DETECTION OF A NODAVIRUS-LIKE AGENT IN HEART-TISSUE FROM REARED ATLANTIC SALMON SALMO-SALAR SUFFERING FROM CARDIAC MYOPATHY SYNDROME (CMS)

The present study shows that a nodavirus-like agent is associated with the lesions of cardiac myopathy syndrome (CMS), a disease of unknown etiology which affects reared adult Atlantic salmon Salmo salar. In ar chive paraffin-embedded heart tissue from Atlantic salmon diagnosed as suffering from CMS, a distinct immunohistochemical reaction was obser ved when using a primary antibody against striped jack nervous necrosi s virus (Nodaviridae). Immunolabeling was detected in the mesothelium and hypercellular lesions of the epicardium and in endothelial cells a nd myocytes within mild multifocal lesions of the atrial and ventricul ar trabeculae. Transmission electron microscopy, per formed on deparaf finized samples of the same tissue blocks, revealed substantial amount s of virus-like particles (VLP) in the cytoplasm of endocardial endoth elium, in myocytes and in mesothelial cells of the epicardium. The VLP were isometric, spherical and unenveloped, with mean capsid diameters of approximately 25 nm, resembling a virus belonging to the Nodavirid ae.