Department of Microbiology, Faculty of Science, Islamic Azad University, Arak, Iran.
Central branch, Razi Vaccine and Serum Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Arak, Iran.
Arch Razi Inst. 2023 Dec 30;78(6):1794-1803. doi: 10.32592/ARI.2023.78.6.1794. eCollection 2023 Dec.
Newcastle disease (ND) is an economically significant and extremely spreadable viral illness affecting a wide variety of avian species. ND can rapidly spread within poultry farms and result in considerable economic losses for the global poultry industry. This disease is endemic in Iran, and despite intensive vaccination efforts in the poultry industry, outbreaks of ND occur unexpectedly. This study aimed to isolate the Newcastle disease virus (NDV) from poultry farms with breathing problems in Markazi province, Iran, and investigate the evolutionary relationship and molecular characteristics of the isolates during 2017-2019. To this end, tissue samples (lung, brain, and trachea) were taken from 42 broiler farms exhibiting respiratory symptoms. The samples were inoculated into 9-11-day-old embryonated eggs, and the virus was isolated from 20 (47.6%) of the 42 farms. Subsequently, RT-PCR was used to amplify partial fusion gene sequences from the new isolates. The amplified products were sequenced and compared phylogenetically to the standard pilot dataset (125 selected sequences) generated by the NDV consortium. As determined by phylogenetic analysis, all nine isolates belonged to subgenotype VII.1.1 of genotype VII and were highly similar to isolates from other parts of Iran and China. Moreover, all isolates possessed a polybasic cleavage site motif (112RRQKRF117), characteristic of virulent strains. Furthermore, the present isolates shared a high nucleotide identity (96%) with viruses previously isolated from other provinces of Iran, as determined by BLAST searches and multiple alignments. In addition, they shared a high degree of sequence similarity but were distinct from the existing NDV vaccines. Therefore, the genetic dissimilarity between current vaccine strains and circulating NDVs must be considered in vaccination programs.
新城疫（ND）是一种经济上重要且极具传染性的病毒病，影响多种禽类。ND 可在禽场迅速传播，给全球家禽业造成巨大经济损失。该病在伊朗流行，尽管禽业进行了密集的疫苗接种，但 ND 仍会不时爆发。本研究旨在从伊朗马赞德兰省出现呼吸问题的禽场分离新城疫病毒（NDV），并在 2017-2019 年期间调查分离株的进化关系和分子特征。为此，从 42 个出现呼吸症状的肉鸡场采集肺、脑和气管组织样本。将样本接种至 9-11 日龄鸡胚中，从 42 个农场中的 20 个（47.6%）分离到病毒。随后，用 RT-PCR 从新分离株扩增部分融合基因序列。对扩增产物进行测序，并与由 NDV 联盟生成的标准试验数据集（125 个选定序列）进行系统发育比较。系统发育分析表明，9 个分离株均属于基因型 VII 的亚群 VII.1.1，与伊朗和中国其他地区的分离株高度相似。此外，所有分离株均具有毒力株特征的多碱性裂解位点基序（112RRQKRF117）。此外，通过 BLAST 搜索和多重比对，发现本研究中的分离株与之前从伊朗其他省份分离的病毒具有高度核苷酸同一性（96%）。此外，它们与现有的 NDV 疫苗具有高度序列相似性，但与疫苗株不同。因此，在免疫接种计划中必须考虑当前疫苗株与流行 NDV 之间的遗传差异。
