Feline Infectious Peritonitis (FIP) – What Happened, Why It Happened. What Will Happen To My Cat And What Are My Options?

Ron Hines DVM PhD
Original article: Feline Infectious Peritonitis (FIP) - What Happened, Why It Happened. What Will Happen To My Cat And What Are My Options?

Some time ago, a Latin teacher at Mount Holyoke College who loved cats decided to change her profession. She chose the prestigious American Veterinary School of the time, Cornell, and found a place in America’s best veterinary hospital, Angell. She became the first specialist in cat medicine. In 1962, she reported her observations of a strange and always fatal cat disease, which she called "chronic fibrinous peritonitis." Two years later, a veterinarian in PennVet informed about a cat with a similar disease. Humans have lived with domestic cats for thousands of years and have been writing about them for centuries. It is unlikely that a serious disease such as FIP will go unnoticed and unrecorded for so long. I believe that an important coronavirus mutation occurred in the late 1950s. Some experts believe that there is a combination of the intestinal form of canine and feline coronavirus. (read here)

Today, veterinarians call the widespread and rarely dangerous intestinal (enteric) feline coronavirus FCoV (= feline enteric coronavirus alias FECV) and its dangerous mutated form, FIPV (feline infectious peritonitis virus). When a coronavirus mutation occurs, they are often viral spike proteinswhich changes the selection of the target (cells) they attack. (read here) A group of Dr. Niels Pedersen of Davis came up with the hypothesis that something like this happened to cats. (read here) He confirmed this in 2009. (read here)

When the virus reaches the mutation of interest, this new mutated form prevails. This is not the case with FIP coronavirus. A mild form of feline coronavirus FCoV still predominates. It is never in the virus's interest to kill the host it inhabits. Most veterinarians and scientists now believe that the mutated FIPV form of feline coronavirus must come from the mild intestinal form of FCoV in every new cat that becomes ill with FIP (or manages to overcome it). In most cats, this mutation is unlikely to ever occur. We currently believe that this will happen in about 8-10% cats. Of these cats, some will overcome the virus on their own and survive, some will not. Until recent discoveries at the Veterinary School in Davis, California, all cats that began to show signs of the disease died. Genetic factors unique to your cat are undoubtedly another factor that depends on whether or not FIP breaks out in a cat. It is also known that experimental transmission of mutated FIPV coronavirus from a sick cat to a healthy cat causes FIP to break out in most cats. (read here)

How common is the common mild intestinal form of feline coronavirus?

Common, mild, feline coronavirus (FCoV) is quite common in cats around the world. Some studies show that almost half of the world's domestic cats have been exposed to it. In some urban areas, up to nine out of ten cats have encountered the virus. However, it is quite important which cats are actually sampled. (read here, here, here and here) In these studies, the number of FCoV-positive cats living in groups is much higher than in those living in individual households. Cats in remote isolated areas appear to live their lives without coronavirus. (read here and here)

Detection of previous FCoV exposure by routine antibody-based tests does not necessarily mean that the virus is still present in your cat. And a lack of antibodies can also occur at the onset of a true FCoV infection. Whatever the actual numbers, the virus is much more common than veterinarians would like. When cats are not more concentrated than nature would like, the mild form of feline coronavirus and the mutated form of FIP are not significant problems. Only your cat's 4% wild European ancestors show signs that they have ever encountered a coronavirus - and even that has probably happened to an accidental encounter with a domestic cat. (read here)

Does the common mild intestinal form of feline coronavirus (FCoV) cause the disease?

This mild form of coronavirus is most common in cats less than two years old. Many cats (probably most) do not show any symptoms related to the health condition. For those who show symptoms, these are usually mild diarrhea lasting only a few days. Most cats eventually eliminate the active virus from their bodies - although it is not certain whether the virus in some cats does not persist in an inactive form, incapable of replication, the so-called provirus. We all carry viruses in our bodies.

Is my cat's age important for the common coronavirus mutation to FIPV?


Most cats that develop FIP are young - usually between the ages of three and sixteen months. More than half are less than one year old. In one California study, laboratory-bred cats developed increased resistance to FIP infections at 6 to 12 months of age. This means that FIP occasionally develops in older cats. Veterinarians do not know whether older cats' immune systems are more likely to kill coronavirus mutants (destroy them before they can multiply) or whether the virus is less likely to mutate older cats or whether other unknown factors are involved. (read here)

How does a common coronavirus infection become a case of FIP?

