FIP (Feline Infectious Peritonitis) is a serious, progressive disease caused by a mutation of the feline coronavirus. In most cats, feline coronavirus causes no symptoms or only mild digestive upset. In a small percentage of cases, the virus mutates into FIPV — triggering a damaging immune response that attacks blood vessel walls and organs throughout the body.

FIP presents in two main forms. Wet (effusive) FIP causes fluid accumulation in the abdomen or chest, producing visible swelling and breathing difficulty. Dry (non-effusive) FIP causes inflammatory lesions in organs such as the brain, eyes, kidneys, or liver, with a wider range of less obvious symptoms. Some cats develop both forms simultaneously or transition from one to the other.

Until recently, FIP was considered almost universally fatal. The development of antiviral treatments — particularly GS-441524 — has fundamentally changed this, with recovery rates above 80% in cats that complete the full treatment protocol.

Feline Infectious Peritonitis. Named after peritoneal inflammation seen in wet cases, though the disease affects many organs beyond the abdomen.

Wet (effusive) FIP causes fluid accumulation in the abdomen or chest cavity, producing visible swelling and laboured breathing. Progresses rapidly — most untreated cats survive only days to weeks.

Nucleoside analogue antiviral that blocks FIPV RNA replication inside cat’s cells. Most extensively studied FIP treatment, with >80% clinical recovery rates across multiple independent studies.

~92% combined success rate across 650+ cats in clinical studies. Most cats completing the full 84-day protocol reach sustained remission and live normal lives.

Persistent fever unresponsive to antibiotics, weight loss, loss of appetite, lethargy, dull coat. Later: swollen abdomen (wet) or neurological/eye changes (dry).

FCoV (common intestinal coronavirus) mutates randomly inside an individual cat into FIPV. FCoV spreads via shared litter boxes and bowls. FIP itself cannot spread cat-to-cat.

FCoV exposure likely occurred in early life (breeder, cattery, shelter). FCoV can remain dormant for months/years before randomly mutating. Not caused by current care environment.

FIP itself is NOT contagious between cats. Underlying FCoV is contagious via litter boxes and close contact. Standard hygiene precautions are sufficient during treatment.

FIP cannot be passed between cats. FCoV can spread. Clean litter boxes, separate bowls, monitor other household cats for appetite/weight changes during treatment.

FIP cannot be passed between cats. FCoV can spread. Clean litter boxes, separate bowls, monitor other household cats for appetite/weight changes during treatment.

FIP is NOT transmitted between cats. The underlying FCoV spreads via faeces, shared litter boxes, and close contact. The FIP mutation occurs individually and spontaneously.

Rare overall (~0.3–1.4% of vet deaths) but more prevalent in multi-cat environments. ~5–12% of FCoV-positive cats develop FIP. Higher risk: young, male, purebred cats.

No single definitive test. Combination: A/G ratio blood test, Rivalta test (wet FIP), FIPV immunofluorescence, AGP, RT-PCR on effusion fluid, or tissue biopsy.

No guaranteed prevention. Reduce FCoV spread: clean litter boxes frequently, avoid overcrowding, isolate and test new cats before mixing. FIP vaccine has limited efficacy.

Without treatment: median survival ~9 days. Wet FIP: days to weeks. Dry FIP: weeks to months. With GS-441524: majority achieve sustained remission and live normal lives.

Yes — with treatment. ~85% success rate with GS-441524 across 650+ cats. Key factors: early start, correct weight-based dosing, completing full 84 days. Contact team immediately.

Yes. Most cats completing the 84-day protocol show no long-term health consequences. Residual effects from neurological/ocular cases may occur but typically resolve post-treatment.