Nathanson N, Wilesmith J, Griot C
Department of Microbiology, University of Pennsylvania Medical Center, Philadelphia, USA.
Am J Epidemiol. 1997 Jun 1;145(11):959-69. doi: 10.1093/oxfordjournals.aje.a009064.
Bovine spongiform encephalopathy (BSE) is a transmissible spongiform encephalopathy (TSE) or prion disease of cattle first recognized in 1986 in the United Kingdom, where it produced a common source epidemic that peaked in January 1993 and has subsided markedly since that time. The epidemic began simultaneously at many geographic locations and was traced to contamination of meat and bone meal (MBM), a dietary supplement prepared from rendering of slaughterhouse offal. It appears that the epidemic was initiated by the presence of the agent of scrapie (a long-standing TSE of sheep) that was first transmitted to cattle, beginning in the early 1980s, when most rendering plants abandoned the use of organic solvents in the preparation of MBM. The epidemic was probably accelerated by the recycling of infected bovine tissues prior to the recognition of BSE. To terminate the epidemic, a prohibition on the feeding of ruminant-derived protein to ruminants was introduced in the United Kingdom in July 1988. The ruminant feed ban accounts for the decline of the epidemic after an interval of about 5 years, approximately equivalent to the average incubation period of BSE. Relatively few cases of BSE have occurred in cattle born after 1993, and it is predicted that the epidemic will terminate about the year 2000 based on an extrapolation of the present declining curve. A comparison of data from the United Kingdom with data from relatively low incidence countries, such as Switzerland, indicates that this epidemic has been mainly confined to the United Kingdom because of a unique concatenation of risk factors, including: 1) a high ratio of sheep to cattle; 2) a relatively high rate of endemic scrapie; 3) the heavy feeding of MBM to dairy cattle; and 4) changes in the rendering process used to prepare MBM. Recently, cases of a variant form of Creutzfeldt-Jakob disease (a TSE of humans) have been reported in the United Kingdom. These cases, at least 10 of which had onset in 1994-1995, are distinguished by their occurrence in subjects under age 40 years, by their clinical presentation, and by their neurohistopathologic picture. The appearance of this novel disease and its concentration in the United Kingdom have raised the question that it might represent the transmission of BSE to humans. However, the cases gave no history indicating an unusual exposure to live cattle, to the preparation of beef products, or of dietary exposure to bovine tissues, and it remains to be determined whether they are associated with BSE.
牛海绵状脑病（BSE）是一种牛的传染性海绵状脑病（TSE）或朊病毒病，1986年首次在英国被确认。在英国，它引发了一场共同来源的疫情，该疫情于1993年1月达到顶峰，此后显著平息。疫情在许多地理位置同时爆发，并被追溯到肉骨粉（MBM）的污染，肉骨粉是一种由屠宰场废弃物加工而成的膳食补充剂。疫情似乎是由羊瘙痒病病原体（羊的一种长期存在的TSE）的存在引发的，这种病原体在20世纪80年代初开始首次传播给牛，当时大多数加工厂在制备肉骨粉时放弃了使用有机溶剂。在BSE被确认之前，受感染牛组织的回收利用可能加速了疫情的传播。为了终止疫情，英国于1988年7月禁止向反刍动物投喂反刍动物来源的蛋白质。反刍动物饲料禁令导致疫情在大约5年的间隔后下降，这大约相当于BSE的平均潜伏期。1993年以后出生的牛中发生的BSE病例相对较少，根据目前下降曲线的外推预测，疫情将在2000年左右终止。将英国的数据与瑞士等发病率相对较低的国家的数据进行比较表明，由于一系列独特的风险因素，这场疫情主要局限于英国，这些因素包括：1）羊与牛的比例高；2）地方性羊瘙痒病发病率相对较高；3）向奶牛大量投喂肉骨粉；4）制备肉骨粉所使用的加工过程的变化。最近，英国报告了变异型克雅氏病（一种人类TSE）病例。这些病例中至少有10例在1994 - 1995年发病，其特点是发病年龄在40岁以下、临床表现以及神经组织病理学特征。这种新型疾病的出现及其在英国的集中发生引发了一个问题，即它可能代表BSE向人类的传播。然而，这些病例没有表明有接触活牛、制备牛肉产品或通过饮食接触牛组织的异常暴露史，它们是否与BSE有关仍有待确定。
