Al-Ebshahy Emad, AboElkhair Mohammed, Shehata Awad, Elgendy Emad
Department of Microbiology, Faculty of Veterinary Medicine, Alexandria University, Abees10th, Alexandria, 21944, Egypt.
Department of Virology, Faculty of Veterinary Medicine, University of Sadat City, Sadat City, 32897, Egypt.
Braz J Microbiol. 2024 Dec;55(4):4199-4204. doi: 10.1007/s42770-024-01537-1. Epub 2024 Oct 24.
Since its first description in 1991 in Egypt, egg drop syndrome 1976 (EDS-76) virus has received a little attention as a potential cause for the drop in egg production as well as the reduction in egg quality. To date, no studies have been carried out to describe the genetic characteristics of the circulating field EDS-76 virus strains. Thus, the present study was attempted to estimate the emergence of EDS-76 virus in layer flocks and to determine the genetic diversity between the field strains and the vaccine strain 127. During 2022, a total of 5 apparently healthy backyard layer flocks were investigated for the presence of EDS-76 virus infection following complaints of sudden drop in egg production (25-30%), accompanied by high incidence of eggshell defects. EDS-76 virus DNA was detected in the oviduct samples of 4 (80%) flocks by polymerase chain reaction (PCR) assay targeting the hexon gene of the viral capsid. Attempts of viral isolation in duck embryo revealed no embryonic mortality, however, the allantoic fluids of inoculated eggs exhibited a sustained increase in the hemagglutinating (HA) activity throughout three consecutive passages. The obtained strain, designated BH-1, was characterized on the basis of partial hexon gene sequence analysis (GenBank accession number OR531368). The BH-1 strain displayed 99.6% nucleotide identity with the vaccine strain 127. However, amino acid alignments with the vaccine strain 127 revealed that the BH-1 strain carried 5 non-synonymous mutations. In addition, two of these mutations were incorporated into the hexon hypervariable regions (HVRs), which are strictly responsible for eliciting serotype-specific neutralizing antibodies. In conclusion, the present study represents a starting point for genetic characterization of EDS-76 virus in Egypt and highlights the importance for continuous monitoring and characterization of the circulating field EDS-76 virus strains, in order to determine the proper control strategy.
自1991年在埃及首次被描述以来，1976年禽蛋下降综合征（EDS - 76）病毒作为产蛋量下降以及蛋品质降低的潜在原因，一直未受到太多关注。迄今为止，尚未开展任何研究来描述流行的田间EDS - 76病毒株的遗传特征。因此，本研究旨在评估EDS - 76病毒在蛋鸡群中的出现情况，并确定田间毒株与疫苗株127之间的遗传多样性。在2022年期间，共有5个看似健康的后院蛋鸡群因出现产蛋量突然下降（25 - 30%）并伴有蛋壳缺陷高发的投诉，而被调查是否感染EDS - 76病毒。通过针对病毒衣壳六邻体基因的聚合酶链反应（PCR）检测，在4个（80%）鸡群的输卵管样本中检测到了EDS - 76病毒DNA。在鸭胚中进行病毒分离的尝试未发现胚胎死亡，但接种蛋的尿囊液在连续三代传代过程中血凝（HA）活性持续增加。所获得的毒株命名为BH - 1，基于部分六邻体基因序列分析（GenBank登录号OR531368）对其进行了特征鉴定。BH - 1毒株与疫苗株127的核苷酸同一性为99.6%。然而，与疫苗株127的氨基酸比对显示，BH - 1毒株携带5个非同义突变。此外，其中两个突变位于六邻体高变区（HVRs），这些区域严格负责引发血清型特异性中和抗体。总之，本研究是埃及EDS - 76病毒遗传特征研究的起点，并强调了持续监测和鉴定流行的田间EDS - 76病毒株以确定适当控制策略的重要性。
