Avian and Rabbit Diseases Department, Faculty of Veterinary Medicine, University of Sadat City, Egypt.
Department of Poultry and Fish Diseases, Faculty of Veterinary Medicine, Alexandria University, Alexandria, Egypt.
Poult Sci. 2019 Jun 1;98(6):2371-2379. doi: 10.3382/ps/pez011.
A total of 50 poultry farms of commercial broilers (N = 39) and commercial layers (N = 11) suffered from respiratory problems and mortality during the period from January 2016 to December 2017 were investigated. Also, samples were collected from quail (N = 4), Bluebird (Sialis, N = 1), and Greenfinch (Chloris chloris, N = 1) for analysis. Respiratory viral pathogens were screened by PCR and positive samples were subjected to virus isolation and genetic identification. Antigenic relatedness of isolated avian influenza (AI) H5 subtype was evaluated using cross-hemagglutination inhibition. Results revealed that the incidence of single virus infections in commercial broilers was 64.1% (25/39), with the highest incidence for ND (33.3%) and H9N2 (20.5%), followed by H5N1 (7.7%) and H5N8 (2.7). Meanwhile, H9N2/ND mixed infection was the most observed case (7.7%). Other mixed infections H5N1/ND, H5N1/H9N2/ND, H5N1/H9N2/ND/IB, H9N2/IB, and H9N2/ILT were also observed (2.6% each). In commercial layers, H5N1 and ILT were the only detected single infections (18.1% each). Mixed H9N2/ND was the most predominant infection in layers (27.3%). Other mixed infections of H9N2/IB, H5N1/H5N8/H9N2, and H9N2/ND/IB were observed in 3 separate farms (9.1% each). The H5N8 virus was detected in one quail farm and 2 out of 3 wild bird's samples. Partial HA gene sequence analysis showed the clustering of the selected AI H5N8 within the 2.3.4.4 clade, while H5N1 clustered with the clade 2.2.1.2. Interestingly, the H5N8 isolated from chickens possessed 6 amino acids substitutions at HA1 compared to those isolated from wild birds with low antigenic relatedness to AI H5N1 clades 2.2.1 or 2.2.1.2. In conclusion, mixed viral infections were observed in both broiler and layer chickens in Egypt. The detected triple H5N1, H9N2, and H5N8 influenza co-infection raises the concern of potential AI epidemic strain emergence. The low genetic and antigenic relatedness between AI H5N1 and H5N8 viruses suggest the need for modification of vaccination strategies of avian influenza in Egypt along with strict biosecurity measures.
2016 年 1 月至 2017 年 12 月期间，共有 50 家商业肉鸡（N=39）和商业蛋鸡（N=11）养殖场因呼吸道问题和死亡率而遭受损失。此外，还从鹌鹑（N=4）、蓝鸟（Sialis，N=1）和绿雀（Chloris chloris，N=1）中采集样本进行分析。通过 PCR 筛选呼吸道病毒病原体，对阳性样本进行病毒分离和遗传鉴定。使用交叉血凝抑制评估分离的禽流感（AI）H5 亚型的抗原相关性。结果表明，商业肉鸡的单病毒感染发生率为 64.1%（25/39），其中以 ND（33.3%）和 H9N2（20.5%）的发生率最高，其次是 H5N1（7.7%）和 H5N8（2.7%）。同时，观察到 H9N2/ND 混合感染的病例最多（7.7%）。还观察到其他混合感染 H5N1/ND、H5N1/H9N2/ND、H5N1/H9N2/ND/IB、H9N2/IB 和 H9N2/ILT（各占 2.6%）。在商业蛋鸡中，H5N1 和 ILT 是唯一检测到的单感染（各占 18.1%）。H9N2/ND 是蛋鸡中最主要的混合感染（占 27.3%）。其他混合感染 H9N2/IB、H5N1/H5N8/H9N2 和 H9N2/ND/IB 在 3 个单独的农场中各观察到 1 例（各占 9.1%）。在一个鹌鹑养殖场和 3 个野生鸟类样本中的 2 个中检测到 H5N8 病毒。部分 HA 基因序列分析表明，所选 AI H5N8 病毒在 2.3.4.4 分支内聚类，而 H5N1 聚类在 2.2.1.2 分支内。有趣的是，与具有低抗原相关性的野生鸟类分离株相比，鸡分离株的 HA1 具有 6 个氨基酸取代，与 AI H5N1 分支 2.2.1 或 2.2.1.2 无明显关系。总之，在埃及的肉鸡和蛋鸡中均观察到混合病毒感染。检测到的三重 H5N1、H9N2 和 H5N8 流感混合感染引起了对潜在 AI 流行株出现的关注。AI H5N1 和 H5N8 病毒之间的低遗传和抗原相关性表明，需要对埃及的禽流感疫苗接种策略进行修改，并采取严格的生物安全措施。
