Feline Infectious Peritonitis (FIP): Treatment Hope On The Horizon

Feline infectious peritonitis (FIP) is a viral disease of cats first described in the late 1950s that continues to challenge our understanding today. Until recently, FIP was considered a death sentence.

This Saturday is National Bring Your Cat to the Vet Day so it seemed like a good time to cover FIP.

Dr. Niels Pedersen, now professor emeritus at U.C. Davis, California, has studied FIP since the 1960s. I had the honor to interview Dr. Pederson for an article about FIP that appeared in CATS Magazine (no longer printed) back in the 1990s, and later to hear him speak at prestigious veterinary conferences and at the Cat Writers’ Association events. You can read a 2017 Winn Feline Foundation recap of one of Dr. Pedersen’s sessions on the topic here.  

Today, FIP can be treated, and some cats like Wizard (in the pictures) possibly cured of the disease.

Putting A Furry Face On FIP

Deborah Felin reached out to me about the heartbreak and new hope of dealing with feline infectious peritonitis in a rescue situation:

Our rescue organization, having taken in over 1000 cats in recent years, has endured the heartbreak of losing kittens and young cats to FIP too many times. Until now, all we could do is keep them as comfortable as possible and watch helplessly as they stopped playing, stopped eating and their lives slipped away.

Thanks to groundbreaking decades-long research by Neils Pederson of UC Davis, there is medication now available commercially, although of course not yet FDA approved. It doesn’t help every cat, and some cats will relapse, but others have cleared the virus completely. It gives us hope when we previously had none, and finally a weapon with which to fight back, so we are grateful for that.

FIP

Courtesy photo of Wizard by Erica Elliott

Hi Amy. I’m Erica, Wizard’s foster mom.

I have been with Helen Sanders CatPaws for 5 years and unfortunately and fortunately have dealt with FIP more times than anyone should have to. I say fortunately, though, because I got to care for some of the most amazing little souls. Each touched my life and I will never forget them.

How Does FIP Affect Cats?

FIP mutates from a relatively benign and very common virus (Feline Enteric Coronavirus/FECV). This cat coronavirus is highly contagious and shed in the cat’s stool. Up to 40 percent of pet cats and 80-100 percent of cats in shelters or breeding colonies harbor the cat coronavirus. Pretty much all cats will be exposed to FECV during their lifetime, but it rarely produces illness–usually only mild diarrhea in kittens and young cats.

Once it mutates into FIP, though, the virus lives inside white blood cells and no longer is shed in the stool (experts don’t believe FIP-infected cats transmit FIP to other felines). The mutated FIP virus acts on tiny blood vessels throughout the cat’s body. At least three specific mutations have now been associated with this coronavirus-to-FIP virus biotype conversion. It is estimated that FIP affects as many as one in 300 cats.

Nobody knows exactly why the coronavirus mutates in some cats but not others. Most cats with FIP are between six months to two years old.

feline infectious peritonitis

Courtesy photo of Wizard by Erica Elliott

What Are The Signs of FIP?

An FIP-infected cat may get sick suddenly, or slowly over time. Loss of appetite, weight loss, depression, and persistent fever are common. In addition, two major forms of FIP develop, distinguished by the accumulation of fluid, or its absence, within the body.

I saw Wiz at the shelter one day when I went to pick up another cat. At three months old he was a handsome little fellow. He was with another foster at first and had a series of illnesses right away. He got past them, we got him neutered and it was time for him to enter into our adoption center.

A month later I was informed something wasn’t right. I was told he wasn’t really eating and he was not gaining any weight but maintaining. It was a red flag to me right away. I became suspicious it was FIP having been through it so many times…[Erica Elliott]

Most cats develop the effusive, or “wet” form of the disease characterized by progressive, painless swelling of the abdomen with yellowish fluid, jaundice, and anemia. Fluid may also accumulate in the chest cavity, and make breathing difficult. Cats typically survive only two to three months after the onset of clinical signs.

The noneffusive or “dry” form is more typical of Birman and Burmese cats and is the more prolonged form of FIP. These cats suffer incoordination and partial or complete paralysis of the hind legs, convulsions, personality changes, and eye disease. Some of these cats may survive a year or more after clinical signs first appear.

fip treatment

Courtesy photo of Wizard by Erica Elliot

Diagnosing FIP Isn’t Easy

Sadly, there’s no easy definitive test to diagnose FIP. Tests for the cat coronavirus aren’t considered accurate, since nearly all cats test positive (since nearly all have been exposed) yet won’t be sick with FIP. More likely, veterinarians consider the cat’s age, where acquired, and clinical signs. A persistent fever unresponsive to antibiotics is highly suggestive when partnered with “wet” or “dry” signs of the disease. Indirect tests of the cat’s blood, analysis of the effusions, and ultrasound may further confirm the suspicion.

We took Wiz to the vet where we did blood work. The vet could read my mind and it was what he was suspecting, too. The bloodwork had the markers for (dry) FIP which confirmed what I had already known. I decided it would be best for me to foster him.

