Cardiomyopathy in farmed Norwegian salmon

Abstract

This paper describes the gross findings, histopathology, and ultrastructural and scanning electron microscopical (SEM) appearance of farmed Norwegian Atlantic salmon dying from a disease known locally as 'acute heart failure' Pathological findings were mainly cardiac, and some fish showed haemopericardium due to rupture of the atrial wall. Lesions were largely restricted to the spongy portion of ventricle and atrium, and comprised myocardial degeneration and necrosis, with variable degrees of endocardial-associated hypercellularity, plus macrophage and lymphocyte infiltration; epicarditis was also present in most fish. Transmission electron microscope findings confirmed the myofibrillar disruption , while the SEM showed crater-like discontinuities in the endocardial plasmalemma. The cause and pathogenesis of these remarkably severe lesions are unknown; whether they are primarily degenerative or inflammatory must await a more in-depth study. Until more is known, use of the term cardiomyopathy syndrome would seem most appropriate.