FIP in Cats: Complete Guide to Symptoms and Treatment

The vet calls you into the consult room and says the three letters every cat parent dreads: F, I, P. You leave the clinic with a folder of blood reports, a head full of questions, and a phone full of half-read forum threads. You are not alone, and you are not out of options.

FIP in Cats: Complete Guide to Symptoms and Treatment

This guide is written for Indian cat parents who have just heard those letters, or who suspect them. It explains what Feline Infectious Peritonitis (FIP) actually is, how it is diagnosed in Indian veterinary settings, and how modern antiviral treatment with GS-441524 and EIDD-1931 has changed what was once considered a hopeless diagnosis into a treatable disease with strong recovery rates.

What Is FIP in Cats? The Full Form and the Real Story

The full form of FIP is Feline Infectious Peritonitis. It is a disease caused by a mutated form of the feline coronavirus (FCoV), a common gut virus that most cats encounter at some point in their lives. In a small percentage of cats, that harmless gut virus mutates inside the body and becomes the FIP virus (FIPV), which can invade white blood cells and trigger widespread inflammation.

A few important points to anchor before we go deeper:

1. FIP is not contagious from cat to cat in the way the common coronavirus is. Cats catch the gut virus, not FIP itself.

2. FIP cannot pass to humans or dogs.

3. FIP was historically considered fatal. That changed after Dr. Niels Pedersen of UC Davis published landmark research on the nucleoside analogue GS-441524, which reports a 92% success rate in his clinical trial.

4. More than 100,000 cats worldwide have been treated with GS-441524 based protocols since 2019.

For Indian cat parents, the practical question is rarely "what is FIP in cats" in the textbook sense. It is: my cat has this, what do I do next.

The Four Forms of FIP

FIP is not one disease. It presents in four distinct forms, and the form your cat has decides the entire treatment plan.

1. Wet (Effusive) FIP

The most recognisable form. Fluid accumulates in the abdomen, the chest, or both. The belly looks distended even though the cat is losing weight. Breathing may become laboured if fluid sits in the chest cavity.

2. Dry (Non-Effusive) FIP

No visible fluid. Instead, granulomas form on internal organs such as the liver, kidneys, intestines, and lymph nodes. Symptoms are vaguer and harder to pin down: persistent fever, weight loss, lethargy, jaundice.

3. Ocular FIP

The virus invades the eyes. You may notice colour changes in the iris, cloudiness, uneven pupils, or sudden vision loss. Ocular FIP is a separate form and must be treated as such.

4. Neurological FIP

The virus crosses the blood-brain barrier. Signs include wobbling gait, head tilt, seizures, behavioural changes, or sudden incontinence. Neurological FIP is also a separate form and requires higher antiviral dosing to penetrate the central nervous system.

Never merge ocular and neurological FIP. They are two distinct presentations, and each requires its own dosing strategy.

FIP Symptoms in Cats: What to Actually Look For

The earliest symptoms of FIP are deceptively ordinary. That is part of what makes the diagnosis so frightening when it finally arrives.

Common early signs:

1. A fever that does not respond to standard antibiotics, often fluctuating between 39.5 and 41 degrees Celsius.

2. Gradual loss of appetite, even for treats the cat normally loves.

3. Weight loss despite the belly appearing larger (a hallmark of wet FIP).

4. Lethargy. The cat stops jumping, stops greeting you, stops grooming.

5. Pale or yellow gums (jaundice), especially in dry FIP affecting the liver.

6. Eye changes: colour shifts, cloudiness, or visible inflammation.

7. Neurological signs: stumbling, head tilt, seizures, or sudden behavioural changes.

FIP most commonly affects cats under two years of age, particularly those from multi-cat households, shelters, or catteries. Stress (a recent move, a new pet, surgery, vaccination) is frequently a trigger.

Diagnosing FIP in India

There is no single test that confirms FIP with 100% certainty in a living cat. Diagnosis is built from a pattern of evidence.

Bloodwork

Key markers your vet will look at:

1. Albumin to Globulin (A:G) ratio below 0.6 raises suspicion.

2. Elevated total protein with high globulins.

3. Lymphopenia (low lymphocyte count).

4. Mild to moderate non-regenerative anaemia.

5. Elevated bilirubin without obvious liver disease.

Fluid Analysis (for wet FIP)

If there is effusion, your vet can tap a sample. FIP fluid is typically yellow, sticky, high in protein, and has a low cell count. The Rivalta test, while old, is still widely used in India and can be useful as a quick screening tool.

PCR and Imaging

PCR testing of effusion or tissue can detect coronavirus RNA. Ultrasound is useful for identifying granulomas in dry FIP. Ocular and neurological FIP often require an ophthalmic exam or MRI where available.

A pragmatic rule from the field: all FIP cats show visible signs of improvement after 7 days of GS-441524 treatment. If there is no improvement after a week of correctly dosed antiviral therapy, the diagnosis itself should be questioned.

Treatment: How BasmiFIP Treats FIP in Cats

The modern FIP treatment landscape rests on two nucleoside analogues: GS-441524 and EIDD-1931. BasmiFIP is built around both, with protocols matched to the form of FIP your cat is fighting.

BasmiFIP GS-441524 Injectable (40 mg/ml)

The primary FIP antiviral. 99.4% purity, 8 ml vial. Daily subcutaneous injection, 7 days a week, for the standard 84-day (12-week) protocol.

