus gets around.

In one Sidney Australian study, the number of positive house cats was 34% (ref) . In ordinary house cats in Sweden, 17% (ref). In the street cats of Lisbon, 7%. (ref)

In each of the studies that record it, the number of positive cats living in group situations was much higher than the those that lived in individual homes or on their own. Cats in the isolated Falkland and Galapagos Islands, apparently live their lives free of coronavirus. (ref1, ref2)

Detection of exposure to a virus through antibody tests does not necessarily mean that the virus is still present, and lack of antibody could occur early in a true infection – the numbers are soft. Whatever the true number, the virus is considerably more common than we would like.

When cats are not concentrated closer together than Nature intended, feline coronavirus is not a significant problem. Only 4% of your cats’ wild European relatives show evidence of having met coronavirus – probably through an encounter with a domestic cat. (ref)

How Does An Ordinary Unimportant Coronavirus Infection Develop Into A Case of FIP?

Only a very small percentage of coronavirus-infected cats go on to develop FIP.

Veterinarians are still uncertain as to how much, FIP depends on changes in the cat, how much FIP depends on changes in the virus and how important virus dose and timing is to development of the disease. We all do agree on one thing, once a cat shows FIP symptoms that have been positively associated with coronavirus, nothing veterinarians can currently do will save that cats life.

I personally believe that the “cures” that are occasionally reported, represent cases where cats were carrying only non-fatal intestinal coronavirus but exhibited signs similar to FIP due to other health problems. In no reports that am aware of, was it ever verified that the coronavirus had left the intestine and invaded the cat’s body. (monocyte/macrophage tropism) – something that has to happen for a cat to have FIP.

All infectious disease is a battle between the strength of invading disease organisms and the body’s defense mechanisms. Much like a battlefield, FIP occurs when the strength of the virus invaders is greater than the strength of the body’s defenders (the cat’s immune system). Because we still do not understand why this disease occurs in some cats and not in others, I am just going to say that FIP occurs at a point of no return when the cat and the virus are in alignment for a disaster.

The internal genetic mutation theory still appears to be the most acceptable explanation as to why some cats that are infected with feline coronavirus go on to develop FIP. Scientists know that coronavirus taken from cases of FIP has certain subtle structural differences from coronavirus taken from cats that have not developed FIP. The common explanation for that is that the coronavirus changed into a lethal form after it entered your cat. Some change has occurred in the virus in your cat that altered the type of cells it prefers to live in. This internal mutation theory was first proposed by Dr. Pedersen in 1987. (ref). This change in the virus’ preference (a change in biotype) as to where it resides is called enhanced macrophage tropism.

Viral tropism changes are thought to be due to changes in the structure of surface proteins of the virus that alter its ability to lock onto or dock with animal cells. When those proteins mutate or change their structure, cells that were once their targets may no longer be; and cells, which they could not efficiently enter earlier (eg monocytes /macrophages), suddenly become targets. It is a bit as if Nature had confiscated the virus’s apartment keys but issued them new and different ones. Doors that they could once open, they no longer can and doors that resisted their entry are now freely opened. Protein changes mean genetic changes and genetic changes mean mutation. Since the proteins that form the viral spikes (corona) are known to be responsible for docking and entry, scientists are concentrating on that area looking for the specific things (S genes) that may have changed there. It has been hard to sort out which changes are important – after all, coronavirus seem to be in constant change. But please remember that not all cats that form mutant virus will go on to develop FIP.

Once this transformation or change in tropism (preference) has occurred, the body’s immune system runs amuck with severe inflammation attacking cells that harbor the virus (liberation of pro-inflammatory cytokines). (ref1 , ref2)

This is the world of the biochemist-virologist, not a veterinarian like me attempting to helping pets with their every-day needs. And you might be thinking ……. “is all this technical mumbo jumbo really relevant to helping my cat ?” Discovering what these mutations are really does have a very practical significance. As of today, your veterinarian has no test that can distinguish between ordinary intestinal coronavirus and lethal FIP coronavirus. We must locate the virus in tissue or fluid where it should not be – outside of the intestine – to diagnose FIP with certainly. That can be very difficult – or impossible in a living cat. If we knew what the important molecular change(s) in this virus were, we could design an effective diagnostic test for the disease. Looking more distantly into the future, if we understood the critical changes in the virus’ docking process, perhaps we might design drugs or vaccines that prevented it from happening. Understanding how something happens is no guarantee you can stop it from happening – but you cannot do one without the other.

Occasionally, chronic diarrhea is attributed to the non-lethal, intestinal form of coronavirus. It is still unclear to me if the coronavirus is the true cause or if these cats have multiple intestinal issues related to their genetics or other concurrent diseases. So many cats are coronavirus positive that it is likely that cats with non-related intestinal problems also carry it.

You Said That Most Blood Tests Are For Antibodies. If My Cat Has Lots Of Antibodies Against Feline Coronavirus/FIP, Why Isn’t He/she Protected?


You cat has two defense mechanisms. The one most of us think about are the antibodies that pets produces against specific invaders. Just about any protein-containing material injected or absorbed into your cat’s body will cause antibodies to be produced. Similar to virus tropism, it is also a lock-and-key mechanism, in that the custom-designed antibody fits over “keys” on the surface of the invader and either destroys it outright or tags it for later removal by other soldiers of the immune system. Antibodies are produced by certain cells in your cat’s blood (plasma cells, B-cells) .
These and other antibodies form the portion (faction) of your cat’s blood that you see on its lab-work as globulin(s). Your veterinarian may have told you that that portion of your cat’s blood was abnormally high.

