Background: Despite treatment with antivirals (e.g., GS-441524), a subset of cats with feline infectious peritonitis (FIP) remain critically ill, developing signs consistent with sepsis that are often fatal. Viral-associated sepsis has been rarely reported in veterinary medicine but is hypothesized to explain these presentations.
Hypothesis/
Objectives: To describe presence of suspected FIP-associated sepsis in cats and associated clinicopathological findings, and outcomes.
Animals: 66 client-owned cats admitted to hospitals across 12 institutions worldwide between 2021 and 2025.
Methods: This retrospective case series included cats with suspected or confirmed FIP and concurrent clinicopathologic findings consistent with published criteria for sepsis or systemic inflammatory response syndrome (SIRS). Data collection included results of diagnostic evaluations, comorbidities, and outcomes.
Results: Most common physical examination findings on presentation consistent with sepsis included pale mucous membranes (92% of cats), weak or absent femoral pulses (83%), tachypnea (77%), and hypothermia (74%). Clinicopathologic abnormalities included hyperbilirubinemia (median 3.40 mg/dL [interquartile range (IQR) 2.1–4.4 mg/dL]), hypoalbuminemia (median 1.7 g/dL [IQR, 1.6–1.9 g/dL]), and anemia (median hematocrit 19.7% [IQR, 17.1–22.9%]). No bacteria were seen on cytology. Reported comorbidities at the time of hospitalization were immune-mediated hemolytic anemia (14%) and myocarditis (7%). Cats with FIP-associated viral sepsis had an overall survival rate of 32% with antivirals, and median hospitalization time prior to death/euthanasia was 3.5 days (IQR 1-4).
Conclusions and Clinical Importance: Viral-associated sepsis secondary to FIP is associated with a high mortality rate, and early recognition is important to facilitate aggressive supportive care and improve outcomes in these cats.
