Viral Erythrocytic Necrosis (VEN) in Marine Fishes

Abstract

Viral erythrocytic necrosis (YEN) is a unique viral infection of marine and anadromous teleosts. Our studies have focused on VEN in cod (Gadus morhua) and herring (Clupea harengus h .) with emphasis on characterization of the virus and its interaction with the host. Ultrastructural studies in our laboratory have shown that VEN virus of cod is structurally larger (330 nm) and more complex than VEN virus in herring (145nm); both are icosohedral in shape with a central nucleoid which may or may not be toroid. The virus from herring and Greenland cod have no structures external to the capsid whereas VEN virus from cod in North America have an amorphous peplos. Horizontal transmission of the virus in cod was accomplished although the attack rate was low; intraspecific tranmission was not accomplished. Infection with VEN virus resulted in a reduced resistance to stress, but no direct mortalities were noted. The oxygen transport function of VEN infected erythrocytes was not altered. An in vitro system for long term maintenance of cod erythrocytes was developed. Further work with this system revealed that VEN infected cells of both cod and herring lysed more rapidly than did uninfected cells. Incorporation of thymidine and amino acids, but not uridine, was significantly higher. in VEN infected cells than in uninfected cells, indicating virus replication had occurred. The effect of VEN infection on several blood parameters, including serum electrolytes, formed element composition and morphology, and cellular and serum enzymes are currently being studied.