Coronavirus is an expert in evading your cat’s defense system by hiding stealthily within its cells were antibodies can not attack it. (ref)

In FIP, these antibodies are not only ineffective in cleansing the cat’s body of coronavirus; they appear to instigate (begin) most of the symptoms of the disease, by forming factors (antigen-antibody complexes) that make matters worse. This phenomenon is called Antibody-dependent enhancement (ADE). (ref) But the virus may be confusing the pet’s immunological defenses in other ways as well. (ref)

You need to remember that antibody tests are not real-time (current situation) tests for the virus. It takes your cat up to 3 weeks after contracting the virus before its coronavirus antibody levels rise. Also, antibodies in young kittens can be those that were passed to them from their mother – not necessarily an indication that the kitten itself is infected.

Cell-Mediated Immunity

There is a second form of immunity or protection. It is called cell-mediated immunity. It does not rely on antibodies. It is a process by which infected or undesirable cells are engulfed by white blood cells to rid the body of unnecessary or undesirable elements. Lymphocytes (T-cells=Thymic lymphocytes=killer T cells(aka CD8+, cytotoxic T cells) & Helper T cells(aka CD4+) ) patrol the body constantly looking for suspicious invaders or unnecessary elements through the release of  lymphokines. This form of immunity appears to be the cat’s best defense against coronavirus. Its success or failure seems to determine which cats go on to develop FIP. (ref)

(If you want to understand the basics of the immune system, you can read the University of Hartford’s immunology course notes)

Is One Breed Of Cat More Susceptible To FIP Than Another ?
Where Are The Highest Number of FIP+ Cats Found?

Any cat has the potential to develop FIP; the stray that wanders up to your door for a handout, the kitten from a neighborhood litter, the designer cats you read about in Cat Fancy. But all high-risk cats are cats that have spent time in high-risk environments.

The prime factors responsible for FIP are crowding, poor sanitation and the stress that always occur when cats are kept in unnaturally large numbers. Cats are not, by nature, flock animals. Even though some veterinarians believe bloodlines account for much of the issue in cattery, I believe that genetics ranks far below crowding, hygienics and stress as a cause of the current FIP problem. That said, if one momma repetitively gives birth to FIP-prone offspring or one tom persistently sires more FIP-prone kittens than another, it should be take out of the breeding program.


Commercial cattery have the highest rate of FIP. The cat breeding community, and veterinarians who assist them see that some breeds and breeders of purebred cats have more of an FIP problem than others. Since FIP is a battle between cat genes and virus genes, it seems logical to assume that some breeds of cat or strains (bloodlines) within breeds of cats will be more likely to develop FIP than others. Many veterinarians suspect that this is one of the many negative effects of inbreeding. When you breed for a visible trait of any kind, you both concentrate and loose other traits that are not visible. Robust immunity can be one of these non-visible traits. Cats that repeatedly produce FIP+ offspring should not be bred. If they must be bred, they should be bred to a different tom.

One ought not be too fast to jump to conclusions. It can be extremely difficult – and sometimes impossible – to sort out why disease occurs in clusters. The environment in no two cattery are identical and it is quite easy to mistake environmental causes for genetic causes. Behavior also influences disease susceptibility. Within a group, is one cat more likely to come in contact with coronavirus than another? How about nutrition and the strain of too frequent breeding ? And what about other diseases present in certain facilities and cat stocks? We already know that FLV+ cats are more likely to develop FIP. It is even possible that the presence of other virus in the cats make them resistant to FIP. Cats have their herpes virus, mice have their own. Mice infected with their herpes are transiently more resistant to other infections, possibly due to continual stimulation of their immune system. (ref) Could similar things be going on in cats? No one, as yet, knows.


Cat shelters and well-meaning folks who take in stray cats also suffer greatly from FIP.
Every disease (other than those of easy living like diabetes and FUS) occur more frequently there. In those places, over-crowding, poor sanitation, stress and other coexisting diseases are almost certainly the culprits. It could be expected that institutional living would favor certain diseases – it occurs in human institutions as well. (ref)

I am not a fan of spay and release, programs, but feral cat colonies have enough space that the virus tends to fizzle out there. Adequate space can substitute for many failings because cats are, by nature, more sanitary than we often allow them to be.

FIP is primarily a disease of young cats – the ones that find their way to shelters in high numbers. Many of these cats are no more than kittens when they arrive; with immune systems that have not fully matured. Somewhat older cats arrive too. The virus load they face at many of these facilities must be tremendous – perhaps enough to overwhelm an otherwise adequate immune system.

The longer their stay at the shelter the more likely they are to catch coronavirus. (ref) The more mature they are when they enter the shelter, the less likely they are to develop FIP.

Coronavirus is most common where multiple cats live. It moves between cats through stool-contamination; so the litter box in multiple cat households is a good place to find the virus. For the same reason, it is more common when cats are crowded into limited space. The initial mild disease lasts up to a few months. In closed households with up to five cats, the virus should eventually burns itself out. But if new cats are continually being introduced or the cattery is large, the virus may lurk there forever.
Coronavirus is not a hardy virus outside the body – most household cleaning agents destroys it quickly. A few days of room temperature and sunshine do the same thing. An excellent disinfectant is ordinary generic household bleach diluted one part bleach in twenty parts water. For the bleach to be effective, removed heavy soiling first with detergent. Although the virus cannot survive in a dry environment outside the cat for more than a day or two, in damp cool areas it can survive longer.

How Long After Exposure to Coronavirus Might It Take Before My Cat Becomes ill?

As I mentioned earlier, the vast majority of cats that are exposed to feline coronavirus do not ever appear to become ill. When the virus stays in the cat’s intestines where it belongs, the most you might see are a short period of soft stools and diarrhea. Infection is most likely immediate, but it cam take a few days before sufficient virus load is present to be detected in laboratory tests. (ref) After the initial infection, most cats appear to eliminate the virus from their bodies, but a few become intermittent or persistent shedders of the virus and a few do go on to develop the mutant FIP form of disease. (ref)The time it takes from infection with this mild form of coronavirus until the development of FIP is considerably more variable. In the laboratory, it can occur with in a matter of weeks, but we really do not know what the dynamics of FIP in home or cattery situations might be. The long lag-times that often occur between the time a cat was likely exposed to coronavirus in a group situation and the time it shows illness can be quite long – months or even years and it is often a stress or trauma that appears to trigger full blown disease. (ref) This is particularly sad, because by the time the cat becomes ill, you are already so attached to it.

