FELV, FIV, FIP – The “Big Three” Feline Viruses – Part 3: FIP



Feline Infectious Peritonitis arises when a relatively common feline virus known as Feline Enteric Coronovirus (FeCV) undergoes a mutation in an individual cat and transforms into the FIP virus. Researchers don’t yet know what causes this mutation although there is speculation that there may be a genetic predisposition in some cats for aiding this mutation’s occurrence. It’s estimated that 40% of the cat population are asymptomatic carriers of the FeCV virus. This virus itself doesn’t cause disease – only its mutant offspring create disease. 


There are two different primary forms of FIP known as the “wet” and “dry” forms. Most cats with either form will show fairly vague signs such as loss of appetite, weight loss, difficulty breathing and a fever which does not respond to antibiotics.  Most affected cats are between the age of 3 months and 2 years. We assume older cats may be able to fight this off.

 The wet form causes a characteristic yellow fluid accumulation in the abdomen or chest with the abdomen being the most common. This is where the name comes from – peritonitis refers to inflammation of  peritoneum – the tissue lining the abdominal cavity.

The dry form instead causes accumulation of inflammatory materials on various organs leading to organ failure and signs related to which organs are affected. 


The FeCV virus lives in the intestinal tract of carrier cats (remember this does not cause disease) and is shed in feces. Uninfected cats can be exposed through litter pans and in the outdoors.  The FIP virus is contained within blood cells and does not pass into the stool.  Despite its name FIP is rarely, if ever, contagious. Since it results from a mutation within an individual cat we don’t currently consider it transmissible. 


According to the Association of Feline Practitioners, there is no reliable test currently available for this disease.  Laboratories are able to test for FeCV but there is no way of determining if a carrier cat will have the mutation which helps  FIP to occur. Genetic testing is currently under investigation but current DNA tests are not reliable. Your veterinarian must piece together different symptoms and tests to presume this disease is present. Analysis of the fluid is often helpful as it can be quite characteristic. The only definitive test is confirmation on biopsy, usually done after death. 


There is no treatment for this disease. FIP is almost always fatal. Several research groups are working on ways to treat FIP but currently all the profession can offer is palliative care, keeping a cat as comfortable as possible. 


Since FIP results from an unpredictable mutation within a cat there is no real way to prevent this from occurring.  Limiting exposure to unknown cats by keeping your cat indoors and adopting only healthy cats seems the wisest course to follow.  There is a vaccine recently on the market but it doesn’t appear to be very effective and its use is limited. 


So there you have it.  Quite a cheery bit of information isn’t it?  Cats are certainly a unique challenge to us veterinarians as they have several serious diseases only they can catch.  But if you share your life with a cat I don’t have to tell you what a unique creature it is. You already know that.  

The best way to keep your feline friend healthy?  Keep it indoors, feed the best cat food you can and take your cat to your veterinarian at least once a year.  Let’s get those viruses out of here!



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