title: Polymorphism in the infectious salmon anemia virus hemagglutinin gene: importance and possible implications for evolution and ecology of infectious salmon anemia disease.
abstract: Infectious salmon anemia (ISA) is an emerging disease in farmed Atlantic salmon with important commercial consequences. The pathogenicity of the ISA virus (ISAV; an orthomyxovirus) varies, observed as differences in disease development and clinical signs. A small polymorphic region (PR) in the ISAV genomic segment encoding the hemagglutinin (HA) has been described. An analysis of 33 HA gene sequences from historical and recent ISA outbreaks was performed, added to a selection of previously published HA sequences. A differential deletion model explaining the generation of HA polymorphism is proposed. The European ISAV sequences could be grouped according to deletion patterns in PR. Cell-culture replication and cytopathic effect varied between viruses from different PR groups. A rather complex epidemiology is suggested, as (a) HA sequences representing several PR variants were detected in three samples; (b) identical mutations occurred in different genetic lineages; and (c) large genetic differences were present in closely related viruses.
authors.affiliation: Norwegian School of Veterinary Science, Department of Pharmacology, Microbiology, and Food Hygiene, PO Box 8146 Dep N-0033 Oslo, Norway. siri.mjaaland@veths.no
authors.forename: Siri
authors.initials: S
authors.lastname: Mjaaland
authors.forename: Olav
authors.initials: O
authors.lastname: Hungnes
authors.forename: Ann
authors.initials: A
authors.lastname: Teig
authors.forename: Birgit H
authors.initials: BH
authors.lastname: Dannevig
authors.forename: Kristin
authors.initials: K
authors.lastname: Thorud
authors.forename: Espen
authors.initials: E
authors.lastname: Rimstad
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D004463:Ecology; D005393:Fish Diseases / Q000821:virology*; D006389:Hemagglutinins, Viral / Q000235:genetics*; D008969:Molecular Sequence Data; D009975:Orthomyxoviridae / Q000145:classification / Q000235:genetics* / Q000502:physiology; D009976:Orthomyxoviridae Infections / Q000662:veterinary* / Q000821:virology; D011110:Polymorphism, Genetic; D020317:Salmo salar / Q000821:virology*; D014779:Virus Replication
chemical_list: D006389:Hemagglutinins, Viral