CATS · Condition guide
Feline infectious peritonitis (FIP): real veterinary cases
Feline infectious peritonitis was once a guaranteed death sentence — a fatal immune-mediated disease triggered when an ordinary feline coronavirus mutates inside the cat and the immune system responds catastrophically. The "wet" (effusive) form fills the abdomen or chest with thick, straw-coloured fluid; the "dry" (non-effusive) form causes granulomatous lesions in the eyes, brain, kidneys, or liver. Young cats (under 2) and cats from multi-cat environments are most at risk.
The landscape changed dramatically in 2019 when GS-441524 proved curative in the vast majority of cases. Legally accessible antiviral treatment is now available in many countries and published cure rates exceed 80-90% for the effusive form. FIP has gone from uniformly fatal to genuinely treatable — one of the biggest recent advances in feline medicine.
What vets typically check for
- Fluid analysis (if effusive): high protein, low cellularity, positive Rivalta test.
- Bloodwork: hyperglobulinemia, low albumin:globulin ratio, elevated bilirubin.
- Coronavirus titre + immunofluorescence or RT-PCR on fluid/tissue for confirmation.
- Ocular exam + neurological exam — dry FIP frequently involves the eyes (uveitis) or CNS.
- Treatment: GS-441524 antiviral for 84 days (12 weeks); monitoring with bloodwork every 2-4 weeks.
Not a replacement for veterinary care. Use this to walk into the conversation prepared, not to self-diagnose.
Real cases from the veterinary literature
Peer-reviewed reports our semantic search surfaces for Feline infectious peritonitis (FIP). Click into any case for the full abstract — or run a personalised search with your pet's exact details.
- GS-441524 Treatment in a Cat With Feline Infectious Peritonitis Virus and Pyogranulomatous Transverse Colon Lesion.
In vivo (Athens, Greece) · 2025 · South Korea
A 7-year-old male domestic shorthair cat was diagnosed with feline infectious peritonitis (FIP), a serious disease caused by a virus, along with a rare type of inflammation in his colon. He had stopped eating and was vomiting, and tests showed some abnormal blood results and a mass in his colon. After receiving a treatment called GS-441524 for 12 weeks, the cat showed significa
- Update on Treatment of Feline Infectious Peritonitis: European Advisory Board on Cat Diseases (ABCD) Guidelines.
Viruses · 2026 · United Kingdom
Feline infectious peritonitis (FIP) is a serious illness caused by a virus that affects cats. In the past, it was often considered fatal, leading many veterinarians to recommend euthanasia after diagnosis. However, new antiviral treatments, especially a medication called GS-441524, have changed this situation significantly, making FIP a treatable and often curable disease. Rece
- Antiviral treatment using the adenosine nucleoside analogue GS-441524 in cats with clinically diagnosed neurological feline infectious peritonitis.
Journal of veterinary internal medicine · 2020 · United States
Feline infectious peritonitis (FIP) is a serious disease caused by a mutated virus that affects cats, often leading to problems in the brain and eyes. In this study, four cats with neurological FIP were treated with an antiviral drug called GS-441524 for at least 12 weeks. The cats were regularly checked by veterinarians, and one cat underwent detailed imaging and testing to mo
- Treatment of non-effusive feline infectious peritonitis using oral remdesivir or GS-441524: a randomized, double-blind, non-inferiority trial.
Journal of feline medicine and surgery · 2026 · United States
ObjectivesFeline infectious peritonitis (FIP) is a fatal disease caused by feline coronavirus. The nucleoside analog GS-441524, the parent nucleoside of remdesivir, is the most commonly used FIP antiviral. Remdesivir is Food and Drug Administration approved to treat COVID-19 in humans and has been used primarily as an adjunctive treatment for FIP. Data on its efficacy as a f
- An Optimized Bioassay for Screening Combined Anticoronaviral Compounds for Efficacy against Feline Infectious Peritonitis Virus with Pharmacokinetic Analyses of GS-441524, Remdesivir, and Molnupiravir in Cats.
Viruses · 2022 · United States
Feline infectious peritonitis (FIP) is a serious and often deadly disease in cats caused by a virus called feline infectious peritonitis virus (FIPV). There are two main forms of FIP: the "wet" form, which involves fluid buildup, and the "dry" form, which can affect the nervous system or eyes. This study looked at several antiviral medications to see how well they work against
Frequently asked questions
- Is FIP still a death sentence?
- No. GS-441524 has changed FIP from uniformly fatal to curable. Published studies report cure rates of 80-90%+ for effusive FIP. Neurological and ocular forms are harder to treat but still respond in many cases. Early diagnosis and prompt treatment give the best odds.
- Is FIP contagious to other cats?
- The parent feline coronavirus is very common and spreads easily in multi-cat settings, but the mutation to FIP happens inside an individual cat. You can't "catch FIP" directly — but cats in the same household share the underlying coronavirus exposure.
- How do I know it's FIP and not something else?
- Definitive diagnosis is tricky. A combination of clinical signs, a very low albumin:globulin ratio, positive Rivalta test on fluid, and immunostaining or PCR is the current gold standard. No single test rules FIP in or out on its own.