General clinical symptoms of FIP include: depression, lethargy, fever, loss of appetite, weight loss, muscle wasting, poor coat condition, jaundice, anemia and diarrhea.
What is FIP?
Feline infectious peritonitis (FIP) is a serious and often fatal viral disease that is specific to cats. FIP is a mutation of three different genes and it is caused by a mutation of the feline coronavirus (FCoV). It can affect cats of any age, breed, or gender. This type of coronavirus cannot infect people or other species. FIP is more common in young cats and in multi-cat households where cats are in close contact with each other.
What are the symptoms of FIP?
A variety of symptoms can be seen in cats with FIP, outlined in the box diagram above.
FIP can affect the liver, kidneys, pancreas, or other organ systems. Most cats will start showing symptoms of simply not feeling well—eating poorly, running a fever, or acting lethargic. Some animals will develop other diseases, depending on the type of the disease present.
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There are two main forms of FIP: Wet (effusive) or Dry (non-effusive). These forms are mainly used for diagnostic purposes, and one cat may show symptoms from both forms. Cats with FIP can also experience ocular (eye) or neurological (brain) symptoms.
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FIP can be very difficult to diagnose because it can infect many organ systems, ranging from the abdomen to the eyes to the central nervous system. FIP symptoms also resemble symptoms from several other conditions, and the exact nature of your cat’s symptoms will depend on what form of the disease your cat has and which organs are affected.
Causes of FIP in cats?
Feline infectious peritonitis is caused by a coronavirus that is unique to cats—it is not contagious to people, dogs, or other species of animal. This virus typically lives in the cat’s intestinal system. It’s spread through contact with feces in most cases, as infected cats shed the virus into litter boxes. Respiratory transmission is possible but less common. Because the most common route of infection is contact with feces, cats living in multi-cat households that share litter boxes are most likely to get infected.
Infection with feline coronavirus is very common among cats, but it’s estimated that less than 5% of cats infected with feline coronavirus will go on to develop FIP. Cats with compromised immune systems are at higher risk of developing FIP, including kittens and cats with chronic diseases.
Is there a cure for FIP?
In a word, YES! In recent years, antiviral medications such as GS-441524 and Remdesivir have shown remarkable success in treating FIP. Thanks to the FDA and Health Canada's recent decision to permit compounding pharmacies in the United States and Canada to fill prescriptions for GS products, it is now widely available through veterinarians.
Is there a vaccine for FIP?
An existing vaccine has been developed and is available.
That said:
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It has to be used in kittens at least 16 weeks of age (most cats are already exposed to coronavirus at this age)
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It is not effective in cats already exposed to coronavirus (which is most cats)
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It is not effective against the common serotype of FIPV, and even when all factors are optimal
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It has low efficacy
In short, it does not work in the environments where it is needed most (catteries and shelters) and is not justified in older pet cats where FIP is hardly seen.
A new, promising mRNA-based preventative FIP vaccine is in development at UC Davis, though its availability is still pending licensing and regulatory approval. While a less effective vaccine has existed for decades, the UC Davis team is working on a next-generation approach to avoid past complications like antibody-dependent enhancement (ADE).
More information can be found here: https://www.vetmed.ucdavis.edu/news/preventing-deadly-fip-cats
What is GS-441524?
GS-441524, or simply put, "GS" is an anti-viral drug (nucleoside analog) that has cured cats with FIP in field trials conduced at UC Davis by Dr. Niels Pedersen and his team as well as hundreds of thousands of cats world-wide since its discovery.
What is the treatment length?
Based on Dr. Pedersen’s original field trial, the recommended treatment is a MINIMUM of 12 weeks or 84 days of daily sub-cutaneous injections or oral medication. Blood work should be checked at week 4, week 8, and just before the end of the 12 week treatment period to confirm treatment can be stopped.
Oral versus Injections?
FIP causes inflammation of the intestinal tract. While some cats will be fine starting on oral meds, asking an inflamed colon to now absorb multiple pills a day can be challenging. Absorption through injection is easier on the sick cat's body. For critical patients, it is recommended to at least start with injections until cat is stable before considering switching to oral meds. Each patient should be evaluated to determine the best route of administration of GS.
What are the side effects of treatment?
The most common side effects of GS injections are pain during administration and the possibility of skin lesions forming at or near the injection sites
Rarely allergic reactions have been reported where there is hair loss or other skin conditions and can be treated symptomatically
After a series of injections, some cats’ skin becomes thicker and harder to inject. Massaging the skin around all injection areas to help break up the fascia-the layer under the skin-that gets so tight and tough sticking to the outer layer
A paper describing uroliths composed of GS found in 2 cats can be read here: https://pubmed.ncbi.nlm.nih.gov/38032049/
Side effects from oral GS are rare to non-existant.
Can GS be Used in FCoV Shedders?
Misuse of GS-441524 to try and control FCoV is dangerous as it can potentially cause the virus to become resistant to GS. The available anti-virals should only be used to treat active FIP cases.
Read Dr Pederson's statement here:
Is FIP contagious?
No. Feline Coronavirus (FCoV), the virus that can mutate into FIP, is highly contagious among cats. It is shed through feces, and cats who share litter boxes or groom each other are at risk of exposure. However, most cats who are exposed to FCoV will pass it without issue, experiencing only mild symptoms such as diarrhea or cold-like symptoms.
Once FCoV mutates into FIP, the mutated virus is no longer contagious. FIP is not directly contagious between cats. However, it is believed that FIP has a genetic component, meaning that littermates or cats with a genetic predisposition may be more likely to develop FIP. A family history of FIP increases the risk of FIP in siblings.
Should cats with FIP be quarantined?
It is not considered necessary to quarantine a cat who has been diagnosed with FIP as horizontal transmission of the mutated FIP virus is considered extremely uncommon, if it happens at all. Studies have confirmed that even in cases where cats in close contact with each other developed FIP, the virus mutated independently from FECV within each cat rather than horizontal transmission of the mutated FIP virus.
That said, research has shown that FIPV is present in the feces of some cats with FIP, which does make horizontal transmission theoretically possible. Additionally, research has also shown that even when the mutated virus is shed, it does not seem very contagious.
Recent research has supported a "circulating virulent–avirulent FCoV" theory (as opposed to horizontal transmission) as an explanation for clusters of cases sometimes seen in multi-cat environments, particularly shelters, catteries and rescues.