Comparison of European systemic piscine and amphibian iridoviruses with Epizootic Haematopoietic Necrosis Virus and Frog Virus 3

Iridovirus-like agents isolated from systemic infected fish (Silurus glanis, SFIR; Ictalurus melas CFIR I, CFIR II, CFIR III) and from frogs (Rana esculenta, REIR) in Europe, Epizootic Haematopoietic Necrosis Virus (EHNV) isolated in Australia from redfin perch (Perca fluviatilis), and Frog virus 3 (FV 3) isolated from frogs (Rana pipiens) in the USA were investigated by electron microscopy, polypeptide composition, immunofluorescence, restriction endonuclease digestion, Southern-blot hybridization and polymerase chain reaction (PCR) amplification. All virus isolates proved to be similar in morphology and in size and reacted with EHNV polyclonal antiserum in the immunofluorescence. Whilst DNA restriction profiles of the European piscine isolates cleaved by BamH I were similar, they differed clearly from those of EHNV, REIR and FV 3. Southern-blot analysis of viral BamH I-digested DNA using an EHNV DNA probe revealed cross-hybridization with the DNA of the investigated iridoviruses. Using a set of primers designed for an open reading frame of the EHNV genome, PCR products of about 250 bp mere obtained with the DNA of systemic piscine and amphibian iridoviruses. The data suggest that the systemic piscine and amphibian iridoviruses should be regarded as members of the genus Ranavirus within the family Iridoviridae.