Nature created viruses to randomly change their structure in an endless battle to defeat the immune system and continue to invade a new susceptible host. It is a random but very effective approach. Most of these random genetic changes in the composition of the virus (mutation) are unsuccessful. The viruses that carry these failed mutations are destroyed and no one has heard of them. But sometimes, by complete coincidence, there is a mutation that brings some benefits to the virus. When this happens, this mutated virus becomes the predominant form. Coronavirus is known for frequent mutations that allow them to jump between species or attack new parts of the body that they could not before. An attack on a new species or area of the body often involves changes in the surface spike viral proteins that I have already mentioned. In the case of an FCoV to FIPV mutation, this allows the virus to infect a new cell type, macrophages and monocytes in your cat. This transformation or change in the virus's preferences (tropism) causes the cat's immune system to start up, causing severe inflammation because the cells of the immune system attack the cat's cells that carry the virus (the release of pro-inflammatory cytokines). (read here, here and here)

I do not believe that a mild mutation in feline enteric coronavirus (FCoV) to a highly pathogenic (dangerous) feline infectious peritonitis virus (FIPV) offers any benefits to coronavirus. Killing a host is never an advantage for the virus. I therefore believe that FIP only occurs in a small number of cats that carry FCoV. FIPV mutations are likely to occur in many more cats than those who have developed FIP. But in these cats, their body recognizes and destroys these mutants shortly after they appear. Some sources report that FIP develops in 5-10% cats infected with FCoV. However, the actual numbers are probably much lower than in the general cat population. The reason is that a large proportion of healthy cats never visit a veterinarian, or if they do, it is only for regular vaccinations. If you find out which patients come to the clinic, most of them are sick.

Are there more forms of FIP?


Veterinarians usually distinguish between two forms of FIP, wet and dry. In the "wet" form, inflammatory fluids are produced on the surface of the cat's abdominal and / or thoracic organs. In the "dry" form, inflammation occurs in the body's organs without the production of excess fluids. The same cat occasionally has symptoms of both forms.

Wet or effusive form of FIP

This was the first form of FIP that veterinarians such as Jean Holzworth recognized. With the effusive or moist form of FIP, fluid accumulates in your cat's chest or abdomen, or both. This leaked fluid is mainly the result of the cat's immune system attacking what it perceives as a threat from a foreign attacker (presence of proteins that do not belong to the cat's body = antigens). Most veterinarians believe that this accumulated fluid (exudate) is not caused by any direct damage that the virus causes to the cells in the body of the cat it inhabits. It is the cat's own cytokine-induced inflammatory response that releases a mixture of fluid (blood serum) and proteins (globulin and fibrin) as well as white blood cells, which would normally be limited to your cat's bloodstream. This fluid has a characteristic dense ("fibrinous") consistency with a yellowish appearance, which always hurts my heart when I see it slowly being sucked into the syringe.

Your veterinarian will probably tap (pull) to check the fluid to confirm suspicions, and then perform tests to confirm that the fluid is indeed exudate. In X-rays, this liquid has a characteristic grainy appearance (the appearance of "cut glass"). When fluid is found in your cat's abdomen, other possible causes will fly through your veterinarian's mind. Lymphoma tumors, heart or liver disease, or even a ruptured bladder are occasionally the cause of abdominal fluid. Other laboratory tests rule out these causes. When there is fluid in the cat's chest (pleural effusion), other tests distinguish inflammatory fluid (exudate) from lymph nodes. When cats have fluids in their chest, your veterinarian may note that your cat's heart sounds are muffled and difficult to hear through a stethoscope (difficult to aculture). When a cat's liver is affected, its gums, in addition to being pale from anemia, may have a slight yellowish tinge (jaundice). When an effusive FIP develops in a kitten, the pup may appear to be wilting or has stopped growing satisfactorily.

Dry, or non-fusible, pyogranulomatous form of FIP

Granulomas are made up of cells from the immune system that gather around objects and diseased organisms that the body is trying to separate or eliminate. When FIP coronavirus-infected cells are primarily located in organs, this is the way the cat attacks them. These events can take place in your cat's liver, kidneys, lymph nodes, eyes or nervous system, or any combination of these. Needless to say, the symptoms seen by cat owners and veterinarians are very variable. Veterinarians call this form the "dry" form of FIP because, unlike the effusive form, excess fluid does not accumulate - or at least does not predominate. The dry form is sometimes called "parenchymatous". Functional cells of various organs are called parenchyma.

