What Is Feline Infectious Peritonitis?

Feline infectious peritonitis, commonly shortened to FIP, is caused by a mutation of a common feline coronavirus (FCoV). Most cats exposed to FCoV experience mild digestive issues or no symptoms at all. However, in a small number of cases, the virus mutates inside the body and triggers FIP — a condition that causes severe inflammation in organs and body cavities.

FIP is not directly contagious in the same way as a cold or flu. While the original coronavirus can spread through faeces, FIP itself results from a change inside a single cat’s body. This means one cat developing FIP does not automatically mean others in the same household will.

Wet FIP vs Dry FIP: Understanding the Two Main Forms

FIP typically appears in one of two ways — though some cats show a combination of both.

Wet (Effusive) FIP

• Build-up of fluid in the abdomen or chest cavity
• Swollen or distended belly
• Difficulty breathing or panting
• Persistent fever and tiredness

Dry (Non-Effusive) FIP

• Inflammation of organs such as the liver, kidneys, or eyes
• Gradual weight loss and poor appetite
• Increased thirst or urination
• Possible neurological signs (unsteady walking, confusion, or seizures)

Both types can cause fever, fatigue, and loss of appetite, but their specific signs differ based on where inflammation occurs.

How Do Cats Get FIP?

A cat becomes exposed through infected faeces, often in multi-cat households, catteries, or outdoor environments where litter trays are shared or not frequently cleaned.

The feline coronavirus can survive for several days on surfaces, though good hygiene drastically reduces risk. Because the virus can stay dormant, a cat may appear healthy for months or years before showing symptoms.

Preventive tip: Keep your cat’s litter area spotless and use a low-dust, high-absorption litter like Pacha Litter to help minimise bacterial growth and contamination risks.

Diagnosing FIP

Diagnosing FIP can be challenging because there isn’t a single test that gives a clear yes-or-no answer. Vets typically use a combination of:

• Blood tests and biochemistry results
• Imaging (such as ultrasound or X-ray)
• Sampling of any abdominal or chest fluid
• Observation of clinical signs over time

A positive coronavirus test alone doesn’t confirm FIP, since many healthy cats also test positive for FCoV. Instead, diagnosis relies on a combination of findings and professional judgement.

Treatment Options: What Has Changed

For decades, FIP was considered almost always fatal. However, scientific progress has changed that view dramatically.

New antiviral therapies — such as GS-441524 and remdesivir — have shown promising results in clinical trials, with many cats making full recoveries when treated early and consistently under veterinary supervision.

While treatment can be lengthy and expensive, it has given hope to thousands of cat owners worldwide. Discuss options directly with your vet to find the safest and most effective approach.

Important: Avoid “black market” FIP treatments sold online. These unregulated products can cause harm and delay proper care. Always consult your vet before giving any medication.

Supporting Your Cat at Home

Comfort and stability are key while your cat is being treated or recovering.

Practical home care tips:

• Create a quiet, cosy area for rest away from noise or other pets.
• Keep water and food nearby to encourage steady hydration and nutrition.
• Offer smaller, frequent meals to help digestion and maintain weight.
• Track daily changes in appetite, energy levels, and breathing patterns.
• Maintain a regular cleaning routine for litter trays to reduce reinfection risk.

A clean litter box also supports emotional comfort — cats are naturally hygienic animals. Using Pacha Litter, which helps monitor subtle health changes through colour variation, may give you early clues if your cat’s condition shifts unexpectedly.

Preventing Future Infections

You can’t entirely prevent feline coronavirus exposure, but you can significantly lower the risk of FIP developing by:

• Limiting the number of cats sharing litter trays
• Cleaning trays at least once daily
• Providing good ventilation and reducing household stress
• Keeping cats indoors or supervised outdoors
• Ensuring regular vet check-ups and a balanced diet

Cats thrive in calm, predictable environments. Stress reduction alone can have a huge positive impact on their immune system.

Common Misconceptions About FIP

Myth 1: “FIP spreads easily between cats.”

No — while feline coronavirus can pass between cats, FIP itself arises from a mutation inside one cat’s body.

Myth 2: “There’s no hope once a cat has FIP.”

Outdated. Modern antivirals have changed the prognosis for many cats when diagnosed early.

Myth 3: “A positive coronavirus test means my cat has FIP.”

False. Many healthy cats carry the virus without ever becoming ill.

Final Thought

Feline infectious peritonitis is serious, but no longer hopeless. Veterinary medicine continues to advance, and cats are now surviving and thriving after diagnoses once considered untreatable.

Early detection, responsible veterinary care, and compassionate home support are your best defences. Keep your cat’s environment clean, calm, and consistent — and remember, the small details, like using a health-monitoring litter such as Pacha Litter, can make a big difference in spotting changes before they become serious.