Isolation and Identification of a Novel Variant Rhabdovirus from Cultured Chinese Rice-Field Eels (Monopterus albus) in China

Chinese rice-field eels (Monopterus albus) are a commercially farmed freshwater fish species in China. In recent years, the rapid expansion of aquaculture has been accompanied by frequent outbreaks of viral diseases, posing a serious threat to the sustainability of the Chinese rice-field eel farming industry. In this study, a rhabdovirus strain was isolated from diseased Chinese rice-field eels at a farm located in Xiantao, Hubei Province, China. Although the complete genomic sequence of CrERV-XT showed higher identity to the infectious hemorrhagic syndrome virus (IHSV) (96.16%) than to CrERV (94.39%), phylogenetic analysis based on the L protein placed CrERV-XT within the same clade as CrERV, supporting its tentative classification as a novel variant of CrERV. Furthermore, the amino acid sequence of the L protein showed greater similarity to that of CrERV (97.89%) than to IHSV, while the N, P, M and G proteins exhibited higher homology with their counterparts in IHSV. CrERV-XT displayed considerable genetic divergence from known CrERV isolates, which is presumably attributed to its geographic isolation in different locations. Alignment of the G protein sequences from five strains (CrERV-XT, CrERV, CrERV-TYY25, CrERV-XY0907 and IHSV) revealed a total of 39 amino acid mutation sites. These findings provide valuable insights for investigating conserved functional domains within the CrERV G protein for the rational design of vaccine antigens against this emerging virus.