Epidemiological and Clinical Insights from 68 Veterinarian-Reported Cases of Feline Infectious Peritonitis During the Documented FIP Epizootic in Cyprus

In 2023, Cyprus experienced a large-scale epizootic of feline infectious peritonitis (FIP) temporally associated with the emergence of a novel feline coronavirus, FCoV-23. While molecular investigations have elucidated the recombinant origin of FCoV-23, field-based clinical and other epidemiological data from FIP cases reported during the epizootic period were needed to characterize the outbreak better. A prospective study was conducted using a structured 31-item questionnaire embedded in veterinary management software to characterize FIP cases diagnosed during the epizootic period (late 2022–2025). Data were voluntarily submitted by registered veterinarians across Cyprus. Cases were included based on a clinical diagnosis of FIP; virological confirmation of FCoV-23 infection was not required for inclusion. Data from 68 FIP cases reported by 22 clinics (response rate 21.0%) were analyzed. Affected cats were older than typically reported for FIP (mean age 3.9 years; median 3.0; range 0.4–12.9 years; SD 3.41). Most cases were documented in Limassol (51.5%) and Nicosia (25.0%). The most frequently reported clinical signs were non-specific, like anorexia (60.3%) and weight loss (54.4%), while a variety of neurological and mental manifestations were documented in 35.3% of cases. An albumin-to-globulin ratio < 0.8 was observed in 86.8% of tested cats. Antiviral therapy (GS-441524 or molnupiravir) was administered in 92.2% of cases, with reported clinical improvement of 88.9%. These findings demonstrate the value of questionnaire-based surveillance in documenting outbreak-associated FIP patterns. Although individual cases were not uniformly confirmed as FCoV-23 infections, the increased proportion of neurological presentations among FIP cases reported during the epizootic period supports previous molecular evidence suggesting that neurological involvement was associated with FCoV-23 circulation.