Institute of Biotechnology, University of Gondar, Gondar, Ethiopia.
College of Veterinary Medicine and Animal Sciences, University of Gondar, Gondar, Ethiopia.
Virol J. 2023 Mar 8;20(1):45. doi: 10.1186/s12985-023-02003-4.
Marek's disease virus (MDV) is a highly contagious, immunosuppressive, and oncogenic chicken pathogen causing marek's disease (MD). In this outbreak-based study, 70 dual-purpose chickens that originated from poultry farms in Northwest Ethiopia and suspected of MD were sampled for pathological and virological study from January 2020 to June 2020. Clinically, affected chickens showed inappetence, dyspnea, depression, shrunken combs, and paralysis of legs, wings, and neck, and death. Pathologically, single or multiple greyish white to yellow tumor-like nodular lesions of various size were appreciated in visceral organs. In addition, splenomegaly, hepatomegaly, renomegaly, and sciatic nerve enlargement were observed. Twenty-seven (27) pooled clinical samples i.e. 7 pooled spleen samples and 20 pooled feathers samples were aseptically collected. Confluent monolayer of Chicken Embryo Fibroblast cells was inoculated with a suspension of pathological samples. Of this, MDV-suggestive cytopathic effects were recorded in 5 (71.42%) and 17 (85%) pooled spleen and feather samples respectively. Molecular confirmation of pathogenic MDV was conducted using conventional PCR amplifying 318 bp of ICP4 gene of MDV-1, of which, 40.9% (9/22) tested positive. In addition, 5 PCR-positive samples from various farms were sequenced further confirming the identity of MDV. The ICP4 partial gene sequences were submitted to GenBank with the following accession numbers: OP485106, OP485107, OP485108, OP485109, and OP485110. Comparative phylogenetics showed, two of the isolates from the same site, Metema, seem to be clonal complexes forming distinct cluster. The other three isolates, two from Merawi and one from Debretabor, appear to represent distinct genotypes although the isolate from Debretabor is closer to the Metema clonal complex. On the other hand, the isolates from Merawi appeared genetically far related to the rest of the 3 isolates and clustered with Indian MDV strains included in the analysis. This study presented the first molecular evidence of MDV in chicken farms from Northwest Ethiopia. Biosecurity measures should strictly be implemented to hinder the spread of the virus. Nationwide studies on molecular characteristics of MDV isolates, their pathotypes, and estimation of the economic impact associated with the disease may help justify production and use of MD vaccines within the country.
马立克氏病病毒（MDV）是一种高度传染性、免疫抑制性和致瘤性的鸡病原体，可引起马立克氏病（MD）。在这项基于暴发的研究中，我们从 2020 年 1 月至 6 月从埃塞俄比亚西北部的家禽养殖场采集了 70 只疑似 MD 的两用鸡进行病理和病毒学研究。临床上，受感染的鸡表现出食欲不振、呼吸困难、抑郁、鸡冠萎缩和腿部、翅膀和颈部瘫痪，以及死亡。病理上，在内脏器官中观察到单个或多个大小不一的灰白色至黄色肿瘤样结节状病变。此外，还观察到脾肿大、肝肿大、肾肿大和坐骨神经肿大。无菌采集了 27 份（7 份脾样和 20 份羽毛样）混合临床样本。其中，5 份（71.42%）混合脾样本和 17 份（85%）混合羽毛样本中记录到与 MDV 一致的细胞病变效应。使用常规 PCR 扩增 MDV-1 的 ICP4 基因 318bp 对致病性 MDV 进行分子确认，其中 22 份中有 40.9%（9/22）为阳性。此外，还对来自不同农场的 5 个 PCR 阳性样本进行了进一步测序，进一步证实了 MDV 的身份。ICP4 部分基因序列已提交给 GenBank，登录号为 OP485106、OP485107、OP485108、OP485109 和 OP485110。比较系统发育显示，来自同一地点梅塔马的两个分离株似乎是形成独特聚类的克隆复合体。另外三个分离株，两个来自梅拉维和一个来自德布雷塔博尔，虽然来自德布雷塔博尔的分离株与梅塔马克隆复合体更为接近，但似乎代表了不同的基因型。另一方面，来自梅拉维的分离株在遗传上与其余 3 个分离株关系较远，与包括在分析中的印度 MDV 株聚类。本研究首次提供了埃塞俄比亚西北部鸡场存在 MDV 的分子证据。应严格实施生物安全措施，以阻止病毒的传播。在全国范围内研究 MDV 分离株的分子特征、它们的病原性以及与疾病相关的经济影响，可能有助于证明在该国生产和使用 MD 疫苗的合理性。
