A Novel Virus of Associated with Sexual Precocity in .

Since 2010, sexual precocity, a typical sign of the iron prawn syndrome (IPS), resulting in the reduced size of farmed giant freshwater prawns , has caused substantial production losses. However, the cause of IPS was not clear. We ran tests for eight major shrimp pathogens, but none were detected from IPS-affected prawns. We performed the histopathological examination of tissues and identified an eosinophilic inclusion in the perinuclear cytoplasm of cells in various tissues associated with nervous and endocrinal functions in the compound eyes. A subsequent bioassay with viral extracts of IPS-affected samples reproduced the gross signs of IPS. Metatranscriptomic sequencing identified a novel virus of in all IPS-affected prawns, which was not found in samples without IPS. This virus contains a positive-sense, single-stranded RNA genome of 12,630 nucleotides (nt). Phylogenetic analysis of the conserved RdRp and NS3 domains showed that it may belong to a new genus between Jingmenvirus and . Under transmission electron microscopy (TEM), putative virus particles showed as spherical with a diameter of 40 to 60 nm. hybridization found hybridization signals consistent with the histopathology in the compound eyes from IPS-affected . We provisionally name this virus infectious precocity virus (IPV) and propose the binominal Latin name gen. nov., sp. nov. We developed a nested reverse transcription-PCR diagnostic assay and confirmed that all IPS-affected prawns tested IPV positive but normal prawns tested negative. Collectively, our study revealed a novel virus of associated with sexual precocity in . The iron prawn syndrome (IPS), also described as sexual precocity, results in the reduced size of farmed prawns at harvest and significant economic losses. IPS has been frequently reported in populations of farmed since 2010, but the cause was heretofore unknown. Here, we reported a novel virus identified from prawns with IPS using infection experiments, metatranscriptomic sequencing, and transmission electron microscopy and provisionally named it infectious precocity virus (IPV). Phylogenetic analysis showed that IPV represents a new genus, proposed as gen. nov., in the family . This study provides novel insight that a viral infection may cause pathological change and sexual maturation and subsequently affect crustacean growth. Therefore, we call for quarantine inspection of IPV in transboundary trade of live and enhanced surveillance of IPV in aquaculture in the region and globally.