Feline Infectious Peritonitis (FIP): A 2025 Veterinary Guide to Causes, Symptoms & Treatment 🐱🦠

By Dr. Duncan Houston, BVSc

Feline Infectious Peritonitis (FIP) is a complex and often fatal disease in cats, caused by a mutation of the feline coronavirus (FCoV). This comprehensive 2025 guide delves into the causes, symptoms, diagnosis, treatment, and prevention of FIP in felines.

Understanding Feline Infectious Peritonitis 🧬

FIP arises when the typically benign feline coronavirus mutates into a virulent form, leading to a severe inflammatory response. This mutated virus targets various organs, causing a range of clinical signs that can be challenging to diagnose and treat.

Prevalence

While FCoV is common among cats, especially in multi-cat environments, only a small percentage develop FIP. The disease is more prevalent in young cats under two years of age and those in high-stress environments.

Causes of Feline Infectious Peritonitis 🧬

Several factors contribute to the development of FIP:

• Viral Mutation: A spontaneous mutation of FCoV within an individual cat leads to the pathogenic form causing FIP.
• Immune Response: An abnormal immune reaction to the mutated virus results in widespread inflammation.
• Environmental Stressors: Overcrowding, poor sanitation, and high-stress levels can increase the risk of FIP development.

Recognizing the Symptoms 🔍

FIP manifests in two primary forms, each with distinct clinical signs:

Effusive (Wet) FIP

• Abdominal or thoracic effusion: Accumulation of fluid in the abdomen or chest, leading to distension and respiratory distress.
• Fever: Persistent and unresponsive to antibiotics.
• Lethargy and anorexia: Decreased activity and appetite.
• Weight loss: Progressive wasting despite adequate nutrition.

Non-Effusive (Dry) FIP

• Neurological signs: Seizures, ataxia, or behavioral changes.
• Ocular abnormalities: Inflammation, vision loss, or eye discoloration.
• Organ-specific symptoms: Depending on the affected organ, signs may include jaundice, kidney dysfunction, or lymphadenopathy.

Some cats may exhibit a combination of both forms, complicating the clinical picture.

Diagnosis 🩺

Diagnosing FIP is challenging due to its nonspecific symptoms and lack of a definitive test. A combination of the following is often employed:

• Clinical evaluation: Assessment of history, symptoms, and physical examination findings.
• Laboratory tests: Blood work may reveal anemia, elevated globulins, or lymphopenia.
• Imaging: Ultrasound or radiographs to detect fluid accumulation or organ abnormalities.
• Analysis of effusions: Fluid analysis can support the diagnosis, especially if high protein content and low cellularity are present.
• PCR testing: Detection of viral RNA in tissues or fluids can aid in diagnosis.

Treatment Options 💊

Historically, FIP was considered fatal, but recent advancements have introduced promising treatments:

• Antiviral therapy: GS-441524, a nucleoside analog, has shown efficacy in treating FIP, leading to remission in many cases.
• Supportive care: Includes fluid therapy, nutritional support, and management of secondary infections.
• Anti-inflammatory medications: Corticosteroids may be used to reduce inflammation and improve comfort.
• Immunomodulators: Agents like interferons may help modulate the immune response.

Early intervention with antiviral therapy significantly improves the prognosis.

Prognosis 📈

The prognosis for FIP has improved with the advent of antiviral treatments. While untreated FIP remains fatal, cats receiving GS-441524 therapy have demonstrated remission rates exceeding 80%. Early diagnosis and treatment initiation are critical for favorable outcomes.

Preventive Measures 🛡️

Preventing FIP involves minimizing exposure to FCoV and reducing stress:

• Hygiene: Maintain clean litter boxes and feeding areas to reduce viral transmission.
• Population control: Limit the number of cats in a household or cattery to decrease stress and viral load.
• Isolation: Quarantine new or sick cats to prevent the spread of FCoV.
• Regular veterinary care: Routine check-ups can help detect and manage health issues promptly.

Currently, there is no effective vaccine against FIP.

When to Consult a Veterinarian 👩‍⚕️

Immediate veterinary attention is warranted if your cat exhibits:

• Persistent fever unresponsive to antibiotics
• Abdominal swelling or breathing difficulties
• Neurological signs such as seizures or incoordination
• Ocular changes or vision loss
• Sudden weight loss or lethargy

Early diagnosis and treatment are crucial for improving the chances of recovery.

Conclusion 📝

Feline Infectious Peritonitis is a serious disease, but recent advancements in antiviral therapy offer hope for affected cats. Understanding the disease's manifestations and seeking prompt veterinary care can make a significant difference in outcomes. For personalized advice and support, consider reaching out to veterinary professionals through platforms like Ask A Vet. Their expertise can guide you through diagnosis, treatment options, and ongoing care tailored to your cat's specific needs.

Stay proactive in your cat's health to ensure a happy and healthy life together. 🐾