Genetic diversity and multiple infection with more CPV variants.

Canine parvovirus type 2 (CPV-2), a DNA virus was first observed to cause severe hemorrhagic gastroenteritis in dogs in 1978, in subsequent years was replaced by new variants, type 2a (CPV-2a) and type 2b (CPV-2b) which differ between them by a single epitope localized in residue 426 of the VP2 protein. The new variants have gained the feline host range whereas the original CPV-2 does not replicate in cats. Recently, in the residue 426 of the VP2 protein has been observed a new antigenic change (N/DíE) and the novel variant was tentatively named type 2c. We report the detection of co-infection by multiple CPV variants and the high genetic complexity of two CPV-2 strains detected in a dog and a domestic cat. The CPV variants selected by cloning the VP2 gene were sequenced and genetic diversity and selection pressure were investigated. Recombination was examined using different but complementary approaches. Comparison of the nucleotide sequences has evidenced different viral populations and it was seen that, in the same animal, two CPV variants coexist: the type 2a and the new variant N/D426E. Our analysis seems to exclude the fact that the recombination events happened during infection and negative selection has acted on VP2 gene. Different viral populations were evidenced and it was seen that the variant 2a and 2c coexist. These findings display the remarkable genetic heterogeneity of CPV-2 reassembling to the quasispecies distribution found in RNA virus population. Furthermore this is the first report about the detection of more CPV variants in the same animal that confirms how multiple infection can be occurred also for CPV as just observed for other parvoviruses.