title: Infectious salmon anemia (ISA) virus: infectivity in seawater under different physical conditions.
abstract: Infectious salmon anemia (ISA) virus (genus Isavirus, family Orthomyxoviridae), present in all major salmon producing countries, is the causative agent for a serious and commercially important disease affecting Atlantic Salmon Salmo salar. Nearly all ISA outbreaks occur in the marine production phase and knowledge about survival time for ISA virions in seawater is crucial for an adequate strategy to combat the disease. To acquire knowledge about this important factor, a study of ISA virus exposed to four different physical conditions was carried out. The virions' survival was tested in sterile seawater, sterile seawater with normal ultraviolet light radiation (UVR), natural seawater, and natural seawater with UVR. During the 72-h experiment both presence of ISA virus RNA and the infectivity of ISA virions were monitored. The result of this study showed that the infectivity of ISA virions is lost within 3 h of exposure to natural seawater or sterile seawater with UVR. However, it was possible to detect ISA virus RNA throughout the experimental period. This indicates that the effect of both UVR and biological activity of natural seawater limits the survival time of ISA virions under normal conditions. The survival time of ISA virions in sterile seawater was less than 24 h. Based on the available literature and the present study it is not very likely that passive horizontal transmission in seawater over long distances can occur. This is due to the following factors: (1) the effect of UVR and biological activity on ISA virions infectivity found in the present study, (2) the speed and dilution effect in seawater currents in salmon farming areas, (3) the temperature during the major outbreak periods, and (4) the need for an infective dose of ISA virions to reach naive Atlantic Salmon.
authors.affiliation: a Cermaq , Dronning Eufemias gate 16 , Oslo , N-0102 , Norway.
authors.forename: Siri
authors.initials: S
authors.lastname: Vike
authors.forename: Karin
authors.initials: K
authors.lastname: Oelckers
authors.forename: Henrik
authors.initials: H
authors.lastname: Duesund
authors.forename: Svein Rune
authors.initials: SR
authors.lastname: Erga
authors.forename: Javier
authors.initials: J
authors.lastname: Gonzalez
authors.forename: Børge
authors.initials: B
authors.lastname: Hamre
authors.forename: Oyvind
authors.initials: O
authors.lastname: Frette
authors.forename: Are
authors.initials: A
authors.lastname: Nylund
mesh_terms: D000818:Animals; D005393:Fish Diseases / Q000821:virology*; D046829:Isavirus / Q000472:pathogenicity* / Q000502:physiology* / Q000528:radiation effects; D009976:Orthomyxoviridae Infections / Q000662:veterinary* / Q000821:virology; D012367:RNA, Viral; D020317:Salmo salar; D012623:Seawater; D014466:Ultraviolet Rays
chemical_list: D012367:RNA, Viral