Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey 08544, USA.
Evolution. 2012 Feb;66(2):391-401. doi: 10.1111/j.1558-5646.2011.01461.x. Epub 2011 Oct 3.
Many pathogens and parasites are transmitted through hosts that differ in species, sex, genotype, or immune status. In addition, virulence (here defined as disease-induced mortality) and transmission can vary during the infectious period within hosts of different state. Most models of virulence evolution assume that transmission and virulence are constant over the infectious period and that the host population is homogenous. Here, we examine a multispecies susceptible-infected-recovered (SIR) model where transmission occurs within and between species, and transmission and virulence varied during the infectious period. This allows us to understand virulence evolution in a broader range of situations that characterize many emerging diseases. Because emerging pathogens are by definition new to their host populations, they should be expected to rapidly adapt after emergence. We illustrate these evolutionary effects using the framework of adaptive dynamics to examine how virulence evolves after emergence in response to the relative strength of selection on pathogen fitness and mutational variance for virulence. We illustrate the role of evolution by simulating adaptive walks to an evolutionarily stable virulence. We found that the magnitude of between-species transmission and the relative timing of transmission and mortality across species were of primary importance for determining the evolutionarily stable virulence.
许多病原体和寄生虫通过在物种、性别、基因型或免疫状态上不同的宿主进行传播。此外，在不同状态的宿主的感染期内，毒力（这里定义为疾病引起的死亡率）和传播能力可能会有所不同。大多数毒力进化模型假设在感染期内传播和毒力是恒定的，并且宿主群体是同质的。在这里，我们研究了一个多物种易感染-恢复（SIR）模型，其中在物种内和物种间发生传播，并且在感染期内传播和毒力发生变化。这使我们能够在更广泛的情况下理解许多新兴疾病的毒力进化。由于新兴病原体对其宿主群体来说是新的，因此应该预期它们在出现后会迅速适应。我们使用适应性动态的框架来说明这些进化效应，以研究在出现后，病原体适应性和毒力突变方差对病原体适应性的相对选择压力下，毒力如何进化。我们通过模拟适应性进化到一个进化稳定的毒力来演示进化的作用。我们发现，种间传播的幅度和种间传播和死亡率的相对时间对确定进化稳定的毒力至关重要。
