Alkie Tamiru N, Embury-Hyatt Carissa, Signore Anthony V, Baldwin Frank, Hisanaga Tamiko, Xu Wanhong, Moffat Estella, Giacinti Jolene A, Soos Catherine, Berhane Yohannes
Canadian Food Inspection Agency, National Centre for Foreign Animal Disease, Winnipeg, Manitoba, Canada.
Prairie Region Wildlife and Habitat Assessment Section, Canadian Wildlife Service, Environment and Climate Change Canada, Delta, British Columbia, Canada.
mSphere. 2025 Jun 25;10(6):e0002125. doi: 10.1128/msphere.00021-25. Epub 2025 May 22.
Long-distance migratory ducks play a critical role in the maintenance and dissemination of A(H5N1) viruses. Comparative pathogenicity studies were conducted on blue-winged teal (BWTE; ) using three distinct genotypes of A(H5N1) clade 2.3.4.4b viruses (A1, B1.3, and B4.1) isolated from wild ducks in Canada. Twenty-four hours post-intranasal infection of BWTE, contact turkeys and chickens were introduced into each of the groups to evaluate viral transmission. The levels of viral shedding in BWTE increased from 3 to 7 days post-infection (dpi) and continued at lower levels until 14 dpi. The A1 genotype virus (MALL/NS/22) was found to be the least pathogenic to BWTE compared to the reassortant genotypes, B4.1 (RBME/BC/22) and B1.3 (BWTE/MB/22). The B1.3 genotype was the most virulent to BWTE and caused 66.7% mortality compared to 12.5% mortality caused by the B4.1 genotype. The extent of transmission from infected BWTE to contact turkeys and chickens showed variations. Turkeys housed with BWTE infected with either virus died within 6 to 10 days post-contact (dpc). Conversely, the transmission and mortality among contact chickens varied. The highest mortality (3 out of 5) occurred in chickens exposed to BWTE infected with the B1.3 genotype. Whilst in the B4.1 genotype, 2 out of 6 chickens died, none of the chickens in the A1 genotype succumbed to infection. No shedding or seroconversion was noted in all surviving chickens. This research underscores variations in the pathogenic traits and transmissibility among the different genotypes of A(H5N1) clade 2.3.4.4b viruses. This finding is vital for understanding the role of migratory birds in the epidemiology of A(H5N1) and the need for continuous monitoring of these viruses.
The recurrent incursions of A(H5N1) clade 2.3.4.4b viruses into North America have resulted in the emergence of reassortant virus genotypes. These genotypes exhibit variations in pathogenicity and host ranges. Blue-winged teal (BWTE) are the most common dabbling ducks in North America and play a crucial role in maintaining and dispersing influenza A viruses (IAVs). In some areas, the migratory pathways of BWTE overlap with densely populated commercial poultry facilities. Despite this, the role of BWTE in the maintenance and spread of A(H5N1) is not well understood, and there is limited data on their susceptibility to A(H5N1) clade 2.3.4.4b viruses. Our study demonstrates differences in BWTE susceptibility to distinct genotypes of A(H5N1) clade 2.3.4.4b viruses. The virus transmission from infected BWTE and lethality in turkeys and chickens were also influenced by the virus genotypes. The findings suggest that BWTE could contribute to the maintenance and spread of highly pathogenic avian influenza (HPAI) viruses, and active surveillance in BWTE is essential.
长途迁徙的鸭子在A(H5N1)病毒的维持和传播中起着关键作用。利用从加拿大野鸭中分离出的三种不同基因型的A(H5N1) 2.3.4.4b分支病毒（A1、B1.3和B4.1），对蓝翅鸭（BWTE）进行了致病性比较研究。在BWTE经鼻内感染24小时后，将接触火鸡和鸡引入每组以评估病毒传播。BWTE的病毒排泄水平在感染后3至7天（dpi）升高，并在较低水平持续至14 dpi。与重组基因型B4.1（RBME/BC/22）和B1.3（BWTE/MB/22）相比，A1基因型病毒（MALL/NS/22）对BWTE的致病性最低。B1.3基因型对BWTE的毒性最强，导致66.7%的死亡率，而B4.1基因型导致的死亡率为12.5%。从感染的BWTE传播到接触火鸡和鸡的程度存在差异。与感染任何一种病毒的BWTE饲养在一起的火鸡在接触后6至10天内死亡。相反，接触鸡之间的传播和死亡率各不相同。接触感染B1.3基因型的BWTE的鸡死亡率最高（5只中有3只）。而在B4.1基因型中，6只鸡中有2只死亡，A1基因型的鸡没有一只感染。所有存活的鸡均未出现病毒排泄或血清转化。这项研究强调了A(H5N1) 2.3.4.4b分支病毒不同基因型之间致病特征和传播性的差异。这一发现对于理解候鸟在A(H5N1)流行病学中的作用以及持续监测这些病毒的必要性至关重要。
A(H5N1) 2.3.4.4b分支病毒反复侵入北美导致了重组病毒基因型的出现。这些基因型在致病性和宿主范围上存在差异。蓝翅鸭（BWTE）是北美最常见的涉禽，在甲型流感病毒（IAV）的维持和传播中起着关键作用。在一些地区，BWTE的迁徙路线与人口密集的商业家禽设施重叠。尽管如此，BWTE在A(H5N1)的维持和传播中的作用尚不清楚，关于它们对A(H5N1) 2.3.4.4b分支病毒易感性的数据有限。我们的研究证明了BWTE对A(H5N1) 2.3.4.4b分支病毒不同基因型的易感性存在差异。感染BWTE的病毒传播以及火鸡和鸡的致死率也受病毒基因型影响。研究结果表明，BWTE可能有助于高致病性禽流感（HPAI）病毒的维持和传播，对BWTE进行主动监测至关重要。
