Molecular Characterization of a Feline Panleukopenia Virus Strain Isolated from a Dog with Clinical Gastroenteritis in Spain.

Canine parvovirosis is a fatal disease state traditionally caused by canine parvovirus (CPV), which evolved from feline panleukopenia virus (FPV). While FPV was historically restricted to felids, FPV-like strains were recently reported to be causing clinical disease in dogs. This study aims to characterize an FPV-like strain detected in an eight-week-old unvaccinated female dog in Spain exhibiting hemorrhagic diarrhea and severe leukopenia. After fecal DNA isolation, a 1745-base-pair fragment of the VP2 gene was sequenced for phylogenetic and molecular analysis. Our results revealed that this strain shared high homology with local feline FPV strains; the sequence was clustered near to other FPV strains detected in dogs elsewhere. Molecular analysis identified an isoleucine-to-threonine substitution at position 101 (I101T) of the VP2 protein. This mutation, common in contemporary FPV and CPV variants, has been described as a structural modification that optimizes interaction with the canine transferrin receptor, suggesting a potential role in canine host adaptation. In conclusion, this study represents the first report in Spain of FPV associated with clinical gastroenteritis in dogs. These findings underscore the necessity of continuous genomic surveillance of these highly evolving viruses for monitoring host-switching events.