The etiological agents involved in a bovine respiratory disease (BRD) outbreak were investigated in a dairy heifer calf rearing unit from southern Brazil. A battery of PCR assays was performed to detect the most common viruses and bacteria associated with BRD, such as bovine viral diarrhea virus (BVDV), bovine respiratory syncytial virus (BRSV), bovine alphaherpesvirus 1 (BoHV-1), bovine coronavirus (BCoV), bovine parainfluenza virus 3 (BPIV-3), Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, and Mycoplasma bovis. Bronchoalveolar lavage fluid (BALF) samples were taken from 21 heifer calves (symptomatic n = 15; asymptomatic n = 6) that, during the occurrence of the BDR outbreak, were aged between 6 and 90 days. At least one microorganism was detected in 85.7 % (18/21) of the BALF samples. Mixed infections were more frequent (72.2 %) than single infections (27.7 %). The interactions between viruses and bacteria were the most common in coinfections (55.5 %). The frequencies of BRD agents were 38.1 % for BRSV, 28.6 % for BVDV, 33.3 % for BCoV, 42.85 % for P. multocida, 33.3 % for M. bovis, and 19 % for H. somni. BoHV-1, BPIV-3, and M. haemolytica were not identified in any of the 21 BALF samples. Considering that BALF and not nasal swabs were analyzed, these results demonstrate the etiological multiplicity that may be involved in BRD outbreaks in dairy calves.

中文翻译：

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奶牛饲养单位牛呼吸道疾病暴发的病因涉及微生物多样性。

在巴西南部的一个乳牛犊牛饲养单元中调查了与牛呼吸道疾病（BRD）爆发有关的病原体。进行了一系列的PCR检测，以检测与BRD相关的最常见病毒和细菌，例如牛病毒性腹泻病毒（BVDV），牛呼吸道合胞病毒（BRSV），牛α疱疹病毒1（BoHV-1），牛冠状病毒（BCoV） ），牛副流感病毒3（BPIV-3），溶血曼海姆氏菌，多杀巴斯德氏菌，索氏嗜血杆菌和牛支原体。支气管肺泡灌洗液（BALF）样品取自21头小母牛（有症状的n = 15；无症状的n = 6），它们在BDR爆发期间年龄在6至90天之间。在85.7％（18/21）的BALF样品中检测到至少一种微生物。混合感染更为常见（72。2％）比单一感染（27.7％）高。病毒和细菌之间的相互作用在合并感染中最为常见（55.5％）。BRD剂的频率对于BRSV为38.1％，对于BVDV为28.6％，对于BCoV为33.3％，对于多杀毕赤酵母为42.85％，对于牛分枝杆菌为33.3％，对于Somni。Somni为19％。在21个BALF样品中均未鉴定出BoHV-1，BPIV-3和溶血支原体。考虑到已对BALF而非鼻拭子进行了分析，这些结果证明了奶牛犊牛BRD暴发可能与病原学多样性有关。在21个BALF样品中均未发现溶血性阿米巴。考虑到已对BALF而非鼻拭子进行了分析，这些结果证明了可能与奶牛BRD爆发有关的病因学多样性。在21个BALF样品中均未发现溶血性阿米巴。考虑到已对BALF而非鼻拭子进行了分析，这些结果证明了奶牛犊牛BRD暴发可能与病原学多样性有关。