Infectious laryngotracheitis (ILT) is a respiratory disease that causes significant economic losses in the poultry industry worldwide. In this study, ILT outbreaks were reported on 30 farms located in eight Egyptian governorates between January 2018 and May 2019. Gross examination of diseased chickens revealed congestion and hemorrhage of laryngeal and tracheal mucosa with fibrinohemorrhagic casts and/or caseous material in the lumens. Histopathological examination showed epithelial sloughing, syncytium formation, heterophilic exudation, and development of eosinophilic intranuclear inclusion bodies. Infectious laryngotracheitis virus (ILTV) antigen was detected in the tracheal epithelium, infiltrated inflammatory cells, and syncytial cells, using immunohistochemistry. PCR targeting a portion of the thymidine kinase gene was further utilized to confirm the presence of ILTV DNA. The complete coding sequences of three envelope glycoprotein genes, gG, gD, and gJ, and a partial sequence of the infected cell polypeptide 4 (ICP4) gene from samples representing all of the farms and disease outbreaks were determined. Five prototype strains with unique sequences were chosen for detailed molecular characterization. Sequence comparisons and phylogenetic analysis of the partial ICP4 gene revealed that two strains were chicken embryo origin (CEO)-vaccine-like strains, and three were tissue culture origin (TCO)-vaccine-like strains. Analysis of the gJ gene sequence indicated that all of the strains were CEO vaccine-like strains. It was predicted that the latter three strains were recombinants of CEO- and TCO-vaccine-like strains. In conclusion, immunohistochemistry coupled with multi-genomic PCR sequencing proved to be efficient for identification and typing of ILTV strains during disease outbreaks. Both CEO-vaccine-like and recombinant virus strains were circulating in Egypt during the 2018 and 2019 outbreaks.

中文翻译：

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2018年和2019年爆发期间在埃及传播的传染性喉气管炎病毒株的分子特征和遗传多样性。

传染性喉气管炎（ILT）是一种呼吸道疾病，在全世界的家禽业中造成重大的经济损失。在这项研究中，据报道，在2018年1月至2019年5月之间，埃及八个省的30个农场爆发了ILT暴发。对病鸡的总体检查显示，喉和气管粘膜充血和出血，管腔内有纤维性出血性铸型和/或干酪样物质。组织病理学检查显示上皮脱落，合胞体形成，嗜异性渗出和嗜酸性核内包涵体的发展。使用免疫组织化学方法在气管上皮，浸润的炎症细胞和合胞细胞中检测到传染性喉气管炎病毒（ILTV）抗原。靶向胸腺嘧啶激酶基因一部分的PCR被进一步用于证实ILTV DNA的存在。确定了三个包膜糖蛋白基因gG，gD和gJ的完整编码序列，以及代表所有农场和疾病暴发的样品中被感染的细胞多肽4（ICP4）基因的部分序列。选择了五个具有独特序列的原型菌株用于详细的分子表征。ICP4基因的部分序列比较和系统发育分析表明，有两个菌株是鸡胚起源（CEO）疫苗样菌株，三个是组织培养起源（TCO）疫苗样菌株。对gJ基因序列的分析表明，所有菌株均为CEO疫苗样菌株。据预测，后三种菌株是CEO-和TCO-疫苗样菌株的重组体。总而言之，免疫组化与多基因组PCR测序相结合可有效地识别和控制疾病暴发期间ILTV菌株的分型。在2018年和2019年爆发期间，CEO疫苗样和重组病毒株都在埃及传播。