|GROSS, LYNDEN - Department Of Fisheries And Oceans Canada|
|MARTY, GARY - British Colombia Ministry Of Agriculture And Lands|
|GARVER, KYLE - Department Of Fisheries And Oceans Canada|
Submitted to: BMC Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/27/2022
Publication Date: 8/10/2022
Citation: Polinski, M.P., Gross, L., Marty, G.D., Garver, K.A. 2022. Heart inflammation and piscine orthoreovirus genotype-1 in Pacific Canada Atlantic salmon net-pen farms: 2016-2019. BMC Veterinary Research. https://doi.org/10.1186/s12917-022-03409-y.
Interpretive Summary: Piscine Orthoreovirus (PRV) is a common virus of salmon with regional variability in manifesting disease. In Norway, the virus appears commonly associated with a disease known as Heart and Skeletal muscle inflammation (HSMI); however, in British Columbia, the virus appears to have less disease causing potential. It is also unclear in British Columbia as the exact prevalence of the virus and what reservoirs account for its regional persistence. In this study, we examined PRV prevalence across the regional breadth of the salmon farming industry to identify that i) the primary regional viral reservoir is marine, ii) this marine reservoir likely includes both farmed and wild fish populations, and iii) heart inflammatory disease akin to HSMI in Norway is rare.
Technical Abstract: Piscine orthoreovirus genotype-1 (PRV-1) is a virus commonly associated with Atlantic salmon aquaculture with global variability in prevalence and association with disease. From August 2016 to November 2019, 2,070 fish sampled at 64 Atlantic salmon net-pen farm sites during 302 sampling events from British Columbia, Canada, were screened for PRV-1 using real-time qPCR. Nearly all populations became PRV-1 positive within one year of seawater entry irrespective of location, time of stocking, or producer. Cohorts became infected between 100-300 days at sea in >90% of repeatedly sampled sites and remained infected until harvest (typically 500-700 days at sea). Heart inflammation, which is sometimes attributed to PRV-1, was also assessed in 783 production mortalities from 47 cohorts with known PRV status. Mild heart inflammation was common in mortalities from both PRV+ and PRV- populations (67% and 68% prevalence, respectively). Moderate and severe heart inflammation was rare (11% and 3% prevalence, respectively); however, mainly arose (66 of 77 occurrences) in populations with PRV-1. Detection of PRV-1 RNA was also accomplished in water and sediment for which methods are described. These data cumulatively identify that PRV-1 ubiquitously infects farmed Atlantic salmon in British Columbia during seawater production but rarely correlated with heart inflammation.