Can My Other Cats Catch FIP From My Sick Kitty?

That probably will not happen. When feline coronavirus looses it’s interest in living in the cats intestine (a change in tropism) and moves deeper into the cats body causing FIP, much less virus is shed in the cat’s feces. Although it is theoretically possible, we just don’t see Much cat-to-cat transmission of coronavirus in its dangerous FIP-form in the real World. Recent studies in the Netherlands confirmed this. (ref) When more than one cat in a household develops FIP, each is likely to have had a mutation event of its own, not transmission from one cat to another.

What Signs Will I See If My Cat Had FIP And What Signs Might My Veterinarian Notice On The Initial Examination?

Early signs of FIP are subtle and can be easily missed. Lethargy, rough coat and poor appetite are often the signs that first bring these cats to the animal hospitals. Weight loss and a cat that just seems worn out might be all that alerts you. But that can be due to so many things. During the exam, it’s common for those cats to be running low-level fevers. Your vet might suspect a bacterial infection and treat the cat with antibiotics. But antibiotics do not make these fevers go away.
When these cats have struggled with FIP longer, they are often anemic (non-regenerative anemia) as well. If the effusive form of FIP, the form where organ surfaces (polyserositis) and blood vessel inflammation (vasculitis) cause liquids to accumulate, is centered in their chest, they will show  breathing difficulties  (dyspnea). When the problem is centered in their abdomen, a bloated, pear-shaped or pot-belly is a typical finding. Manipulating the tummy of these cats does not cause them any pain – there is a characteristic jelly-belly feel to the fluid felt in that way. As the intestines slip through my fingers, a lumpiness (enlarged mesenteric lymph nodes) can sometimes be felt. Either of those symptoms, when they develop gradually, will make your veterinarian put FIP right at the top of the list of possible causes.

In the less common, non-effusive form of FIP, fluids do not accumulate. The non-effusive for of FIP tends to develop slower and less dramatically. Non-effusive FIP is much more likely to be confused with a host of other diseases that give similar signs. What those signs are depends entirely on which organs are being attacked.
Occasional cats show symptoms of both the effusive and non-effusive forms.

Can Other Disease Be Mistaken For FIP?

It is rare for that to happen but occasionally it does. As I mentioned, the “dry/non-effusive” form of FIP when it affects the brain produces symptoms that can be indistinguishable from epilepsy and various neuro degenerative diseases. The January 2021 issue of the AVMA Journal reported on an 11 year old cat that fulfilled all the diagnostic criteria for the “wet/effusive” form of FIP. Yet when the cat passed away, the underlying problem was found to be a widespread malignant tumor of the lungs.   

More About The Effusive (aka “Non-parenchymatous” or “Wet”) Form Of FIP

The signs you see in the effusive form of FIP are believed to be the result of your cat’s immune system attacking what it perceives as a threat from foreign invader. It is not due to the damage the virus, itself, causes to the body-cells it inhabits. This inflammatory response liberates a mixture of fluid (blood serum) proteins (globulins) and white blood cells that would normally be confined to your cat’s blood stream (= an exudate). This fluid has a characteristic thick (fibrinous), yellowish tinge that has always been quite chilling to me. (It never ceases to make my heart sink when I see it well up in my syringe)

Your veterinarian will probably tap and examine this fluid to confirm his/her suspicions and run some tests to confirm that it is, indeed, an exudate. On x-rays, it has a characteristic finely granular appearance (a ground glass look). When the fluid is in the abdomen other than FIP, things that might pass through your vets mind are tumors and liver disease. He’ll run some tests on the fluid to rule those things out. When the fluid is in the chest, she’ll run some tests to distinguish inflammatory fluid (exudate) from chyle (lymph). In cats that have fluid accumulations in their chest (pleural effusions) your veterinarian may remark that the cat’s heart is difficult to hear (to auscultate). Besides being pale from anemia, the cat’s gums might have a yellowish tinge (jaundice) when inflammatory damage is occurring in their liver. When effusive FIP is occurring in a kitten, it may just appear to be fading away or not growing satisfactorily.

The Non-effusive (aka “Pyogranulomatous” or “Dry”) Form

Granulomas are whorls of tissue and cells of the immune system that form around objects and disease organisms the body is attempting to wall off. When coronavirus-infected body-cells are primarily located within organs, this is the way the cat attacks them. It might be the cat’s liver, kidneys, lymph nodes, liver, eye or nervous system where this event is occurring or it might be a combination of any or all of these. Needless to say, the symptoms one sees are highly variable. It was called the “dry” form of FIP because unlike the effusive form, excess fluid was not present or at least did not predominate. It is sometimes called the “parenchymatous” form because the internal, functional, cells of an organ are called its parenchyma.

These changes, when they occur, tend to be quite gradual and non-specific. So it is quite exceptional for the underlying FIP cause to be identified during initial examinations. (Besides this ambiguity in symptoms, it’s just human nature to first look for something curable, don’t be cross with your veterinarian because of that )
Inflammatory changes in an eye (uveitis) are a textbook symptom of non-effusive FIP and will probably set off FIP alarm bells early on. Particularly when they are accompanied by nervous system changes.

Cats with the dry form of the disease sometimes have neurological problems that result in lameness, seizures, or a tipsy gait.
In both forms of FIP, it is quite common for owners to tell me that their cat experienced a major stress within the past six months. Things like boarding, the addition of a new cat to the family. a move, a rival cat in the neighborhood, or some other health issue that resolved. Another typical history is that the cat came from a shelter, cat collector or cattery in the not-to-distant past.

