Department of Veterinary Pathology, College of Veterinary Medicine, Iowa State University, Ames, IA 50011.
Department of Veterinary Diagnostic & Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011.
Avian Dis. 2024 Sep;68(3):272-281. doi: 10.1637/aviandiseases-D-23-00085.
In 2022, a new epornitic of H5N1 highly pathogenic avian influenza (HPAI) virus clade 2.3.4.4b emerged in U.S. domestic poultry with high prevalence in wild bird populations. We describe pathological findings of HPAI H5N1 in nine wild birds encompassing eight different species, including Accipitriformes (red-tailed hawk, bald eagle), Cathartiforme (turkey vulture), Falconiforme (peregrine falcon), Strigiforme (one adult great-horned owl, one juvenile great-horned owl), Pelecaniforme (American white pelican), and Anseriformes (American green-winged teal, trumpeter swan). All these birds died naturally (found dead, or died in transit to or within a rehabilitation center), except for the bald eagle and American green-winged teal, which were euthanized. Gross lesions were subtle, characterized by meningeal congestion observed in the turkey vulture, bald eagle, and adult great-horned owl. Histologically, encephalitis was observed in all cases (9/9, 100%). Leukocytoclastic and fibrinoid vasculitis with necrotizing encephalitis was observed in the red-tailed hawk, great-horned owls, and American white pelican (5/9, 55.6%), and perivascular lymphohistiocytic encephalitis was seen in the turkey vulture, peregrine falcon, green-winged teal, and bald eagle (4/9, 44.4%). Coagulative necrosis or lymphohistiocytic/lymphoplasmacytic inflammation was identified in the kidney (6/8, 75%), liver (6/9, 66.7%), heart (5/9, 55.6%), and lung (2/9, 22.2%). Immunopositive signals against Influenza virus A nucleoprotein were predominantly detected within the brain (9/9, 100%), air sac (7/9, 77.8%), lung (7/9, 77.8%), kidney (6/8, 75%), heart (6/9, 66.7%), and liver (5/9, 55.6%). Additionally, other organs, such as the pancreas, spleen, intestines, gonads, and adrenals occasionally exhibited positive viral protein signals. In these organs, in addition to parenchymal cells, viral protein signals were often identified in endothelial cells. Our results suggest that the 2022-2023 HPAIV H5N1 clade 2.3.4.4b replicated systemically in all examined birds, with brain lesions being the most prevalent and associated with a subset of birds displaying clinical signs observed perimortem.
2022 年，美国国内家禽中出现了一种新型 H5N1 高致病性禽流感（HPAI）病毒 2.3.4.4b 分支，在野生鸟类种群中发病率很高。我们描述了 9 只野生鸟类中 HPAI H5N1 的病理学发现，包括猛禽类（红尾鹰、白头鹰）、秃鹫类（土耳其秃鹰）、隼形目（游隼）、鸮形目（一只成年大角猫头鹰、一只幼年大角猫头鹰）、鹈形目（美洲白鹈鹕）和雁形目（美洲绿翅鸭、喇叭天鹅）。除白头鹰和美洲绿翅鸭被安乐死外，所有这些鸟类都是自然死亡（发现死亡，或在运往或在康复中心的途中死亡）。大体病变不明显，仅见于土耳其秃鹰、白头鹰和成年大角猫头鹰的脑膜充血。所有病例均观察到脑炎（9/9，100%）。红尾鹰、大角猫头鹰和美洲白鹈鹕（5/9，55.6%）观察到白细胞碎裂性和纤维蛋白样血管炎伴坏死性脑炎，土耳其秃鹰、游隼、绿翅鸭和白头鹰（4/9，44.4%）观察到血管周围淋巴样组织细胞性脑炎。肾脏（6/8，75%）、肝脏（6/9，66.7%）、心脏（5/9，55.6%）和肺脏（2/9，22.2%）均发现凝固性坏死或淋巴样组织细胞/淋巴浆细胞性炎症。针对甲型流感病毒核蛋白的免疫阳性信号主要在大脑（9/9，100%）、气囊（7/9，77.8%）、肺脏（7/9，77.8%）、肾脏（6/8，75%）、心脏（6/9，66.7%）和肝脏（5/9，55.6%）中检测到。此外，胰腺、脾脏、肠道、性腺和肾上腺等其他器官偶尔也会出现阳性病毒蛋白信号。在这些器官中，除实质细胞外，内皮细胞中也常检测到病毒蛋白信号。我们的结果表明，2022-2023 年 HPAIV H5N1 2.3.4.4b 分支在所有检查的鸟类中均能进行系统性复制，大脑病变最为普遍，并与一部分表现出围死亡期临床症状的鸟类有关。