These changes caused by the dry form of FIP tend to start gradually. They are so non-specific that they could have many explanations that are not related to the FIP. Inflammatory changes in the eye (uveitis) are a textbook symptom of a non-fusive form of FIP. This symptom is likely to trigger a FIP alarm sooner than most others. This is especially true if it is accompanied by other changes in the nervous system or eyes. These neurological problems may include bleeding, seizures, or just strenuous and unstable gait in the back (ataxia). It is not uncommon for both forms of FIP for the owner to tell me that the cat has experienced a major stressful event in recent months. Events such as a diet, a new domestic cat, a move, a rival cat in the neighborhood, or another problem that has been thought to be resolved. Another typical anamnesis is that the cat was recently acquired from a shelter, home with numerous cats or a private kennel. (read here and here)

How is the common milder coronavirus (FECV) transmitted between cats?

The more common, milder, non-mutated form of feline coronavirus FCoV lives in the cells that line your cat's gut. Upon release, these viruses are excreted in large amounts in cat feces. (read here) Cats that modify or share a toilet are the most common ways of transmitting this virus to another cat. Although no one has documented the survival of feline coronavirus in the environment, coronavirus generally survives in the environment for a maximum of several days. Therefore, most veterinarians do not believe that contaminated objects in your cat's environment are the source of many (if any) infections. But regular litter changes in households with multiple cats is always a good idea. When you bring a new cat into your home, a PCR test (FCoV RT-PCR) of her feces can tell your veterinarian if there is FCoV in the stool at that time. However, FCoV shedding is often interrupted. And at the onset of infections, test results may be negative, even if the virus is already present in the cat's stool - but in a number that is too low for the PCR test to detect.

How is dangerous FIP-mutated coronavirus transmitted between cats?

Veterinarians do not believe that the natural transmission of FIP virus from cat to cat is common. FIV-infected cats are known to excrete very little or no mutated virus in the faeces. (read here) Most veterinarians currently believe that each case of FIP requires a new mutation in the common FCoV virus after it infects a new cat. One article questions this. However, no one was able to duplicate these results. (read here)

When a new mutation produces a dangerous feline infectious peritonitis virus (FIPV), a certain percentage of cats develop FIP. But this will not happen with all cats. Experimentally, scientists can extract the FIP virus from a sick cat and inject it directly into another cat. This often leads to an outbreak of FIP in the second cat. However, we do not think that this is happening in the real world. In contrast, the complex interactions between the virus and the cat's immune system, the myriad ways in which the virus can mutate, and the unique genetics of each cat make the utter statements unreasonable. (read here) Few things in medicine are absolute.

How long after this mutation can my cat get sick?

I have already mentioned that the vast majority of cats that are exposed to the common feline coronavirus have never become seriously ill. When the virus stays in the intestines of your cat, where it belongs, you can most often notice only a short period of soft stools or diarrhea. Infection of the cat's intestinal lining (its enterocytes) most likely occurs immediately after the cat's coronavirus ingestion. However, it may take several days for a sufficient number of viruses to be detected in laboratory tests. (read here) After this initial infection, most cats seem to eliminate the virus from their bodies relatively quickly. However, some cats become intermittent or persistent carriers of the non-mutated form of the virus, and several develop FIP. (read here)

The time that elapses from infection with a mild coronavirus form to a possible mutation and possible outbreak of FIP is highly variable. It would be very difficult to design valid studies to address this. In the laboratory, FIP-related disease can begin within a few weeks. But it was then that the already mutated FIP virus was experimentally transmitted from cat to cat. Apart from the laboratory environment and "purposefully" cats, it tells us little about what is happening in the real world. Veterinarians really do not know the dynamics of FIP in a domestic or breeding situation when "wild" strains of the virus and genetically diverse cats are present. Between the time the cat was probably exposed to the "wild" coronavirus and the time it begins to show signs of disease, there are often long breaks - several months or even years. As I mentioned, many veterinarians associate FIP with stress or trauma. Factors such as overcrowding, frequent pregnancies, genetic predisposition, inbreeding, and surgery have been discussed as triggers that could upset the balance in favor of FIP. This is especially sad for me, because when a cat gets sick, my clients are already emotionally attached to it.

What are the symptoms of FIP?

I mentioned that the initial symptoms of FIP are often insignificant and can be easily overlooked. Lethargy, rough hair, little interest in grooming or playing, increased sleepiness, picky eating and weight loss are often the first reasons to visit a vet. However, these symptoms can have many other causes.

