Salmonid alphavirus subtype I isolated from clinically-diseased Atlantic salmon, Salmo salar, in freshwater culture

Abstract

Abstract Pancreas disease (PD) is a disease of cultivated salmonids caused by salmonid alphavirus (SAV) and it is responsible for significant losses within the aquaculture industry, at the marine stage, in Ireland, Norway and Scotland. In May 2018, an increased mortality of Atlantic salmon at a freshwater hatchery on the west coast of Scotland was reported to Marine Scotland Science, Fish Health Inspectorate. Site staff suspected an infectious pancreatic necrosis (IPN) outbreak, a condition frequently diagnosed at salmonid freshwater sites, but the RT-qPCR results were negative for IPNV and positive for salmonid alphavirus. This detection was subsequently confirmed as SAV subtype I by partial sequence analysis of the E2 gene. Histological examination revealed lesions in the pancreas, heart and skeletal muscle consistent with PD pathology. This is the first published description of a confirmed clinical field case of SAV with pathology consistent with PD in freshwater Atlantic salmon.