Why Do Some Cats Relapse?

While we don't know all the answers, here's some information about relapse that may be helpful regarding the individual cat. Relapses can happen for many reasons, but the main reason is that not all of the virus was eradicated during the initial treatment.

Causes for this viral retention are generally because neurological issues can progress slowly and have little or no symptoms, causing a missed Neurological FIP diagnosis. A lower dose may successfully suppress the virus in the brain throughout treatment, producing a neurological relapse once the treatment ends. This is why providing everything we ask for during the initial intake and anytime your cat has a setback during treatment is important.

It's possible that lesions (in any part of the body) didn't receive enough GS during treatment, and the virus lingered, producing a relapse

Some cats may develop partial resistance to the GS, requiring a higher dose. While the lower dose suppresses the virus, it likely didn't kill it, thus producing a relapse.

Sometimes cats are under-dosed due to failing to re-calculate the dose as the weight changes, significant leakage after injection, or failing to take all their pills can contribute to relapses. The good news is that everyone makes mistakes during treatment; in most cases, following the protocol closely can compensate for these minor lapses in treatment.

There's no effective test to tell if the virus was fully eliminated from the body. Looking at the clinical picture and bloodwork gives your treatment team essential clues. However, cats that relapse for the above reasons can sometimes still have an excellent clinical appearance and lab values.

This is why staying in touch with your treatment team and providing all the necessary data to give your cat the best possible outcome is important. It's also why stopping treatment is never wise because your cat is acting or appears "normal".