A definitive diagnosis requires either a biopsy or post mortem examination of tissue and/or fluid to find viral RNA using PCR-based tests or identifying viral proteins in samples. Immunohistochemistry and real-time RT-PCR are very useful for identifying FIPV antigens in tissues with lesions or effusions and, if done properly, can provide a definitive diagnosis.

FIP Treatments & Hope for the Future?

Experimental treatments have historically included one or more combinations of drugs designed to inhibit viral replication, control the inflammatory response, or stimulate the immune system non-specifically so that it might overcome the infection. Providing good nursing care and feeding a balanced, high nutrition diet makes the cat more comfortable in the terminal stages of the disease.

Recently, an experimental treatment from Gilead Sciences studied by Dr. Pedersen has shown great promise not only in remission but cure of FIP. The antiviral agent named GS-441524 blocks the virus’s ability to replicate. UC-Davis studies by Pedersen and Gilead scientists (some funded by Winn Feline Foundation) were published in 2018 and 2019. Treatment with GS-441524 in 31 cats naturally infected with FIP resulted in an amazing 25 of the cats cured.

Gilead Sciences, however, won’t license the drug for use in animals. The company sought FDA-approval for a nearly identical drug called Remdesiver designed to treat Ebola and didn’t want anything else to interfere with that goal. While Remdesiver failed to gain approval for Ebola treatment, it has shown some positive benefits in treating another human illness (another coronavirus), by shortening the treatment of some COVID-19 cases.

Note: You cannot catch FIP or cat coronavirus from your cat. Learn more about diseases that are transmissible here.

FIP

Courtesy photo of Wizard by Erica Elliot

Online Options: Buyer Beware

Since Gilead Sciences refuses to license the drug for animals, that slammed the door on the possibility of “officially” using GS-441524 to treat FIP. Cat lovers, though, are nothing if not purr-sistent and a handful of kitties have found other outlets for the drug. Since it is NOT an FDA-approved treatment, FIP treatment with GS-441524 is considered an off-label option.

There are a number of sources now offering the drug for sale. These are unregulated online sources and Dr. Pedersen cautions in this post that they vary in terms of drug concentrations and purity. Products may be labeled in creative ways to get past legal issues. Because they’re technically black market products circumventing the licensed tested products, veterinarians may not be able legally to help you or may require a signed release. If you suspect FIP, please work with a veterinarian to ensure the best possible outcome.

The current recommended treatment protocol is the administration of the drug for 12 weeks (84 days). Some cats require a second round of treatment. If interested in details, you can download information from Dr. Diane D. Addie’s Cat Virus site, an expert on feline coronavirus and FIP. NOTE: This information is for veterinarians, not DIY treatments.

Meet Wizard the Wonder Kitten

Erica got help for Wizard from a private online community called FIP FIGHTERS and learned about several options. She ordered Mutian capsules (described by the company as a supplement), which were delivered via USPS. The capsules were given orally, starting with one daily and gradually increasing up to three capsules a day, for a twelve-week treatment plan. Observation for another 84-days follows the initial treatment for signs of a relapse, which can happen, in which case the treatment is repeated. The cost was roughly $3,000 for 84 days.

I gave it at night and Wizard quickly learned the routine. I always gave him a tiny bit of his favorite treat (Inaba Churu) right after he took his medicine. He learned this quickly so as soon as I’d grab the blanket I wrapped him in he would race over to our spot! He’s smart! Within three days I saw improvement. It was like a miracle.

His 84 days of treatment and observation period have ended. We did bloodwork again which was drastically different from the first time. His vet was very surprised and happy!

FIP

Courtesy photo of Wizard by Erica Elliot

Foster Fail–No, a Foster Win!

Erica says she and her husband have fallen hard for Wizard over the last six months. So, they’ve decided to officially adopt him.

I have fostered other FIP cats for our organization and none of them made it. Now, there is a chance. Stay calm. I truly believe cats feed off of our energy. I know you’re scared, sad…it’s emotional. But stay positive. I would tell Wizard “you are going to LIVE!”

And just spoil your cat with love. I promise it makes a difference. If you read up on FIP, look up Veterinary sites. Koret is one I like. Make sure you’re getting correct, reliable information.

Wiz is so funny, and he makes us laugh every day. He plays fetch with his favorite pink spring, he hides around corners and jumps out at you – he’s truly one of a kind! Wiz will celebrate his first birthday this October and what a celebration it will be. He made it!

Have you ever experienced the heartbreak of FIP with one of your cats? What advice would you share? I hope you’ll never need this information but at least now, cats like Wizard and caring fosters, and researchers pave the way to a brighter hope for a cure.

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Feline Infectious Peritonitis (FIP): Treatment Hope On The Horizon — 5 Comments

  1. Thank you Amy, for this comprehensive information. In the early 70s we had a cat with an illness the vets couldn’t diagnose at that time. I can’t say for sure but in retrospect, I think it may have been FIP.

    • It’s a horrible disease. I remember assisting in a necropsy of a cat back in the 80s and seeing the inflammation and abdominal fluid. And the veterinarian couldn’t tell the owner what had happened to her cat. Heartbreaking.

  2. Pingback: (Podcast) CatPAWS: The Price of a Miracle - CUDDLY Blog

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