Post-FIP Cats and Progressive Hydrocephalus: What Every Vet Needs to Know

Feline infectious peritonitis has long been one of the most dreaded viral diseases in cats. The introduction of antiviral therapy using GS-441524 has dramatically shifted outcomes, turning what was once a fatal diagnosis into one with hope for survival. However, as with any breakthrough, new questions arise about the long-term consequences of treatment. A recent case series shines a spotlight on a complication that clinicians should be aware of: progressive hydrocephalus following successful treatment for FIP.

The study evaluated four cats who had completed the standard 84-day course of GS-441524 therapy. All cats initially improved both clinically and neurologically. Despite this success, three of the cats returned 13 to 15 months later exhibiting neurologic decline, specifically vestibular signs such as head tilt and imbalance. One cat remained neurologically stable throughout the follow-up period. MRI findings revealed progressive hydrocephalus in the three affected cats. Interestingly, cerebrospinal fluid analysis showed no evidence of ongoing infection or inflammation, and FCoV PCR was negative in all tested samples. These findings underscore an important distinction: the neurologic decline was not due to FIP relapse, but rather a delayed post-infectious complication.

For the three cats with symptomatic hydrocephalus, ventriculoperitoneal shunt placement provided notable clinical improvement. The fourth cat demonstrated a reduction in ventricular size on follow-up imaging, reinforcing that post-FIP hydrocephalus can manifest variably and may be manageable with either surgical or conservative approaches. Necropsy in one case confirmed severe hydrocephalus without signs of active infection, further supporting the post-infectious nature of this condition. This case series highlights a critical consideration for veterinary professionals: progressive hydrocephalus should now be included in differential diagnoses for cats presenting with new or worsening neurologic signs months after successful FIP treatment. Differentiating post-FIP hydrocephalus from true relapse is essential, as prognosis, treatment, and client counseling differ significantly.

As GS-441524 becomes more widely available legally in the United States, clinicians should anticipate an increase in long-term survivors of FIP. Vigilant follow-up, including neurologic exams and imaging when indicated, will be key to detecting and managing late complications like hydrocephalus. Proactive recognition of this syndrome can help veterinarians provide targeted interventions and improve quality of life for their feline patients.

To read the full case report: click here