Aquaculture mediates global transmission of a viral pathogen to wild salmon

Abstract

Global expansion of aquaculture and agriculture facilitates disease emergence and catalyzes transmission to sympatric wildlife populations. The health of wild salmon stocks critically concerns Indigenous peoples, commercial and recreational fishers, and the general public. Despite potential impact of viral pathogens such as Piscine orthoreovirus-1 (PRV-1) on endangered wild salmon populations, their epidemiology in wild fish populations remains obscure, as does the role of aquaculture in global and local spread. Our phylogeographic analyses of PRV-1 suggest that development of Atlantic salmon aquaculture facilitated spread from Europe to the North and South East Pacific. Phylogenetic analysis and reverse transcription polymerase chain reaction surveillance further illuminate the circumstances of emergence of PRV-1 in the North East Pacific and provide strong evidence for Atlantic salmon aquaculture as a source of infection in wild Pacific salmon. PRV-1 is now an important infectious agent in critically endangered wild Pacific salmon populations, fueled by aquacultural transmission.

Genetic grouping and geographic distribution of Piscine orthoreovirus-1 (PRV-1) in farmed Atlantic salmon in Norway

“…However, in Canada as well as Faroe Islands, little clinical disease has been identified, although the virus is prevalent [ 12 , 13 ]. PRV-1 is relatively widespread in wild Atlantic salmon and there appears to be transmission of PRV between farmed and wild salmon [ 14 , 15 ]. However, HSMI has not been reported from wild fish.…”

Genomic Epidemiology of Salmonid Alphavirus in Norwegian Aquaculture Reveals Recent Subtype-2 Transmission Dynamics and Novel Subtype-3 Lineages

“…Data such as that reported here, ideally expanded in spatial and temporal resolution, can be used by producers and regulating authorities to support a range of actions aimed at disease control. Moreover, the sequencing approach utilized here and in related studies, e.g., [13,14,16,17], can be readily transferred to other salmonid viruses. Beyond the identification of candidate disease transmission routes, salmonid viruses warrant routine genomic surveillance to capture variants of concern.…”

“…While it is recognized that genomic epidemiology can deliver much to support disease control efforts in aquaculture [11] and other sectors [12], large-scale genomic sequencing to monitor aquaculture pathogens is not a widespread practice, even for high-value species. Nonetheless, several studies highlight the value of genomic epidemiology for linking viral genetic diversity to disease outbreaks and identifying viral transmission scenarios [13][14][15][16][17].…”

Non-Lethal Sampling Supports Integrative Movement Research in Freshwater Fish

“…Anthropogenic influences of aquaculture-related pathogens, contaminants, and water usage can alter the movement of fishes ( Brander, 2007 ; Nathan et al, 2008 ; Bozinovic et al, 2011 ; Miller et al, 2014 ). Salmonids making reproductive migrations may be further challenged by increased, or novel, pathogen spillover from aquaculture facilities resulting in elevated infection pressure in a critical stage of their life cycle ( Cicco et al, 2018 ; Mordecai et al, 2021 ). Additionally, hormones such as 17β-estradiol can be introduced into aquatic systems from anthropogenic activities and have been demonstrated to alter migration behavior in both Atlantic and sockeye salmon ( Madsen et al, 2004 ; Veldhoen et al, 2013a ).…”