I was recently asked a difficult question by a very inquisitive client: “Doc, why do cats get FIP?”
I was caught off-guard, as this particular client has two very healthy cats, but he went on to further explain that he had read an article on the Internet somewhere and it piqued his interest. After a lengthy discussion on the intricacies of FIP, my client thanked me for my time and walked out of the office with the signs of someone on information overload.
Unlike a discussion about diabetes or feline leukemia, FIP (feline infectious peritonitis) can be difficult to explain. As a veterinary community, there is a lot we know about FIP, however, there is a great deal that we don’t yet understand. Therein lies the difficulty in answering a question such as, “Why do cats get FIP?” In short, we don’t completely know the answer. Here is what we do know.
FIP develops in cats from a mutated coronavirus. Many cats (upwards of 40% of the cat population) have been infected with feline coronavirus. Usually, it causes mild gastrointestinal disease (if any clinical signs) and the cat recovers uneventfully. However, in cats that have a genetic predisposition, have a high level of stress, live in overcrowded or multi-cat households , or are immunocompromised (such as those infected with FIV or FeLV, Feline Leukemia Virus), this virus can mutate into an incredibly virulent form resulting in the disease we call FIP. There is no single factor that guarantees a cat will develop FIP, and cats with any combination of the above mentioned characteristics may never develop FIP. As you can see, the picture is as clear as mud.
FIP is a disease that we generally see in young purebred cats (less than 3 years of age) that live in multiple cat households (such as catteries, where large numbers of cats are housed). It is a progressive, fatal disease that cannot be treated or cured. We can symptomatically treat it for a period of time to improve a cat’s quality of life, but the disease will inevitably take the cats life. There is a vaccine for FIP, but its effectiveness and use is controversial within the veterinary community (if you have further questions about the vaccine, please contact your veterinarian).
So, what exactly does FIP look like in a cat? The clinical signs of FIP are vague and nonspecific. Many cats will have lethargy, weight loss, vomiting, diarrhea, fever, pale mucous membranes, a bloated abdomen and/or anorexia. Some cats present with neurologic signs (funny eye movement, seizures and walking unsteadily, to name a few), or inflammation within their eyes. There is no indication that a cat with FIP can transmit the disease to another cat.
How do we diagnose FIP? Not easily. It is a VERY difficult disease to diagnose, because there is no single test that is conclusive. Diagnosis is made based on the cat’s history, clinical signs, response to therapy, and a combination of various laboratory tests (bloodwork, ultrasound, radiographs, cytology of body fluids and histopathology of tissue samples). This is a very frustrating disease for pet parents and veterinarians alike. It is difficult to diagnose, and as I mentioned previously, inevitably fatal.
As you can see, the question “Doc, why do cats get FIP?” is not an easy one to answer. FIP is a complex and frustrating disease. The good news? FIP is NOT that common. Many veterinarians will go years without ever seeing a case of FIP in their clinic. Hopefully, yours will be one of them.
To more waggin’ and purrin’. rwkj