Pathogenic mechanisms and molecular features of a novel UL2 gene-deficient duck enteritis virus endemic to China

Duck enteritis virus (DEV) was identified as the etiological agent responsible for an outbreak of morbidity and mortality in adult ducks on a farm in Jiangsu, China. Diagnostic approaches confirmed that the outbreak was caused by the highly pathogenic DEV-JS2024 isolate. The clinical progression of the disease, characterized by lethargy, anorexia, ocular discharge, and high mortality, was accompanied by extensive hemorrhagic lesions in critical organs such as the liver, spleen, lungs, and bursa of Fabricius, consistent with known signs of DEV infection. Genomic analysis of DEV-JS2024 revealed a 45% G+C content and 76 open reading frames. BLASTn analysis revealed that the genome of DEV-JS2024 shares the highest sequence similarity with the Chinese virulent strain CV and the DEV attenuated vaccine strain C-KCE in the database. These results indicate a close genetic relationship between DEV-JS2024 and both the virulent and attenuated strains, suggesting potential similarities in their genomic architecture. Comparative genomic analysis identified 28 nucleotide mutations, including 15 non-synonymous mutations potentially related to virulence factors. The study also highlighted the first reported 528 base pairs deletion in the <i>UL2</i> gene of a virulent strain, challenging its utility as a marker for distinguishing virulent from attenuated strains. Phylogenetic analysis suggested that DEV-JS2024 may result from recombination between the vaccine and virulent strains, further complicating our understanding of DEV pathogenicity. This study provides new insights into the molecular evolution of DEV and stresses the importance of continued genomic surveillance to enhance vaccine development and control measures for duck plague.

鸭肠炎病毒（Duck enteritis virus, DEV）被鉴定为中国江苏省某农场成年鸭群暴发疫病并导致发病与死亡的病原。经诊断检测方法确认，此次暴发由高致病性毒株DEV-JS2024引发。该病的临床特征表现为精神沉郁、食欲废绝、眼部分泌物增多及高死亡率，同时伴随肝脏、脾脏、肺脏、法氏囊等关键器官的广泛性出血性病变，与鸭肠炎病毒感染的典型临床症状相符。对DEV-JS2024的基因组分析结果显示，其G+C含量为45%，共编码76个开放阅读框（open reading frames, ORFs）。BLASTn分析结果显示，DEV-JS2024的基因组序列与数据库中中国强毒株CV及鸭肠炎病毒减毒疫苗株C-KCE的同源性最高。上述结果表明，DEV-JS2024与该强毒株及减毒株具有紧密的遗传亲缘关系，提示三者的基因组结构可能存在相似性。比较基因组分析共鉴定出28个核苷酸突变，其中包含15个可能与毒力因子相关的非同义突变。本研究同时首次报道了强毒株UL2基因中存在528 bp的缺失突变，这一发现对利用该位点作为区分强毒与减毒株的分子标记的实用性提出了挑战。系统发育分析结果表明，DEV-JS2024可能由疫苗株与强毒株重组产生，这进一步增加了我们对鸭肠炎病毒致病机制理解的复杂性。本研究为鸭肠炎病毒的分子演化研究提供了新的视角，并强调了持续开展基因组监测的重要性，以助力鸭瘟的疫苗研发与防控措施优化。