A quantitative test of the relationship between parasite dose and infection probability across different host-parasite combinations
A quantitative test of the relationship between parasite dose and infection probability across different host-parasite combinations
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DOI：
10.1098/rspb.2007.1544
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发表时间：
2008-04-07
影响因子：
4.7
通讯作者：
Ebert, Dieter
中科院分区：
文献类型：
--
作者：
Ben-Ami, Frida;Regoes, Roland R.;Ebert, Dieter
流行病学模型通常假设在单位时间内感染的易感个体的数量取决于宿主的密度和寄生虫的浓度（即质量作用原理）。然而，实证研究发现，由于生物和非生物因素，如季节性，宿主种群的空间结构和宿主的异质性，免疫力和易感性显着偏离这一假设。在本文中，我们研究了细菌性内寄生虫多枝巴斯德氏菌的剂量水平对其宿主大型水蚤感染率的影响。使用7个宿主克隆和2个寄生虫分离株，我们测量了感染宿主暴露于8种不同寄生虫剂量后的分数，以确定不同宿主克隆-寄生虫分离株组合的感染过程中是否存在变异。在五个组合中，一个明显的剂量依赖性的感染patterns. Using一个似然方法，我们比较这五个组合的感染数据的三个数学模型的拟合：一个大规模的行动模型，寄生虫拮抗模型（即寄生虫剂量的增加导致不成比例的增加，每个主机的感染率）和异质主机模型。我们发现，主机异质性模型，其中我们假设存在的非遗传性表型差异的主机affiliatibilities寄生虫，提供了最佳的拟合。我们的分析表明，在14个宿主克隆-寄生虫分离物组合中，有5个导致明显感染，非遗传宿主异质性起着重要作用。
Epidemiological models generally assume that the number of susceptible individuals that become infected within a unit of time depends on the density of the hosts and the concentration of parasites (i.e. mass-action principle). However, empirical studies have found significant deviations from this assumption due to biotic and abiotic factors, such as seasonality, the spatial structure of the host population and host heterogeneity with respect to immunity and susceptibility. In this paper, we examine the effect of the dose level of the bacterial endoparasite Pasteuria ramosa on the infection rate of its host, the water flea Daphnia magna. Using seven host clones and two parasite isolates, we measure the fraction of infected hosts after exposure to eight different parasite doses to determine whether there is variation in the infection process across different host clone-parasite isolate combinations. In five combinations, a pronounced dose-dependent infection pattern was found. Using a likelihood approach, we compare the infection data of these five combinations to the fit of three mathematical models: a mass-action model, a parasite antagonism model (i.e. an increase in the parasite dose leads to an under-proportionate increase in the infection rate per host) and a heterogeneous host model. We found that the host heterogeneity model, in which we assumed the existence of non-inherited phenotypic differences in host susceptibilities to the parasite, provides the best fit. Our analysis suggests that among 5 out of the 14 host clone-parasite isolate combinations that resulted in appreciable infections, non-genetic host heterogeneity plays an important role.