In young cattle, bovine respiratory disease (BRD) is a major cause of death and Mannheimia haemolytica is a frequent pathogen. Knowledge of fatal BRD in adult cattle is more limited. We assessed the importance of infectious BRD as a cause of death in adult cattle and determined the associated pathogens. We analyzed data from 737 adult cattle necropsies at the Pathology Unit for Large Animals at Oniris, Nantes, France over a 6 year period (2013–2019). Each carcass was subjected to a complete necropsy. Lungs showing macroscopic lesions were classified into three categories: infectious primary pulmonary (IPP) lesions, thromboembolic pneumonia (TEP) and others (aspiration pneumonia, verminous pneumonia, and local extension of an extra-pulmonary inflammatory process). Half of the lungs with IPP macroscopic lesions were sampled for histology and submitted for polymerase chain reaction. BRD was the second leading cause of death (15.7%) after digestive diseases (32.2%). A strong predominance of IPP lesions (42.3%) and TEP lesions (39.6%) was also demonstrated. In IPP macroscopic lesions, fibrinous, hemorrhagic and/or hecrotic (FHN) bronchopneumonia accounted for 77.6% of macroscopic lesions. Mannheimia haemolytica was significantly associated with FHN bronchopneumonia macroscopic lesions. This study suggests that Mannheimia haemolytica should be included in the differential diagnosis of BRD in adult cattle.

中文翻译：

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成年牛的传染性牛呼吸道疾病：一项广泛的尸检和病因学研究

在幼牛中，牛呼吸系统疾病 (BRD) 是导致死亡的主要原因，而溶血性曼海姆病是一种常见的病原体。对成年牛致命 BRD 的了解更为有限。我们评估了传染性 BRD 作为成年牛死亡原因的重要性，并确定了相关的病原体。我们分析了来自法国南特 Oniris 大型动物病理学部门 6 年（2013-2019 年）的 737 头成年牛尸体剖检数据。每具尸体都进行了完整的尸检。显示肉眼可见病变的肺分为三类：传染性原发性肺 (IPP) 病变、血栓栓塞性肺炎 (TEP) 和其他（吸入性肺炎、虫性肺炎和肺外炎症过程的局部扩展）。对具有 IPP 肉眼可见病变的一半肺进行组织学取样并提交聚合酶链反应。BRD 是第二大死因 (15. 7%) 消化系统疾病后 (32.2%)。还证明了 IPP 病变 (42.3%) 和 TEP 病变 (39.6%) 的强烈优势。在 IPP 肉眼可见病变中，纤维蛋白性、出血性和/或血肿性 (FHN) 支气管肺炎占肉眼可见病变的 77.6%。溶血曼海姆氏菌与 FHN 支气管肺炎肉眼可见病变显着相关。该研究表明，溶血性曼海姆氏菌应包括在成年牛 BRD 的鉴别诊断中。