Piscine reovirus in wild and farmed salmonids in British Columbia, Canada: 1974–2013

Abstract

Piscine reovirus (PRV) was common among wild and farmed salmonids in British Columbia, western Canada, from 1987 to 2013. Salmonid tissues tested for PRV by real-time rRT-PCR included sections from archived paraffin blocks from 1974 to 2008 (n = 363) and fresh-frozen hearts from 2013 (n = 916). The earliest PRV-positive sample was from a wild-source steelhead trout, Oncorhynchus mykiss (Walbaum), from 1977. By histopathology (n = 404), no fish had lesions diagnostic for heart and skeletal muscle inflammation (HSMI). In some groups, lymphohistiocytic endocarditis affected a greater proportion of fish with PRV than fish without PRV, but the range of Ct values among affected fish was within the range of Ct values among unaffected fish. Also, fish with the lowest PRV Ct values (18.4-21.7) lacked endocarditis or any other consistent lesion. From 1987 to 1994, the proportion of PRV positives was not significantly different between farmed Atlantic salmon, Salmo salar L. (44% of 48), and wild-source salmonids (31% of 45). In 2013, the proportion of PRV positives was not significantly different between wild coho salmon, Oncorhynchus kisutch (Walbaum), sampled from British Columbia (5.0% of 60) or the reference region, Alaska, USA (10% of 58).

Occurrence of salmonid alphavirus (SAV) and piscine orthoreovirus (PRV) infections in wild sea trout Salmo trutta in Norway

“…However, PRV infections are ubiquitous in farmed Atlantic salmon (Løvoll et al 2012), common in escaped farmed salmon (Garseth et al 2013b and are widespread in wild salmon (Garseth et al 2013b. High concentrations of the virus have been detected in apparently healthy farmed and wild salmonids without the histopathological changes observed in HSMI (Garseth et al 2013b, Marty et al 2015. This suggests that PRV infection may be a prerequisite for HSMI, but additional factors may be needed for the disease to develop.…”

“…Hence, we found no evidence for an influence from salmon farming on PRV prevalence in the trout. Garseth et al (2013b) and Marty et al (2015) found no association between the occurrence of PRV infections in wild salmonids and the number of HSMI cases or salmon farming activities. Our analyses did not reveal any association between PRV occurrence and weight, length, sex or sampling time of year.…”

Population biology of infectious diseases shared by wild and farmed fish

“…Parasite dispersal connects the population dynamics of disease among farms within a region as well as between farmed salmon and the wild salmon populations that migrate through the aquaculture regions as juveniles and as adults. flammation disease; Palacios et al 2010) are considered exotic to the North Pacific Ocean, but PCR tests of farmed and wild salmon have indicated that strains of these ancestrally Norwegian viruses may now be present in both wild and farmed salmon in British Columbia (Kibenge et al 2013(Kibenge et al , 2016Marty et al 2015). These examples underscore the need for continuing and increasing biosecurity practices that focus on the trade and movement of seafood products -including aquaculture products, feed, eggs, and broodstock -at regional and global scales.…”

De novo assembly of Sockeye salmon kidney transcriptomes reveal a limited early response to piscine reovirus with or without infectious hematopoietic necrosis virus superinfection

“…Subsequent studies have confirmed the presence of PRV in farmed Atlantic salmon in British Columbia [3, 13, 14], and also identified PRV in wild salmonids in both BC and US (Washington and Alaska) waters [3, 14, 15]. Interestingly, although infection with PRV is common in farmed Atlantic salmon in BC, disease manifestations impacting fish performance as observed in Norway has never been reported (reviewed in [16]).…”

“…As PRV has been shown to establish long-term infections in its hosts [17] and is common in natural systems along the western cost of Canada [14], it is inevitable that such co-infections will (or do) occur. One pathogen that is sympatric with PRV is infectious hematopoietic necrosis virus (IHNV); which occurs naturally in the waters of western North America and can cause acute disease (IHN) in nearly all salmonid species given appropriate viral, host, and environmental conditions.…”