FIP in Cats: The New Global Standard for Diagnosis and Treatment
Dr. Geoff Carullo, DVM, FPCCP, DPCVSCA
- Articles
- 5 min read
For decades, Feline Infectious Peritonitis (FIP) was considered one of the most heartbreaking diagnoses in feline medicine. Nearly every veterinarian has experienced the pain of telling a pet owner that nothing could be done.
But the world has changed.
Today, FIP is one of the most rapidly evolving fields in veterinary medicine, with breakthroughs in diagnostics and antiviral treatment producing survival rates once thought impossible. In many countries, remission now reaches 80 to 90 percent when modern protocols are applied correctly.
This article summarizes the most up-to-date global guidance on how veterinarians can diagnose and treat FIP confidently and accurately.
FIP develops when a common intestinal coronavirus (FCoV) mutates into a disease-causing form that triggers widespread inflammation and organ damage. It appears in two major presentations:
Effusive (wet) FIP
High-protein fluid in the abdomen or chest, fast progression.
Non-effusive (dry) FIP
Granulomas in organs, ocular or neurologic signs, gradual progression.
Any young cat from a multi-cat environment with fever that does not respond to antibiotics should raise immediate suspicion.
Global guidelines, including AAFP and ABCD Europe, now emphasize a multi-step diagnostic strategy. No single test can confirm FIP alone. Instead, veterinarians are encouraged to build a diagnosis by combining clinical signs, laboratory changes, imaging, and molecular tests.
A. Clinical Red Flags
B. Laboratory Markers
Typical patterns include:
These findings do not confirm FIP but form the biochemical backbone of diagnosis.
C. Effusion Analysis
If fluid is present, it is the best sample to analyze. Key features:
D. Imaging Findings
Ultrasound may reveal:
For ocular or neurologic FIP, CT or MRI is ideal if available.
E. Tissue Confirmation
When needed, the definitive test is:
This remains the gold standard when diagnosis is unclear or when ruling out lymphoma, fungal disease or toxoplasmosis.
This is where global FIP management has transformed dramatically.
A. Antiviral Therapy
The backbone of modern treatment is nucleoside analog antivirals, mainly:
These drugs directly inhibit viral replication. Across multiple countries and cohort studies, survival rates reach:
Most protocols run for a continuous treatment period lasting several weeks to months followed by a close observation window.
Key principles:
Oral therapy is now preferred for most non-neurologic cases. Severe, unstable or neurologic cases may benefit from an initial injection phase before switching to oral.
B. Supportive Care
Supportive treatment remains essential and includes:
Corticosteroids are no longer recommended as primary therapy. They may mask disease progression and interfere with antiviral effectiveness.
During Treatment
Every 2 to 4 weeks:
Improvement is often visible within the first week.
After Treatment
There is a silent risk window after the antiviral course.
Watch for:
Early relapse can be managed with an adjusted protocol.
Untreated FIP is still almost always fatal.
But with modern therapy:
Around the world, veterinary organizations are updating their guidelines to reflect the new reality:
FIP is treatable.
FIP is survivable.
FIP is no longer a guaranteed death sentence.
Veterinarians must stay updated, teach owners accurate information and dismantle outdated beliefs that persist in social media and some clinical circles. Early detection, correct diagnosis and proper antiviral therapy give cats the best chance of long-term remission.
Dr. Geoff Carullo is a Fellow and the current President of the Philippine College of Canine Practitioners.
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