During a veterinary inspection, it is common for FIP cats to have low temperatures. Keep in mind, however, that normal cats often have mild fevers due to travel, stress, fear, or being manipulated by strangers. You may have mentioned to the receptionist that your cat has more problems in the toilet. Sick cats care less about their hygiene. Therefore, your veterinarian may suspect a bacterial infection and treat the cat with antibiotics. But antibiotics do not reduce these fevers. When these cats fight the FIP virus for a longer time, it is common for them to become anemic (non-regenerative anemia = there are too few reticulocytes in their blood).

Symptoms of the effusive (wet) form of FIP

Once the cat has entered the effusive wet form of FIP, the mediator compounds (inflammatory cytokines) released by the feline immune system result in inflammation of the blood vessels on the external surfaces of the body's organs (polyserositis). (read here) When this happens in the abdomen, the cats develop a fluid-filled, enlarged pear-shaped abdomen. When this happens in the chest (chest), breathing becomes strenuous. When fluid accumulates in your cat's abdomen, its weight may not change, even if it is a proper eater. This is due to the weight of the excess fluid in the abdomen. However, when you run your finger over the cat's spine, you will notice that it is bony and many cats have also lost the muscle mass of their legs. This condition is accompanied by malaise and cachexia.

Symptoms of non-fusible dry form of FIP

With this less common non-fusible (= granulomatous FIP) fluid, they do not tend to accumulate in your cat's chest or abdomen. This form of FIP is also developing more slowly. The non-fusible, dry form of FIP is also more likely than the wet form to be initially confused with diseases other than FIP that exhibit similar symptoms. Neurological health problems, such as epilepsy, seizures, tremors, balance problems, personality changes, or increased sensitivity to touch resulting from FIP, can be easily confused with other causes. So are vision problems. It is common for the dry form of FIP to affect the nerves and brain. But other organs may also be affected: the eye (s) (read here), liver, kidneys, respiratory tractread here) intestinal tract, skin. (read here)

What other diseases can be confused with FIP?

Diseases that can be mistaken for FIP include toxoplasmosis, cryptococcosis, hemobartonella, middle ear infections, trauma, drug intoxication, lymphoma, FeLV, FIV and tumors. Occasionally, cats show signs of both effusive and non-fusive forms. (read here)

How does my vet confirm that my cat has FIP?

The wet form of FIP is relatively simple for your veterinarian. Young cats, which come with mild fevers and fluid build-up in the chest or abdomen or both, are likely to suffer from the disease. Blood samples received by your veterinarian usually show mild to moderate anemia. Blood albumin levels are often low, A: G ratios are low, blood globulin levels are high, giving an albumin to globulin ratio <0.6. However, this test serves more as an exclusion test than as a test to confirm the diagnosis of FIP. (read here) Total lymphocyte counts are often low and neutrophil counts increased. Examination of the specific gravity of the fluid confirms that it is an exudate (> 1030).

When a cat develops a dry form of FIP, diagnosis is much more difficult. High levels of globulin in the blood (hyperglobulinemia) - often in combination with low levels of albumin in the blood suggest FIP. Although tissue biopsies can confirm the disease with certainty, their implementation is often difficult or impossible. Advanced diagnostic centers use useful tools for magnetic resonance imaging (MRI) and CSF analysis. (read here and here)

Most veterinarians diagnose FIP in dry form based on the predominance of evidence, not 100% certainty. Prevalence is a very relative term and is probably responsible for the FIP miracle drugs that are sometimes mentioned. Just because a cat is coronavirus positive and has some of the common symptoms of the dry form of FIP, doesn't mean it has FIP. None of the more common tests alone can confirm that the cat has a dry form of FIP. But a few tests, along with the symptoms your cat shows, are usually enough for your veterinarian to make a reasonable diagnosis. Even the presence or absence of antibodies against the coronavirus or the virus itself is insufficient, as many healthy cats appear in this way, so that the levels of antibodies against the virus and the coronavirus do not correspond well with FIP.

Some, including Idexx Laboratories, believe that high FCoV antibody titers increase the suspicion of FIP. In 2014, the company introduced its FIP Virus RealPCR ™ test, which claimed to be able to recognize (distinguish) common FCoV coronavirus from mutated FIP coronavirus. The test was designed based on some German studies. (read here, here and here) Despite some recent studies not sponsored by the company, they raised considerable doubts about the value of their patented test. (read here)

What treatment can veterinarians offer to my cat?

