Yehia Nahed, El-Sayed Hemat S, Omar Sabry E, Erfan Ahmed, Amer Fatma
Reference Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute, Agricultural Research Center, Dokki, Giza 12618, Egypt.
Department of Poultry Diseases, Benha Provincial Laboratory, Animal Health Research Institute, Agricultural Research Center, Giza, Egypt.
Vet World. 2021 May;14(5):1342-1353. doi: 10.14202/vetworld.2021.1342-1353. Epub 2021 May 28.
The Marek's disease virus (MDV) is a neoplastic disease causing serious economic losses in poultry production. This study aimed to investigate MDV occurrence in poultry flocks in the Lower Egypt during the 2020 breakout and genetically characterized , , genes in field strains of MDV.
Forty samples were collected from different breeds from eight Egyptian governorates in 2020. All flocks had received a bivalent vaccine (herpesvirus of turkey FC-126 + Rispens CVI988). However, weight loss, emaciation, reduced egg production, paralysis, and rough/raised feather follicles occurred. Samples were collected from feather follicles, liver, spleen, and nerve tissue for diagnosis by polymerase chain reaction. MDV genetic characterization was then performed by sequencing the , genes of five positive samples representing different governorates and breeds.
A total of 28 samples were positive for MDV field strains, while two were related to MDV vaccinal strains. All samples tested negative for ALV (A, B, C, D, and J) and REV. Phylogenetic analysis of the gene of sequenced samples revealed that all MDVs were related to the highly virulent European viruses (Gallid herpesvirus 2 ATE and PC12/30) with high amino acid (A.A.) identity 99.2-100%. Alternatively, there was low A.A. identity with the vaccine strains CVI988 and 3004 (up to 82.5%). These results indicate that further investigation of the efficacy of current Egyptian vaccines is required. The Egyptian strains also harbor a specific mutation, allowing clustering into two subgroups (A and B). By mutation analysis of the gene, the Egyptian viruses in our study had R101K, P217A, and E263D mutations present in all Egyptian viruses. Furthermore, R176A and T180A mutations specific to our strains contributed to the high virulence of highly virulent strains. There were no mutations of the or genes.
Further studies should evaluate the protection contributed by current vaccines used in Egypt.
马立克氏病病毒（MDV）是一种导致家禽生产严重经济损失的肿瘤性疾病。本研究旨在调查2020年疫情爆发期间埃及下埃及家禽群中MDV的发生情况，并对MDV田间毒株的 、 、 基因进行遗传特征分析。
2020年从埃及八个省份的不同品种中采集了40份样本。所有鸡群都接种了二价疫苗（火鸡疱疹病毒FC - 126 + 里默斯CVI988）。然而，出现了体重减轻、消瘦、产蛋量下降、麻痹以及羽毛毛囊粗糙/凸起的情况。从羽毛毛囊、肝脏、脾脏和神经组织采集样本，通过聚合酶链反应进行诊断。然后对代表不同省份和品种的五个阳性样本的 、 基因进行测序，以进行MDV遗传特征分析。
共有28个样本的MDV田间毒株呈阳性，而两个样本与MDV疫苗毒株有关。所有样本的禽白血病病毒（A、B、C、D和J型）和网状内皮组织增殖症病毒检测均为阴性。对测序样本的 基因进行系统发育分析表明，所有MDV均与高致病性欧洲病毒（鸡疱疹病毒2型ATE和PC12/30）相关，氨基酸同一性高达99.2 - 100%。相比之下，与疫苗毒株CVI988和3004的氨基酸同一性较低（最高82.5%）。这些结果表明需要进一步研究当前埃及疫苗的效力。埃及毒株还存在一个特定突变，可分为两个亚组（A和B）。通过对 基因的突变分析，我们研究中的埃及病毒在所有埃及病毒中都存在R101K、P217A和E263D突变。此外，我们毒株特有的R176A和T180A突变导致了高致病性毒株的高致病性。 或 基因没有突变。
应进一步研究评估埃及目前使用的疫苗所提供的保护作用。
