A molecular investigation of the dynamics of piscine orthoreovirus in a wild sockeye salmon community on the Central Coast of British Columbia

Many Pacific salmon (Oncorhynchus sp.) populations are declining due to the action of multiple stressors, possibly including microparasites such as piscine orthoreovirus (PRV), whose host range and infection dynamics in natural systems are poorly understood. First, in comparing three methods for RNA isolation, I find different fish tissues require specific approaches to yield optimal RNA for molecular PRV surveillance. Next, I describe PRV infections among six fish species and three life-stages of sockeye salmon (O. nerka) over three years in Rivers Inlet, BC. Screening reveals a 3% overall prevalence of PRV in this system, along with the first evidence of PRV in Dolly Varden (Salvelinus malma) and eulachon (Thaleichthys pacificus). Among sockeye, the prevalence declined by 4% from the fry to smolt stages for the 2014 and 2015 cohorts.