Mass mortality in Korean bay scallop (Argopecten irradians) associated with Ostreid Herpesvirus-1 μVar.

Since November 2017, mass mortalities of larvae of bay scallop (Argopecten irradians) were reported in hatcheries located at the southern area of Republic of Korea. Over 90% of larvae aged 5-10 days sank to the bottom of the tank and died. The hatcheries could not produce spat, and thus artificial seed production industry incurred huge losses. We identified Ostreid Herpesvirus-1 μVar (OsHV-1 μVar) associated with mass mortality by PCR, sequencing and transmission electron microscopy (TEM). All the samples were positive for OsHV-1 μVar with 99% sequence identity to previously reported OsHV-1 μVar sequences. Partial sequence of ORF-4 of OsHV-1 detected in this study was more closely related to sequences isolated from Europe. This is the first report to confirm the mortality caused by an OsHV-1 infection in the bay scallop.