Characterization of epidemic diarrhea outbreaks associated with bovine torovirus in adult cows
Characterization of epidemic diarrhea outbreaks associated with bovine torovirus in adult cows
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DOI：
10.1007/s00705-011-1183-9
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发表时间：
2012-03-01
影响因子：
2.7
通讯作者：
Tsunemitsu, Hiroshi
中科院分区：
文献类型：
--
作者：
Aita, Tsunehiko;Kuwabara, Masaki;Tsunemitsu, Hiroshi
牛圆环病毒（BToV）是公认的犊牛肠道病原体，但其在成年奶牛腹泻和流行病学特征的病因学作用尚不清楚。2007-2008年，日本新泻县3个奶牛场发生3起成年奶牛流行性腹泻疫情。BToV是在这些爆发中检测到的唯一肠道病原体，如通过电子显微镜、逆转录PCR、粪便样本的细菌和寄生虫检测以及配对血清的抗体检测所确定的。3起疫情的流行病学特征与牛冠状病毒感染相似，只是没有出现血性腹泻，腹泻在大多数成年母牛中传播，但不会在犊牛中传播，在数天内，腹泻持续3-5天，并伴有厌食症。在其中两次暴发中还观察到产奶量减少和轻微的呼吸道症状。对BToV核衣壳、刺突和血凝素酯酶（HE）基因的核苷酸序列分析显示，从每次爆发中检测到的BToV毒株与日本BToV毒株Aichi/2004之间存在密切的相关性。此外，我们使用人直肠肿瘤细胞系从粪便样品中分离出BToV株，命名为新泻（TC）。该分离株和Aichi/2004的序列分析表明，这两种菌株都具有通过细胞培养适应发生的在30区域中缺失的截短的HE基因。通过电子显微镜在这些培养的菌株中未观察到被认为是由病毒颗粒上的HE蛋白形成的短突起。综上所述，这些结果表明，BToV引起成年奶牛流行性腹泻，应纳入成年奶牛腹泻的鉴别诊断。此外，我们的研究结果表明，BToV的HE蛋白可能不是病毒复制所必需的。
Bovine torovirus (BToV) is recognized as an enteric pathogen of calves, but its etiological role in diarrhea and epidemiological characterization in adult cows remain unclear. In 2007-2008, three outbreaks of epidemic diarrhea occurred in adult cows at three dairy farms in Niigata Prefecture, Japan. BToV was the only enteric pathogen detected in these outbreaks, as determined by electron microscopy, reverse transcription-PCR, bacteria and parasite tests of fecal samples, and antibody tests with paired sera. The epidemiological features of the three outbreaks were similar to those of bovine coronavirus infection, except for the absence of bloody diarrhea, with diarrhea spreading among most adult cows, but not in calves, within several days and diarrhea lasting for 3-5 days with anorexia. Decreased milk production and mild respiratory symptoms were also observed in two of the outbreaks. Nucleotide sequence analysis of the BToV nucleocapsid, spike, and hemagglutinin-esterase (HE) genes revealed a close relatedness among the detected BToV strains from each outbreak and those of Japanese BToV strain Aichi/2004. Furthermore, we isolated a BToV strain, designated Niigata (TC), from a fecal sample using a human rectal tumor cell line. Sequence analysis of this isolate and Aichi/2004 indicated that both strains have truncated HE genes with deletions in the 30 region that occurred through cell culture-adaptation. The short projections that are believed to be formed by the HE protein on virus particles were not observed in these cultured strains by electron microscopy. Taken together, these results suggest that BToV causes epidemic diarrhea in adult cows and should be included in the differential diagnosis of diarrhea in adult cows. In addition, our findings indicate that the HE protein of BToV may not be necessary for viral replication.