FIP was once fatal - but GS-441524 antiviral achieves ~80% remission in cats for $3,000-$8,000. Caused by mutated feline coronavirus. Strikes cats under 3 and over 10 most often. Progresses rapidly; early diagnosis is critical.
What Causes FIP
FECV (common coronavirus) infects 40% of cats harmlessly. In 5-10% it mutates into virulent FIPV, invades immune cells, triggers fatal inflammation. Stress, genetics, and immunity influence risk.
Mutated coronavirus attacking immune cells
Symptoms Wet vs. Dry Form
Wet: abdominal or chest fluid, fever, weight loss, lethargy - progresses in weeks. Dry: organ lesions (eyes, brain, kidney), uveitis, seizures, wobbling - slower but harder to diagnose.
Fever, weight loss, lethargy common to both
Diagnosis $400-$1,000
Fluid analysis: high-protein, yellow fluid suggests FIP. Rivalta test (inexpensive). Blood panel: elevated globulins. FCoV PCR. Immunostaining is gold standard. Ultrasound ($300-$500). No single test definitive.
Fluid + elevated globulins are key
Treatment $3,000-$8,000
GS-441524 (Xraphconn, FDA 2024): 84 days daily injections/oral. ~80% remission. Cost: $3,000-$8,000 by weight. Post-treatment: 12-week monitoring - ~10% relapse.
~80% remission with GS-441524
Total Cost $4,000-$9,000
Drug course + diagnostics + monitoring. Neurological FIP may require a higher dose and longer treatment, pushing costs toward $8,000-$12,000.
Breed Risk Young & Multi-Cat
Persians, Birmans, Ragdolls, and Abyssinians have higher reported prevalence. Cats under 3 and over 10 most at risk. Multi-cat households and catteries increase exposure.
Prognosis ~80% with Treatment
Without treatment: near 100% fatal within days to weeks. With GS-441524: ~80% achieve sustained remission. Neurological FIP has a slightly lower response rate (~70%). Early treatment before severe organ damage improves outcomes.
Prevention
No reliable vaccine available in the US. Reduce FECV exposure: keep multi-cat groups small, separate litter boxes, reduce stress. Test breeding cats for FCoV status.
The Real Cost
$5,000typical cost
84-day antiviral course + diagnostics + monitoring.
Diagnosis $400-$1,000
Treatment (84 days) $3,000-$8,000
Total Cost $4,000-$9,000
Red flags
Insurance Traps
A newly treatable disease - but insurance coverage is evolving. Here's what to know.
Coverage Basics Coverage
FIP is covered as illness by most policies - not pre-existing if enrolled before diagnosis. FDA approval of GS-441524 (2024) makes coverage more consistent than the prior compounding/import era.
The Pre-Existing Trap Pre-existing
Symptoms before enrollment (weight loss, fever, lethargy) may trigger pre-existing exclusion. Risk alone isn't pre-existing, but documented symptoms create vulnerability.
High Treatment Cost vs Limits Cost
FIP treatment ($3,000-$8,000 drug + diagnostics) is one of the costliest cat illnesses. Policies with annual limits may cap reimbursement below cost. Verify your limit covers $8,000+.
Waiting Period Details Waiting period
Standard illness waiting period is 14 days. FIP progresses so rapidly there's no time to enroll after symptoms appear. Enroll kittens early - before any illness.
Common Questions
Real answers about FIP diagnosis, treatment, and insurance coverage.
What is FIP and how do cats get it?
FECV (common coronavirus) mutates in 5-10% of infected cats into virulent FIPV, causing fatal inflammation. Up to 40% of cats carry FECV harmlessly. FIP itself isn't contagious - only FECV spreads between cats.
What are the signs of FIP in cats?
Wet: abdominal/chest fluid, fever, weight loss, lethargy. Dry: uveitis, wobbling, seizures, kidney/liver dysfunction, weight loss. Both fatal without treatment.
Can FIP be cured?
~80% of cats achieve remission with GS-441524 (84-day daily treatment). Xraphconn FDA-approved 2024. Neurological FIP: ~70% response. Before this, FIP was nearly always fatal.
How much does FIP treatment cost?
Drug course (84 days): $3,000-$8,000 by cat weight. Diagnostics: $400-$1,000. Monitoring adds hundreds. Total: $4,000-$9,000. Neurological FIP can exceed $12,000.
How is FIP diagnosed?
No single test. Combines: elevated globulins, yellow high-protein fluid, Rivalta test, FCoV PCR. Biopsy/immunostaining is gold standard but requires surgery. Most diagnoses confirmed without biopsy.
What breeds are most prone to FIP?
Persians, Birmans, Ragdolls, Bengals, Abyssinians show higher prevalence - possibly from catteries or genetics. Cats under 2 and over 10 most affected. Multi-cat homes/catteries increase FECV exposure and FIP risk.
Is FIP contagious to other cats?
FIP isn't contagious - healthy cats can't catch it from FIP cats. But FECV (which mutates into FIP) spreads via feces/shared litter. Reducing FECV spread lowers FIP risk. Treated FIP cats don't shed virus.
How long does FIP treatment take?
84 days daily injections/oral medication. Cats improve in 1-2 weeks but full course needed. Post-treatment: 12-week monitoring with bloodwork at weeks 4, 8, 12. Neurological FIP may need extended course.
What's the difference between wet FIP and dry FIP?
Wet: abdominal/chest fluid, fever, weight loss, lethargy - weeks to progress. Dry: inflammatory lesions in eyes/brain/spinal cord/organs - slower, harder diagnose. Both treated with GS-441524; wet responds faster.
Where can I get GS-441524 (Xraphconn) for my cat?
FDA-approved 2024: Xraphconn available through any US vet - no referral needed, but internists have more experience. Previously owners imported or used compounders. Ask for internal medicine referral if your vet is unfamiliar.
Does pet insurance cover FIP treatment?
Most accident and illness policies cover FIP. FDA approval improved consistency. Key risks: pre-existing if symptoms appeared before enrollment; annual limits below $9,000 cost. Verify your limit exceeds $9,000.
My mother-in-law's boxer. Problem. $1,200 in tests, no answers. Another vet solved it with $8 pills. When you're scared, you'll pay anything - and some vets price accordingly. So I built what I couldn't find: real costs, real exclusions, plain language. Not selling policies.
Sources
Research and data used to compile this profile.
- 1 Pedersen NC, Perron M, Bannasch M, Montgomery E, Murakami E, Liepnieks M, Liu H. Efficacy and safety of the nucleoside analog GS-441524 for treatment of cats with naturally occurring feline infectious peritonitis. J Feline Med Surg. 2019;21(4):271-281.
- 2 Addie DD, Paltrinieri S, Pedersen NC. Recommendations from workshops of the second international feline coronavirus/feline infectious peritonitis symposium. J Feline Med Surg. 2004;6(2):125-30.