Feline infectious peritonitis (FIP) is a diagnosis no cat parent wants to hear. FIP is a devastating illness that affects domestic and big cats when a mild feline coronavirus mutates. According to a study in the Canadian Veterinary Journal, the coronavirus mutation occurs in about 10% of infected cats. In most cases, it’s fatal, but a new drug could change that.
If your cat contracts feline enteric coronavirus (FECV), her immune system normally mounts a response that easily defeats the virus. Your kitty might display no symptoms or very mild ones. A bout of feline diarrhea and/or mild respiratory symptoms may resolve quickly on their own. However, trouble can start when the FIP virus mutates.
Sometimes a mutation occurs that causes FECV to infect a cat’s white blood cells. The infected cells travel throughout the cat’s body as part of their normal mission. As they do, they spread the mutated coronavirus version called feline infectious peritonitis virus (FIPV). While some cats successfully fend off this version, others become very ill.
When a cat’s immune system interacts with a runaway FIPV infection it can cause an extreme inflammatory response. The inflammatory response may then trigger FIP, a progressive and usually fatal disease.
Here’s what cat owners need to know about the heartbreaking FIP illness and the outlook for treating it.
Some Cats May Be More Vulnerable
Feline infectious peritonitis is a disease that most often strikes kittens. Age at the time of infection, genetics, and stressors at the time of virus exposure can be significant. Factors like other infections, early weaning, overcrowding, surgeries, and vaccinations can all contribute to a cat’s vulnerability to FIP.
It’s important to note that FIPV lives inside white blood cells and not in the intestine. Therefore, it’s not shed or transmitted through a cat’s feces.
Feline Infectious Peritonitis Symptoms
The two forms of FIP — known as “wet” and “dry” — both cause cats to lose their appetite, drop weight, become lethargic or depressed, develop rough fur, and run a persistent fever. Since cats can experience these clinical signs for many reasons, they don’t (singularly or collectively) definitively point to FIP.
As the disease progresses, an infected cat who suffers from wet FIP can develop fluid buildup in their abdominal and/or chest cavities. Those with fluid buildup in the chest are likely to experience labored breathing, while cats with fluid in the abdomen get big, distended bellies.
In its dry FIP form, it causes cells to form granulomas in blood vessels and various organs. When the disease affects a cat’s kidneys, it can show up as excessive thirst and frequent urination. Cat vomiting and weight loss may also occur. Liver involvement can cause jaundice and affect the eyes, brain, spinal cord, and nerves.
Obtaining a Diagnosis for FIP Cats
It can be nerve-racking to wonder if your cat has feline infectious peritonitis, especially since there’s no single conclusive test for it. A test for FECV may be done — however, this test can’t distinguish between FECV and the far more dangerous FIP.
A positive FECV test by itself is inconclusive. However, a negative test usually means a cat is unlikely to have FIP.
If a cat has the suspected wet form of the disease, an analysis of the resulting fluid accumulation may support a FIP diagnosis. A diagnosis of the dry form may require a biopsy of affected organs by a trusted veterinarian.
A review inThe Veterinary Journal suggests that through a combination of clinical observation and tests including blood work, vets can more accurately determine whether or not a cat has FIP.
A Drug Trial Provides Hope for Cats With FIP
A drug with promising trial results in treating this feline coronavirus infection is GS-441524, an antiviral manufactured by pharmaceutical giant Gilead. Interestingly, it’s nearly identical to their drug GS-5734 (a.k.a. Remdesivir), which treats MERS.
According to a study published in the Journal of Feline Medicine and Surgery, the University of California, Davis recently conducted a feline infectious peritonitis drug trial. Each cat received treatment with GS-441524 by its owner’s consent.
Of the 31 cats enrolled in the study, 26 completed at least 12 weeks of FIP treatment. The cats, which ranged in age from 3 to 73 months, had dramatically positive responses to the drug with fevers resolving within 12 t0 26 hours. Researchers also recorded improvements in the cats’ activity levels, appetites, and weight.
In cats suffering from the wet FIP, abdominal fluid dissipated within 10 to 14 days of starting treatment. Those with dry FIP also responded well, as did cats both young and old.
When the results of the study were published in February 2019, 24 of the 26 cats were still healthy, with one having succumbed to FIP and one to unrelated heart disease. Eighteen of the cats had undergone just one round of treatment. The remaining eight relapsed but were successfully treated by their veterinarian with further rounds of FIP treatment at a higher dose.
In March 2020, Drew Weigner, president of Winn Feline Foundation and practicing feline specialist noted, “Some of these cats were treated over three years ago and are still disease-free.”
Setbacks & Copycats
It seems uncertain that GS-441524 can cross the blood-brain barrier to treat cats with neurologic manifestations of FIP. Another setback is that the drug’s manufacturer is unwilling to pursue approval from the FDA for its use in treating FIP — or to give up its patent.
Enter the copycats. Some pet owners buy knockoffs of GS-441524 through a black market. According to the administrator of a Facebook Group called FIP Warriors, four such brands — Andy’s Mark’s, Shire, and Mutian II — have been lab-tested and confirmed to match the drug concentrations and biological activity advertised.
Niels Pederson, leader of the UC Davis clinical trial, won’t tell pet owners whether or not they should purchase these drugs. Instead, he shares his knowledge about the disease and his research with them so that they can make an informed decision.
The UC Davis School of Veterinary Medicine maintains an up-to-date collection of resources on feline infectious peritonitis. This information may prove valuable for pet owners whose cats suffer from the disease or those who just want to keep up on feline health news and breakthroughs.