Characterization of a strain of feline calicivirus isolated from a dog faecal sample

To expand the epidemiological understanding of feline calicivirus (FCV) in dogs, genotypic and phenotypic characterizations of a FCV strain isolated from a puppy showing enteritis were performed. After isolation in cell culture, the novel isolate was analysed by RT-PCR and the amplicons obtained were sequenced. In order to characterize the growth properties of the isolate, the size of the plaques, the temperature of inactivation and the kinetics of growth were evaluated. Moreover, the novel strain was used to perform a serological study on 86 canine serum samples and 81 feline sera by virus-neutralization assay. The comparative analysis of nucleotide and amino acid sequences of the isolate, named FCV-Te/10/07, revealed the highest identity to strain FCV-F65. The growth kinetic revealed that strain Te/10/07 grew more rapidly than F9 strain. By virus-neutralization assay, dogs from the same region of the isolate showed antibodies against the FCV-F9 vaccinal strain in 63.9% (55/86) of sera, while antibodies against the Te/10/07 were found in seven sera (8.13%). In cats neutralizing antibodies against Te/10/07 strain were recovered in 50.62% (41/81) of samples tested, even if 38 sera were positives for F9 strain with similar titres or higher. In three cats neutralization to Te/10/07 alone was seen. Our results confirmed the interspecific circulation of FCV strains among different animal species, but new investigations are needed to establish whether FCV is pathogenic in the dog and the role of interspecies circulation in pathogen spreading.