Bovine coronaviruses (BoCVs) have been found in respiratory tissues in cattle and frequently associated with bovine respiratory disease (BRD); however, pathogenesis studies in calves are limited. To characterize the pathogenesis and pathogenicity of BoCV isolates, we used 5 different BoCV strains to inoculate colostrum-deprived calves, ~ 2–5 wk of age. Later, to determine if dual viral infection would potentiate pathogenicity of BoCV, calves were inoculated with BoCV alone, bovine viral diarrhea virus (BVDV) alone, or a series of dual-infection (BVDV–BoCV) schemes. A negative control group was included in all studies. Clinical signs and body temperature were monitored during the study and samples collected for lymphocyte counts, virus isolation, and serology. During autopsy, gross lesions were recorded and fixed tissues collected for histopathology and immunohistochemistry; fresh tissues were collected for virus isolation. Results suggest increased pathogenicity for isolate BoCV OK 1776. Increased body temperature was found in all virus-inoculated groups. Lung lesions were present in calves in all dual-infection groups; however, lesions were most pronounced in calves inoculated with BVDV followed by BoCV inoculation 6 d later. Lung lesions were consistent with mild-to-moderate interstitial pneumonia, and immunohistochemistry confirmed the presence of BoCV antigen. Our studies demonstrated that BVDV–BoCV dual infection may play an important role in BRD pathogenesis, and timing between infections seems critical to the severity of lesions.

牛冠状病毒（BoCVs）已在牛的呼吸组织中发现，并经常与牛呼吸道疾病（BRD）有关。但是，犊牛的发病机理研究有限。为了表征BoCV分离株的发病机理和致病性，我们使用了5种不同的BoCV菌株接种了约2-5周龄的初乳剥夺的小牛。后来，为了确定双重病毒感染是否会增强BoCV的致病性，分别给牛犊单独接种BoCV，单独接种牛病毒性腹泻病毒（BVDV）或一系列双重感染（BVDV–BoCV）方案。所有研究均包括阴性对照组。在研究期间监测临床体征和体温，并收集样本进行淋巴细胞计数，病毒分离和血清学检查。验尸期间 记录总的病变并收集固定的组织用于组织病理学和免疫组织化学；收集新鲜组织用于病毒分离。结果表明，分离的BoCV OK 1776的致病性增强。在所有病毒接种组中均发现体温升高。所有双重感染组的小腿都有肺部病变。但是，在接种BVDV的小牛，随后接种BoCV的6天后，病变最明显。肺部病变与轻度至中度的间质性肺炎一致，免疫组织化学证实存在BoCV抗原。我们的研究表明，BVDV-BoCV双重感染可能在BRD发病机理中起重要作用，并且感染之间的时间间隔似乎对病变的严重程度至关重要。结果表明，分离的BoCV OK 1776的致病性增强。在所有病毒接种组中均发现体温升高。所有双重感染组的小腿都有肺部病变。但是，在接种BVDV的小牛，随后接种BoCV的6天后，病变最明显。肺部病变与轻度至中度的间质性肺炎一致，免疫组织化学证实存在BoCV抗原。我们的研究表明，BVDV-BoCV双重感染可能在BRD发病机理中起重要作用，并且感染之间的时间间隔似乎对病变的严重程度至关重要。结果表明，分离的BoCV OK 1776的致病性增强。在所有病毒接种组中均发现体温升高。所有双重感染组的小腿都有肺部病变。但是，在接种BVDV的小牛，随后接种BoCV的6天后，病变最明显。肺部病变与轻度至中度的间质性肺炎一致，免疫组织化学证实存在BoCV抗原。我们的研究表明，BVDV-BoCV双重感染可能在BRD发病机理中起重要作用，并且感染之间的间隔时间似乎对病变的严重程度至关重要。在接种BVDV的小牛，然后接种BoCV 6 d后，皮损最明显。肺部病变与轻度至中度的间质性肺炎一致，免疫组织化学证实存在BoCV抗原。我们的研究表明，BVDV-BoCV双重感染可能在BRD发病机理中起重要作用，并且感染之间的时间间隔似乎对病变的严重程度至关重要。在接种BVDV的小牛，然后接种BoCV 6 d后，皮损最明显。肺部病变与轻度至中度的间质性肺炎一致，免疫组织化学证实存在BoCV抗原。我们的研究表明，BVDV-BoCV双重感染可能在BRD发病机理中起重要作用，并且感染之间的时间间隔似乎对病变的严重程度至关重要。