FIP in Young Cats: Swollen Belly, Lasting Fever, and Treatment Today
🚨 Check first
If a young cat aged a few months to 2 years (or an immunocompromised senior cat) has a persistent fever over 39.5°C (103.1°F) that does not respond to antibiotics for days, loses weight and appetite while their belly or chest swells like a balloon with fluid, develops yellow eyes, gums, or urine (jaundice), or suddenly shows hind-leg wobbliness or cloudy eyes, strongly suspect feline infectious peritonitis (FIP) and visit an experienced vet immediately.
📌 The answer in 3 seconds
- FIP develops when the harmless feline enteric coronavirus, carried by many cats in their gut, undergoes a sudden genetic mutation inside the body due to stress or genetics (FIP itself is not directly airborne-contagious between cats).
- Once considered an incurable fatal disease, major advances in antiviral drugs mean that early diagnosis and appropriate medication treatment (typically around 84 days) now result in high rates of remission (successful recovery). Treatment options and costs vary by clinic and by country, so consult your veterinarian.
- There are two forms: the 'wet type' with fluid accumulation in the abdomen or chest (progresses very rapidly, requiring urgent care), and the 'dry type' without fluid, which causes organ, brain, or eye lesions and neurological signs. Early blood work (high total protein, low A/G ratio, high SAA) and ultrasound are lifesaving.
📊 Flowchart
- Step 1If unexplained fever, lethargy, loss of appetite, and weight loss persist for over 3–5 days after stressors like adoption, spay/neuter, or moving, and standard antibiotics fail entirely, get blood work done immediately (focusing on the albumin-to-globulin ratio [A/G ratio] and inflammatory marker SAA).
- Step 2If the belly is bloated with fluid (ascites) or breathing is rapid (pleural effusion), get an ultrasound and run PCR or fluid analysis tests.
- Step 3If your vet strongly suspects FIP, do not give up. Get a referral or second opinion the same day from an animal hospital experienced in FIP antiviral treatments to start therapy immediately.
⭕ Step-by-step fix
Step 1 · What you can do at home right now
If unexplained fever, lethargy, loss of appetite, and weight loss persist for over 3–5 days after stressors like adoption, spay/neuter, or moving, and standard antibiotics fail entirely, get blood work done immediately (focusing on the albumin-to-globulin ratio [A/G ratio] and inflammatory marker SAA).
Step 2
If the belly is bloated with fluid (ascites) or breathing is rapid (pleural effusion), get an ultrasound and run PCR or fluid analysis tests.
Step 3
If your vet strongly suspects FIP, do not give up. Get a referral or second opinion the same day from an animal hospital experienced in FIP antiviral treatments to start therapy immediately.
❌ Never do this
- Assuming a distended belly is just 'gaining weight from eating well' or 'constipation' and waiting over a week (pear-shaped abdominal swelling with a bony, emaciated spine is a hallmark of ascites).
- Giving up after reading outdated online information that 'FIP is 100% fatal' and missing the treatment window.
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