Cutlip R C, Miller J M, Lehmkuhl H D
United States Department of Agriculture, National Animal Disease Center, Ames, Iowa 50010, USA.
J Comp Pathol. 1997 Oct;117(3):271-5. doi: 10.1016/s0021-9975(97)80022-9.
Scrapie and bovine spongiform encephalopathy are similar chronic neurodegenerative diseases of sheep and cattle. An earlier study showed that, on first passage in cattle, a US scrapie agent caused an encephalopathy that was distinct from bovine spongiform encephalopathy (BSE). The present report describes a second passage in cattle, carried out because diseases caused by the spongiform encephalopathy agents often change in character with additional passages in abnormal hosts. For this work, young calves were inoculated intracerebrally with a pooled suspension of brain from cattle that had died of encephalopathy after experimental inoculation with brain from scrapie-affected sheep. The second passage disease was essentially identical with the first passage disease, as judged by clinical signs, histopathological findings and distribution of "prion protein scrapie" (PrPsc). This represents additional evidence to suggest that the US sheep scrapie agent tested is incapable of causing BSE in cattle.
羊瘙痒病和牛海绵状脑病是绵羊和牛的类似慢性神经退行性疾病。一项早期研究表明，美国的一种羊瘙痒病病原体首次接种到牛身上时，引发了一种与牛海绵状脑病（BSE）不同的脑病。本报告描述了在牛身上进行的第二代接种，之所以这样做是因为海绵状脑病病原体所引发的疾病往往会随着在异常宿主体内的进一步接种而改变特征。在这项研究中，将死于实验性接种感染羊瘙痒病绵羊脑的牛的脑匀浆悬浮液经脑内接种给幼龄犊牛。根据临床症状、组织病理学发现以及“瘙痒病朊病毒蛋白”（PrPsc）的分布判断，第二代接种所引发的疾病与第一代接种引发的疾病基本相同。这进一步证明，所检测的美国绵羊瘙痒病病原体无法在牛身上引发牛海绵状脑病。
