朊病毒之谜

苏黎世—最终导致370万头牛被扑杀、重创英国畜牧业的疯牛病爆发极为隐秘。1986年,一头英国母牛染上了一种未知的脑病。一年后,检查表明这头牛的大脑被大量小液泡腐蚀,形成海绵状的形态,于是这种病的学名被称为牛海绵状脑病。几个月之内,这种病开始在全英国出现。

一种类似的被称为痒病的疾病在羊中间流行,但此前从未在牛身上发现症状。而在整个20世纪,一种几乎完全相同的致命疾病——库鲁病(kuru)在巴布亚新几内亚土著居民中间肆虐。库鲁病和痒病都是传染病。

库鲁病通过食人习俗传播,巴布亚新几内亚直到20世纪50年代一直有这种习惯。类似地,在英国和其他地方,健康的牛被喂以用病牛骨肉制作的斯料。由此引发的家畜传染病影响了28万多头牛。在1992年疯牛病高发期,每周都有近1000头牛报告发病。

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