Functional treatment

Antiviral drugs: Protease inhibitors, polymerase inhibitors, nucleoside analogues

Protease inhibitors and similar compounds are the only drugs that currently offer hope to cats that fight FIP. Their existence dates back to studies conducted in the early 1990s to screen drugs for their ability to treat human hepatitis C and to suppress human AIDS. The research was later prompted by the 2003 SARS coronavirus epidemic. The general interest in antiviral drugs motivated a veterinary school in Manhattan, Kansas, to investigate some of these compounds. (read here) Some were already known to be effective against coronavirus. As it was a group of biochemists at a veterinary school, their interest naturally turned to the hitherto incurable FIP feline coronavirus and feline calicivirus. In 2015, they confirmed that of the 13 compounds studied, several were effective against feline coronavirus. Among them was GC-376. (read here) This information reached a veterinary school in Davis, California, where a veterinary virologist, Dr. Niels Pedersen, began attempts to administer GC376 to cats owned by wet or dry FIP clients. (read here) The results were very promising; although the drug appeared to be more effective in treating wet than dry forms of the disease. In another study from 2018, this group in Davis, in collaboration with Gilead Sciences, identified another closely related compound, GS-441524, which was also effective against FIP. (read here and here) Patent for GS-441524 owned by Gilead. This particular compound is a metabolite of its precursor remdesivir (aka GS-5734), which the company currently markets for the treatment of human Covid-19. Most information about the use of Remdesivir in cats is spread over the Internet. There are probably correct but also wrong advice on the Internet. Contact Bova Australia for more information.


Dr. Pedersen has documented the effectiveness of the drug in many cases. The problem was getting it. Gilead is a publicly traded company. Shareholders expect maximum profit. The company argues that selling products such as Remdesivir / Veklury® for human use is much more profitable than drugs for veterinary use. As I mentioned, remdesivir is a prodrug or prodrug that the body then metabolises to GS-441524. The precursor form of the drug will help him enter the right cells of the immune system, where the immunosuppressive coronaviruses reside. In the studies of dr. Pedersen on cats, GS-441524 was administered unchanged FIP, with a unprecedented success rate. Gilead's refusal to release GS-441524 for the treatment of FIP in cats quickly led desperate cat owners to turn to Chinese biochemical companies on the black market, which operate in violation of international patent law.


In other studies at veterinary schools in Kansas and California, another similar compound, a protease inhibitor, GC376, appears to help cats infected with FIP. A compound with similar potential is GC373 (read here and here) GC376 is licensed by the company Anivive Lifesciences. I don't know what their marketing plans are with this drug, but usually profit maximization comes into play.

One of the Chinese drug suppliers, MUTIAN Biotechnology Co. Ltd., based in Nantong, sells a drug called Mutian® xraphconn. The last time I checked their website, it was no longer available in capsular form. Previously, however, the FDA's list of non-approved drugs included active ingredients such as: fruiting body inonotus obliquus, nicotinamide ribotide, crocin, S-adenosylmethionine, and hake / silymarin inotodiol. The FIP is unlikely to cure anything. I was told that this product was sold as a "dietary supplement intended exclusively for cats with FIP," to strengthen their immune system and overall well-being. " Mutian is also available as an injectable form. As for the likely composition of these products, you will probably need to go to a website Sock FIP and FIP Warriors. But Gilead has his suspicions.

I was told that the Mutian solution for injection was selling for about $ 4,000 at a time for a 6.6 / 3 kg cat. Friends in Russia told me that the price there in 2021 had dropped to $ 1,000. This is probably due to competing suppliers in China, but I have no further information. Sock FIP and FIP Warriors would be much better sources of this kind of information. Mutian has stated that the composition of their product is a trade secret. But I also read that Gilead, the manufacturer of the remdesivir, sued them for patent infringement. Cat owners must be aware of the type of people they are dealing with, as well as the possibility that these drugs could be obtained by the US Customs Service if discovered.

It is almost certain that more antiviral compounds effective in the treatment of FIP-positive cats will be discovered in the near future. (read here and here) I believe there will be some among the 3CLpro inhibitors. Pfizer is already testing two of them on humans. So treatment options for FIP + cat owners should soon be much greater. I do not believe that some of these future drugs will be cheap. However, the costs will hopefully fall sharply as one drug competes with the other in the human coronavirus treatment market.

