Kao R R, Gravenor M B, Baylis M, Bostock C J, Chihota C M, Evans J C, Goldmann W, Smith A J A, McLean A R
Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK.
Science. 2002 Jan 11;295(5553):332-5. doi: 10.1126/science.1067475. Epub 2001 Nov 22.
Because there is a theoretical possibility that the British national sheep flock is infected with bovine spongiform encephalopathy (BSE), we examined the extent of a putative epidemic. An age cohort analysis based on numbers of infected cattle, dose responses of cattle and sheep to BSE, levels of exposure to infected feed, and number of BSE-susceptible sheep in the United Kingdom showed that at the putative epidemic peak in 1990, the number of cases of BSE-infected sheep would have ranged from fewer than 10 to about 1500. The model predicts that fewer than 20 clinical cases of BSE in sheep would be expected in 2001 if maternal transmission occurred at a rate of 10%. Although there are large uncertainties in the parameter estimates, all indications are that current prevalence is low; however, a simple model of flock-to-flock BSE transmission shows that horizontal transmission, if it has occurred, could eventually cause a large epidemic.
由于存在英国全国羊群感染牛海绵状脑病(BSE)的理论可能性,我们研究了假定疫情的规模。基于感染牛的数量、牛和羊对BSE的剂量反应、接触受感染饲料的程度以及英国BSE易感羊的数量进行的年龄队列分析表明,在1990年假定的疫情高峰期,BSE感染羊的病例数将在不到10例至约1500例之间。该模型预测,如果母源传播发生率为10%,2001年预计绵羊中BSE临床病例数将少于20例。尽管参数估计存在很大不确定性,但所有迹象表明目前的流行率很低;然而,一个羊群间BSE传播的简单模型表明,如果发生水平传播,最终可能导致大规模疫情。