Table_1_Duck Tembusu virus in North Vietnam: epidemiological and genetic analysis reveals novel virus strains.DOC

Tembusu virus (TMUV) is an important infectious disease, causing economic losses in duck production. Since the first report of TMUV infection in Vietnam in 2020, the disease has persisted and affected poultry production in the country. This study conducted epidemiological and genetic characterization of the viral strains circulating in north Vietnam based on 130 pooled tissue samples collected in six provinces/cities during 2021. The TMUV genome was examined using conventional PCR. The results indicated that 21 (16.15%) samples and 9 (23.68%) farms were positive for the viral genome. The positive rate was 59.26% for ducks at ages 2–4 weeks, which was significantly higher than for ducks at ages >4 weeks and < 2 weeks. Genetic analysis of the partial envelope gene (891 bp) sequences indicated that the five Vietnamese TMUVs shared 99.55–100% nucleotide identity, while the rates were in the range 99.59–100% based on the pre-membrane gene sequences (498 bp). The five Vietnamese TMUV strains obtained formed a novel single subcluster. These strains were closely related to Chinese strains and differed from the vaccine strain, suggesting that Vietnamese TMUV strains were field viruses. It needs to be further studied on vaccine development to prevent effects of TMUV infection on poultry production across Vietnam.

坦布苏病毒（Tembusu virus, TMUV）是一种可造成鸭养殖业经济损失的重要传染性疫病。自2020年越南首次报道TMUV感染病例以来，该疫病在越南持续流行，对当地家禽养殖业造成了不良影响。本研究基于2021年在越南北部6个省市采集的130份混合组织样本，对当地流行的TMUV毒株开展了流行病学与遗传特性分析。本研究采用常规聚合酶链式反应（conventional PCR）对TMUV基因组进行检测，结果显示，共有21份样本（阳性率16.15%）与9个养殖场（阳性率23.68%）呈TMUV基因组阳性。其中2至4周龄鸭只的阳性率达59.26%，显著高于4周龄以上及2周龄以下的鸭群。对部分囊膜基因（891碱基对，bp）序列的遗传分析显示，5株越南TMUV的核苷酸同源性为99.55%~100%；而基于前膜蛋白基因（498碱基对，bp）序列的同源性则为99.59%~100%。本次分离得到的5株越南TMUV毒株共同构成了一个全新的独立亚簇，这些毒株与中国分离株亲缘关系较近，且与疫苗株存在差异，表明越南TMUV毒株为野毒株。为防控TMUV感染对越南全境家禽养殖业造成的影响，相关疫苗的研发仍需开展进一步研究。