Department of Biochemistry and Biophysics, University of California, San Francisco, California, 94158, USA.
U. S. Geological Survey, Alaska Science Center, Anchorage, AK, 99508, USA.
Virol J. 2018 Jun 15;15(1):100. doi: 10.1186/s12985-018-1008-5.
Avian keratin disorder (AKD) is an epizootic of debilitating beak deformities, first documented in black-capped chickadees (Poecile atricapillus) in Alaska during the late 1990s. Similar deformities have now been recorded in dozens of species of birds across multiple continents. Despite this, the etiology of AKD has remained elusive, making it difficult to assess the impacts of this disease on wild populations. We previously identified an association between infection with a novel picornavirus, Poecivirus, and AKD in a small cohort of black-capped chickadees.
To test if the association between Poecivirus and AKD holds in a larger study population, we used targeted PCR followed by Sanger sequencing to screen 124 symptomatic and asymptomatic black-capped chickadees for Poecivirus infection. We further compared the efficacy of multiple non-terminal field sampling methods (buccal swabs, cloacal swabs, fecal samples, and blood samples) for Poecivirus screening. Finally, we used both in situ hybridization and a strand-specific expression assay to localize Poecivirus to beak tissue of AKD-positive individuals and to determine if virus is actively replicating in beak tissue.
Poecivirus was detected in 28/28 (100%) individuals with AKD, but only 9/96 (9.4%) asymptomatic individuals with apparently normal beaks (p < 0.0001). We found that cloacal swabs are the most sensitive of these sample types for detecting Poecivirus in birds with AKD, but that buccal swabs should be combined with cloacal swabs in evaluating the infection status of asymptomatic birds. Finally, we used both in situ hybridization and a strand-specific expression assay to localize Poecivirus to beak tissue of AKD-positive individuals and to provide evidence of active viral replication.
The data presented here show a strong, statistically significant relationship between Poecivirus infection and AKD, and provide evidence that Poecivirus is indeed an avian virus, infecting and actively replicating in beak tissue of AKD-affected BCCH. Taken together, these data corroborate and extend the evidence for a potential causal association between Poecivirus and AKD in the black-capped chickadee. Poecivirus continues to warrant further investigation as a candidate agent of AKD.
禽类角蛋白紊乱（AKD）是一种衰弱性喙畸形的流行疾病，于 20 世纪 90 年代末在阿拉斯加的黑头山雀（Poecile atricapillus）中首次记录。现在，这种畸形已经在多个大洲的几十种鸟类中被记录。尽管如此，AKD 的病因仍然难以捉摸，这使得评估这种疾病对野生种群的影响变得困难。我们之前在一小部分黑头山雀中发现了一种新型小核糖核酸病毒——Poecivirus 与 AKD 之间的关联。
为了在更大的研究人群中检验 Poecivirus 与 AKD 之间的关联，我们使用靶向 PCR 联合 Sanger 测序，对 124 只出现症状和无症状的黑头山雀进行 Poecivirus 感染筛查。我们进一步比较了多种非末端现场采样方法（口腔拭子、泄殖腔拭子、粪便样本和血液样本）在筛查 Poecivirus 方面的效果。最后，我们使用原位杂交和链特异性表达测定法，将 Poecivirus 定位到 AKD 阳性个体的喙组织中，并确定病毒是否在喙组织中活跃复制。
Poecivirus 在 28/28（100%）只出现 AKD 的个体中被检测到，但在 9/96（9.4%）只出现无症状且喙组织外观正常的个体中仅检测到 9 只（p<0.0001）。我们发现，在出现 AKD 的鸟类中，泄殖腔拭子是检测 Poecivirus 最敏感的样本类型，但在评估无症状鸟类的感染状态时，应将口腔拭子与泄殖腔拭子相结合。最后，我们使用原位杂交和链特异性表达测定法，将 Poecivirus 定位到 AKD 阳性个体的喙组织中，并提供病毒活跃复制的证据。
这里呈现的数据表明，Poecivirus 感染与 AKD 之间存在强烈的、统计学上显著的关系，并提供了证据表明，Poecivirus 确实是一种禽类病毒，在受 AKD 影响的黑头山雀的喙组织中感染并活跃复制。总的来说，这些数据证实并扩展了 Poecivirus 与黑头山雀 AKD 之间潜在因果关系的证据。Poecivirus 仍然值得进一步研究，作为 AKD 的候选病原体。
