Carlson College of Veterinary Medicine

Unusual lesions were observed in a redstriped rockfish (Sebastes proriger) collected during a survey of marine fishes off the coast of British Columbia, Canada. This particular fish exhibited prominent hepatomegaly, with large, coalescing, multiple hemorrhages. The affected liver exhibited remarkable histological changes that, taken together, strongly suggested infection by a virus of the herpesvirus group. Multiple, multinucleated giant cells or syncytia of hepatocytes occurred throughout the liver and were associated with massive, coalescing areas of coagulation necrosis, edema, congestion and cavernous hemorrhages (peliosis hepatis) with thrombosis. In addition, the liver showed multifocal inflammation, characterized by perivascular and peribiliary cuffing of mononuclear inflammatory cells. High magnification of the syncytia revealed that the nuclei were pleomorphic, hyperchromatic, and typically contained eosinophilic to densely amphophilic inclusion bodies of varying size, closely resembling Cowdry Type A inclusions. These inclusions stained red to purple in Feulgen's stain, indicating presence of DNA. Electron-lucent spheres (approximately 100 nm diameter) were observed within hepatocyte nuclei by transmission electron microscopy, suggestive of herpesvirus capsids. To our knowledge, this is the first report of a putative or confirmed herpesvirus infection in any rockfish of the genus Sebastes.