Parvin Rokshana, Helal Sumyea Binta, Uddin Md Mohi, Tasnim Shadia, Hossain Md Riabbel, Shila Rupaida Akter, Begum Jahan Ara, Nooruzzaman Mohammed, Ahrens Ann Kathrin, Harder Timm, Chowdhury Emdadul Haque
Department of Pathology, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh.
Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Vet Sci. 2025 Jul 23;12(8):689. doi: 10.3390/vetsci12080689.
Scavenging domestic ducks significantly contribute to the transmission and maintenance of highly pathogenic H5N1 clade 2.3.4.4b avian influenza viruses in Bangladesh, a strain of growing global concern due to its broad host range, high pathogenicity, and spillover potential. This study investigates the molecular epidemiology and pathology of HPAI H5N1 viruses in unvaccinated scavenging ducks in Bangladesh, with the goal of assessing viral evolution and associated disease outcomes. Between June 2022 and March 2024, 40 scavenging duck flocks were investigated for HPAI outbreaks. Active HPAIV H5N1 infection was detected in 35% (14/40) of the flocks using RT-qPCR. Affected ducks exhibited clinical signs of incoordination, torticollis, and paralysis. Pathological examination revealed prominent meningoencephalitis, encephalopathy and encephalomalacia, along with widespread lesions in the trachea, lungs, liver, and spleen, indicative of systemic HPAIV infection. A phylogenetic analysis of full-genome sequences confirmed the continued circulation of clade 2.3.2.1a genotype G2 in these ducks. Notably, two samples of 2022 and 2023 harbored HPAIV H5N1 of clade 2.3.4.4b, showing genetic similarity to H5N1 strains circulating in Korea and Vietnam. A mutation analysis of the HA protein in clade 2.3.4.4b viruses revealed key substitutions, including T156A (loss of an N-linked glycosylation site), S141P (antigenic site A), and E193R/K (receptor-binding pocket), indicating potential antigenic drift and receptor-binding adaptation compared to clade 2.3.2.1a. The emergence of clade 2.3.4.4b with the first report of neurological and systemic lesions suggests ongoing viral evolution with increased pathogenic potential for ducks. These findings highlight the urgent need for enhanced surveillance and biosecurity to control HPAI spread in Bangladesh.
在孟加拉国，散养鸭在高致病性H5N1 2.3.4.4b分支禽流感病毒的传播和维持中起着重要作用。由于其广泛的宿主范围、高致病性和溢出潜力，该毒株日益引起全球关注。本研究调查了孟加拉国未接种疫苗的散养鸭中高致病性禽流感H5N1病毒的分子流行病学和病理学，目的是评估病毒进化及相关疾病结果。在2022年6月至2024年3月期间，对40个散养鸭群进行了高致病性禽流感疫情调查。使用逆转录定量聚合酶链反应（RT-qPCR）在35%（14/40）的鸭群中检测到活跃的H5N1高致病性禽流感病毒感染。受感染的鸭子表现出共济失调、斜颈和麻痹等临床症状。病理检查显示有明显的脑膜脑炎、脑病和脑软化，以及气管、肺、肝和脾的广泛病变，表明存在全身性高致病性禽流感病毒感染。对全基因组序列的系统发育分析证实了2.3.2.1a基因型G2在这些鸭子中持续传播。值得注意的是，2022年和2023年的两个样本携带2.3.4.4b分支的高致病性禽流感H5N1病毒，与在韩国和越南传播的H5N1毒株具有遗传相似性。对2.3.4.4b分支病毒的血凝素（HA）蛋白进行突变分析发现了关键替换，包括T156A（N-连接糖基化位点缺失）、S141P（抗原位点A）和E193R/K（受体结合口袋），表明与2.3.2.1a分支相比存在潜在的抗原漂移和受体结合适应性。2.3.4.4b分支的出现以及首次报告的神经和全身病变表明病毒在持续进化，对鸭子的致病潜力增加。这些发现凸显了加强监测和生物安全措施以控制孟加拉国高致病性禽流感传播的迫切需求。
