Evolution of the Piscine orthoreovirus Genome Linked to Emergence of Heart and Skeletal Muscle Inflammation in Farmed Atlantic Salmon ( Salmo salar )

• Published in: Viruses Vol. 11; no. 5; p. 465
• Main Authors: Dhamotharan, Kannimuthu, Tengs, Torstein, Wessel, Øystein, Braaen, Stine, Nyman, Ingvild B, Hansen, Elisabeth F, Christiansen, Debes H, Dahle, Maria K, Rimstad, Espen, Markussen, Turhan
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 22.05.2019; MDPI
• Subjects: Aquaculture; Coevolution; Disease; Epidemics; Evolution; Genomes; Heart; HSMI; Infections; Inflammation; Musculoskeletal system; Mutation; Phylogeny; Piscine orthoreovirus; Proteins; PRV-1; reassortment; Salmo salar; Salmon; Skeletal muscle; Strains (organisms); Trout; viral evolution; Viral infections; virulence; Viruses; Canada; Chile; Norway; Germany; Faroe Islands; viral evolution; reassortment; Piscine orthoreovirus; virulence; PRV-1; HSMI
• ISSN: 1999-4915; 1999-4915
• DOI: 10.3390/v11050465

Heart and skeletal muscle inflammation (HSMI) in farmed Atlantic salmon ( was first diagnosed in Norway in 1999. The disease is caused by -1 (PRV-1). The virus is prevalent in farmed Atlantic salmon, but not always associated with disease. Phylogeny and sequence analyses of 31 PRV-1 genomes collected over a 30-year period from fish with or without HSMI, grouped the viral sequences into two main monophylogenetic clusters, one associated with HSMI and the other with low virulent PRV-1 isolates. A PRV-1 strain from Norway sampled in 1988, a decade before the emergence of HSMI, grouped with the low virulent HSMI cluster. The two distinct monophylogenetic clusters were particularly evident for segments S1 and M2. Only a limited number of amino acids were unique to the association with HSMI, and they all located to S1 and M2 encoded proteins. The observed co-evolution of the S1-M2 pair coincided in time with the emergence of HSMI in Norway, and may have evolved through accumulation of mutations and/or segment reassortment. Sequences of S1-M2 suggest selection of the HSMI associated pair, and that this segment pair has remained almost unchanged in Norwegian salmon aquaculture since 1997. PRV-1 strains from the North American Pacific Coast and Faroe Islands have not undergone this evolution, and are more closely related to the PRV-1 precursor strains not associated with clinical HSMI.