Abstract
Piscine orthoreovirus (PRV) belongs to the family Reoviridae and has been described mainly in association with salmonid infections. The genome of PRV consists of about 23,600 bp, with 10 segments of double-stranded RNA, classified as small (S1 to S4), medium (M1, M2 and M3) and large (L1, L2 and L3); these range approximately from 1000 bp (segment S4) to 4000 bp (segment L1). How the genetic variation among PRV strains affects the virulence for salmonids is still poorly understood. The aim of this study was to describe the molecular phylogeny of PRV based on an extensive sequence analysis of the S1 and M2 segments of PRV available in the GenBank database to date (May 2020). The analysis was extended to include new PRV sequences for S1 and M2 segments. In addition, subgenotype classifications were assigned to previously published unclassified sequences. It was concluded that the phylogenetic trees are consistent with the original classification using the PRV genomic segment S1, which differentiates PRV into two major genotypes, I and II, and each of these into two subgenotypes, designated as Ia and Ib, and IIa and IIb, respectively. Moreover, some clusters of country- and host-specific PRV subgenotypes were observed in the subset of sequences used. This work strengthens the subgenotype classification of PRV based on the S1 segment and can be used to enhance research on the virulence of PRV.
Highlights
IntroductionHeart and skeletal muscle inflammation (HSMI) is an infectious disease caused by Piscine orthoreovirus (PRV) and was described for the first time in Norway [1,2,3]
New sequences for the S1 and M2 segments were added in preparation for this work, resulting in the obtainment of between 38 and 390 sequences with respect to the Piscine orthoreovirus (PRV) segments used in the study (Table 1)
We extended the geographical range of the already characterized PRV isolates by compiling all the available sequences to date (May 2020) associated with the National Center for Biotechnology Information (NCBI) Taxonomy
Summary
Heart and skeletal muscle inflammation (HSMI) is an infectious disease caused by Piscine orthoreovirus (PRV) and was described for the first time in Norway [1,2,3]. PRV has been detected in numerous wild and farmed salmonid species in Norway [5,6,7,8,9], Canada [10,11,12,13,14], Chile [10,15], the United States [12,16], Japan [17], Scotland, Ireland, the Faroe Islands, Iceland, Germany, Sweden, Denmark, Italy, France [18,19,20,21,22,23] and the Czech Republic [24]. During PRV infection, the presence of intracytoplasmic inclusion bodies in erythrocytes has been described [26,27,28]
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