The ecology of parasites with complex life cycles in multi-host systems: Echinococcus multilocularis transmission dynamics at multiple spatial scales

多宿主系统中具有复杂生命周期的寄生虫的生态学：多房棘球蚴在多个空间尺度上的传播动力学

• 批准号: RGPIN-2016-04077
• 负责人: Massolo, Alessandro
• 金额: $ 2.04万
• 依托单位: University of Calgary
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=614825
• 关键词: ecology; parasites; complex; life; cycles

The ecology of parasites with both definitive (DH) and obligatory intermediate hosts (IH) is characterized not only by host-parasite interactions, but also by multifaceted interactions between DH and IH, that depend on the ecological relations (i.e. predator-prey) between host species and on the diversity of host communities. Echinococcus multilocularis (Em) is a tapeworm parasite of wild and domestic canids (DH) whose eggs are shed in the environment through feces and if accidentally ingested they can infect IHs (mostly rodents), or even humans (in which can cause alveolar echinococcosis, AE, a fatal disease). DHs get infected predating on infectious IHs. Modeling the dynamics of these host-parasite systems advances the knowledge on properties of complex biological systems and helps predicting their ‘behavior’ that, in case of parasite cycles, may dramatically affect ecosystem and human health. Yet, data on host-parasite and on DH and IH interactions are still scarce limiting reliability of existing models. Moreover, these models are commonly compartment population-based, describing simplified systems with only one DH and one IH species. In reality, these parasite cycles usually involve many host species with great individual diversity (DH feeding ecology and response to infections) and high spatial heterogeneity of infections in both DH and IH. Ecological processes (e.g., prey selection, dilution effect) at IH and DH spatio-temporal scales affect transmission dynamics, and only spatially explicit models can describe the emergence of properties at these scales in particular for parasites in highly heterogeneous environments and host assemblages. The objective of my research program is to describe processes and properties at different scales in host populations, and study how these affect transmission dynamics within multi-hosts systems, using Em as model. The study will be conducted in 10 areas in Calgary where the DH ecology will be studied applying GPS-collars to 4 coyotes per area. Their movements will be monitored for up to 18 months, and their feces collected and analyzed to assess their diet and infection status. Prey assemblages, infections in IHs and their associations with predator-prey interactions will be assessed in the same areas. I will then combine system dynamics and agent based modelling approaches using individual coyotes as agents moving in a virtual heterogeneous landscape with infections in IHs represented in grid cells. Infections dynamics within IH species (in cells), rate of parasite transmission from DHs (agents) to IHs (cells) and viceversa, and within individual DHs will be described by sets of differential equations. Through model simulations I will not only shed light on the properties and dynamics of this complex host-parasite system, but also provide data and scenarios to support decision making in the management of possible outbreaks of AE in Canada.

寄生虫与定殖和专性中间宿主的生态学特征不仅在于宿主-寄生虫相互作用，而且在于定殖和专性中间宿主之间的多方面相互作用，这取决于宿主物种之间的生态关系（即捕食者-被捕食者）和宿主群落的多样性。 多房棘球绦虫（Em）是野生和家养犬科动物（DH）的绦虫寄生虫，其卵通过粪便在环境中脱落，如果意外摄入，它们可以感染IH（主要是啮齿动物）甚至人类（其中可以引起泡状棘球蚴病，AE，一种致命的疾病）。DHs在感染性IH之前就被感染了。 对这些宿主-寄生虫系统的动态进行建模，可以提高对复杂生物系统特性的认识，并有助于预测它们的“行为”，在寄生虫周期的情况下，这些行为可能会极大地影响生态系统和人类健康。然而，宿主-寄生虫和DH和IH相互作用的数据仍然很少，限制了现有模型的可靠性。此外，这些模型通常是隔室人口为基础的，描述简化的系统只有一个DH和一个IH物种。 实际上，这些寄生虫周期通常涉及许多宿主物种，这些宿主物种具有很大的个体多样性（DH饲养生态和对感染的反应）和DH和IH中感染的高度空间异质性。生态过程（例如，猎物选择，稀释效应）在IH和DH时空尺度影响传播动力学，只有空间明确的模型可以描述这些尺度的出现，特别是在高度异质性的环境和主机组合的寄生虫的属性。 我的研究计划的目标是描述过程和属性在不同尺度的主机种群，并研究这些如何影响多主机系统内的传输动态，使用Em作为模型。 这项研究将在卡尔加里的10个地区进行，每个地区将对4只土狼使用GPS项圈研究DH生态。他们的运动将被监测长达18个月，他们的粪便收集和分析，以评估他们的饮食和感染状况。将在同一地区评估猎物组合，感染的IH及其与捕食者-猎物相互作用的关联。然后，我将结合联合收割机系统动力学和代理基于建模的方法，使用个别土狼作为代理移动在一个虚拟的异构景观与感染的IH表示在网格单元。IH物种内的感染动力学（在细胞中），寄生虫从DH（代理）到IH（细胞）的传播速率，反之亦然，以及在单个DH内的感染动力学将由微分方程组描述。 通过模型模拟，我将不仅阐明这个复杂的宿主-寄生虫系统的特性和动态，而且还提供数据和情景，以支持决策管理可能爆发的AE在加拿大。