How Will My Veterinarian Confirm That My Cat Has FIP?

Since there is no specific test at this time that can distinguish between ordinary, mild-mannered intestinal coronavirus and coronavirus that has morphed into its fatal form, your veterinarian will have to combine tests that affirm exposure to coronavirus with blood and fluid tests that look for the changes that usually accompany the disease. Like a jury trial, we usually make FIP diagnoses based on preponderance of evidence – not a confession.

Signs That Hint At FIP

None of these tests, taken alone, is positive evidence that your cat has FIP. But several, together with the symptoms the cat is experiencing, are usually sufficient to make the diagnosis.

When the fluid your veterinarian collects from effusive cases of FIP contains large amounts of globulin protein and inflammatory cells (neutrophils, macrophages and lymphocytes) FIP is often the cause. (There are vets who use the rivalta test . It is no more accurate)

When macrophages from that fluid stain (Immunostaining) specifically for coronavirus, FIP is highly likely. If they do not stain, FIP has not been ruled out.

When your cat has a very high titer to coronavirus accompanied by physical signs of FIP, FIP is often the cause. (Many cats with FIP do not have these high titers, so lack of them is no guarantee that the cat does not have FIP, nor is a high titer a guarantee that the cat has FIP).

When your cat has low blood lymphocyte numbers (lymphopenia) in the presence of other suspicious FIP signs, FIP is often the cause.

When you cat has significantly elevated blood globulin protein (hyperglobulinemia) in the presence of other FIP signs, FIP is often the cause. In those instances, the cat’s Albumin to Globulin ratio is often low. (The A:G ratio is still one of the few ways, baring multiple biopsies, for your vet to add to his/her suspicions that your cat is suffering from FIP when inflammatory fluids are accumulating in its body or when neurological signs point to that disease; it is not that helpful when the cat’s symptoms are vague and might be due to a number of health issues [ref] ).

The other major blood protein, albumin, may be low – as it often is in chronic inflammations. (ref) Other common blood chemistry values are also often abnormal. But they are not helpful in ruling in or ruling out FIP.

Antibody Tests

Antibody tests tell us if your cat has ever met coronavirus. They do not tell us if the virus is still present and they do not tell us if the cat has the dangerous or non-dangerous version of the virus. It would be nice if they did; and from time to time, laboratories and veterinarians think they have found interpretive schemes that tell us more. So far, none have been any more predictable than tossing a coin. Different veterinary laboratories perform these tests in modified ways. So it is never wise to compare absolute number (titer) values of one lab to another. There is also some degree of variation and subjectivity in determining what absolute number to assign to a test result. Be sure apples are compared to apples. Some cats are better antibody responders to coronavirus than others. And late in the disease, their immune systems may be too weakened to produce antibody in quantity. Antech Diagnostics, the largest provider of veterinary diagnostic services in the World, offers their Elisa 7B protein (FIPSE “FIP-specific) ELISA test for FIP. (It is test T 605 in the Serology/Immunology column). It was hoped that this test could distinguish unimportant intestinal coronavirus infections from fatal mutant coronavirus FIP. It does not now appear to be able to do that. But a positive result is as good as other antibody tests in detecting coronavirus exposure. If you are using test results in an attempt to eliminate coronavirus from a group of cats, or rule coronavirus in or out of a cat’s possible diagnosis, be sure that the most sensitive tests are used.

Antigen Tests – Tests That Tell Us That Coronavirus Is Alive Right Now In The Cat

Antigens are protein portions of the actual virus. When they are present, the virus is present. But just like antibody tests, current antigen tests cannot tell the difference between lethal and non-lethal coronavirus. They are predictive of FIP if the antigen is found in inflammatory fluids (exudates) that are taken from the cat. They may be predictive of FIP when they are found in large quantities outside of the cat’s intestines. Veterinarians are still working that out. The most sensitive antigen test, to date, appears to be the Real Time (or Reverse Transcriptase) Polymerase Chain Reaction Test (RT-PCR). (ref) A number of labs around the World perform it. Polymerase Chain Reaction tests amplify the small amounts of viral antigen (RNA) in samples to a level that can be detected.
Auburn Veterinary School offers their mRNA version of the RT PCR test. Some laboratories look for coronavirus particles using custom-made antibodies that have been attached to a dye (fluorescein) that glow in ultraviolet light. These FA (fluorescent antibody) tests are particularly valuable in detecting coronavirus in the macrophages found in fluids withdrawn from sick cats or in tissue samples (usually taken after death). Veterinary pathologists can also detect the characteristic granulomas of non-effusive FIP and the surface inflammation and vascular changes of effusive FIP, when they are given tissue samples from the cat to study microscopically. It is not often possible to collect such samples from living cats. I really can not tell you which one of these tests is the best one for your particular pet. Rely on your veterinarian to make that judgment.

On rare occasions, liver shunts (which are often curable) have been confused with the dry form of FIP. That is particularly true when periodic seizures and mental issues predominate and symptoms persist without much change for over 6 months. So a bile acid assay might be a prudent test to run in those cats. When confirmed, it is the inability to eliminate waste products of metabolism and toxins (hepatic encephalopathy) that is the real problem.

Was There Something I Could Have Done To Prevent This Disease From Happening?

“Maybe I should have noticed earlier that there was a problem. I feel so so guilty about that. Now that I know, what should I do ?  I don’t want my cat to suffer – he’s my best friend and I will miss him so much.”

Learning that your cat has FIP is simply horrible and it devastates most cat owners. I do not want you to feel guilty because the truth really is that there was absolutely nothing you or your veterinarian could have done to prevent it or predict that it would occur. Letting you know that was my main reason for writing this article. If you are a typical cat owner, your pet was carrying coronavirus long before he came to you. By the time you saw the first signs of his illness, the battle was already lost and nothing anyone can currently do will prevent its imminent departure from this World. Dealing with sadness like that is hard without a loving support group. Go look for one among people who have had to deal with this or similar tragedies in their lives. Friends and empathetic veterinarians can ease the grief cat owners experiences watching their pet slowly decline. There are also professionals that focus on dealing with these situations.

