Parasite transmission modes and the evolution of virulence
Parasite transmission modes and the evolution of virulence
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DOI：
10.1111/j.0014-3820.2001.tb00754.x
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发表时间：
2001-12-01
期刊：
影响因子：
3.3
通讯作者：
Day, T
中科院分区：
文献类型：
--
作者：
Day, T
提出了一个数学模型，探讨当只有单一寄生虫菌株可以感染每个宿主时，水平传播寄生虫的传播模式与毒力进化之间的关系。该模型是通过将寄生虫传播分解为两个过程来构建的，即宿主之间的接触率和每次接触的传播概率。这些传播率组成部分以及寄生虫总死亡率在感染过程中可以发生变化。提出了一种一般的进化稳定条件，将毒力对寄生虫适应性的影响分为三个部分：繁殖力收益、死亡率成本。和发病成本。先前理论的这种扩展使我们能够探索各种传播模式的进化后果。然后，我将注意力集中在一种特殊情况上，其中寄生虫密度在感染期间保持大致恒定，并且我展示了传播模式影响毒力进化的两种重要方式：通过对寄生虫施加不同的发病成本以及通过改变感染期间寄生虫繁殖的时间表。两者均通过示例进行说明。其中一项研究检验了媒介传播的寄生虫比非媒介传播的寄生虫毒性更强的假设（Ewald 1994）。该假设的有效性取决于这两种效应相互作用的方式，并且不一定普遍成立。
A mathematical model is presented that explores the relationship between transmission patterns and the evolution of virulence for horizontally transmitted parasites when only a single parasite strain can infect each host. The model is constructed by decomposing parasite transmission into two processes, the rate of contact between hosts and the probability of transmission per contact. These transmission rate components, as well as the total parasite mortality rate, are allowed to vary over the course of an infection. A general evolutionarily stable condition is presented that partitions the effects of virulence on parasite fitness into three components: fecundity benefits, mortality costs. and morbidity costs. This extension of previous theory allows us to explore the evolutionary consequences of a variety of transmission patterns. I then focus attention on a special case in which the parasite density remains approximately constant during an infection, and I demonstrate two important ways in which transmission modes can affect virulence evolution: by imposing different morbidity costs on the parasite and by altering the scheduling of parasite reproduction during an infection. Both are illustrated with examples. including one that examines the hypothesis that vector-borne parasites should be more virulent than non-vector-borne parasites (Ewald 1994). The validity of this hypothesis depends upon the way in which these two effects interact, and it need not hold in general.