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Piscine Orthoreovirus from Western North America Is Transmissible to Atlantic Salmon and Sockeye Salmon but Fails to Cause Heart and Skeletal Muscle Inflammation.

ABSTRACT: Heart and skeletal muscle inflammation (HSMI) is a significant and often fatal disease of cultured Atlantic salmon in Norway. The consistent presence of Piscine orthoreovirus (PRV) in HSMI diseased fish along with the correlation of viral load and antigen with development of lesions has supported the supposition that PRV is the etiologic agent of this condition; yet the absence of an in vitro culture system to demonstrate disease causation and the widespread prevalence of this virus in the absence of disease continues to obfuscate the etiological role of PRV with regard to HSMI. In this study, we explore the infectivity and disease causing potential of PRV from western North America-a region now considered endemic for PRV but without manifestation of HSMI-in challenge experiments modeled upon previous reports associating PRV with HSMI. We identified that western North American PRV is highly infective by intraperitoneal injection in Atlantic salmon as well as through cohabitation of both Atlantic and Sockeye salmon. High prevalence of viral RNA in peripheral blood of infected fish persisted for as long as 59 weeks post-challenge. Nevertheless, no microscopic lesions, disease, or mortality could be attributed to the presence of PRV, and only a minor transcriptional induction of the antiviral Mx gene occurred in blood and kidney samples during log-linear replication of viral RNA. Comparative analysis of the S1 segment of PRV identified high similarity between this North American sequence and previous sequences associated with HSMI, suggesting that factors such as viral co-infection, alternate PRV strains, host condition, or specific environmental circumstances may be required to cause this disease.

SUBMITTER: Garver KA

PROVIDER: S-EPMC4701501 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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Piscine Orthoreovirus from Western North America Is Transmissible to Atlantic Salmon and Sockeye Salmon but Fails to Cause Heart and Skeletal Muscle Inflammation.

Garver Kyle A KA Johnson Stewart C SC Polinski Mark P MP Bradshaw Julia C JC Marty Gary D GD Snyman Heindrich N HN Morrison Diane B DB Richard Jon J

PloS one 20160105 1

Heart and skeletal muscle inflammation (HSMI) is a significant and often fatal disease of cultured Atlantic salmon in Norway. The consistent presence of Piscine orthoreovirus (PRV) in HSMI diseased fish along with the correlation of viral load and antigen with development of lesions has supported the supposition that PRV is the etiologic agent of this condition; yet the absence of an in vitro culture system to demonstrate disease causation and the widespread prevalence of this virus in the absen ...[more]

PMID: 26730591

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Project description:BACKGROUND:Piscine orthoreovirus (PRV) is an emergent virus in salmon aquaculture belonging to the family Reoviridae. PRV is associated with a growing list of pathological conditions including heart and skeletal inflammation (HSMI) of farmed Atlantic salmon. Despite widespread PRV infection in commercially farmed Atlantic salmon, information on PRV prevalence and on the genetic sequence variation of PRV in Atlantic salmon on the north Pacific Coast is limited. METHODS:Feral Atlantic salmon caught in Washington State and British Columbia following a large containment failure at a farm in northern Puget Sound were sampled. Fish tissues were tested for PRV by RT-qPCR assay for segment L1 and conventional RT-PCR for PRV segment S1. The PCR products were sequenced and their relationship to PRV strains in GenBank was determined using phylogenetic analysis and nucleotide and amino acid homology comparisons. RESULTS:Following the escape of 253,000 Atlantic salmon from a salmon farm in Washington State, USA, 72/73 tissue samples from 27 Atlantic salmon captured shortly after the escape tested PRV-positive. We estimate PRV-prevalence in the source farm population at 95% or greater. The PRV found in the fish was identified as PRV sub-genotype Ia and very similar to PRV from farmed Atlantic salmon in Iceland. This correlates with the source of the fish in the farm. Eggs of infected fish were positive for PRV indicating the possibility of vertical transfer and spread with fish egg transports. CONCLUSIONS:PRV prevalence was close to 100% in farmed Atlantic salmon that were caught in Washington State and British Columbia following a large containment failure at a farm in northern Puget Sound. The PRV strains present in the escaped Atlantic salmon were very similar to the PRV strain reported in farmed Atlantic salmon from the source hatchery in Iceland that was used to stock commercial aquaculture sites in Washington State. This study emphasizes the need to screen Atlantic salmon broodstock for PRV, particularly where used to supply eggs to the global Atlantic salmon farming industry thereby improving our understanding of PRV epidemiology.

Project description:Quantifying the variability in the delivery of ecosystem services across the landscape can be used to set appropriate management targets, evaluate resilience and target conservation efforts. Ecosystem functions and services may exhibit portfolio-type dynamics, whereby diversity within lower levels promotes stability at more aggregated levels. Portfolio theory provides a framework to characterize the relative performance among ecosystems and the processes that drive differences in performance. We assessed Pacific salmon Oncorhynchus spp. portfolio performance across their native latitudinal range focusing on the reliability of salmon returns as a metric with which to assess the function of salmon ecosystems and their services to humans. We used the Sharpe ratio (e.g. the size of the total salmon return to the portfolio relative to its variability (risk)) to evaluate the performance of Chinook and sockeye salmon portfolios across the west coast of North America. We evaluated the effects on portfolio performance from the variance of and covariance among salmon returns within each portfolio, and the association between portfolio performance and watershed attributes. We found a positive latitudinal trend in the risk-adjusted performance of Chinook and sockeye salmon portfolios that also correlated negatively with anthropogenic impact on watersheds (e.g. dams and land-use change). High-latitude Chinook salmon portfolios were on average 2·5 times more reliable, and their portfolio risk was mainly due to low variance in the individual assets. Sockeye salmon portfolios were also more reliable at higher latitudes, but sources of risk varied among the highest performing portfolios. Synthesis and applications. Portfolio theory provides a straightforward method for characterizing the resilience of salmon ecosystems and their services. Natural variability in portfolio performance among undeveloped watersheds provides a benchmark for restoration efforts. Locally and regionally, assessing the sources of portfolio risk can guide actions to maintain existing resilience (protect habitat and disturbance regimes that maintain response diversity; employ harvest strategies sensitive to different portfolio components) or improve restoration activities. Improving our understanding of portfolio reliability may allow for management of natural resources that is robust to ongoing environmental change. Portfolio theory provides a straightforward method for characterizing the resilience of salmon ecosystems and their services. Natural variability in portfolio performance among undeveloped watersheds provides a benchmark for restoration efforts. Locally and regionally, assessing the sources of portfolio risk can guide actions to maintain existing resilience (protect habitat and disturbance regimes that maintain response diversity; employ harvest strategies sensitive to different portfolio components) or improve restoration activities. Improving our understanding of portfolio reliability may allow for management of natural resources that is robust to ongoing environmental change.

Dataset Information

Piscine Orthoreovirus from Western North America Is Transmissible to Atlantic Salmon and Sockeye Salmon but Fails to Cause Heart and Skeletal Muscle Inflammation.

Publications

Piscine Orthoreovirus from Western North America Is Transmissible to Atlantic Salmon and Sockeye Salmon but Fails to Cause Heart and Skeletal Muscle Inflammation.

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