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Bohle iridovirus (BIV) is a species within the genus Ranavirus , family Iridoviridae , first isolated from the ornate burrowing frog Limnodynastes ornatus in Australia. The BIV genome confirms it is closely related to isolates from boreal toad Anaxyrus boreas and leaf-tailed gecko Uroplatus fimbriatus within the United States and Germany, respectively.

Megalocytiviruses, such as infectious spleen and kidney necrosis virus (ISKNV), induce lethal systemic diseases in both ornamental and food fish species. In this study, we investigated an epizootic affecting Nile tilapia Oreochromis niloticus cultured in the US Midwest. Diseased fish displayed lethargy, gill pallor, and distension of the coelomic cavity due to ascites. Histopathological examination revealed a severe systemic abundance of intravascular megalocytes that were especially prominent in the gills, kidney, spleen, liver, and intestinal submucosa. Transmission electron microscopic examination revealed abundant intracytoplasmic polygonal virions consistent with iridovirus infection. Comparison of the full-length major capsid protein nucleotide sequences from a recent outbreak with a remarkably similar case that occurred at the same facility many years earlier revealed that both epizootics were caused by ISKNV. A comparison of this case with previous reports suggests that ISKNV may represent a greater threat to tilapia aquaculture than previously realized.

The pike-perch iridovirus (PPIV) was isolated in Finland from apparently healthy pike-perch fingerlings during routine disease surveillance. Our phylogenomic analysis revealed that PPIV is the first fish member of a clade of ranaviruses previously described from European and Chinese amphibians.

The Iridoviridae is a family of large, icosahedral viruses with double-stranded DNA genomes ranging in size from 103 to 220 kbp. Members of the subfamily Alphairidovirinae infect ectothermic vertebrates (bony fish, amphibians and reptiles), whereas members of the subfamily Betairidovirinae mainly infect insects and crustaceans. Infections can be either covert or patent, and in vertebrates they can lead to high levels of mortality among commercially and ecologically important fish and amphibians. This is a summary of the current International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Iridoviridae, which is available at www.ictv.global/report/iridoviridae.

‘Gold standard’ OIE reference PCR assay was utilized to detect the presence of infectious spleen and kidney necrosis virus (ISKNV) in freshwater ornamental fish from Malaysia. From total of 210 ornamental fish samples representing 14 species, ISKNV was detected in 36 samples representing 5 fish species. All positive cases did not show any clinical signs of ISKNV. Three restriction enzymes analyses showed that the fish were infected by identical strains of the same virus species within Megalocytivirus genus. Major capsid protein (MCP) genes of 10 ISKNV strains were sequenced and compared with 9 other reference nucleotide sequences acquired from GenBank. Sequence analysis of MCP gene showed that all strains detected in this study were closely related to the reference ISKNV with nucleotide sequence identity that was ranging from 99.8% to 100%. In addition, phylogenetic analysis of MCP gene revealed that viruses from genus Megalocytivirus can be divided into three genotypes: genotype 1 include reference ISKNV and all other strains that were detected in this study, genotype 2 include viruses closely related to red sea bream iridovirus (RSIV), and genotype 3 include viruses closely related turbot reddish body iridovirus (TRBIV).

Ranaviruses have been isolated from Atlantic cod ( Gadus morhua ) and turbot ( Scophthalmus maximus ) in Denmark. Phylogenomic analyses revealed that these two ranaviruses are nearly identical and form a distinct clade at the base of the ranavirus tree branching off near other fish ranaviruses.

The advancement in nucleic acid amplification has improved the diagnostic methods for many diseases. In the current study, an improved technique for the detection of infectious spleen and kidney necrosis virus (ISKNV) based on loop-mediated isothermal amplification (LAMP) is described. The addition of acridine orange at the end of the reaction causes distinct color change which can be recognized by the naked eye. In addition, a new set of primers was designed based on the ISKNV major capsid protein (MCP) gene sequences. The primers are highly specific for ISKNV and there was no cross amplification with red sea bream iridovirus (RSIV), white spot syndrome virus (WSSV), Aeromonas hydrophila or Vibrio parahaemolyticus. The detection limit of LAMP assay was 1.4 × 104 copies of the virus DNA and the optimum temperature and time for assay was 65°C and 60 min respectively, and this protocol could successfully detect the virus from asymptomatically infected fish. This improved LAMP assay is a simple and inexpensive diagnostic tool for the detection of ISKNV without the need of specialized equipment.

The short-finned eel ranavirus (SERV) was isolated from short-finned eel imported to Italy from New Zealand. Phylogenomic analyses revealed that SERV is a unique member of the genus Ranavirus , family Iridoviridae , branching at the base of the tree near other fish ranaviruses.