FIP - three initials that strike fear into every cat owner who knows how deadly this disease can be. While the virus that causes FIP is incredibly common, up until now treatment has been hopeless. Thankfully, there could soon be a brand new treatment that offers an infected cat a much better chance of survival. What exactly is FIP and are there any new treatments out there because this disease scares so many cat owners: FIP stands for Feline Infectious Peritonitis and is caused by a cat-specific coronavirus that poses no risk to humans.

In most cats, the coronavirus normally stays in the intestines and either causes no problems or just mild diarrhea. Infection in this way is really common, with about 40% of household cats becoming infected at some point in their lives. For cats living in the same home as other cats, infection is even more common with about 60% being infected. In cat colonies, infection rates are pretty much 100%.

In a small proportion of cats, there is a mutation* of the virus which results in one of the body’s white blood cells, the macrophage, becoming infected. Once this mutation takes place, the virus then readily replicated in these cells and is carried around the rest of the body. At this stage, the body’s immune system may recognize and destroy the virus, preventing infection. If the immune system is not able to kill this new FIP virus, there is a reaction between the immune system and virus. This causes inflammation of the blood vessels, known as vasculitis, and the disease known as FIP.

FIP is most commonly seen in young cats, with 80% being under 2 years of age and the majority of these being between 4 and 12 months old. The disease is more common in cats living in more crowded and stressful living conditions, such as multi-cat households and breeding colonies. Genetics may also be a role as certain breeds, include the Abyssinian, Bengal, Birman, Himalayan, Ragdoll, and Devon Rex appear more prone to developing FIP. Other purebred cats, such as Burmese, Exotic Shorthairs, Manxes, Persians, Russian Blues and Siamese, are at no extra risk from FIP. Overall, Feline Infectious Peritonitis is thought to kill about 1% of cats worldwide.

The early signs of FIP can be vague and non-specific, and this phase can last for days to months: Fever, Lethargy, Inappetence. Once the disease progresses, there are 2 forms, wet FIP and dry FIP, which have different symptoms and different diagnostic challenges.

In wet FIP, the blood vessels become leaky which results in fluid building up somewhere in the body. This is most often in the abdomen followed by the chest. The fluid often has a fairly characteristic appearance - clear yellow, thick, and “sticky”.

In dry FIP inflammatory lesions form around the blood vessels. This most commonly affects the eyes or brain**, but can also affect the kidneys, liver, lungs, and skin. Signs of dry FIP are often still vague, and depend on the areas of the body most seriously affected. In a cat showing some FIP symptoms, the cat’s age, breed, and lifestyle are considered. A young cat of an at-risk breed, living in a multicat environment is much more likely to be suffering from FIP than an older cat who does not have contact with others. Blood testing is then likely to be carried out.

Unfortunately, there is no specific FIP blood test. A titer test can be run, but this can only check for coronavirus exposure. This is not helpful if positive, as most cases of coronavirus infection are "normal" intestinal infections, and there is no way to differentiate this from FIP infection. A negative result, however, is likely to mean that FIP can be ruled out.There are some common, non-specific, changes in general blood test parameters that don’t confirm FIP but, if present, give another clue FIP could be the cause of a cat’s illness.

If fluid is present within the abdomen or chest, then this can be sampled. Feline Infectious Peritonitis fluid is normally clear, yellow, thick and sticky in character, and high in protein when tested. The fluid can also be checked for the presence of coronavirus within the fluid itself. Again, this test can’t differentiate between the intestinal and FIP versions of coronavirus but if found in the fluid, then infection is much more likely.

Finally, biopsy of affected tissues can be carried out. This is a much more invasive test requiring anesthetic and surgery. Because a cat is normally very unwell by this stage, it is not a test that is commonly carried out because of the high risk involved.

Unfortunately, FIP is currently a fatal disease in cats. Once an individual becomes unwell, they will often die only days to weeks later. Treatment involves providing supportive, symptomatic care but all this really does is delay their inevitable death.

There is hope on the horizon that there may soon be a new FIP treatment that really works! This is a human antiviral drug currently known as "GS-441524". In the initial study***, 31 cats with FIP were treated with 26 completing the planned 12 weeks of treatment: 1 cat subsequently died from FIP, another from heart disease, 18 remain healthy with no further treatment needed, 8 cats required repeat treatment but were also health when the study was published. These surviving cats, at the time of publishing of the study, were last treated between 9 months and 20 months previously. This means that a massive 77% of cats not only survived FIP, but remained healthy for at least 9 months after infection. I’m sure there will be more studies looking into the long-term survival of cats with FIP treated with GS-441524. And I’m also sure we’ll be calling this drug by a different name!

While there is a vaccine available in some countries, it is generally not recommended. This is because it should only be administered to a kitten older than 16 weeks that have no antibodies to coronavirus. This rules out most at-risk cats. If you are bringing a new kitten of an at-risk breed into a house with multiple cats, however, and the vaccine is available, there is no harm in getting them titer tested and then vaccinated if negative.

Other prevention strategies include: Keeping fewer cats living together - the more cats the higher the risk, meticulous hygiene, low stress and good general care.

One important fact to remember too is that in most cases, the FIP version of coronavirus is not shed in an infected cat’s poop. As a result, FIP is not readily transmitted from one infected cat to another. It is the standard, common, intestinal coronavirus mutating within a cat that results in FIP.

