Egyptian Company for Biological & Pharmaceutical Industries (Vaccine Valley), 6th October City, Giza, 12511, Egypt.
Laboratory for Veterinary Quality Control On Poultry Production, Animal Health Research Institute, Agricultural Research Center, Dokki, Giza, 12618, Egypt.
Virol J. 2024 Nov 30;21(1):312. doi: 10.1186/s12985-024-02559-9.
Infectious bursal disease virus (IBDV) induces severe immunosuppression in chickens, leading to significant economic losses in the global poultry industry. This study investigated 52 chicken flocks, including commercial broilers, layers, and baladi, from various Egyptian governorates in 2023. These flocks exhibited symptoms of depression, along with kidney and bursa lesions, indicative of IBDV infection. Pooled Bursal homogenates were tested using RT-PCR with VP2-specific primers, revealing that 20 flocks tested positive for IBDV. Six representative samples were selected from 20 positive flocks for isolation in embryonated chicken eggs. The embryonic lesions observed included haemorrhage, skull swelling, and liver necrosis with a pale-yellow appearance, in addition to congestion and thickening in the chorioallantoic membrane (CAM). Partial amplification of the VP2 gene from the harvested embryo suspensions of the six IBDV isolates was performed for sequencing. Phylogenetic analysis of the sequences revealed that five IBDV isolates (VV4, VV5, VV6, VV10, and VV16) belonged to the very virulent strain group A3 cluster, whereas one isolate (VV2) clustered with Chinese Variant strains in the A2d group. Sequence analysis of the hypervariable region (HVR) of VP2 compared to that of Egypt-USC-IBD-1-2019 and vvIBDV/Beh21/Egypt/18 highly virulent IBDV strains revealed several amino acid mutations. The VP2 HVR of all isolates maintained the serine-rich heptapeptide sequence SWSASGS, which is adjacent to the major hydrophilic peak B and serves as a virulence marker. Histopathological examination revealed that bursae from chickens infected with vvIBDV exhibited marked interlobular oedema and lymphoid depletion. In contrast, bursae from chickens infected with Variant IBDV showed massive lymphoid depletion, with hyperplasia of the bursal capsule. These findings highlight the circulation of both virulent and Variant IBDV strains in Egyptian chicken flocks, complicating disease control. Consequently, there is a need to update vaccination programs and vaccine strains for IBDV in Egypt.
传染性法氏囊病病毒（IBDV）可引起鸡的严重免疫抑制，给全球家禽业造成重大经济损失。本研究于 2023 年调查了来自埃及不同省份的 52 个鸡群，包括商品肉鸡、蛋鸡和巴拉丁鸡。这些鸡群表现出抑郁症状，同时伴有肾脏和法氏囊病变，提示存在 IBDV 感染。使用 VP2 特异性引物的 RT-PCR 对混合的法氏囊匀浆进行检测，结果显示 20 个鸡群的 IBDV 检测呈阳性。从 20 个阳性鸡群中选择 6 个代表性样本，在鸡胚中进行分离。观察到的胚胎病变包括出血、头骨肿胀、肝脏坏死呈浅黄色，以及绒毛尿囊膜（CAM）充血和增厚。对 6 个 IBDV 分离株的胚胎收获物悬浮液进行部分 VP2 基因扩增，用于测序。序列的系统进化分析显示，5 个 IBDV 分离株（VV4、VV5、VV6、VV10 和 VV16）属于强毒力株 A3 簇，而一个分离株（VV2）与 A2d 群中的中国变异株聚类。与埃及-USC-IBD-1-2019 和 vvIBDV/Beh21/Egypt/18 高致病性 IBDV 株相比，VP2 高变区（HVR）的序列分析显示存在几个氨基酸突变。所有分离株的 VP2 HVR 均保持富含丝氨酸的七肽序列 SWSASGS，该序列与主要亲水峰 B 相邻，是毒力标志物。组织病理学检查显示，感染 vvIBDV 的鸡的法氏囊表现出明显的小叶间水肿和淋巴样细胞耗竭。相比之下，感染变异型 IBDV 的鸡的法氏囊表现出大量淋巴样细胞耗竭，法氏囊囊泡增生。这些发现强调了强毒力和变异型 IBDV 株在埃及鸡群中的循环，使疾病控制复杂化。因此，有必要更新埃及的 IBDV 疫苗接种计划和疫苗株。
