Detection of duck circovirus in China: A proposal on genotype classification.

Since the first description of duck circovirus (DuCV)-associated disease, there are several reports about the distribution of the disease. However, the information regarding the genetic variation of DuCV in recent years is unclear. In the present study, the complete genomic sequences of 9 DuCV strains, which were obtained by PCR screening from 90 dead or diseased ducks collected from different regions in China between 2008 and 2010, were determined and compared with previously available DuCV sequences in public databases. Phylogenetic analysis on the basis of genomic and ORF C1 sequences demonstrated that the DuCV strains could be divided into two genotypes, designated genotypes 1 and 2. In pairwise comparisons of complete genomic sequences and ORF C1 nucleotide and amino acid sequences, DuCVs of the same genotype were clearly distinguished from those of heterologous genotypes. Analysis of the amino acid sequences of the capsid protein exhibited the existence of 18 genotype-specific substitutions. Our analysis also showed that genotypes 1 and 2 were co-circulating in China in recent years. The present work contributes to the understanding of DuCV molecular epidemiology.