Source: https://ourpetshealth.com/podcast/fip-in-cats?rq=FIP [Sept. 2020]

*The exact trigger for the mutation is still unknown. General observations indicate that low immunity due to stress, neutering, and poor living condition may causeh the onset of the FCOV mutation into FIPV [basmifipturkey.com]. Although FIP can occur in cats of any age, it is most often seen in young cats. Around 80% of cases diagnosed are in cats less than 2 years old, and many cases are seen in kittens around 4-12 months old. FIP is also more common in cats kept in groups or colonies (especially breeding households) as this is an environment where FCoV infections are spread easily. A crowded environment may also contribute to stress, which can be a factor in disease development as it compromises the cat’s immune response. There is evidence that genetics can also play a role in susceptibility to disease, although this is complex. Many cats that develop FIP are now in single cat homes, despite coming from multi-cat environments [icatcare.org/advice].

** https://m.youtube.com/watch?si=L_Sfarlqo1UPkj_L&v=xeACdrksmTs&feature=youtu.be

***Dr. Niels Pedersen’s initial study (2019): https://journals.sagepub.com/doi/full/10.1177/1098612X19825701

Dr. Niels Pedersen’s Publications by Year: https://www.lunasfiplegacy.com/research

THE NEUROLOGICAL FORM OF FELINE INFECTIOUS PERITONITIS AND GS-441524 TREATMENT

WHAT IS THE HISTORY OF FIP? (an interview with Dr. Niels C. Pedersen by Nancy Reeves , published in October 2008) at https://www.sockfip.org/about-fip/: FIP was first recognized as a specific clinical entity in the late 1950’s. This timeline was based on decades of meticulous necropsy records kept by pathologists at the Angell Memorial Animal Hospital. There was a steady increase in the incidence of the disease in the 1960’s onward, and it is currently one of the leading infectious causes of death among young cats from shelters and catteries. The reason for the sudden emergence of FIP is not known, but there are at least two possible explanations. First, it is noteworthy that FIP appeared within a decade of the initial descriptions of transmissible gastroenteritis (TGE) of pigs in North America.The causative virus of FIP is closely related to TGEV of pigs and canine coronavirus (CCV), although they are still genetically distinguishable. However, mixtures between these three viruses are known to occur. At least one strain of canine coronavirus can induce mild enteritis in cats and enhance a subsequent infection with FIPV, indicating a special closeness to feline coronaviruses. Therefore, CCV may be a more likely parent of FECV in this scenario. Another related possibility is that the FIP mutation occurs only in a relatively new strain of FECV, and that this new strain only evolved in the 1950’s. Coronaviruses such as FECV are continuously mutating as a result of the manner in which their genetic material (RNA) is replicated. Therefore, genetic change, either among themselves or through genetic mixing with closely related coronaviruses from other species, could have either allowed a coronavirus of another species to take up host in cats or to alter a strain that existed prior to the 1950s. An alternative non-genetic explanation may involve changes in how cats were viewed as pets and their husbandry. There was a dramatic shift in the status, keeping, and breeding of cats as pets after WWII.The numbers of pet cats greatly increased, pure breeding and cattery rearing became increasingly popular, and more cats, and in particular kittens, found themselves in shelters. These large multiple cat indoor environments are known to favor feline enteric coronavirus (FECV) infection and FIP. Interestingly, feline leukemia virus (FeLV) infection also became rampant among indoor multiple cat households during this period, and FeLV infection was a significant enhancing factor for FIP until it was pushed back into nature as a result of testing, elimination/isolation, and eventual vaccination in the 1970s and 1980s.

See also

"How research of an FIP treatment for cats is saving human lives" at dvm360.com
2023 article "How far would you go to save your cat?" at the Guardian
Feline Infectious Peritonitis (FIP) – What Happened, Why It Happened. What Will Happen To My Cat And What Are My Options? / https://vetspace.2ndchance.info/feline-infectious-peritonitis-fip-and-your-cat/?amp=1
Differential Diagnosis: If your cat has been diagnosed with FIP, your first step is to ensure you have the correct diagnosis, because errors are frequent... It is estimated that 70 to 80% of cats diagnosed with non-effusive FIP turn out to have another condition, usually treatable. The likelihood of error in the case of effusive (wet) FIP is lower but still varies widely depending on the cat's age and breed... 95% of cats are FCoV (Feline Coronavirus) carriers at one point or another. It does not mean they will develop FIP. Only 5% of them end up developing Feline Infectious Peritonitis. Also, be aware that there is NO DEFINITIVE TEST for FIP... FIP is a difficult diagnosis to reach, and is a process of exclusion, particularly with the dry (non-effusive) form.

GLOBAL RESEARCH ARTICLES

, Nov. 2023]

Further information for veterinarians can be found here [May 2024]

Concerning feline infectious peritonitis outbreak in Cyprus (FCoV-2023-outbreak): biorxiv.org, icatcare.org, bvajournals.onlinelibrary, fecava, fipwarriors.eu, hvms.gr

Σύμφωνα με τον κτηνίατρο Μάριο Μιχαήλ, εκατοντάδες ήταν και οι περιπτώσεις γάτων που μεταφέρθηκαν σε κτηνιατρικές κλινικές με συμπτώματα χτυπήματος από αυτοκίνητα, αλλά οι εξετάσεις έδειξαν τελικά πως επρόκειτο για νευρολογικά προβλήματα που προκαλούνται από την λοιμώδη περιτονίτιδα [dw]