Hagag Ibrahim Thabet, Mansour Shimaa M G, Zhang Zerui, Ali Ahmed A H, Ismaiel El-Bakry M, Salama Ali A, Cardona Carol J, Collins James, Xing Zheng
Department of Virology, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt; Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, Twin Cities, Saint Paul, Minnesota, United States of America.
Department of Virology, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt.
PLoS One. 2015 May 11;10(5):e0120061. doi: 10.1371/journal.pone.0120061. eCollection 2015.
Highly pathogenic avian influenza virus (HPAIV) H5N1 has been endemic in Egypt since 2006, and there is increasing concern for its potential to become highly transmissible among humans. Infection by HPAIV H5N1 has been described in experimentally challenged birds. However, the pathogenicity of the H5N1 isolated in Egypt has never been reported in naturally infected chickens and ducks. Here we report a 2013 outbreak of HPAIV H5N1 in commercial poultry farms and backyards in Sharkia Province, Egypt. The main symptoms were ecchymosis on the shanks and feet, cyanosis of the comb and wattles, subcutaneous edema of the head and neck for chickens, and nervous signs (torticollis) for ducks. Within 48-72 hrs of the onset of illness, the average mortality rates were 22.8-30% and 28.5-40% in vaccinated chickens and non-vaccinated ducks, respectively. Tissue samples of chickens and ducks were collected for analyses with cross-section immunohistochemistry and real-time RT-PCR for specific viral RNA transcripts. While viral RNA was detected in nearly all tissues and sera collected, viral nucleoprotein was detected almost ubiquitously in all tissues, including testis. Interestingly, viral antigen was also observed in endothelial cells of most organs in chickens, and clearly detected in the trachea and brain in particular. Viral nucleoprotein was also detected in mononuclear cells of various organs, especially pulmonary tissue. We performed phylogenetic analyses and compared the genomic sequences of the hemagglutinin (HA) and nonstructural proteins (NS) among the isolated viruses, the HPAIV circulated in Egypt in the past and currently, and some available vaccine strains. Further analysis of deduced amino acids of both HA and NS1 revealed that our isolates carried molecular determinants of HPAIV, including the multibasic amino acids (PQGERRRK/KR*GLF) in the cleavage site in HA and glutamate at position 92 (D92E) in NS1. This is the first report of the pathogenicity of the HPAIVH5N1 strain currently circulating in naturally infected poultry in Egypt, which may provide unique insights into the viral pathogenesis in HPAIV-infected chickens and ducks.
高致病性禽流感病毒（HPAIV）H5N1自2006年以来在埃及呈地方性流行，人们越来越担心其在人类中变得高度传播的可能性。在实验感染的禽类中已描述了HPAIV H5N1感染情况。然而，埃及分离出的H5N1的致病性从未在自然感染的鸡和鸭中报道过。在此，我们报告了2013年埃及谢赫村省商业家禽养殖场和后院发生的HPAIV H5N1疫情。主要症状为鸡的小腿和足部瘀斑、鸡冠和肉髯发绀、头部和颈部皮下水肿，以及鸭的神经症状（斜颈）。在发病后的48 - 72小时内，接种疫苗的鸡和未接种疫苗的鸭的平均死亡率分别为22.8% - 30%和28.5% - 40%。采集鸡和鸭的组织样本，用于横断面免疫组织化学分析和针对特定病毒RNA转录本的实时逆转录聚合酶链反应。虽然在几乎所有采集的组织和血清中都检测到了病毒RNA，但病毒核蛋白几乎在所有组织中都普遍检测到，包括睾丸。有趣的是，在鸡的大多数器官的内皮细胞中也观察到了病毒抗原，尤其在气管和脑中明显检测到。在各种器官的单核细胞中也检测到了病毒核蛋白，特别是肺组织。我们进行了系统发育分析，并比较了分离病毒、过去和当前在埃及流行的HPAIV以及一些可用疫苗株之间血凝素（HA）和非结构蛋白（NS）的基因组序列。对HA和NS1推导氨基酸的进一步分析表明，我们的分离株携带了HPAIV的分子决定因素，包括HA裂解位点的多个碱性氨基酸（PQGERRRK/KR*GLF）和NS1中第92位的谷氨酸（D92E）。这是目前在埃及自然感染家禽中流行的HPAIV H5N1毒株致病性的首次报告，这可能为HPAIV感染的鸡和鸭的病毒发病机制提供独特见解。
