Table 1_Comparative thoracic radiography in healthy and tuberculosis-positive sun bears (Helarctos malayanus).pdf

Early and accurate diagnosis of pulmonary tuberculosis (TB) is key to effective outbreak management, and in humans thoracic radiography is used extensively for screening purposes. In wildlife TB radiography is a relatively accessible diagnostic tool, particularly in under-resourced settings, however its use is limited by body size. Sun bears are susceptible to human-associated TB, and their small body size makes thoracic radiography feasible. However, there are no established guidelines on normal thoracic radiographs or radiographic manifestations of TB in this species. We provide a first description of thoracic radiographs from healthy and TB affected sun bears at a bear rescue sanctuary, including correlation with postmortem results for a subset of bears. Findings of two veterinary radiologists, blinded to clinical information, revealed high agreement on broad categorization of radiographic studies as normal, abnormal, or needing correlation with further information. Agreement was lower for the presence of specific lung patterns, reflecting inherent subjectivity when classifying these features. Very few studies were identified as definitively normal, however definitively abnormal studies were significantly associated with TB cases. Diffuse bronchial and/or bronchointerstitital lung patterns were commonly reported, with a high proportion needing correlation with age and/or clinical signs to further interpret. Interstitial, interstitial-to-alveolar, alveolar and nodular lung patterns, along with radiographic signs of lymphadenomegaly and pleural fluid, were almost exclusively found in TB cases, however the sensitivity of the presence of any of these changes for detecting TB was below 70%. Radiographic reporting of thoracic lymph node enlargement detected at postmortem was low (4/17; 23%), and aortic outflow tract dilation and positional atelectasis were differential diagnoses for radiographic changes that could also represent TB. Together these findings demonstrate the importance of developing species-specific criteria for interpretation, to differentiate between common findings and manifestations of TB, and to highlight areas where radiographic techniques can be optimized to assist this. Given TB remains a global health challenge in humans and other animals (wild or domestic), and detection is key to control, we recommend development of standardized approaches to radiographic studies and their interpretation to bolster diagnostic pathways for detecting TB in sun bears, and other novel or understudied hosts.

早期精准诊断肺结核（pulmonary tuberculosis, TB）是有效管控疫情暴发的核心环节；在人类临床中，胸部放射成像（thoracic radiography）被广泛用于结核病筛查。在野生动物领域，胸部放射成像是一种相对易于获取的诊断工具，尤其适用于资源匮乏的场景，但其应用受限于动物体型。马来熊（sun bears）对人兽共患结核病易感，且其体型较小，使得胸部放射成像成为可行的诊断手段。然而，目前尚无针对该物种的正常胸部放射影像标准，以及结核病放射影像学表现的规范指南。本研究首次对马来熊救助中心内健康个体与结核病感染个体的胸部放射影像进行描述，并对部分个体的影像结果与死后剖检结果（postmortem results）进行了关联分析。对临床信息设盲的两名兽医放射科医师的评估结果显示，在将放射影像大致归类为正常、异常或需结合额外信息进行判读这一分类上，两位医师具有较高的一致性；但在判断是否存在特定肺部影像表现时，一致性有所降低，这反映了在分类此类影像特征时存在固有的主观性。被明确判定为正常的影像样本极少，但明确异常的影像结果与结核病感染个体显著相关。弥漫性支气管型和/或支气管间质型肺部影像表现较为常见，其中多数需要结合年龄和/或临床症状才能进一步明确判读。间质型、间质-肺泡混合型、肺泡型与结节型肺部影像表现，以及淋巴结肿大（lymphadenomegaly）和胸腔积液（pleural fluid）的放射影像学征象，几乎仅见于结核病感染个体，但上述任一影像改变用于检测结核病的灵敏度均低于70%。针对死后剖检中发现的胸部淋巴结肿大，放射影像报告的检出率较低（4/17，23%）；而主动脉流出道扩张与体位性肺不张（positional atelectasis）可作为与结核病表现相似的放射影像改变的鉴别诊断。综合上述研究结果可见，建立针对该物种的专属影像判读标准至关重要，此举可用于区分常见影像表现与结核病特异性征象，并明确可通过优化放射摄影技术辅助诊断的环节。鉴于结核病仍是人类与其他动物（野生或家养）面临的全球性公共卫生挑战，而早期检测是防控的核心环节，本研究建议制定标准化的放射摄影检查流程与影像判读方法，以完善马来熊及其他新型或研究不足的宿主物种的结核病诊断路径。