IRIDOVIRUSES ASSOCIATED WITH EPIZOOTIC HEMATOPOIETIC NECROSIS (EHN) IN AQUACULTURE

Systemic infections of teleost fishes caused by iridoviruses have rece ntly been recognized in Australia, Asia, Europe and the USA. These iri doviruses are different from those of the established genera Lymphocys tivirus and Goldfish Virus 1-like Viruses of the family Iridoviridae. The agents exhibit similar physicochemical properties, are antigenical ly related and prove to be of high virulence to different teleost fish es in aquaculture. The first iridovirus, epizootic haematopoietic necr osis virus, responsible for an epizootic outbreak of haematopoietic ne crosis in redfin perch, was reported in Australia. Some years later, s imilar iridovirus epizootics occurred in sheatfish and catfish in Euro pe. The Australian and the European isolates proved to be antigenicall y related and showed properties in common with frog virus 3, the type species of the genus Ranavirus of the Iridoviridae. Further iridovirus isolates from fish, amphibians and reptiles exhibited a close relatio nship with each other and with frog virus 3. It is important to note t hat the Australian amphibian iridovirus, Bohle iridovirus, was experim entally transmitted to teleost fish inducing high mortalities. The occ urrence of similar viruses in different host species in the aquatic en vironment and their inter-species transmission emphasize the importanc e of health control in aquaculture.