title: Cardiomyopathy syndrome of atlantic salmon (Salmo salar L.) is caused by a double-stranded RNA virus of the Totiviridae family.
abstract: Cardiomyopathy syndrome (CMS) of farmed and wild Atlantic salmon (Salmo salar L.) is a disease of yet unknown etiology characterized by a necrotizing myocarditis involving the atrium and the spongious part of the heart ventricle. Here, we report the identification of a double-stranded RNA virus likely belonging to the family Totiviridae as the causative agent of the disease. The proposed name of the virus is piscine myocarditis virus (PMCV). On the basis of the RNA-dependent RNA polymerase (RdRp) sequence, PMCV grouped with Giardia lamblia virus and infectious myonecrosis virus of penaeid shrimp. The genome size of PMCV is 6,688 bp, with three open reading frames (ORFs). ORF1 likely encodes the major capsid protein, while ORF2 encodes the RdRp, possibly expressed as a fusion protein with the ORF1 product. ORF3 seems to be translated as a separate protein not described for any previous members of the family Totiviridae. Following experimental challenge with cell culture-grown virus, histopathological changes are observed in heart tissue by 6 weeks postchallenge (p.c.), with peak severity by 9 weeks p.c. Viral genome levels detected by real-time reverse transcription (RT)-PCR peak earlier at 6 to 7 weeks p.c. The virus genome is detected by in situ hybridization in degenerate cardiomyocytes from clinical cases of CMS. Virus genome levels in the hearts from clinical field cases correlate well with the severity of histopathological changes in heart tissue. The identification of the causative agent for CMS is important for improved disease surveillance and disease control and will serve as a basis for vaccine development against the disease.
authors.affiliation: Department of Basic Sciences and Aquatic Medicine, Norwegian School of Veterinary Science, Oslo, Norway. oystein.evensen@nvh.no
authors.forename: Oyvind
authors.initials: O
authors.lastname: Haugland
authors.forename: Aase B
authors.initials: AB
authors.lastname: Mikalsen
authors.forename: Pål
authors.initials: P
authors.lastname: Nilsen
authors.forename: Karine
authors.initials: K
authors.lastname: Lindmo
authors.forename: Beate J
authors.initials: BJ
authors.lastname: Thu
authors.forename: Trygve M
authors.initials: TM
authors.lastname: Eliassen
authors.forename: Norbert
authors.initials: N
authors.lastname: Roos
authors.forename: Marit
authors.initials: M
authors.lastname: Rode
authors.forename: Oystein
authors.initials: O
authors.lastname: Evensen
mesh_terms: D000818:Animals; D009202:Cardiomyopathies / Q000473:pathology / Q000662:veterinary* / Q000821:virology; D016000:Cluster Analysis; D005393:Fish Diseases / Q000473:pathology / Q000821:virology*; D006321:Heart / Q000821:virology; D006651:Histocytochemistry; D017403:In Situ Hybridization; D008853:Microscopy; D008969:Molecular Sequence Data; D009206:Myocardium / Q000473:pathology; D016366:Open Reading Frames; D010802:Phylogeny; D012327:RNA Virus Infections / Q000473:pathology / Q000662:veterinary* / Q000821:virology; D012330:RNA, Double-Stranded / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics; D012194:RNA-Directed DNA Polymerase / Q000235:genetics; D020317:Salmo salar; D017422:Sequence Analysis, DNA; D019196:Totiviridae / Q000302:isolation & purification* / Q000472:pathogenicity; D014764:Viral Proteins / Q000235:genetics
chemical_list: D012330:RNA, Double-Stranded; D012367:RNA, Viral; D014764:Viral Proteins; D012194:RNA-Directed DNA Polymerase