Davis also considered Merck's drug MK-4482 / EIDD-2801 (Molnupiravir®), which is being developed for oral use against coronavirus. However, I do not believe that the owner of the Merck patent would make this drug available to them. I may be wrong. But in April 2021, one in two clinical trials of the compound in people with Covid-19 was stopped because of its ineffectiveness in severely ill hospitalized patients. I see on the Internet that experiments with people in less severe cases of Covid-19 can continue. Pharmaceutical companies tend to be very cautious about disclosure - especially if they are negative and can affect their stock prices.

None of these drugs is completely risk-free. Skin reactions, tenderness and ulcers occasionally occur at the injection site. Rarely were they serious. Most of this can be caused by errors in injection technology. Minor kidney damage was once attributed to one of the Chinese drugs. The severity of your cat's condition at the time these medications are started also affects the success of the treatment. Some of these cats require infusion therapy. When secondary infections are present, they need to be treated with antibiotics and nutritional support. These measures, which may even include a blood transfusion, can give your cat the best chance of survival. It is always wise to perform a complete blood test (CBC and biochemistry, including A: G ratio) shortly before and regularly during treatment. They allow your veterinarian to scientifically monitor your cat's overall health and evaluate the course of treatment. However, a good appetite, a return to your cat's normal weight and a slow return to her old cheerful nature are always the best signs. If the cat does not want to eat, several days of corticosteroids (eg prednisolone) are allowed. Non-steroidal appetite stimulants such as Entyce® are available, but we have no idea if they interact negatively with any of these drugs. If you have been taking this medicine or mirtazapine, let me know the result. Elimination of effusion fluid is only desirable if it affects your cat's ability to breathe. Some cat owners use tonics such as SAMe, silymarin /, S-adenosylmethionine, probiotics, vitamin B3, etc. to support the liver or kidneys. However, none of these products affect the results of the treatment.

According to Dr. Pedersen et al., Cats less than seven years old are more likely to be cured than cats that develop FIP at an older age. And as I mentioned, cats with a dry form of FIP will be more likely to succeed than cats with a dry form - especially those that already have neurological and / or eye problems. FIP relapses have also been reported after a 12-week GS-441524 cycle. Sometimes another 8 weeks of medication was enough, and sometimes not. Sometimes, cats that have developed a neurological form (dry form) of FIP and have been successfully treated with authentic or Chinese GS-441524 to remove the FIPV virus have not fully recovered from the disability. This is especially true if it involves paralysis and weakness of the legs due to damage to the central nervous system. Some believe that a higher dose of the drug can prevent this. However, in general medicine, peripheral nerves (hands, feet, etc.) often regenerate slowly: but once central nervous system neurons are destroyed, the changes may no longer be irreversible. (read here) However, most cats recover - if not completely, enough to lead a happy future.

Drugs with no proven effect

I mentioned that the cytidine nucleoside analogue Molnupiravir (EIDD-2801), which is or was developed by Merck for severe coronavirus disease in humans, may be effective in cats with FIP. But we still don't know for sure, or at least I don't.

Japanese veterinarians generally publish high-quality veterinary studies. One veterinarian in Japan thought that the combination of an anti-rheumatoid arthritis drug, Humira®, in combination with an antifungal drug, itraconazole, could be of some benefit to FIP cats. (read here) It may prove useful, maybe it won't. I don't know of any controlled studies. Itraconazole is primarily used in cats to treat severe skin conditions.


Curcumin is obtained from spices, curcuma. It is sold in health food stores with various health claims. One study from 2020 reported that curcumin had laboratory suppressive effects on the FIP virus. However, they never got to try it in FIP + cats. (read here) Curcumin is gaining great fame. However, as far as I know, it has never been found to be beneficial or curative for any human disease. (read here) We really have no idea what he could offer to FIP-positive cats.


In 2020, four veterinarians at the University of Sydney looking for treatment options for FIP were investigating how cats metabolize the compound mefloquine used to treat human malaria. (read here) Sold as Lariam® in the USA. They were interested in the medicine because a previous study had shown that it was effective against feline coronavirus. (read here) I do not know whether these studies are ongoing. Clinical trials have also been launched in Russia to determine whether the drug could be beneficial for patients with Covid-19. No results were reported.

A treatment I don't trust

For many years, I believe that occasional "drugs" against FIP are likely to be cases where cats have only had a non-fatal intestinal coronavirus, but have FIP-like signs due to some other unrecognized health problems. No report I know of has ever verified that the coronavirus left the gut and attacked the cat's body. (monocyte / macrophage tropism). This must happen until the cat develops FIP.


