Genetic characterization of canine parvovirus and circovirus in dogs in Vietnam

Abstract

Canine parvovirus (CPV-2) emerged and caused severe enteritis in dogs since the 1970s. The last variant, CPV-2c is considered as the high virulent strain and spread ubiquitous worldwide. This strain was early detected in Vietnam since 2002, but the whole genome is still fragmentary. In this study, we attempted to gain the whole genome of CPV-2c from the Vietnamese infected dogs as the first report of the full-length CPV-2c sequence originated from Asia. The Vietnamese CPV-2c exhibited the common mutations in both structural and nonstructural proteins and shared a typical evolutionary pattern with Asian strains. Besides, Vietnamese sequences presented some new mutations and clustered with current Chinese CPV-2 to create a new Asia-IV clade in the phylogeny. The substitution rate was estimated based on the data set of 199 sequences over the last 42 years of viral emergence, and confirmed that CPV-2 is a rapidly evolving ssDNA virus. Moreover, CPV-2 is highly co-infected with other enteric viruses to cause the disease. Among them, Canine circovirus (CanineCV) is the most prevalent, about 19.7%. Then, we further characterized the full-genome of this virus. Phylogenetic analysis revealed that CanineCV is divided into four different genotypes (CanineCV-1, -2, -3, and -4) with typically replaced amino acids in the Replicase and Capsid proteins. Both CanineCV-1 and 4 co-circulated in Vietnam and shared 86-87.6% of nucleotide similarity. The recombination event has occurred at nucleotide position 420-1020 in one Vietnamese CanineCV strain (CanineCV-VN-6) with the major and minor parents derived from America and China, respectively. Future study should be emphasized on the continuous surveillance of CPV-2 and CanineCV in other regions in Vietnam to draw the whole information regarding epidemiology, genotype, mutation and evolution of both enteric viruses.