FIP Symptoms in Cats: Early Signs to Watch Out For
- MolnuFIP™
- 6 days ago
- 4 min read
Feline Infectious Peritonitis (FIP) is a serious and often fatal disease caused by a mutation of the feline coronavirus (FCoV). Because FIP progresses rapidly once clinical signs appear, recognizing the early symptoms can be critical for starting treatment in time—especially now that effective antivirals like MolnuFIP (molnupiravir) are saving lives.
This guide breaks down the early warning signs of FIP, including differences between wet (effusive) and dry (non-effusive) forms, neurological symptoms, and ocular involvement.
🧠 What Causes FIP, and Why Are Symptoms So Varied?
Most cats carry feline coronavirus (FCoV), which typically causes mild gastrointestinal symptoms or no symptoms at all. However, in about 5–10% of cases, the virus mutates into a pathogenic form that causes FIP, which spreads throughout the body via infected white blood cells, leading to widespread inflammation.
Because this inflammation can affect multiple organs, FIP symptoms can appear in various systems:
Abdomen and chest (wet form)
Eyes, brain, and nervous system (dry form)
Lymph nodes, liver, kidneys, and more
That’s why it’s often called a “great imitator” in veterinary medicine.
🚨 Early Symptoms of FIP in Cats
FIP symptoms often start subtly and are easy to dismiss as minor illness or stress. However, early detection is crucial, especially now that antiviral treatment is available.
Here are the most common early signs of FIP, explained in detail:
1. Persistent Fever
Description: A fever that doesn’t respond to antibiotics.
Why it matters: A persistent fever (> 102.5°F or 39.2°C) that lasts for days or weeks is one of the hallmark signs of FIP, especially in young cats.
What to watch: Lethargy, warm ears, or hiding behavior may signal a fever.
2. Lethargy and Low Energy
Description: A noticeable decrease in activity, playfulness, and curiosity.
Why it matters: Cats with FIP often withdraw and become unusually tired or unresponsive.
What to watch: Your usually energetic kitten might start sleeping all day and avoiding social interaction.
3. Loss of Appetite
Description: Reduced interest in food or total refusal to eat.
Why it matters: Appetite loss leads to rapid weight loss and worsens the immune system's ability to fight.
What to watch: Not finishing meals, refusing treats, or avoiding the food bowl entirely.
4. Weight Loss and Muscle Wasting
Description: Gradual or sudden loss of body weight and muscle mass.
Why it matters: FIP causes systemic inflammation that often leads to poor nutrient absorption.
What to watch: Sunken appearance over the back, spine, and hind legs.
5. Dull or Unkempt Coat
Description: Fur that looks rough, greasy, or matted.
Why it matters: Sick cats often stop grooming due to discomfort or weakness.
What to watch: Fur clumping or loss of the cat's usual sleek appearance.
🌊 Symptoms of Wet (Effusive) FIP
This form is characterized by fluid buildup in the body cavities.
1. Swollen Belly (Ascites)
Description: A round, tight, and sometimes painful abdomen due to fluid accumulation.
Why it matters: Often misdiagnosed as bloating or worms, this is a classic sign of wet FIP.
What to watch: Rapidly growing belly in an otherwise thin cat.
2. Labored Breathing or Open-Mouth Breathing
Description: Fluid in the chest (pleural effusion) makes it difficult for the cat to breathe.
Why it matters: This is a veterinary emergency. Immediate drainage may be needed before treatment.
What to watch: Rapid breathing, flaring nostrils, panting, or open-mouth breaths.
🌵 Symptoms of Dry (Non-Effusive) FIP
Dry FIP doesn’t involve fluid buildup but causes granulomas (inflammatory masses) in organs.
1. Enlarged Lymph Nodes
Description: Swollen glands around the neck, armpits, or abdomen.
Why it matters: Indicates systemic immune activation and inflammation.
What to watch: Lumps under the skin or during vet palpation.
2. Jaundice (Yellowing of Skin or Gums)
Description: Yellow coloring due to liver damage.
Why it matters: Liver involvement is common in dry FIP.
What to watch: Yellow tint in the whites of the eyes, gums, or ears.
3. Chronic Diarrhea or Vomiting
Description: Ongoing gastrointestinal issues.
Why it matters: Inflammatory lesions may affect the digestive tract.
What to watch: Loose stool, vomiting after meals, or both.
🧠 Neurological Symptoms of FIP
One of the most dangerous and difficult-to-diagnose forms is neurological FIP (a subtype of dry FIP).
1. Wobbly Gait (Ataxia)
Description: Unsteady walking, swaying, or falling over.
Why it matters: FIP may cause inflammation in the brain or spinal cord.
What to watch: Difficulty jumping, tipping over, or dragging legs.
2. Seizures or Twitching
Description: Full-body convulsions or focal tremors.
Why it matters: Indicates advanced CNS involvement.
What to watch: Facial twitching, sudden collapse, or rigidity.
3. Behavioral Changes
Description: Confusion, disorientation, or unresponsiveness.
Why it matters: Neurological damage can alter personality or mental function.
What to watch: Head pressing, staring into space, loss of litter box training.
👁️ Ocular Symptoms of FIP
FIP may cause eye inflammation, especially in dry FIP.
1. Uveitis (Eye Inflammation)
Description: Swelling inside the eye that causes cloudiness or color changes.
Why it matters: Common in dry FIP and a strong diagnostic clue.
What to watch: Cloudy pupils, red eyes, or excessive tearing.
2. Vision Loss
Description: Sudden or gradual loss of sight in one or both eyes.
Why it matters: It is A result of inflammation or retinal detachment.
What to watch: Bumping into objects or hesitating to move.
🧪 What To Do If You Notice These Symptoms
Step 1: Visit a Veterinarian Immediately
Mention FIP as a possibility, especially if symptoms match multiple categories above.
Step 2: Request Diagnostic Tests
Ask about:
Bloodwork (total protein, A:G ratio)
Ultrasound or x-ray
Rivalta test (for abdominal fluid)
PCR testing (for FCoV)
Step 3: Start Treatment Early
If FIP is suspected, do not delay. Treatments like MolnuFIP (molnupiravir) have saved thousands of lives and are most effective when started early.
🐾 Final Thoughts
Recognizing the early symptoms of FIP in your cat could mean the difference between life and death. Now that antiviral treatments like MolnuFIP are widely available, there is real hope for FIP-affected cats.
If your cat is showing any of these signs, especially in combination, don’t wait. Contact your vet or visit MolnuFIP.com for expert guidance, access to life-saving medication, and compassionate care support.
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