Matthews L, Woolhouse M E, Hunter N
Centre for Tropical Veterinary Medicine, University of Edinburgh, Midlothian, UK.
Proc Biol Sci. 1999 May 22;266(1423):1085-90. doi: 10.1098/rspb.1999.0747.
The basic reproduction number R0 provides a quantitative assessment of the ability of an infectious agent to invade a susceptible host population. A mathematical expression for R0 is derived based on a recently developed model for the spread of scrapie through a flock of sheep. The model incorporates sheep demography, a long and variable incubation period, genetic variation in susceptibility to scrapie, and horizontal and vertical routes of transmission. The sensitivity of R0 to a range of epidemiologically important parameters is assessed and the effects of genetic variation in susceptibility are examined. A reduction in the frequency of the susceptibility allele reduces R0 most effectively when the allele is recessive, whereas inbreeding may increase R0 when the allele is recessive, increasing the chance of an outbreak. Using this formulation, R0 is calculated for an outbreak of scrapie in a flock of Cheviot sheep.
基本再生数R0提供了对感染因子侵入易感宿主群体能力的定量评估。基于最近开发的一个关于羊瘙痒病在一群绵羊中传播的模型，推导出了R0的数学表达式。该模型纳入了绵羊种群统计学、长且可变的潜伏期、对羊瘙痒病易感性的遗传变异以及水平和垂直传播途径。评估了R0对一系列流行病学重要参数的敏感性，并研究了易感性遗传变异的影响。当易感等位基因是隐性时，该等位基因频率的降低最有效地降低R0，而当该等位基因是隐性时，近亲繁殖可能会增加R0，增加暴发的可能性。使用这种公式，计算了一群切维厄特羊中羊瘙痒病暴发的R0。
