Genomic characterization of a novel iridovirus from redclaw crayfish Cherax quadricarinatus: evidence for a new genus within the family Iridoviridae.

A novel iridovirus, Cherax quadricarinatus iridovirus (CQIV), was identified from diseased C. quadricarinatus in 2014. This virus is considered as a new threat to crustacean aquaculture because it is lethal to both peneaid shrimp and crayfish. Here, we determined the complete genome sequence of CQIV. The double-stranded DNA genome is 165 695 bp in length with a G+C content of 34.6 %. A total of 178 open reading frames (ORFs) have been predicted, encoding hypothetical proteins ranging from 50 to 1327 amino acids. Forty-seven of these exhibit similarities to proteins of known functions. Phylogenetic analysis based on multiple alignments of conserved proteins shows that CQIV clusters with the members of the family Iridoviridae, but is placed in a distinct clade from all the five known genera. It indicates that CQIV may represent a new genus in the family Iridoviridae, for which we propose the name Cheraxvirus based on the host organism.