Progress In Treating FIP Reported

Feline infectious peritonitis, or FIP, has long been a diagnosis without hope.


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Feline infectious peritonitis, or FIP, has long been a diagnosis without hope. But a new medication shows promise, and a cutting-edge genetic breakthrough might be within reach.

Niels Pedersen, DVM, PhD, and Al Legendre, DVM, PhD, spoke of hope to a crowd of nearly 200 veterinarians, cat breeders and cat lovers at the recent 33rd annual Winn Foundation Symposium in Reston, Va.

Dr. Pedersen is director of the Center for Companion Animal Health and the Veterinary Genetics Laboratory at the University of California, Davis. Dr. Legendre, Dipl. ACVIM, is a professor of internal medicine and oncology at the University of Tennessee College of Veterinary Medicine, Knoxville.

Once clinical signs occur, FIP has been considered fatal. Most instances of FIP occur in kittens, and it happens a lot, or at least more than previously suspected.

According to Pedersen, one in 100 to one in 300 of all cats under ages 3-5 succumbs to FIP. The incidence can be five to 10 times greater among young cats coming from catteries and shelters.

A Difficult Disease

Since 1963 when FIP was discovered, there had been little real progress affecting the lifespan of those who are diagnosed. Pedersen contributed significantly to what veterinarians know today about several infectious diseases in cats, including FIP.

But he concedes, “FIP is the most complicated disease I have personally studied. And you name it, I studied it.

“FIP is the first disease I studied, and it will be the last. I told myself that I will not retire until I find some sort of solution for this disease.”

His audience greeted this statement with thunderous applause.

As emcee of the symposium, I pointed out that if a disease similar to FIP occurred in dogs, somehow enough money would have been raised to cure it. Again, the crowd cheered. 

For whatever reasons, it’s far more challenging to raise money to study feline health issues than to help dogs.

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Perhaps more significant news about FIP was reported during the three-hour symposium than over the past decade.

Legendre detailed how an investigational drug called polyprenyl immunostimulant (PI)—originally targeted for helping cats with rhinotracheitis—has been studied in cats with dry or non-effusive FIP. The Winn Feline Foundation funded a trial that initially included 102 cats starting in early 2010.

Legendre said PI is a plant-based immunostimulant that guides the immune system toward cell-mediated immunity, which is necessary for control of viral diseases.

Initial studies showed that PI was a safe compound, so a challenge study of kittens with herpesvirus-induced respiratory tract infection was done. Cats treated with PI had decreased severity and duration of clinical signs compared to placebo-treated cats.

“Dry form FIP is often a difficult disease to diagnose,” Legendre noted. “Data from cats with suspected FIP were reviewed and cats that met the inclusion criteria were admitted into the study. From previous experience, we did not see any benefit of PI in cats with the effusive or wet form.”

Today, median survival on PI is 49 days, but that number increases daily as many cats in the study are still alive and seemingly well.

Typically, cats diagnosed with dry FIP might live for months or sometimes years, so there’s no way to know how these cats might have fared without the PI treatment.

Still, the speakers said there’s lots of room for optimism.

For starters, many of the cats in the trial that were doing poorly are not only still alive, but they are nearly or completely symptom-free. And one “poster cat” remains five years out from an earlier study. Typically, cats with dry FIP would only very rarely survive five years.

It’s important to note that not all cats with dry FIP thrive after being given PI. And some that do thrive can deteriorate quickly.

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“We don’t know why that happens,” said Legendre. “Just when their owners think they’re over it, some then tend to deteriorate very rapidly. But even then we presumably extend their lives and improve quality of life.”

Conditional licensing for PI by the USDA for rhinotracheitis is expected any time. When that happens, veterinarians may use their best judgment and consider using the drug off-label for FIP, Legendre said. He wondered aloud if perhaps the solution for cats with dry FIP is using PI in combination with a yet-to-be-determined antiviral drug.

“We’re considering other ways to control replication of the virus and at the same time to enhance the immune system,” he said.

Pedersen agreed.

“We have all these antiviral drugs originally created to potentially treat HIV or hepatitis [in people] sitting in repositories. From these drugs you may find an effective drug [to treat FIP]. But the cost of such an undertaking could be prohibitive.”


While Legendre is focusing on a drug therapy, Pedersen is looking for a genetic solution to FIP.

“We now understand that far more cats are likely infected with the FIP virus than ultimately die. Yet, the disease is fatal.”

So what’s going on?

Pedersen explained that about 20 percent of cats infected with a benign enteric corona virus suffer a mutation that transforms that benign virus into the potentially fatal one. However, only 2 to 5 percent of those cats actually develop clinical signs, ultimately dying of FIP.

“Presumably the remaining 15 to 18 percent manage to mount an effective immune response to the virus,” he added.

Pedersen wants to know what’s in those cats’ genetic makeup that makes it possible for them to fight off the disease.

Pedersen said other factors affecting survival include stress, the amount of active virus being shed and the overall health of the kittens.

Pedersen hopes to identify genetic markers for a greater susceptibility to FIP and perhaps markers that indicate a resistance to the disease.

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At the symposium, he asked breeders and veterinarians to send cheek swabs from cats diagnosed with FIP, or cats that have close relatives with FIP, to his laboratory. Details are available here.

The Winn Feline Foundation has established the Bria Fund to support FIP research. Clients may learn more about FIP on the Winn Feline Foundation website. A free podcast of the entire symposium is available at www.petworldradio.net.

Steve Dale is a syndicated columnist and serves on the Winn Feline Foundation Board of Directors.


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