Abstract: 【Objective】 The aim of this study was to analyze molecular genetics and prevalent characteristics of Duck Tembusu virus (DTMUV) in Guangxi,so as to understand and master the new epidemic characteristics of DTMUV Guangxi strain,and provide data support for opportunely adjustment and formulation of effective prevention and control measures.【Method】 The tissue samples of duck collected in farms of Guangxi during 2019-2021 were detected for DTMUV by Real-time quantitative RT-PCR,the complete genome sequences of DTMUV were acquired by amplification and sequencing from partial positive samples according to detection date and origin area of DTMUV,and the sequence similarity,predominant amino acid,phylogenetic,recombination detection and estimation rate of evolution were analyzed.【Result】 The genome length of 8 DTMUV strains in Guangxi was 10 992 bp.The similarity of nucleotide sequence of open reading frame (ORF), E and NS5 genes among 8 DTMUV strains in Guangxi were 97.9%-99.8%,97.0%-99.9% and 97.8%-99.9%, and the similarity of amino acid sequence were 99.1%-99.9%,99.0%-100% and 99.3%-99.9%,respectively.The similarity of nucleotide sequence of ORF, E and NS5 genes between 8 DTMUV strains in Guangxi and reference strains were 86.4%-99.3%,85.8%-99.5% and 87.1%-99.2%,and the similarity of amino acid sequence were 96.0%-99.8%,94.8%-100% and 97.5%-99.9%,respectively.The similarity of TMUV with waterfowl source was higher than that of other host sources.Compared with vaccine strain FX2010,there were 11 amino acid mutations in DTMUV Guangxi strains,with the amino acids at 43,150,153,326,403,464 and 487 sites mutation were unique for DTMUV in Guangxi.Phylogenetic tree was constructed on ORF indicated that 8 DTMUV strains acquired in this study were belonged to 2.1 subgroup,while GX2011 and GX2015 strains also from Guangxi were formed to 2.2 subgroup,suggesting that the evolutionary trend of DTMUV epidemic strains in Guangxi was divergence.The phylogenetic trees of E and NS5 genes were similar with that of ORF.Recombination analysis results indicated that GXBH01-2019,GXZS02-2020,ziYY150901 and HB2016 strains existed recombination signal.Estimation rate of evolution performed on E and NS5 genes of DTMUV was 1.31×10^-3and 1.30×10^-3 substitution/(sites·year),which suggested that two genes kept similar evolutionary steps.【Conclusion】 At present,the epidemic strains of DTMUV in Guangxi were closely related to predominant prevalence strains,the E protein had unique amino acid mutation,the evolutionary trend was inconsistent,and there were molecular characteristics such as recombination,which provided basic data for formulating effective prevention and control measures.

Key words: Duck Tembusu virus(DTMUV); open reading frame (ORF); E gene; NS5 gene; genetic diversity