IHAP, Université de Toulouse, ENVT, INRAE, 23 Chemin des Capelles, 31076, Toulouse Cedex 3, France.
Sci Rep. 2021 Mar 15;11(1):5928. doi: 10.1038/s41598-021-85109-5.
Highly Pathogenic Avian Influenza viruses (HPAIVs) display a tissue pantropism, which implies a possible spread in feathers. HPAIV detection from feathers had been evaluated for H5N1 or H7N1 HPAIVs. It was suggested that viral RNA loads could be equivalent or higher in samples of immature feather compared to tracheal (TS) or cloacal swabs (CS). We investigated the suitability of feathers for the detection of clade 2.3.4.4b H5N8 HPAIV in ducks and geese field samples. In the six H5N8 positive flocks that were included in this study, TS, CS and immature wing feathers were taken from at least 10 birds. Molecular loads were then estimated using real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) targetting H5 and M genes. In all flocks, viral loads were at least equivalent between feather and swab samples and in most cases up to 10 higher in feathers. Bayesian modelling confirmed that, in infected poultry, RT-qPCR was much more likely to be positive when applied on a feather sample only (estimated sensitivity between 0.89 and 0.96 depending on the positivity threshold) than on a combination of a tracheal and a cloacal swab (estimated sensitivity between 0.45 and 0.68 depending on the positivity threshold). Viral tropism and lesions in feathers were evaluated by histopathology and immunohistochemistry. Epithelial necrosis of immature feathers and follicles was observed concurrently with positive viral antigen detection and leukocytic infiltration of pulp. Accurate detection of clade 2.3.4.4b HPAIVs in feather samples were finally confirmed with experimental H5N8 infection on 10-week-old mule ducks, as viral loads at 3, 5 and 7 days post-infection were higher in feathers than in tracheal or cloacal swabs. However, feather samples were associated with lower viral loads than tracheal swabs at day 1, suggesting better detectability of the virus in feathers in the later course of infection. These results, based on both field cases and experimental infections, suggest that feather samples should be included in the toolbox of samples for detection of clade 2.3.4.4b HPAI viruses, at least in ducks and geese.
高致病性禽流感病毒（HPAIVs）表现出组织泛嗜性，这意味着它们可能在羽毛中传播。已经评估了从羽毛中检测 H5N1 或 H7N1 HPAIV 的方法。有研究表明，与气管（TS）或泄殖腔拭子（CS）相比，未成熟羽毛样本中的病毒 RNA 载量可能相等或更高。我们研究了羽毛是否适合检测鸭和鹅田间样本中的 2.3.4.4b 分支 H5N8 HPAIV。在本研究中包括的六个 H5N8 阳性禽群中，从至少 10 只禽鸟中采集了 TS、CS 和未成熟翼羽。然后使用针对 H5 和 M 基因的实时定量逆转录聚合酶链反应（RT-qPCR）来估计分子载量。在所有禽群中，羽毛和拭子样本之间的病毒载量至少相等，在大多数情况下，羽毛中的病毒载量高达 10 倍以上。贝叶斯模型证实，在感染家禽中，仅应用于羽毛样本的 RT-qPCR 更有可能呈阳性（取决于阳性阈值的估计敏感性在 0.89 到 0.96 之间），而不是同时应用气管和泄殖腔拭子（取决于阳性阈值的估计敏感性在 0.45 到 0.68 之间）。通过组织病理学和免疫组织化学评估病毒的嗜性和病变。在观察到上皮细胞坏死的同时，未成熟羽毛和毛囊中检测到阳性病毒抗原，并伴有白细胞浸润。最后，通过对 10 周龄骡鸭进行 H5N8 感染实验证实了对 2.3.4.4b 分支 HPAIV 羽毛样本的准确检测，感染后 3、5 和 7 天，羽毛中的病毒载量高于气管或泄殖腔拭子。然而，与气管拭子相比，羽毛样本在第 1 天的病毒载量较低，这表明在感染后期，羽毛中病毒的可检测性更好。这些结果基于田间病例和实验感染，表明在检测 2.3.4.4b 分支 HPAI 病毒时，至少在鸭和鹅中，应将羽毛样本纳入检测工具包。
