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What is FIP in cats?

Updated: Jan 18

Feline Infectious Peritonitis (FIP) in cats is caused by feline coronavirus (FCOV). It is estimated that 90% of cats are carriers FCOV. FCOV is found in both indoor and outdoor cats. Generally, the FCOV not harmful. However, when FCOV mutates into feline infectious peritonitis virus (FIPV), it becomes deadly.  

The exact trigger for the mutation is still unknown.  General observations indicate that low immunity due to stress, neutering, and poor living condition may cause the onset of the FCOV mutation into FIPV. From our treatment studies, we see that pure breeds are more prone to this deadly mutation than mixed breeds.  FIPV can occur in cats of all ages.  

There are two forms of FIPV infection: Effusive aka the 'WET' form and non-effusive form aka the 'DRY' form.  


The symptoms for the 'wet' form of FIP is more easily visible due to the bulging of the stomach as pictured on the right.  The bulging is caused by the accumulation of fluids in the abdomen and chest.  The fluid is produced by organ tissues and blood vessels that are inflamed from FIP virus attacks. As the FIP infection progresses, the bulging will increase in size and rate.

Because 'wet' form of FIP can be diagnosed easily, they are generally treated earlier than dry form of FIP. Doctors usually extract fluid from the abdominal area and conduct a FIP Ag test to confirm the diagnosis. You can read more about FIP testing here.

Survival rate of adult cats infected with 'wet' FIP is very high when treated promptly with GS-441524. We have achieved over 90% success rate, when given proper care, nutrition, and treat any complications separately and promptly along with GS-441524 treatment.

Treating kittens with wet FIP is much more challenging. Kittens more often contracts the wet form than the dry form. When they do, it can very deadly. From a diagnosis to death may take in less than a week. They will need to be treated differently than adult cats. You are welcome to contact us regarding 'wet' FIP treatment in kittens.  


The 'dry' form of FIP is very difficult to identify during early stages of infection. There are no symptoms that can definitively point to 'dry' form of FIP until the late stage of disease development. Thus, late diagnosis of 'dry' FIP is the main cause of higher mortality rate when compared to 'wet' FIP.  In the early stages of 'dry' FIP, lesions develop in a cat's internal organs such as kidneys and liver, causing a loss of appetite and physical inactivity. Eventually, the virus enters the central nervous system, causing eyes to become murky (ocular FIP), and a loss of movement control (neurological FIP). In the final stage of disease progression cats become paralysis shortly before death.

A FIP diagnosis should not be ruled out without proper blood tests and a review of the A:G ratio.

Before recent discovery of GS-441524, Feline Infectious Peritonitis was almost always fatal (>90% mortality rate). With the discovery GS-441524,  FIP is now a treatable disease.  Based on the US clinical study, FIP cats treated with GS-441524 achieved a survival rate greater than 80% and relapse rate of less than 18%. Based on our treatment experience, when FIP is treated early, the recovery rate is higher than 90%. With continued research, we expect that one day FIPV will be as easily treated as a common cold.  

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