Genetic heterogeneity of canine bufaviruses

Canine bufavirus (CBuV) is a protoparvovirus, genetically related to human and non-human primate bufaviruses and distantly related to canine parvovirus type 2 (CPV-2). CBuV was initially identified from young dogs with respiratory signs but subsequent studies revealed that this virus is also a common component of the canine enteric virome. In this survey, by assessing archival and recent collections of dogs faecal samples, CBuV DNA was detected with a higher prevalence rate (8.8%) in animals with enteritis than in control animals (5.0%), although this difference was not statistically significant. The rate of co-infections with other enteric viruses in diarrhoeic dogs was high (84.6%), mostly in association with canine parvovirus CPV-2 (90.1%). The complete ORF2 gene was determined in five samples, and the nearly full-length genome was reconstructed for three strains, 62/2017/ITA, 9AS/2005/ITA and 35/2018/ITA. Upon sequence comparison, the viruses appeared highly conserved in the NS1 (97.2%–97.9% nt and 97.5%–98.1% aa identities). In the complete VP2 coding region, three strains were similar to the prototype viruses (99.7–99.8 nt and 99.6%–99.8% aa) whilst strains 9AS/2005/ITA and 35/2016/ITA were distantly related (87.6%–89.3% nt and 93.9%–95.1% aa identities). Interestingly, genetic diversification occurred downstream conserved regions such as the VP1/VP2 splicing signals and/or the G-rich motif in the N terminus of the VP2, suggesting a potential recombination nature. Upon phylogenetic analysis, the two divergent CBuV strains formed a distinct cluster/genotype.