Feline Infectious Peritonitis (FIP): A Once-Fatal Disease Now Treatable

By Dr. Kristen Mitchell

Feline Infectious Peritonitis (FIP) was first discovered over 60 years ago and long considered a fatal disease in cats. It’s caused by a mutation of the common feline coronavirus (FCoV), which spreads easily through the fecal–oral route—especially in catteries, shelters, rescues, or multi-cat homes.

Most cats exposed to FCoV never become sick, but in rare cases, the virus mutates and triggers a severe inflammatory reaction throughout the body. Because symptoms vary, FIP is extremely difficult to diagnose. Cats may show vague signs such as:

• Lethargy, poor appetite, or weight loss

• Persistent or fluctuating fever

• Jaundice or pale gums

• Swollen belly or breathing difficulty (from fluid buildup)

• Eye or neurological changes like vision loss, wobbliness, or seizures

Diagnosis is based on a combination of tests, including bloodwork, fluid analysis (Rivalta’s test), and sometimes tissue biopsies. There’s no single “yes or no” test—veterinarians must build a case based on history and findings.

For many years, FIP was always fatal. But in the past few years, a new FDA-approved antiviral treatment has completely changed the outlook. With early recognition and proper care, many cats with FIP are now surviving and thriving.

If your cat develops unexplained fever, weight loss, or lethargy—especially after recent stress or exposure to other cats—schedule an exam right away. FIP is no longer a hopeless diagnosis, and timely veterinary attention can make all the difference.

💛 Early diagnosis and treatment can make all the difference. Contact our team to schedule an exam or consultation if you’re concerned about your cat’s health.