Feline Kobuvirus in Domestic Cats in Northern Vietnam: Molecular Insights Reveal Adaptive Evolution in VP1 Protein

Feline kobuvirus (FKoV) has been linked to diarrheal disease in cats and has recently emerged in several Asian countries. This study aimed to investigate the epidemiological and genetic characterization of FKoV in domestic cats in northern Vietnam from 2022 to 2025. In total, 244 fecal samples were obtained from both healthy and sick cats in Hanoi, Hungyen, Bacninh, and Ninhbinh in the north of Vietnam. Of 244 fecal samples examined, eight (3.28%) samples were found to be positive for the FKoV genome by using the conventional PCR method. Viral genomes were identified in both healthy and sick cats. The highest FKoV-positive rate was 12.50% in 6–12-month-old cats, significantly higher than those detected in cats aged 3–6 months and >12 months. Eight positive samples were successfully sequenced and characterized for the partial 3D gene and full-length VP1 genes. Results showed that the level of nucleotide identity of the partial 3D gene and full-length VP1 genes among the FKoV strains in this study ranged from 95.86% to 100% and 94.09% to 99.73%, respectively. Phylogenetic analysis revealed that the eight Vietnamese viral strains obtained in this study formed a novel cluster within FKoV and are genetically related to Chinese FKoV strains. Two positive selections were found in the VP1 protein of the Vietnamese FKoV strains.