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چکیده
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Double-stranded DNA viruses are important pathogens of homeothermic and poikilothermic vertebrates. Seven families of such viruses have been characterized among homeothermic vertebrates, but only two (Alloherpesviridae and Iridoviridae) have been well studied among poikilothermic vertebrates (e.g. fish, amphibians, and reptiles). Here, we report the genomic characterization of a fish poxvirus, carp edema virus (CEV), which infects common carp varieties including koi. CEV is a globally emerging pathogen that is seriously impacting facilities that rear common carp for food, sport, or recreation. Our ultrastructural and phylogenetic studies provide unequivocal evidence that CEV is a novel member of the family Poxviridae. Transmission electron microscopy (TEM) showed that CEV displays the features of virion morphogenesis typical of poxviruses, with very large, spheroid particles observed within the cytoplasm of gill epithelial cells, and that virions possess a single lateral body, as reported previously for fish poxviruses. Phylogenetic analyses revealed that CEV is the sister taxon to the more extensively studied poxviruses of mammals and birds (subfamily Chordopoxvirinae). Preliminary comparisons of CEV with other recently discovered fish poxviruses suggest that these viruses represent a novel genus or subfamily in the family Poxviridae. Further research is needed to characterize the diversity of piscine poxviruses and to determine the full extent of the risk that they pose to farmed and feral fish stocks.
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