Complete genome sequence of Ostreid herpesvirus-1 associated with mortalities of Scapharca broughtonii broodstocks

BACKGROUND: Ostreid herpesvirus-1 (OsHV-1) is the major bivalve pathogen associated with severe mortality events in a wide host range. In the early summer of 2012 and 2013, mass mortalities of blood clam (Scapharca broughtonii) broodstocks associated with a newly described variant of OsHV-1 (OsHV-1-SB) were reported. METHODS: In this study, the complete genome sequence of the newly described variant was determined through the primer walking approach, and compared with those of the other two OsHV-1 variants. RESULTS: OsHV-1-SB genome was found to contain 199, 354 bp nucleotides with 38.5 % G/C content, which is highly similar to those of acute viral necrosis virus (AVNV) and OsHV-1 reference type. A total of 123 open reading frames (ORFs) putatively encoding functional proteins were identified; eight of which were duplicated in the major repeat elements of the genome. The genomic organization of OsHV-1-SB could be represented as TR(L)-U(L)-IR(L)-IR(S)-U(S)-TR(S), which is different from that of OsHV-1 reference type and AVNV due to the deletion of a unique region (X, 1.5Kb) between IR(L) and IR(S). The DNA sequence of OsHV-1-SB is 95.2 % and 97.3 % identical to that of OsHV-1 reference type and AVNV respectively. On the basis of nucleotide sequences of 32 ORFs in OsHV-1-SB and the other nine OsHV-1 variants, results from phylogenetic analysis also demonstrated that OsHV-1-SB is most closely related to AVNV. CONCLUSIONS: The determination of the genome of OsHV-1 with distinguished epidemiological features will aid in our better understanding of OsHV-1 diversity, and facilitate further research on the origin, evolution, and epidemiology of the virus. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12985-015-0334-0) contains supplementary material, which is available to authorized users.