Stevenson M A, Wilesmith J W, Ryan J B, Morris R S, Lockhart J W, Lin D, Jackson R
EpiCentre, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand.
Vet Rec. 2000 Sep 23;147(13):349-54. doi: 10.1136/vr.147.13.349.
The objectives of this study were first to determine the cumulative incidence of bovine spongiform encephalopathy (BSE) in the British cattle population from July 1986 to June 1997, secondly, to identify individual animal-associated risk factors that influenced the age of onset of clinical signs in confirmed BSE cases, and, thirdly, to assess the effectiveness of the measures introduced to control BSE during the epidemic. The analyses were based on the population of British cattle at risk, derived from agricultural census data collected between 1986 and 1996, and BSE case data collected up to June 30, 1997. The unit of interest was individual adult cattle recorded on annual agricultural censuses between June 1986 and June 1996. Univariate and multivariate survival analysis techniques were used to characterise the age of onset of clinical signs. In total 167,366 cases of BSE were diagnosed in Great Britain up to June 30, 1997. The cumulative incidence of BSE between July 1986 and June 1997 was 1.10 (95 per cent confidence interval [CI] 1.09 to 1.10) cases per 100 adult cattle at risk. Cattle from the South east, South west and Eastern regions of England had 4.26 to 5.96 (95 per cent CI 4.15 to 6.14) times as great a monthly hazard of being confirmed with BSE as cattle from Scotland. Compared with cattle born before June 1985, those born between July 1987 and June 1988 had 22.5 (95 per cent CI 22.1 to 22.8) times the monthly hazard of being confirmed with BSE, whereas those born in the 12 months after July 1988 had only 7.39 (95 per cent CI 7.24 to 7.54) times the monthly hazard of being confirmed with BSE. This reduction in hazard was directly attributable to the ban on the use of ruminant protein as a feed instituted in July 1988. Successive cohorts from 1989 to 1991 experienced further reductions in the hazard of experiencing BSE. The additional decrease in hazard observed for the 1990 cohort may be attributed to the effect of the Specified Bovine Offal ban instituted in September 1990.
本研究的目的，一是确定1986年7月至1997年6月英国牛群中牛海绵状脑病（BSE）的累积发病率；二是识别影响确诊BSE病例临床症状发病年龄的个体动物相关风险因素；三是评估疫情期间为控制BSE所采取措施的有效性。分析基于1986年至1996年收集的农业普查数据得出的英国有风险牛群，以及截至1997年6月30日收集的BSE病例数据。研究对象是1986年6月至1996年6月年度农业普查记录的成年牛个体。采用单变量和多变量生存分析技术来描述临床症状的发病年龄。截至1997年6月30日，英国共诊断出167,366例BSE病例。1986年7月至1997年6月期间，BSE的累积发病率为每100头有风险成年牛1.10例（95%置信区间[CI]1.09至1.10）。英格兰东南部、西南部和东部地区的牛被确诊感染BSE的月度风险是苏格兰牛的4.26至5.96倍（95%CI 4.15至6.14）。与1985年6月之前出生的牛相比，1987年7月至1988年6月之间出生的牛被确诊感染BSE的月度风险是其22.5倍（95%CI 22.1至22.8），而1988年7月之后12个月内出生的牛被确诊感染BSE的月度风险仅为其7.39倍（95%CI 7.24至7.54）。这种风险降低直接归因于1988年7月实施的反刍动物蛋白饲料禁令。1989年至1991年的连续队列经历了BSE风险的进一步降低。1990年队列观察到的风险额外降低可能归因于1990年9月实施的特定牛下水禁令的影响。
