title: Summer mortalities and detection of ostreid herpesvirus microvariant in Pacific oyster Crassostrea gigas in Sweden and Norway.
abstract: The Pacific oyster Crassostrea gigas has recently expanded its range in Scandinavia. The expansion is presumably a result of northwards larval drift. Massive settlements were recorded in many areas along the Swedish west coast and southern Norway in 2013 and 2014. After the spawning season in 2014, the temperature of the surface water peaked at 24-26°C. After this period, high and sudden mortalities occurred in a Swedish hatchery and in wild populations along the Swedish west coast and south coast of Norway. Surveys and collected data showed that mortalities mainly occurred during 3 wk in September. All size classes were affected, and affected populations displayed a patchy distribution with heavily affected and unaffected populations in close proximity. Flat oysters Ostrea edulis and blue mussels Mytilus edulis were unaffected. Ostreid herpesvirus (OsHV) was detected in moribund Pacific oyster spat as well as in surviving adults. The virus was identified as OsHV-1 μvar. This is the first detection of this variant in Scandinavia, showing that OsHV-1 μvar is present in areas with recent establishments of Pacific oysters, and where there is no aquaculture of this species.
authors.affiliation: Institute of Marine Research, PO Box 1870 Nordnes, 5817 Bergen, Norway.
authors.forename: Stein
authors.initials: S
authors.lastname: Mortensen
authors.forename: Åsa
authors.initials: Å
authors.lastname: Strand
authors.forename: Torjan
authors.initials: T
authors.lastname: Bodvin
authors.forename: Anders
authors.initials: A
authors.lastname: Alfjorden
authors.forename: Cecilie K
authors.initials: CK
authors.lastname: Skår
authors.forename: Anders
authors.initials: A
authors.lastname: Jelmert
authors.forename: Anna
authors.initials: A
authors.lastname: Aspán
authors.forename: Lisbeth
authors.initials: L
authors.lastname: Sælemyr
authors.forename: Lars-Johan
authors.initials: LJ
authors.lastname: Naustvoll
authors.forename: Jon
authors.initials: J
authors.lastname: Albretsen
mesh_terms: D000818:Animals; D001483:Base Sequence; D049896:Crassostrea / Q000821:virology*; D004279:DNA, Viral / Q000302:isolation & purification; D014644:Genetic Variation; D006564:Herpesviridae / Q000235:genetics / Q000502:physiology*; D054884:Host-Pathogen Interactions; D008969:Molecular Sequence Data; D009664:Norway; D016133:Polymerase Chain Reaction; D012621:Seasons; D013548:Sweden
chemical_list: D004279:DNA, Viral