There are few things more frightening than watching your cat fall ill and not knowing why. If your vet has mentioned FIP — Feline Infectious Peritonitis — you are probably feeling overwhelmed. The name sounds clinical. The prognosis used to sound hopeless. But here is the good news: things have changed dramatically. With the right veterinary team on your side, your cat has a real fighting chance.
This article breaks down everything you need to know about FIP — what it is, how to spot it early, and why having an experienced vet who diagnoses and treats it correctly makes all the difference. If you are in Dubai or anywhere across the UAE, PetsFirst offers the specialist expertise and compassionate care your cat deserves during this critical time.
Key Takeaways
- FIP is caused by a mutation of feline coronavirus (FCoV) and can affect any cat, including single indoor cats with no known exposure history.
- Two distinct forms exist — wet (effusive) and dry (non-effusive) — each with different clinical signs, diagnostic challenges, and treatment timelines.
- No single test confirms FIP. Accurate diagnosis requires combining clinical history, bloodwork patterns, imaging, fluid analysis, and PCR testing, all interpreted by an experienced clinician.
- Persistent fever unresponsive to antibiotics, rapid weight loss, abdominal distension, neurological signs, or ocular changes in a cat warrant urgent veterinary investigation.
- Modern antiviral treatments, particularly GS-441524-based protocols, have transformed FIP from a near-certain death sentence into a manageable and often curable disease.
- Early diagnosis dramatically improves outcomes — do not wait for symptoms to worsen before seeking specialist care.
What Exactly Is FIP in Cats?
FIP stands for Feline Infectious Peritonitis. A mutation of the Feline Coronavirus (FCoV) causes it — specifically, a biotype shift from the avirulent feline enteric coronavirus (FECV) to the virulent FIP virus. Here is the tricky part: feline coronavirus itself is incredibly common. Seroprevalence studies show that up to 90% of cats in multi-cat environments carry FCoV antibodies, particularly those who have lived in shelters, breeding catteries, or rescue facilities across the UAE and beyond. Most of the time, the virus causes only mild or asymptomatic gastrointestinal infection.
The problem begins when the virus mutates inside an individual cat’s body — a process that happens unpredictably and can occur months or even years after initial infection. This mutated form triggers a pathogenic immune response, specifically antibody-dependent enhancement, that attacks the cat’s own tissues and organs rather than clearing the virus. It is notoriously unpredictable, can strike any cat regardless of age or breed, and once clinical signs emerge, progression is typically rapid.
Why Is FIP So Hard to Diagnose?
FIP is notoriously difficult, and this is where many cases are missed or delayed — a challenge affecting Dubai and UAE veterinary practices just as it does clinics worldwide. Its clinical presentation overlaps with dozens of other conditions, from feline leukaemia and FIV to lymphoma, pancreatitis, and chronic kidney disease. No single pathognomonic test delivers a definitive yes or no.
In practice, diagnosis demands a systematic approach combining clinical signs, haematology, serology, imaging, and sometimes fluid analysis or tissue biopsy — all interpreted carefully by a vet with genuine FIP experience. A common mistake is relying too heavily on a single positive FCoV titre, which confirms only that a cat has been exposed to coronavirus at some point, not that it has FIP. Many vets also order incomplete diagnostic panels that miss the subtle markers distinguishing FIP from mimicking conditions. This is precisely why having a thorough, experienced vet — such as the specialists at PetsFirst Dubai — matters so much.
The Two Main Forms of FIP in Cats
FIP presents in two clinically distinct forms. Recognising which form your cat has is essential because it changes the treatment approach, prognosis timeline, and monitoring strategy.
Wet (Effusive) FIP: Signs, Symptoms, and Clinical Presentation
This is the more rapid and dramatic form, accounting for approximately 50–60% of FIP cases in clinical practice. Fluid accumulates in the abdomen (peritoneal effusion) or chest cavity (pleural effusion) as a result of increased vascular permeability and inflammatory exudation. You might notice your cat’s belly looking distinctly swollen, or they may present with acute dyspnoea and open-mouth breathing from chest fluid accumulation.
Classic FIP effusion appears as a clear to slightly turbid, sticky, viscous fluid — almost like egg whites — with a high protein content (typically 4–8 g/dL, substantially higher than transudative fluids). Effusion analysis commonly reveals neutrophilic inflammation, elevated albumin-to-globulin ratios within the fluid, and positive FCoV PCR. The Rivalta test — a simple bedside test where a drop of effusion is added to acetic acid — typically produces a positive result (formation of a white precipitate), which is supportive though not independently diagnostic. Wet FIP generally follows an aggressive course, with clinical decline unfolding over weeks rather than months.
Dry (Non-Effusive) FIP: Recognition and Diagnostic Challenges
This form accounts for 40–50% of cases and is notoriously difficult to catch early. Rather than fluid accumulation, the disease creates focal inflammatory lesions — granulomas composed of macrophages, lymphocytes, and plasma cells — on organs such as the kidneys, liver, eyes, central nervous system, or mesentery. Because there is no dramatic effusion, symptoms depend entirely on which organs are affected and to what extent.
