Molecular characterization of a duck hepatitis virus 3-like astrovirus

Using an ORF1b-based astrovirus-specific reverse transcription (RT)-PCR assay, a duck hepatitis virus type 3 (DHV-3)-like astrovirus was detected from four intestinal samples collected from diseased ducks in China. Complete genome sequencing and comparative sequence analysis showed that the four duck astrovirus (DAstV) isolates were closely related and possessed a typical astrovirus genome organization. Genetic analysis of the complete ORF2 region revealed that mean amino acid genetic distances between the DHV-3-like isolates and previously known avastrovirus species were between 0.579 and 0.721, suggesting that the DHV-3-like isolates could be classified as an additional avastrovirus species. In the ORF1a and ORF1b regions, however, mean amino acid genetic distances between the DHV-3-like viruses and the turkey astrovirus 2 (TAstV-2)-like isolates were substantially less than those between TAstV-2-like isolates and DAstV/C-NGB-like astroviruses belonging to the same species. Pairwise comparisons and phylogenetic analyses demonstrated that the DHV-3-like isolates were most closely related to TAstV-2-like viruses in ORF1a and ORF1b, while showed highest similarity with the chicken astrovirus (CAstV) 612-like viruses in ORF2. These findings provide evidence that recombination events may have occurred during evolution of the avastroviruses and support the view that genomic analysis is required for classification of the avastroviruses.