Caraco Thomas, Glavanakov Stephan, Li Shengua, Maniatty William, Szymanski Boleslaw K
Department of Biological Sciences, University at Albany, NY 12222, USA.
Theor Popul Biol. 2006 Jun;69(4):367-84. doi: 10.1016/j.tpb.2005.12.004. Epub 2006 Jan 26.
When pathogen strains differing in virulence compete for hosts, spatial structuring of disease transmission can govern both evolved levels of virulence and patterns in strain coexistence. We develop a spatially detailed model of superinfection, a form of contest competition between pathogen strains; the probability of superinfection depends explicitly on the difference in levels of virulence. We apply methods of adaptive dynamics to address the interplay of spatial dynamics and evolution. The mean-field approximation predicts evolution to criticality; any small increase in virulence capable of dynamical persistence is favored. Both pair approximation and simulation of the detailed model indicate that spatial structure constrains disease virulence. Increased spatial clustering reduces the maximal virulence capable of single-strain persistence and, more importantly, reduces the convergent-stable virulence level under strain competition. The spatially detailed model predicts that increasing the probability of superinfection, for given difference in virulence, increases the likelihood of between-strain coexistence. When strains differing in virulence can coexist ecologically, our results may suggest policies for managing diseases with localized transmission. Comparing equilibrium densities from the pair approximation, we find that introducing a more virulent strain into a host population infected by a less virulent strain can sometimes reduce total host mortality and increase global host density.
当毒力不同的病原体菌株争夺宿主时，疾病传播的空间结构既能决定毒力的进化水平，也能决定菌株共存的模式。我们构建了一个空间细节丰富的重叠感染模型，重叠感染是病原体菌株之间竞争的一种形式；重叠感染的概率明确取决于毒力水平的差异。我们应用适应性动力学方法来研究空间动态与进化之间的相互作用。平均场近似预测进化至临界状态；任何能够动态持续存在的毒力小幅增加都受到青睐。配对近似和详细模型的模拟均表明，空间结构会限制疾病毒力。空间聚类的增加会降低单菌株持续存在所能达到的最大毒力，更重要的是，会降低菌株竞争下的收敛稳定毒力水平。空间细节丰富的模型预测，对于给定的毒力差异，增加重叠感染的概率会增加菌株间共存的可能性。当毒力不同的菌株能够在生态上共存时，我们的结果可能为管理局部传播疾病提供策略。通过比较配对近似的平衡密度，我们发现将一个毒力更强的菌株引入受毒力较弱菌株感染的宿主种群中，有时可以降低宿主的总死亡率并增加全球宿主密度。