What Will Happen To My Cat Now That I Know It Has FIP?

I have never had a cat survive long after a confirmed the diagnosis of FIP. Sometimes, with supportive care, the pets will perk up for a while, but their general health slips down hill rapidly. No disease – not even feline leukemia – is as frustrating for me or my clients to deal with, as is FIP. From the time I first see them, these cats are dejected and depressed and all my attempts to relieve their suffering seem ineffective. When owners resist my suggestions that these cats be kindly put to sleep, I have, in exasperation, referred them out for various alternative medicine and “new age” techniques. I cannot remember a single instance where I felt that the cat benefited. But some owners benefited – they felt some solace and comfort in knowing that they had exhausted all that traditional and alternative medicine had to offer. I regularly get emails from well meaning, but misinformed, people claiming they know of a cure for FIP. There are also individuals who will flat-out take advantage of your grief with half-baked or outright fraudulent treatments. When you know that your pet has FIP, you need to think about what you will do for your cat when life for it is no longer pleasant. Veterinarians can help with life support and some palliative treatments. But FIP is a steady slide down hill. There will come a time, soon, when you will need to make the decision to put your cat to sleep. Do not extend its life beyond what is kind to your pet. Dr Bernard Rollin, of the Department of Philosophy at Colorado State University has written a thoughtful article for veterinarians on letting go. He cautions against keeping suffering animals alive too long. It pertains to end of life issues in old cats, but a lot applies to your situation as well. You can read his article here. My belief is that in making end-of-life decisions for your cat, you owe it to your friend to choose what will cause it the least pain and suffering – even if that means more immediate pain and sadness for you. I wrote an article on dealing with terminally ill pets and the grief that causes. You can read it here.

OK, I Read That And Get Your Message , But I Am Not Ready To Give UP – Can My Cat Be Treated?

Yes, your cat can be treated. Our primary concern is in making the pet as comfortable as we can. That means that TLC and good nursing are far-and-away the best place to start. It will often give your cat temporary relief. When the effusive form of FIP results in large amounts of fluid in the pet’s chest, removing that fluid will give dramatic, temporary relief. However, the fluid will reform and, with repeated removal (taps), the pet’s body will become depleted in protein. The same sort of relief, though less dramatic, occurs when fluid is removed from the pet’s abdomen. These depressed cats seem to enjoy more personal attention – frequent petting, stroking and being talked to as most ill humans do. I encourage you to do that. Take away any factors that irritated your cat in the past. It may be too weak to show its usual reaction to those stresses – but it experiences them nonetheless. Your cat may not feel like drinking or eating. Help it along with water dishes you present, drops of soups and broths on the tongue and pungently-flavored foods and treats. Forget about “institutional” foods like veterinary prescription diets. These cats need to eat and drink what they will actually accept – not what veterinary nutritionists would theoretically like them to eat.

Suppressing Your Pet’s Immune System:

From what we understand of FIP, stimulating your pet’s immune system is not a good idea. It is already over-stimulated. If anything, we want to suppress it.

Prednisolone or Prednisone and Other Corticosteroids

FIP is a disease of inflammation, and corticosteroids are very powerful weapon against inflammation. However, they are not nearly as effective in treating FIP as they are in treating other forms of inflammation in cats – things like chronic autoimmune diseases or sudden shock-like acute inflammations. It may be that the temporary improvement seen when some FIP cats are given steroids, is really due to the euphoria and well-being effects of all cortisone-like drugs. Unfortunately, that uplifting feeling is usually very short lived and is followed by a crash – at least in humans. (ref)
Another good side effect of corticosteroids is appetite stimulation in cats that have lost their interest in food. Other veterinarians have used non-steroidal medications that suppress the immune system. Drugs like cyclophosphamide, and chlorambucil. I am not aware that any of them are effective.

Are There Any New Or Experimental Treatments We Might Try?


There are countless other medications that have been tried. They are generally greeted with great optimism and hope only to fizzle out under closer scrutiny. Veterinarians at the Munich veterinary school published an exhaustive, but gloomy, review in 2008 of all the medications they could find that had been reported used to treat FIP. You can read that study here

Feline Interferon

Interferon plays a part in your cat’s natural resistance to coronavirus (ref). So it would seem that administering interferon to cats with FIP might help them. A 2004 Japanese study suggested that feline interferon might be useful in prolonging the lives of FIP cats. (ref) It was a very poorly constructed study. Only a few animals were treated and there was no definitive proof that the cats ever had FIP. But since we had so little to offer our clients, it caused a lot of excitement at the time. A more recent 2007 study in Munich, found that feline interferon administration had no effect on how long the cats lived or their quality of life. (ref). One could always argue that one did not give enough interferon, gave it the wrong way, etc. so there are still veterinarians who use it. Since 2001, Virbac Corporation’s European division has marketed a recombinant feline interferon product (Virbagen Omega®) not sold in the United States. Some veterinarians believe it helpful in delaying or slowing the downward spiral of FIP. I have made several attempts to determine why the product is not sold in the US – both by contacting Virbac and the FDA. I have not been able to get a straight answer. You can read the FDA’s 2005 import refusal letter here. The best way to determine if a product works or not is to try it in a controlled environment such as a US veterinary school – not to effectively ban its use with bureaucratic red tape. It is particularly unfortunate because interferon does seem to have the ability to help overcome some coronavirus. (ref1 , ref2). Your veterinarian can import Virbagen Omega®. (You can not) It is a complicated and expensive process. You can print out this letter and give it to your vet. To keep the FDA at bay, have the vet read over  this as well. (the pertinent portion is in blue)

I know of no further published studies on Virbac’s Vibragen (feline interferon omega) . None are mentioned by the The European Advisory Board On Cat Diseases in their 2012 synopsis of current FIP treatment options. You can read the table from that article here .

