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

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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.