Dose relationships can exacerbate, mute, or reverse the impact of heterospecific host density on infection prevalence
Dose relationships can exacerbate, mute, or reverse the impact of heterospecific host density on infection prevalence
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DOI：
10.1002/ecy.3422
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发表时间：
2021-07-12
期刊：
影响因子：
4.8
通讯作者：
Duffy, Meghan A.
中科院分区：
文献类型：
--
作者：
Clay, Patrick A.;Cortez, Michael H.;Duffy, Meghan A.
个人被感染的可能性取决于其所处的社区。对于环境传播的寄生虫，宿主群落组成可以改变宿主密度，宿主在环境中遇到的寄生虫密度，以及宿主随后暴露的剂量。虽然一些多宿主理论结合了这些因素中的一些（例如，由于寄生虫与宿主之间的相互竞争关系（即寄生虫与宿主之间的竞争关系），目前没有考虑寄生虫接触剂量与每繁殖体感染性之间的非线性关系（剂量-感染性关系）、接触剂量与受感染宿主死亡率之间的非线性关系（剂量-死亡率关系）以及接触剂量与寄生虫繁殖体排泄之间的非线性关系（剂量-排泄关系）。这使得很难预测宿主物种对彼此感染可能性的影响。为了理解这些非线性剂量关系对多宿主社区的影响，我们首先对已发表的剂量-感染性实验进行了荟萃分析，以量化加速，线性或减速剂量-感染性关系的比例;我们发现大多数实验都表现出减速剂量-感染性关系。然后，我们探讨了剂量-感染性，剂量-死亡率和剂量-排泄关系如何可能改变异源宿主密度对感染性繁殖体密度，感染流行率和使用双宿主，单寄生虫模型的焦点宿主密度的影响。我们发现，剂量关系通过负反馈回路降低了异源宿主密度对繁殖体密度和感染流行率的影响程度（减速剂量-感染性关系、正剂量-死亡率关系和负剂量-排泄关系），或通过正反馈回路增加异源宿主密度对感染流行率的影响程度（加速剂量-感染性关系和正剂量-排泄关系）。此外，正剂量-死亡率关系导致传统上减少疾病的宿主（例如，低竞争力，强大的竞争对手）增加感染率，反之亦然。最后，我们发现，剂量关系可以创造积极的反馈回路，促进友好的竞争（即，增加的异种密度对焦点宿主密度具有积极影响，因为疾病的减少超过种间竞争的负面影响）。这表明，如果不考虑剂量关系，我们可能会错误地预测异源宿主相互作用的影响，从而宿主群落组成，对环境传播的寄生虫。
The likelihood an individual becomes infected depends on the community in which it is embedded. For environmentally transmitted parasites, host community composition can alter host density, the density of parasites that hosts encounter in the environment, and the dose to which hosts are subsequently exposed. While some multi-host theory incorporates some of these factors (e.g., competition among hosts), it does not currently consider the nonlinear relationships between parasite exposure dose and per-propagule infectivity (dose-infectivity relationships), between exposure dose and infected host mortality (dose-mortality relationships), and between exposure dose and parasite propagule excretion (dose-excretion relationships). This makes it difficult to predict the impact of host species on one another's likelihood of infection. To understand the implications of these nonlinear dose relationships for multi-host communities, we first performed a meta-analysis on published dose-infectivity experiments to quantify the proportion of accelerating, linear, or decelerating dose-infectivity relationships; we found that most experiments demonstrated decelerating dose-infectivity relationships. We then explored how dose-infectivity, dose-mortality, and dose-excretion relationships might alter the impact of heterospecific host density on infectious propagule density, infection prevalence, and density of a focal host using two-host, one-parasite models. We found that dose relationships either decreased the magnitude of the impact of heterospecific host density on propagule density and infection prevalence via negative feedback loops (decelerating dose-infectivity relationships, positive dose-mortality relationships, and negative dose-excretion relationships), or increased the magnitude of the impact of heterospecific host density on infection prevalence via positive feedback loops (accelerating dose-infectivity relationships and positive dose-excretion relationships). Further, positive dose-mortality relationships resulted in hosts that traditionally decrease disease (e.g., low competence, strong competitors) increasing infection prevalence, and vice versa. Finally, we found that dose relationships can create positive feedback loops that facilitate friendly competition (i.e., increased heterospecific density has a positive effect on focal host density because the reduction in disease outweighs the negative effects of interspecific competition). This suggests that without taking dose relationships into account, we may incorrectly predict the effect of heterospecific host interactions, and thus host community composition, on environmentally transmitted parasites.