Complete sequence of a novel duck astrovirus

A duck astrovirus isolate CPH (DAstV/CPH) detected from newly hatched ducklings was sequenced. The 7463-nt-long genome contained three open reading frames (ORFs) that were in three different frames, as seen in DAstV/C-NGB. Sequence comparison and phylogenetic analysis based on the full-length amino acid sequences of the three ORFs demonstrated that DAstV/CPH was highly divergent from previously known avastroviruses for which corresponding sequences are available. Genetic analysis of the complete ORF2 region revealed that mean amino acid genetic distances shared by DAstV/CPH with members of the three established avastrovirus species and other avastroviruses (except the chicken astrovirus GA2011 [CAstV/GA2011]-like viruses) were between 0.577 and 0.787, suggesting that DAstV/CPH may represent an additional avastrovirus species. The mean amino acid genetic distance between DAstV/CPH and the CAstV/GA2011-like viruses was 0.366, demonstrating the difficulty in determining the taxonomic relationship of DAstV/CPH to the CAstV/GA2011-like viruses. Interestingly, analysis based on a portion of the ORF1b region indicated that DAstV/CPH was more closely related to the common-teal-origin astrovirus MPK514 than to the CAstV/GA2011-like viruses. The findings are likely to provide new insights into the ecology and evolution of avastroviruses.