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

Heart and skeletal muscle inflammation (HSMI) in farmed Atlantic salmon ( Salmo salar) was first diagnosed in Norway in 1999. The disease is caused by Piscine orthoreovirus -1 (PRV-1). The virus is prevalent in farmed Atlantic salmon, but not always associated with disease. Phylogeny and sequence an...

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Bibliographic Details
Published in:Viruses
Main Authors: Kannimuthu Dhamotharan, Torstein Tengs, Øystein Wessel, Stine Braaen, Ingvild B. Nyman, Elisabeth F. Hansen, Debes H. Christiansen, Maria K. Dahle, Espen Rimstad, Turhan Markussen
Format: Article in Journal/Newspaper
Language:English
Published: MDPI AG 2019
Subjects:
PRV-1
Piscine orthoreovirus
HSMI
virulence
reassortment
viral evolution
Microbiology
QR1-502
Faroe Islands
Pacific
Norway
Atlantic salmon
Salmo salar
Online Access:https://doi.org/10.3390/v11050465
https://doaj.org/article/0575ecd2602b4584b09c0864ea93897c
Description
Summary:Heart and skeletal muscle inflammation (HSMI) in farmed Atlantic salmon ( Salmo salar) was first diagnosed in Norway in 1999. The disease is caused by Piscine orthoreovirus -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.

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