Neurological dry FIP presents with CNS signs including vestibular dysfunction (head tilts, nystagmus), ataxia, seizures, or behavioural changes. Ocular FIP causes anterior uveitis with characteristic aqueous flare, hypopyon, or chorioretinitis visible on ophthalmic examination. Renal or hepatic involvement may show only as organ dysfunction on bloodwork — elevated creatinine or liver enzymes without obvious clinical signs. Dry FIP generally progresses more slowly (weeks to months) but is often diagnosed significantly later because the signs are non-specific and can mimic neurological disease, ophthalmological conditions, or organ failure. That delay is why dry FIP often carries a worse prognosis — the disease establishes itself before treatment can begin.
Some cats also present with mixed or transitional forms, showing elements of both effusive and granulomatous disease simultaneously or sequentially.
Signs to Watch For in Your Cat
Because FIP can mimic so many other conditions, knowing what to watch for is your first line of defence. Do not wait to see every sign, and do not dismiss early suspicions. A cat showing even one concerning symptom warrants investigation — especially if that symptom is a persistent fever or a rapid decline in an otherwise young or middle-aged cat.
Common symptoms across both forms of FIP include:
- Persistent fever (typically 39.5–40.5°C / 103–105°F) that does not respond to standard antibiotic therapy or recurs after treatment cessation
- Progressive lethargy and weakness worsening over days to weeks
- Anorexia or significant weight loss — often 15–30% of body weight over a short timeframe
- Icterus (jaundice) affecting the sclera, ear pinnae, or non-pigmented skin areas
- Lymphadenomegaly (palpable swollen lymph nodes)
- Abdominal distension with a fluid wave on palpation (wet form)
- Dyspnoea, tachypnoea, or open-mouth breathing; muffled heart sounds from pleural effusion (wet form)
- Anterior uveitis, aqueous flare, or chorioretinitis with vision loss (dry form)
- Neurological deficits including vestibular signs (head tilt, nystagmus), loss of balance, ataxia, or seizures (dry form)
- Diarrhoea or vomiting (less specific but can occur)
High-risk populations in the UAE: Cats under two years old and geriatric cats (15+ years) carry the highest incidence of clinical FIP. Male cats may be slightly overrepresented. Purebred cats — particularly Bengals, Siamese, Abyssinians, and Ragdolls — appear to have higher genetic susceptibility, suggesting a heritable component to the biotype shift. Multi-cat households and shelter environments substantially increase exposure risk.
Given Dubai’s warm climate and the concentration of rescue facilities across the emirate, at-risk populations face consistent exposure risk year-round. That said, FIP does not discriminate. Single indoor cats with no known exposure have developed FIP, which is why any unexplained illness in any cat warrants thorough investigation. If your cat shows any combination of the above — especially persistent fever with weight loss, acute neurological signs, or a swollen abdomen — act immediately. Early action saves lives.
How FIP Is Diagnosed: What the Process Looks Like
According to the International Feline Coronavirus and FIP Advisory Panel, and clinical literature from leading feline medicine centres including Cornell University College of Veterinary Medicine and UC Davis, diagnosing FIP definitively remains one of the most challenging tasks in feline medicine. There is no single blood test that confirms it. What experienced practitioners do is build a complete clinical picture, using multiple diagnostic tools in combination and interpreting them within the context of the individual cat’s presentation.
Step 1: Thorough Clinical Assessment and History
Diagnosis always begins with a detailed, methodical history and hands-on physical examination. A skilled vet spends time understanding the cat’s background — age, breed, living situation (single or multi-cat household), any exposure to shelter or cattery environments, vaccination history, previous illnesses, and the precise timeline of symptom onset. That contextual information narrows diagnostic possibilities significantly.
Physical examination focuses on fever measurement, lymph node palpation, abdominal palpation for fluid wave or organ enlargement, eye examination with attention to anterior chamber clarity, and a thorough neurological assessment where CNS signs are suspected. A cat presenting with fever, weight loss, and lymphadenomegaly in a multi-cat household places FIP at the top of the differential list immediately.
Step 2: Haematology, Serology, and Blood Chemistry
Standard bloodwork in a suspected FIP case targets specific patterns that raise clinical suspicion:
- Albumin-to-globulin (A:G) ratio: A reversed or severely low A:G ratio (typically <0.8) is one of the most significant red flags. FIP triggers polyclonal hypergammaglobulinaemia — a dramatic increase in immunoglobulin production — while albumin levels fall. This ratio alone drives many experienced vets to pursue FIP diagnostics with heightened urgency.
- Serum protein elevation: Total protein often exceeds 8.5 g/dL, with most elevation in the globulin fraction. Albumin is typically low-normal or low (2.0–3.0 g/dL).
- Inflammatory markers: Neutrophilic leukocytosis with a left shift is common. Elevated fibrinogen supports an active inflammatory process.
- Anaemia: Non-regenerative anaemia is frequently present due to anaemia of chronic disease.
- FCoV antibody testing: A high titre supports exposure but does NOT confirm FIP. Critically, a negative FCoV serology makes FIP unlikely but does not completely exclude it in rare presentations.
- FIP-specific markers (emerging): Some reference laboratories now offer tests detecting FIP-specific antibodies or antigen