Dosing by form:

1. Wet FIP: 6 mg/kg

2. Dry FIP: 8 mg/kg

3. Ocular FIP: 10 mg/kg

4. Neurological FIP: 10 mg/kg

The higher doses for ocular and neurological FIP reflect the need to push the drug into the eye and central nervous system, where viral suppression is harder to achieve.

BasmiFIP EIDD-1931 Oral Capsules (15 mg)

For wet and dry FIP only. Not appropriate for ocular FIP, neurological FIP, or cats that are not eating and defecating normally. EIDD-1931 is roughly 7.3 times more potent than GS-441524 and up to 10 times more potent than molnupiravir.

Dosing every 12 hours:

1. Under 2.5 kg: 1 capsule

2. 2.5 to 5 kg: 2 capsules

3. Over 5 kg: 3 capsules

Important safety note: EIDD-1931 is potentially teratogenic. It must never be given to pregnant, nursing, or breeding cats.

BasmiFIP Dual Antiviral Oral Capsules (GS-441524 + EIDD-1931)

A once-daily capsule combining both antivirals. Used after roughly 30 days of injections, or once the cat is stable. Not used during active ocular or neurological symptoms, vomiting and diarrhoea, or in cats under one year with wet FIP.

Dosing:

1. Under 2.5 kg: GS 25 mg + EIDD 5 mg

2. 2.5 to 5 kg: GS 35 mg + EIDD 8 mg

3. Over 5 kg: GS 50 mg + EIDD 10 mg

How the Regimen Is Chosen

1. Wet or dry FIP without ocular or neurological signs: may start with EIDD-1931 for 30 days. If symptoms persist, extend. If they continue past 60 days, switch to GS-441524 at 10 mg/kg.

2. Ocular FIP, neurological FIP, or cats not eating and defecating normally: start with GS-441524 injections for 30 days, then may transition to the GS-441524 dual antiviral capsule.

Field evaluation of 46 cats by Li and Cheah (2025) showed that combined oral GS-441524 and EIDD-1931 achieves 78.3% remission, even in slow responders and drug-resistant cases. This is a separate figure from the 92% success rate reported in the UC Davis GS-441524 trial, and the two should not be combined.

What to Avoid During Treatment

Certain drugs and supplements can interfere with antiviral therapy. Avoid the following throughout the 84-day protocol:

1. Fluoroquinolone antibiotics (such as enrofloxacin)

2. Spot-on flea medications

3. Lysine supplements

4. Immune boosters of any kind

Always discuss any concurrent medication with your treating vet or with the BasmiFIP consultation team before adding it to the regimen.

Supportive Care: LiverRx and KidneyRx

FIP and the long antiviral protocol can place stress on the liver and kidneys. BasmiFIP offers two adjunct nutraceuticals from RX Sciences:

1. LiverRx (cats and small dogs): SAMe 90 mg, Silybin A+B 9 mg, Vitamin E 13 mg, Vitamin C 10 mg.

2. KidneyRx: Magnesium carbonate, Vitamin D, Calcium carbonate, L-Carnitine, Chitosan, Omega-3, and Cranberry extract.

These are organ support products only. They are not antivirals and do not treat FIP. They are used alongside veterinary-guided antiviral treatment to support organ health during and after the 84-day protocol.

Why BasmiFIP for Indian Cat Parents

Access used to be the hardest part of FIP treatment in India. Cat parents in Bengaluru, Mumbai, Delhi, Hyderabad, Pune, Chennai, Kolkata, and smaller towns spent weeks chasing imported vials and decoding overseas dosing charts.

BasmiFIP changed that. Pan-India delivery, India-specific dosing guidance, transparent pharmacology, and free expert consultation for every cat parent navigating a new diagnosis. The goal is simple: every Indian cat parent should have evidence-based access to the same antiviral therapy that has helped over 100,000 cats worldwide enter remission since 2019.

Giving cats a second chance is not a slogan. It is a protocol, a timeline, and a daily injection schedule, supported by clinical evidence and decades of research from Dr. Niels Pedersen and the global FIP community.

FAQ

What is the full form of FIP in cats?

FIP stands for Feline Infectious Peritonitis. It is caused by a mutated form of the feline coronavirus and presents in four forms: wet, dry, ocular, and neurological.

Is FIP in cats treatable in India?

Yes. With GS-441524 and EIDD-1931 based protocols, FIP is now treatable. BasmiFIP provides both antivirals with pan-India delivery and free expert consultation. The UC Davis trial reported a 92% success rate, and the Li and Cheah 2025 field study on dual oral therapy reported 78.3% remission.

How long is FIP treatment?

The standard protocol is 84 days, or 12 weeks, of continuous daily antiviral therapy. Some cats, particularly those with neurological or ocular FIP, may need longer treatment or higher dosing. Stopping early is the most common cause of relapse.

What are the first symptoms of FIP in cats?

A persistent fever that does not respond to antibiotics, loss of appetite, weight loss, lethargy, and (in wet FIP) a distended belly. Ocular and neurological signs may appear as the disease progresses.

Can EIDD-1931 be used for all forms of FIP?

No. EIDD-1931 oral capsules are appropriate for wet and dry FIP only. They are not recommended for ocular FIP, neurological FIP, or cats that are not eating and defecating normally. They must also never be given to pregnant, nursing, or breeding cats. In those cases, GS-441524 injections are the appropriate starting point.

Where can I get BasmiFIP in India?

BasmiFIP delivers across India, including Bengaluru, Mumbai, Delhi, Hyderabad, Pune, Chennai, and Kolkata. Visit basmifipindia.com for the product range, dosing guidance, and free expert consultation.