Some claim that a doxycycline antibiotic with or without prednisolone is beneficial to FIP + cats. Doxycycline is a suitable antibiotic for secondary bacterial infections that your FIP cat may encounter. It is also a great drug for the treatment of hemobartonella, which some cats may have positive for FIP. But no one has ever confirmed that it has any effect on the FIP virus. If you are giving your cat doxycycline in capsular or tablet form for any reason, always give it enough water or a piece of soft food, as it may settle in your cat's esophagus and cause damage. This is a good approach when giving your cat any kind of pill.

Prednisolone and other corticosteroids

It is true that prednisolone and similar compounds (corticosteroids) reduce inflammation. However, they have never been shown to affect the downward spiral of the FIP. However, corticosteroids are an excellent stimulator of appetite and positive mood, and in some cases provide FIP-positive cats with a short dose of energy and motivation. Similar effects occur in humans. (read here) It is therefore not harmful to administer them for several days under the supervision of a veterinarian.

Paradoxically, while some veterinarians try to stimulate your cat's immune system with drugs such as interferon and polyprenyl immunostimulant, others administer corticosteroids such as prednisolone or dexamethasone to weaken the cat's immune system.

Polyprenyl immunostimulant (PI) (aka polyprenyl phosphate, Fosprenil®)

In 1996, the founders of the Russian start-up company Micro-plus published an article about the amazing abilities of their compound, polyprenylphosphate (phosprenyl, aka fosprenil), to treat a wide range of diseases. They claimed to be "highly effective" in the treatment of rabies, cancer, canine distemper, hepatitis, enteritis (parvo?) And potentially useful in the treatment of human HIV and human herpes. They obtained a Russian patent for the compound. Polyprenyl immunostimulant (PI) is still commonly sold in Russian pet stores, where it is used to treat anything.

Russian veterinarian about Phosprenyl {2013)

I remain skeptical that polyprenyl immunostimulant has some value to your cat. Mithridates the Great last mentioned a potion with such wide effects in 100 BC If you want, read more about Big Theriak. Nevertheless, in 2009, veterinarians at the University of Tennessee said PI was likely to benefit several cats that were thought to have a dry form of FIP. (read here) Naturally, everyone was excited and full of hope. Even the Winn Feline Foundation contributed financially. But since this initial announcement in 2009, I have not known of any other publications on this drug in human or animal medicine. The effective drugs that veterinarians and cat owners so urgently need are absorbed much faster.

Omega feline interferon

Interferons play a role in your cat's natural resistance to corona and other viruses. (read here) Thus, it could be assumed that administering interferon to cats with FIP could help them. A Japanese study once suggested this. (read here) However, it was a poorly constructed study. Only a few animals were treated and observed, and no evidence was ever provided that any of the cats had FIP. But since the vets at the time had so little to offer cats with FIP, it caused a lot of excitement at the time.

A recent German study found that feline interferon administration had no effect on the life expectancy of FIP-infected cats studied, nor on their quality of life. (read here) You can, of course, say that the Germans did not administer interferon in sufficient doses, or administered it incorrectly or at the wrong stage of the disease, etc. So there are still veterinarians who give or recommend it. Virbac Corporation's European division still sells a recombinant feline interferon product (Virbagen Omega®). It is not currently sold in the US, but some North American cat owners have managed to get it. A British veterinarian published an article in 2020 suggesting that its use was beneficial in treating a cat infected with the dry form of FIP. However, in addition to the omega interferon, the cat received the Chinese drug Mutian. (read here) My belief, the belief of the NIH and others, is that these commercially available interferon products do not have the ability to treat coronavirus and probably not the course of FIP, FeLV or FIV. (read here and here and here) Another with similar claims, Feliferon®, is sold in Russia. I have no idea what's in it.

Alternative and complementary medicine

One person's despair is another person's opportunity. There have always been, and always will be, herbalists, naturopaths, obscure art practitioners, and even several veterinarians who claim to be able to cure incurable diseases. They will raise your hopes by telling you what you want to hear; and then when the money changes hands, they will disappoint you. Tragedy and loss are painful for each of us. But false expectations do not delay the necessary. These options only provide a false sense of comfort, support and consolation to some cat owners facing FIP. These cat owners should have the right to use them if they wish

What to believe? What information can I rely on?

