Woode G N, Reed D E, Runnels P L, Herrig M A, Hill H T
Vet Microbiol. 1982 Jul;7(3):221-40. doi: 10.1016/0378-1135(82)90036-0.
A transmissible agent (Breda agent) was isolated from a calf with diarrhea and shown to be infectious by inoculation orally into gnotobiotic and conventionally reared calves. The "Breda" agent had the morphology of a virus and possessed a hemagglutinin. Antigenic studies showed the virus to be antigenically different from bovine coronavirus, parainfluenza 3 virus, bovine rotavirus, bovine parvovirus and bovine pestivirus (BVD). Attempts to culture the virus in cell or organ cultures or in embryonated eggs, were unsuccessful. The virus was either spherical or kidney shaped, with 7-9 nm peplomers on the surface. A few particles possessed coronavirus processes of 17-20 nm, but these were arranged irregularly and were thought to be tissue debris. Three out of eight experimental calves developed severe diarrhea and the lesions in the small and large intestines were similar to those reported for coronavirus. The virus replicated in the jejunal and ileal regions of the small intestine and in the spiral colon, as judged by immunofluorescence. The virus multiplied in all experimental calves and was excreted in the feces; excretion correlating with the onset of diarrhea or a change in the appearance of the feces. There was little or no malabsorption measured by the uptake of D-xylose and the fact that infection of both the crypt and villus epithelial cells was observed, suggests that the pathogenesis may be different from rotavirus and coronavirus. Fourteen of forty seven calves in the outbreak were infected with the virus, virus was not identified in other farm outbreaks of the disease.
从一头腹泻小牛中分离出一种可传播因子（布雷达因子），通过口服接种到无菌和常规饲养的小牛中证明具有传染性。“布雷达”因子具有病毒形态并拥有一种血凝素。抗原研究表明该病毒在抗原性上与牛冠状病毒、副流感3型病毒、牛轮状病毒、牛细小病毒和牛瘟病毒（牛病毒性腹泻病毒）不同。尝试在细胞或器官培养物或鸡胚中培养该病毒均未成功。该病毒呈球形或肾形，表面有7 - 9纳米的纤突。少数颗粒具有17 - 20纳米的冠状病毒样突起，但这些突起排列不规则，被认为是组织碎片。八头实验小牛中有三头出现严重腹泻，小肠和大肠的病变与冠状病毒报道的相似。通过免疫荧光判断，该病毒在小肠的空肠和回肠区域以及螺旋结肠中复制。该病毒在所有实验小牛中增殖并随粪便排出；排泄与腹泻发作或粪便外观变化相关。通过D - 木糖吸收测量几乎没有吸收不良，并且观察到隐窝和绒毛上皮细胞均被感染，这表明其发病机制可能与轮状病毒和冠状病毒不同。此次疫情爆发的47头小牛中有14头感染了该病毒，在其他农场的该病疫情中未鉴定出该病毒。
