Feline Infectious Peritonitis: From a Death Sentence to a Treatable Disease

In this guide

For decades, a diagnosis of feline infectious peritonitis, FIP, was among the most devastating a cat owner could hear, since the disease was almost universally fatal. That has genuinely changed in the last few years with the arrival of effective antiviral treatment, and it is worth understanding both what FIP is and how much the outlook has improved.

What FIP actually is

FIP develops when the ordinarily mild feline coronavirus mutates inside an individual infected cat into a much more aggressive form that spreads throughout the body rather than staying confined to the gut. It most often affects cats under two years old, along with cats under significant stress or with a weakened immune system, and it comes in two main forms: wet (effusive) FIP, causing fluid to build up in the chest or abdomen, and dry (non-effusive) FIP, causing inflammatory lesions in organs including, in some cases, the brain and eyes.

Recognising it

• Persistent fever that does not respond to antibiotics
• A swollen, fluid-filled abdomen (wet form) or laboured breathing from chest fluid
• Weight loss and poor appetite despite ongoing efforts to eat
• Lethargy and a dull, unkempt coat
• Eye changes, including cloudiness or colour change in the iris
• Neurological signs such as wobbliness, seizures, or behaviour change, in cats where the dry form affects the brain

How it is diagnosed

There is no single perfect test for FIP, which historically made diagnosis frustrating. Vets typically combine bloodwork, analysis of any abdominal or chest fluid present, imaging, and sometimes PCR testing on fluid or tissue samples to build a confident diagnosis, since no individual result alone is fully definitive. A young cat with a persistent fever, weight loss, and fluid buildup that does not fit another obvious explanation is enough to prompt a serious FIP workup.

Treatment: the genuinely good news

An antiviral called GS-441524 has transformed FIP from a fatal diagnosis into a treatable one, with published survival rates commonly cited between 80 and 90 percent or higher when treatment is started promptly and completed in full. It is given daily, either as an injection or increasingly as an oral tablet, for a minimum of 84 days, a course that cannot be shortened even if your cat looks completely recovered partway through, since stopping early is one of the most common causes of relapse. This treatment is now accessible in India through veterinary prescription and specialist suppliers, a real shift from just a few years ago when Indian owners had few options beyond supportive care.

Cost remains a genuine consideration, since a full course runs into a significant sum, and this is worth discussing openly with your vet early rather than partway through treatment. Cats undergoing treatment need regular monitoring, including bloodwork and weight checks, to track progress and catch a poor response early.

What owners should do if FIP is suspected

• Get to a vet promptly rather than waiting to see if symptoms resolve on their own, since early treatment carries a meaningfully better outcome
• Ask directly about GS-441524 treatment availability and cost before deciding on a course of action
• Understand that a coronavirus-positive result in other household cats does not mean they will develop FIP themselves, since the mutation happens individually within each infected cat
• Commit to the full treatment course once started, and keep every recommended recheck appointment

Article content © Ravi Teja. All rights reserved.