Polyprenyl Immunostimulant (aka polyprenyl phosphate, Fosprenil®)

In 1996, the founders of a Russian startup company, Micro-plus, published an article on the amazing abilities of their compound, Polyprenyl phosphate (phosprenyl aka fosprenil) to cure disease. You can read that study here. They claimed its use to be “highly efficient” in the treatment of rabies, cancer, distemper, hepatitis, enteritis (parvo?) and potential useful in treating human HIV and herpes. They took out a Russian patent on the compound but have since gone out of business. The compound is still widely sold in Russian pet shops where it is billed to cure most everything.

I remain skeptical that polyprenyl immunostimulant is of any value to your cat. (The last time I know that that broad a claim was made for a remedy was for Antidotum Mithridaticum in 100BC.) Never-the-less, in 2009, veterinarians at the University of Tennessee reported that this compound seemed to benefit several cats that were assumed to have the dry form of FIP. You can read that study here. Naturally, everyone was elated and hopeful – the product’s US suppliers, still devote a webpage to it’s use in the dry form of FIP.

(But since that initial announcement in 2009, I know of no further publications on the medication in human or animal medicine ; although the Winn Feline Foundation funded a 2010 study on its use. As a rule,, truly effective, break-through medications that are this urgently needed catch on considerably faster than polyphrenyl or feline interferon omega.)Read a Russian veterinarian’s 2013 opinion on the questionable value of this compound in the treatment of FIP  here.

“Alternative” Medicine

There will always be herbalists, naturopaths and other practitioners of the obscure and magical arts that claim to be able to cure the incurable. They will get up your hopes by telling you what you wish to hear; and then they will disappoint you. (read here) I do not suggest you use them, but they do give a sense of comfort and support to some pet owners.

I Understand How Few Options I have For My Cat Now; But Might Things Be Brighter For Other Cats In The Future?

As of 2016 you need to also go here  


Most likely so. Some of what  you are reading I wrote in 2011. The key breakthroughs will probably occur in the push to develop new approaches to treating viral diseases of humans – not cats. Those breakthroughs will then be adapted by veterinarians for use in cats. That is usually how breakthrough treatments for animals occur. The exception is when an animal is itself the laboratory model for a human disease, and that is not the case with FIP. Treatment options for diseases like AIDS, viral hepatitis and the human SARS coronavirus receive most of the World funding and interest. That research is focusing more and more on how the genes of individual human beings interact with the genes of pathogens to influence the severity of disease. That field is called genomics. (ref) It requires an understanding of the code that governs the virus and the code that governs its victim. There have been great strides in recent years in understanding virus code and human code. The genomic code of cats was recently worked out as well. (Garfield Project)

I Want To Get A New Cat, How Long Will It Be Before My Home Is Safe?

I would wait two or three months before bringing a new cat into a home that suffered an FIP loss. If you have other cats, they were almost certainly exposed to coronavirus and have dealt with it one way or the other. But why rush. New cats tend to cause additional stress in a multi-cat household, you and your remaining cats are still getting over the loss and none of you need added stress right now. Have your vet check the FCoV status of your remaining cats and any new cat before making a decision. (Remember, just because they may be coronavirus positive, does not mean they will develop FIP) Unless you are intent on obtaining a cat from a high risk source, it is unlikely that you will again deal with the misery of FIP. If you had but one cat, clean and disinfect everything you can – that is just a basic principal when dealing with any infectious disease.

Should My New Cat Be Vaccinated Against FIP?

There is only one FIP vaccine, it is called PRIMUCELL® FIP and it is marketed by Pfizer Pharmaceutical Co. The mutant FIP coronavirus in that product was modified so that it can grow only in the cooler nasal tract rather than in the rest of the cat’s body. The theory is that the cat’s cell mediated immunity and surface antibodies (IgA) will recognize and kill later invading coronavirus once the cat has experienced the weakened virus in the vaccine. Primucell® is government-approved for use, as a nasal drop, in kittens over 16 weeks of age with a booster 3-4 weeks later. I have never had any problems associate with using it. There is debate as to how effective this vaccine is. The tests submitted to gain approval in the US in 1991 were small. For the theory to work, the cat would need the vaccine before being exposed to coronavirus and many high-risk kittens have been exposed to coronavirus long before 16 weeks of age. There are vets who disregard the product directions and give it to kittens at a younger age or suggest that kittens be weaned early, raised in isolation, and given the vaccine later as indicated on the label. It has been quite difficult to produce vaccines to protect animals and people against pathogens that do not cause good immunity after recovery from a natural infection. That is, if you can catch a disease more than once, it has developed a genome (genes) that help it evade the immune system. None have been produced to fight a serious coronavirus of pigs, TGE (ref), or human SARS coronavirus. Feline coronavirus appears to be a disease that a cat can become infected with more than once – so its immunological memory of the virus must be poor (unless each infection is with a different strain). We do not know enough about that. Some studies find a moderate value to giving Primucell and others do not. Most veterinarians believe that there is no danger in administering the vaccine although a few cite rumors of a possibly more violent reaction to coronavirus if later exposed. None of that has ever been proven. To be effective, the cat would probably have to have a negative titer to coronavirus (seronegative) at the time the vaccine is given. Again, we just do not know. All is based on theoretical possibilities that may not occur in the real World. Neither the American Association of Feline Practitioners AAFP nor the European Advisory Board on Cat Diseases ABCD currently recommend this vaccine other than in certain, specialized instances (not a “core” vaccine). This is why: when Primucell was developed in the 1970s, we did not know much about feline coronavirus. It was developed to protect against what was thought to be a specific strain of coronavirus that circulated among cats and caused FIP – not against common intestinal (enteric) coronavirus. Most vets currently believe that it is the common enteric coronavirus that mutates within each cat to cause FIP. Since the vaccine was not designed to protect against all feline coronavirus, it is unlikely to be able to interrupt virus mutation in susceptible cats. I still give Primucell to cats when clients ask me to or when I think it will comfort them. These are usually clients that have lost a previous cat to FIP or know someone who has. Pfizer recommends annual revaccination.

