Properties of three iridovirus-like agents associated with systemic infections of fish

Three iridovirus-like agents associated with systemic infections in fish were examined by electron microscopy, gel electrophoresis of virion polypeptides and serological cross reactions with hyperimmune rabbit sera. The virus associated with epizootic hematopoietic necrosis (EHN) of redfin perch Perca fluviatilis in Australia, the virus from sheatfish Siluris glanis in Germany and a recently isolated iridovirus-like agent from catfish Ictalurus melas in France shared similar virion morphology and size, number and weight of structural polypeptides and common antigens as shown by cross immunofluorescence tests. The characteristics of these 3 piscine viruses and their strilung similarity to frog virus 3, the type strain of the Ranavirus genus in the family Iridoviridae, suggest that they should be grouped into the same genus. The presence of similar agents in fish and amphibians emphasizes the potential adaptation and evolution of serious viral pathogens among these aquatic hosts and further complicates programs aimed at preventing or controlling the spread of fish viruses.