Possibly the deadliest disease to infect any cat, the cause and cure for feline infectious peritonitis or FIP has eluded researchers for over 30 years, leaving cat lovers and veterinarians with no definitive diagnosis or alternatives for treatment other than comfort measures in a disease that most often strikes kittens and young cats.
What is Feline Infectious Peritonitis, or FIP?
First recognized in the late 1950s with a steady increase in the incidence of the disease from the 1960s to today, FIP kills up to 1 in 100 cats under age 5, and cats coming from more crowded or stressful situations such as shelters or catteries are at five to 10 times greater risk of contracting and developing the disease. It is virtually 100% fatal, meaning no cats have been known to survive for more than a few months beyond diagnosis without symptoms, which can vary widely and mimic other illnesses. Any symptoms can be treated but the treatment is palliative, not curative, and there is currently no known cure for the disease.
FIP begins as feline enteric coronavirus, or FECV, a fairly common intestinal virus among cats and is spread by fecal matter. About 90 percent of cats who come in contact with FECV have only minor symptoms such as mild diarrhea for a few days or no symptoms at all, then recover with no apparent lingering effects.
But in about 10% of infected cats the virus moves from cells in the intestines to a particular white blood cell called a macrophage which exist all over the body. These specialized cells are part of the body’s immune system and have the job of cleaning up dead cells and cellular debris from injuries as well as engulfing disease-causing pathogens and digesting them, sucking it all up like tiny internal vacuum cleaners. However, some pathogens fool the system and avoid being digested and end up living safely inside the macrophage, cleverly hidden from the immune system. This allows the virus to replicate without the body realizing the virus is a pathogen and causing intense inflammation wherever it has decided to settle and replicate. This inflammation is painful but is non-specific and can be generalized all over the cat’s body, which is what leads to the non-specific symptoms which make diagnosis so difficult.
The breakthrough: when FECV becomes FIP
The breakthrough is in determining when and how FECV becomes FIP. “Comparing viral genetics, our lab found exactly what changes when FECV mutates into FIPV. This knowledge will prove pivotal in developing tests, vaccines and treatments to protect cats from this devastating disease,” said Gary Whittaker, virology professor at Cornell’s College of Veterinary Medicine.
But even though FIP cells all start out the same, each rapidly develops its own complications once it begins to replicate. FIP is an RNA-based virus and makes many “mistakes” when it’s replicating—these mistakes are actually mutations so that each incidence of the virus, even within one cat, is different from any other, so tests, vaccines and treatments can’t be determined. “These viruses are so rife with mutations that even samples of the same virus from the same tissue in the same cat rarely match to the letter,” said Whittaker.
Instead of taking piles of samples of the virus to study and look for some similarity or pattern, Whitaker studied a particular area of the FECV virus cell and compared it with the same area on the FIP virus cell and found a mutation. Whittaker was able to consistently locate this mutation across hundreds of feline coronavirus samples he had collected from pet owners, veterinarians, and Cornell’s pathology vault, the school reported.
A few more details about FIP
There are two forms of FIP, referred to as granulomatous, or dry, FIP and effusive, or wet, FIP; the first has no obvious symptoms, the second form causes fluids to build up in the abdominal or pleural cavity. This fluid can be drained but will usually return, and the fluid itself puts a strain on the body’s function and on the immune system. The dry form has little to no fluids developing in the body, but lesions develop on the internal organs and these lesions variously affect the organ’s function and lead to secondary infection.
In both cases the immune system is greatly compromised, secondary infections are common, and neurological symptoms such as changes in eye function or vision loss, or difficulty balancing or walking which develops to functional paralysis. On the outside, however, the cat often looks completely normal.
Oddly enough, FIP itself is not truly contagious. FECV is shed in the feces and can be passed on to other cats, but it is not FIP until the mutation which happens as it replicates inside macrophages, but these cannot be shed.
Why we care deeply about FIP
We care about all health issues involving cats, but FIP is very personal. I’ve often mentioned Lucy, the little black kitten born to Mimi the year before the Fantastic Four were born, and that she developed and died of the effusive form of FIP at 15 months. In part, the propensity to develop the disease is thought to be genetic, and I’ve got five members of Lucy’s family here, and I am in touch with a number of others and their adoptive humans. As research on the disease progresses we want to know, and we certainly don’t want anyone else to lose a kitten in the way we lost Lucy. I think now that this breakthrough has been made, progress will move much faster in diagnosis, treatment and prevention.
As I review photos from six years ago at this time I can clearly see the changes in Lucy so this announcement comes at a time of year when I’m already thinking of this disease and its effects. We lost her on July 10, 2007, so by this time, at the end of June, I could see the changes in her eyes and her fur, and you can read more about our journey beginning here. I look forward to hearing more good news about treatment and cure for FIP.
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The research was funded by Cornell’s Feline Health Center, the Winn Feline Foundation and the Morris Animal Foundation.
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