What Things Can I Do To Protect My Cat?

Things that will protect your cat against FIP protect it against transmissible health threats of all kinds – not just coronavirus. Do not board your cats when you are away. Have a sitter come and tend to them. That minimizes disease contact and the stresses that trigger disease. Any place with lots of cats is a good place to avoid. When visits to the veterinary hospital are unavoidable, make it an in-and-out visit, with your cat securely in your own carrier while you wait. If you can, avoid over-nighting your cat at an animal hospital for any reason, unless the need truly outweighs the risks. Many veterinary hospitals have no overnight staff anyway; you can often return the pet for the procedures that are needed the following day. House call veterinarians are an ideal way to meet your cat’s routine, every-day needs. Your risk of having an FIP kitty increases with the number of cats you keep. Would you be as happy with one cat as with ten? If not, remember that some cats, just like some people, do not fit happily into a specific family group. Try not to confuse your needs with your cat’s needs. Unhappy cats are stressed cats and we think that stressed cats defend themselves poorly against this virus. If you do have multiple cats, it is very important that you give them each the sufficient space and individual attention they deserve. Keep your cat indoors or taken out on a leash. Loose cats are exposed to a myriad of disease and stresses that affect their ability to fight infections of all kinds.

Are There Precautions I Should Take When I Purchasing Or Adopt A New Cat?

Older cats need homes too. They are very appreciative when they find one. If you bring home a shelter cat, a mature one (over 3 yrs old) is much less likely to develop FIP. The safest kittens are those that are born in a home situation where their mother was the only cat and their father was the neighborhood’s ruling tom. These are the “whoops” litters of young adult cats, the unanticipated kittens that occurred when the cats owners didn’t get around to taking her in to be spayed soon enough. You see them in the classified and on Craig’s List – the cat that had her litter in the drawer that was left open and carried them about looking for her perfect nest. Those are the cats that are likely to have the least exposure to coronavirus and to have the mixed, hardy genes (heterogenicity) so important when they do encounter the virus. It was the shift away from that tradition that brought us FIP. That is why the reveres is also true: The institutionalized young cat, the bulk-housed kittens sold indiscriminately in commerce, the kittens of over-bred queens and the kittens of feline hoarders, are the higher risk cats. Animal shelters face a grueling and often overwhelming task as they deal with feline outcasts. The health needs of these cats are so challenging and so specialized that their veterinarians have their own organization, the ASV. When you choose your kitten there, you save a soul and earn points in Heaven – but you take risks. If your municipal shelter will cooperate, ask their wardens to alert you when they get a called for a home litter – before the kittens are handled by the officer and placed on the truck. Be selective when you purchase a pedigree kitten. Your source should be a small conscientious cattery (a maximum of 6 cats). Never purchase a kitten from an intermediate such as a pet store. Never purchase a kitten sight-unseen. That is an invitation to disaster. Put more faith in what you see than what you hear. If you are new to the purebred cat World, bring an experienced friend. All kittens are adorable and to an untrained eye they may seem healthy as well. Evidence of health problems or a high-risk cattery are likely to be small and subtle. Politely ask to see the paperwork on all the cats, relating to their health histories, vaccinations, leukemia tests, etc. Ask for the names and telephone numbers of satisfied buyers. A proud breeder should have no hesitation supplying all this. Inquire as to what veterinarian services the cattery. Inquire independently as to the reputation of that veterinarian. Ask if FIP has occurred in their cattery – how often and how long ago. Ask what type of health guarantee the breeder will give and ask to see it in writing. Ask how that guarantee would specifically apply to FIP. If they say that FIP is just something you can not avoid or that they can make no guarantees because exposure might occur in a confined cat in a single-cat home, cross that cattery off your list. Visit only one cattery a day – there is no sense in tracking virus around.

Become accustomed to the attributes of a healthy litter of kittens and a well-run cattery:

Are they all bright, alert and interested in your presence? Are there runts among the litter? Are there at least five kittens total? (in some breeds 4) Are there crusts on their eyes or nose? Are their 3rd eyelids showing? Do any kittens sneeze? Do any of the cats at the cattery sneeze? What is the quality of the cat food they are feeding? Is the rear of any kittens soiled with feces?  How intense is the odor in the cattery?  What is the demeanor of the momma cat?  When was her last litter ? (too frequent pregnancies sap strength) Are multiple litters being house together or in the same room? (That is never a good idea) Are there a sufficient number of litter trays and are they being cleaned frequently enough?

Purchase your kittens young – at 5-6 weeks of age. When kittens are that young, they are often still shielded by their mother’s immunity to coronavirus and do not yet carry the virus. (Some States have laws against selling kittens that young.)

