What is Feline Infectious Peritonitis?

Feline Infectious Peritonitis (FIP) is a severe viral disease primarily affecting purebred cats aged between 6 months and 2 years living in groups. It results from a mutation of the usually benign feline coronavirus (FCoV), becoming pathogenic in some cats.

Transmission of Feline Coronavirus

FCoV spreads via the fecal-oral route, often through contaminated litter boxes. Transmission through saliva during grooming is possible but less frequent. Infection is widespread in catteries and multi-cat households.

Risk Factors for FIP

Several factors increase the risk of developing FIP:

• Age: Cats under 2 years are most vulnerable.
• Breed predisposition: Bengal, British Shorthair, Persian, Cornish Rex, and Birman.
• Genetic predisposition: Some bloodlines are more affected.
• Living conditions: Higher risk in catteries or shelters.
• Stress: Adoption, neutering, or boarding may weaken immunity.
• Immunosuppression: Concurrent infections increase risk.
• Introduction of new cats: Increased stress and viral transmission.
• Chronic FCoV carriers: Cats shedding the virus long-term pose ongoing infection risks.

Symptoms of FIP

FIP presents in two forms:

• Wet (exudative) form: Fluid accumulation in the abdomen (ascites) or chest cavity, causing abdominal swelling and breathing difficulties.
• Dry (non-exudative) form: Granulomatous lesions on multiple organs, causing intermittent fever, weight loss, loss of appetite, and depression.

Recent Advances in Diagnosing FIP

Diagnosing FIP has traditionally been complex due to symptom variability and the absence of a single specific test. Recent advancements offer faster and less invasive detection:

• Rapid molecular tests: The Astéria® Feline Coronavirus kit (2024) uses LAMP technology to detect FCoV in 40 minutes.
• Quantitative RT-PCR: Evaluates viral load and infectivity, though detection alone isn’t definitive for FIP.
• Serum AGP measurement: Elevated alpha-1 acid glycoprotein is common in FIP cases and serves as a useful supplementary indicator.
• Abdominal or thoracic fluid analysis: In wet-form cases, fluid analysis by cytology and RT-PCR strongly supports diagnosis.

Definitive Diagnosis: Histopathology and Immunohistochemistry

Definitive diagnosis relies on histopathological examination of affected tissues through biopsy or necropsy. Immunohistochemistry (IHC), detecting viral antigens in tissues, confirms virus presence within lesions.

While this method is the gold standard, it remains invasive and impractical for living cats without surgical biopsy. Therefore, veterinarians often rely on presumptive diagnoses using available tests, especially in cats responding positively to new antiviral treatments.

Treatment for FIP: A Major Breakthrough

Previously incurable, FIP now has promising antiviral treatments offering real hope for recovery:

• GS-441524: A derivative of Remdesivir, highly effective in many cats and now legal in several countries.
  • Oral administration available in tablets, simplifying treatment over injections.
  • A standard protocol lasts 12 weeks, adjustable based on clinical progress.
• New antivirals: Molnupiravir (EIDD-1931) is under evaluation; further studies are required for efficacy validation.

All treatments should be supervised by a veterinarian for optimal efficacy and to manage potential side effects.

Prevention of Feline Infectious Peritonitis

Reducing FCoV transmission is essential. Key preventive measures include:

• Strict hygiene: Regular litter box cleaning and disinfecting surfaces.
• Limiting cat population: Minimizing cat numbers per household to reduce spread.
• Stress reduction: Avoiding stressful situations (adoption, boarding, conflicts).
• Vaccination: An intranasal vaccine exists, but its effectiveness remains debated and is not recommended for low-risk cats.

For more information or to schedule a veterinary consultation, please contact us.