The First Comprehensive Phylogenetic Characterization of Feline Coronavirus Types I and II in Türkiye

Feline coronavirus (FCoV), together with an inadequate host immune response, causes feline infectious peritonitis (FIP), one of the most fatal infectious diseases in cats worldwide. This study investigated, for the first time in Konya, Türkiye, the presence and phylogenetic relationships of FCoV Types I and II in cats. Fecal and effusion samples were collected from 30 cats suspected of having FIP. Viral RNA was extracted, and FCoV-I/II genomes were detected using nested reverse transcriptase-polymerase chain reaction (RT-PCR). Six positive samples were sequenced for phylogenetic and amino acid analyses, and results were statistically evaluated. Nested PCR results showed that 30% (9/30) of effusion samples were positive for FCoV-I, 13.33% (4/30) for FCoV-II, and 6.66% (2/30) were positive for both FCoV types. Among fecal samples, 33.33% (10/30) were positive for FCoV-I, while no FCoV-II was detected. No statistically significant association was found between FCoV positivity and factors such as gender or age. This study demonstrates, for the first time at the molecular level, the coexistence of FCoV-I and FCoV-II strains in Türkiye and their genetic similarity with global variants. Evaluating fecal and effusion samples together enhances diagnostic accuracy and enables the use of alternative specimens in FIP diagnosis. These findings are crucial for understanding FCoV evolution, controlling disease spread, and developing effective therapeutic and preventive strategies. Moreover, this study provides the first comprehensive phylogenetic characterization of FCoV Types I and II in Türkiye, contributing valuable data to global feline coronavirus epidemiology and vaccine research.