Whether you can trust my information is something you will have to decide for yourself. But in general, I take my information from a group in Davis, California under Dr. Niels Pedersen. Over the years, I have learned to trust him and the publications and judgment of UC Davis. Equally credible is the information coming from Cornell. When evaluating the quality of a research paper and its findings, I always check who paid for it and the reputation of the journal in which it was published. I am also considering who will benefit financially from these findings. You can find a scientific journal that will publish almost anything today. These two veterinary colleges in the USA and the British Royal Veterinary Academy (RVC) are placed in the top three from year to year. Another veterinary institution with very high standards is the veterinary school in Shut up.

There is no consensus in the RVC on what can currently be done for cats with FIP. Neither what constitutes a sufficiently valid diagnosis of the dry form of FIP nor any treatment of any form after acceptance of the diagnosis. Some doctors still recommend a combination of interferon and prednisolone. Others do not believe in either. Until the results of the UC Davis studies became known, most veterinarians at the institution sucked out pleural effusions as needed and did whatever they thought could do the cat better. They offered consolation to cat owners as well as cats themselves and possible euthanasia.

I have been told that most veterinarians in the RVC are now likely to alert cat owners to the FIP Warriors website - warning that they may spend a lot of money and that the medicine they receive may not be what they thought they paid for. Regulations and thinking in Britain are such that most veterinarians there weigh in direct involvement for fear that they could be "removed from the register" (loss of license). So some veterinarians don't even mention China. Those I spoke to, as well as UC Davis, are opposed to the use of these Chinese drugs in an effort to achieve coronavirus-negative breeding due to fears of drug-resistant FIP strains that will no longer respond to GS-441524 and similar drugs. I agree. Some have fewer reservations about it. (read here)

There are also veterinarians in the RVC who question the likelihood that any common feline coronavirus has the ability to mutate to a variant of FIPV. This is the current theory accepted here in America and the one I have presented to you. These veterinarians from the UK are interested in what are the chances of the same mutation being repeated over and over again in different cats? And they ask, "Isn't it much more likely that cats have several different forms of coronavirus and only one virus (or a group of related viruses) has the ability to cause FIP?" I don't know the answer.

Can my cat be vaccinated against FIP?


Zoetis produces a FIP vaccine, Felocell FIP (IN). It is a vaccine that is given to the cats' noses. The company suggests that it should only be given to cats aged 16 weeks or older as 'help' in preventing the disease. Contains attenuated FIP virus. This particular strain of the virus is believed not to survive at the cat's core (internal) body temperature and to proliferate only in the cat's upper respiratory tract and nose, where it is likely to be harmless.

There is not enough data to tell if this vaccine has any practical use to protect your cats. First, many believe that most cats are exposed to the feline coronavirus before the age of 16 weeks - when they are still too young to receive a vaccine that produces antibodies to the coronavirus. However, we do not know how long these antibodies last or whether they are more effective in preventing FIP than the antibodies that most coronavirus-exposed cats already carry. There are also veterinarians who are concerned that antibodies destroy tissue in FIP-infected cats and that stimulating antibody production may be a negative event. Some early studies concluded that the vaccine was beneficial (read here), while others do not. (read here) If you decide to have your cat vaccinated with this vaccine, you should know if it already has anti-coronavirus antibodies in your blood as a result of previous exposure to feline coronavirus. In these situations, the vaccine is unlikely to be beneficial. (read here)

I have more cats. What should I do to protect them if FIP breaks out at one?

As a rule, I do not recommend isolating a sick cat from a stable household with multiple cats. Watch her, make sure she is not bullied at the time of feeding, meet her special needs if they do occur, but separation from roommates and changes in the household can be another stress for many cats. Assuming mutation theory is correct, if your cat family has been together for some time, all cats have been exposed to feline coronavirus, and are immune or possibly healthy carriers of the non-mutated form of FCoV. Try to reduce conflicts between cats. Kennels should consider a break in breeding and keep in mind that siblings of FIP + cats are at greater risk of developing the disease. In these situations, consideration should also be given to avoiding the stress associated with castration, overcrowding, sales or unnecessary vaccination.

The University of Colorado Veterinary School has the staff of the philosopher Bernard Rollin. He warns against keeping suffering animals alive for too long. He wrote an article about end-of-life problems in old cats, but many also apply to the situation of a cat with FIP. His and my beliefs are that when deciding to end your cat's life, you owe it to your friend to choose what will cause him the least pain and suffering, even if it means more immediate pain and sadness for you. You can read the article read here. If you want, read my thoughts on losing pets here. Over the years, many people have written to me that they blamed themselves for something they did or did not cause to lose their cats. But this is rare, and never so when it comes to the FIP.

Leave a Reply

Your email address will not be published.