Purchase A Coronavirus-free Kitten

Residents of the UK (England) and UK-centered societies have a much greater option in obtaining certified coronavirus-free kittens – basically due to the work of one veterinarian, Diane Addie . I live in the USA. Here catteries tend to be considerably larger and the citizenry less orderly. The more cats that are present in a group and the more in flux that group is, the harder and more expensive it is to clean them of virus. One San Francisco Bay area cattery is coronavirus free. It was established by a physician. I know of another in upstate New York. I am always interested in learning of more US catteries that have taken the steps required to purge their breeding stock of coronavirus. (perhaps you are one of the special people with the drive and dedication to do it).  Purchasing a kitten, based on its being coronavirus antibody or antigen (RT-PCR) negative on a single test does not guarantee the cat cannot develop the intestinal or the “malignant” form of FIP (although it makes it somewhat less likely). First off, if the kitten is younger than 6-10 weeks, antibody in its blood may be that of its mother and not an indication that it is itself infected with coronavirus. Antibody negative kittens can also be in the incubation stage of the disease – before antibodies appear. Antigen (RT-PCR) positive cats are infected. But antigen negative cats may just not be shedding virus at the time the test sample was collected. If you want an assured coronavirus-free kitten, there must be neither antibody nor antigen in any animal in the cattery, based on multiple samplings from every cat. I know those are severe requirements. It just depends on what degree of assurance you require. The sensitivity of the test is also quite important. Some tests are geared more to identifying active coronavirus infection rather than intermittently shedding cats. If the cat has never met coronavirus, and its mothers antibody is no longer in its blood , its titer should be nil. If you cannot find a coronavirus free cattery, follow my suggestions on judging the quality of the cattery. Have the kitten coronavirus antibody tested. If the test is positive, coronavirus is in the cattery. If the test is negative, it may or may not be in the cattery. If a subsequent two tests show a dropping antibody level, the kitten may have successfully fought of the virus or never have been infected. Antibody tests have their limitations because they rely on the cat’s immune system response, which vary between individuals and points in time. So taken individually, there will always be cases where they lead to false conclusions. That is why your vet may decide to combine those tests with RT-PCR tests as well. If you are fortunate enough to have a coronavirus-free cat, it must never be exposed to cats that carry the virus for it to remain so.

Will Catteries Ever Be Rid Of This Horrid Disease?

While those remarkable veterinarians I mentioned were at work in Boston, Baltimore, Davis and Glasgow, I was doing more mundane things. There was a war going on in Indochina. As a veterinarian, fresh out of school, my draft board gave me the choice of serving in Viet Nam, or working for the US Surgeon General in Washington DC. I did the latter .Cancer and basic biomedical research were in their formative years, and scientists could make little sense of their results when their animals models were contaminated with unwanted virus – pathogenic or not. Along with a few other vets, I was assigned the job of developing those virus-free animal models. Starting with the cleanest animals we could find, we cleaned them further and raising them with strict adherence to rules that prevented virus exposure. The womb is a natural barrier to many infections. So we isolated young animals as early as possible from their virus-carrying parents and raised them by hand or on pathogen-free surrogate mothers. Once they were virus-free, we kept them that way generation-after-generation through strict separation from their virus-contaminated brethren. So we already have what we need to rid breeding cats of coronavirus.

Here are some things I have learned. They apply to catteries just as well:

If catteries stay small, and are well-manged, they often clean up on their own. If catteries space out their animals, the virus does not spread as easily. If catteries stay closed to cats of unknown virus status, they no longer import the virus. Animal gatherings, such as shows, are excellent places for virus to find new client cats. Cat-loving visitor can also unknowingly offer the virus a lift. Cattery sanitation is very important but unlikely to be sufficient in itself.
One needs to monitor for virus or virus exposure. Without a well thought out plan and strict adherence to its rules, it is unlikely that a cattery will remain coronavirus free for long.

There are steps that are recommended that isolate known coronavirus-free cats and kittens from known positive and unknown status cats. That is always a good idea. However, having worked in the production of virus-free animals much of my career, I know how hard it is to do that successfully over long periods of time. Eventually, you make a mistake and the virus escapes back into the general colony. I have only been successful when I banished virus completely from the premises. But perhaps in smaller colonies run by one very dedicated and methodical person, isolation of known carriers from coronairus-free cats could be successfully done.

Testing For Coronavirus

Monitoring for coronavirus antibody in multiple cats is quite expensive and one cannot hope to rid a cattery of coronavirus without it (or exceptionally good luck). Multiple tests over an extended period of time are the only ways to truly know the status of a particular cat.If you live in Europe or the UK, the laboratory with the most experience in sorting out coronavirus carrier from non-carrier cats is the Companion Animal Diagnostic Unit of the University of Glasgow Veterinary School. (Dr. Elizabeth Graham) In the United States, we have less experience doing this. Our two main commercial diagnostic labs, Idexx and  Antech Diagnostics  are geared to identifying cats with high antibody titers to coronavirus to help determine why a particular cat is ill – not the seemingly “normal” cats that can carry the virus at low levels. However, with guidance, the Clinical Laboratory Service of The UC Davis Veterinary School can do so. (there is also some pricing flexibility when multiple tests will be required). I currently prefer multiple low-dilution antibody titer tests over RT-PCR tests for identifying non-carrier cats. The problem arises when a highly desired breeding cat is positive at low corona antibody titer levels (1:10 – 1:25). In those cats, multiple RT-PCR tests can tell if the animals is actually shedding the virus and western blot tests can confirm if the titers are real. Because some cats only shed coronavirus intermittently, you can never be entirely certain that those cats are coronavirus-free until their stools have been checked periodically for a considerable period of time. Bringing such cats into a coronavirus- free cattery is a personal decision you must make based on risk and benefits. If PCR tests are required, I would send those samples to the UC Davis PCR lab .Although it is possible for coronavirus to transfer through the womb, it is thought to be quite uncommon. So fostering pure-bred kittens on FCoV-negative queens might also be quite effective.

What Can Animal Shelters Do To Lower The Threat Of FIP ?

Breaking the spread of coronavirus in shelters is a much more difficult task than doing so in a catteries. One could offer a lot of impractical suggestions, but having worked in cat shelters for most of my life, I know the realities they confront every day. I do not believe that one can eliminate coronavirus spread in shelters with the current tools that veterinarians and shelter workers have. But we can lower the incidence of FIP that occurs there, or soon after the cats are placed in homes. Good shelter managers know what the stress and health risks are at their facilities. Their number one problem is their lack of money to deal with the endless flow of homeless animals. It has been my experience that their rate of FIP drops proportionately to the space, sanitation and general veterinary care their wards receive.

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