Matthews L, Haydon D T, Shaw D J, Chase-Topping M E, Keeling M J, Woolhouse M E J
Centre for Tropical Veterinary Medicine, University of Edinburgh, Easter Bush, Roslin EH25 9RG, UK.
Proc Biol Sci. 2003 Aug 22;270(1525):1659-66. doi: 10.1098/rspb.2003.2429.
We present a model of a control programme for a disease outbreak in a population of livestock holdings. Control is achieved by culling infectious holdings when they are discovered and by the pre-emptive culling of livestock on holdings deemed to be at enhanced risk of infection. Because the pre-emptive control programme cannot directly identify exposed holdings, its implementation will result in the removal of both infected and uninfected holdings. This leads to a fundamental trade-off: increased levels of control produce a greater reduction in transmission by removing more exposed holdings, but increase the number of uninfected holdings culled. We derive an expression for the total number of holdings culled during the course of an outbreak and demonstrate that there is an optimal control policy, which minimizes this loss. Using a metapopulation model to incorporate local clustering of infection, we examine a neighbourhood control programme in a locally spreading outbreak. We find that there is an optimal level of control, which increases with increasing basic reproduction ratio, R(0); moreover, implementation of control may be optimal even when R(0) < 1. The total loss to the population is relatively insensitive to the level of control as it increases beyond the optimal level, suggesting that over-control is a safer policy than under-control.
我们提出了一种针对畜牧场群体中疾病爆发的控制程序模型。通过在发现感染场时扑杀感染场以及对被认为感染风险增加的场进行预防性扑杀来实现控制。由于预防性控制程序无法直接识别受感染场，其实施将导致感染场和未感染场都被清除。这导致了一个基本的权衡：更高的控制水平通过清除更多受感染场而使传播减少得更多，但会增加被扑杀的未感染场数量。我们推导出了疫情期间被扑杀场总数的表达式，并证明存在一种最优控制策略，可将这种损失降至最低。使用一个集合种群模型来纳入感染的局部聚集情况，我们研究了局部传播疫情中的邻里控制程序。我们发现存在一个最优控制水平，它随着基本再生数(R(0))的增加而增加；此外，即使(R(0) < 1)，实施控制也可能是最优的。随着控制水平超过最优水平，种群的总损失对其相对不敏感，这表明过度控制比控制不足是更安全的策略。
