(1) Background: Feline coronavirus infection (FCoV) is common in multi-cat environments. A role of FCoV in causing diarrhea is often assumed, but has not been proven. The aim of this study was to evaluate an association of FCoV infection with diarrhea in multi-cat environments. (2) Methods: The study included 234 cats from 37 catteries. Fecal samples were analyzed for FCoV RNA by reverse transcriptase quantitative polymerase chain reaction (RT-qPCR). Potential co-infections were determined by applying a qPCR panel on different potential enteropathogens and fecal flotation. A fecal scoring system was used to categorize feces as diarrheic or non-diarrheic. (3) Results: Of the 234 cats included, 23 had diarrhea. The prevalence of FCoV infection was 87.0% in cats with and 58.8% in cats without diarrhea. FCoV infection was significantly associated with diarrhea (Odds Ratio (OR) 5.01; p = 0.008). In addition, presence of Clostridium perfringens α toxin (OR 6.93; p = 0.032) and feline panleukopenia virus (OR 13.74; p = 0.004) were associated with an increased risk of diarrhea. There was no correlation between FCoV load and fecal score. FCoV-positive cats with co-infections were not more likely to have diarrhea than FCoV-positive cats without co-infections (p = 0.455). (4) Conclusions: FCoV infection is common in cats from catteries and can be associated with diarrhea.
Keywords: FCoV; FECV; FIP; RT-PCR; endoparasites; enteritis; enteropathogen; feces; feline enteric coronavirus; feline infectious peritonitis.