From individuals to communities: investigating the snail-schistosome system across scales Restricted; Files & ToC
Shaw, Kelsey (Summer 2023)
Published
Abstract
Hosts and parasites are inextricable from their greater ecological community, and interactions with other species may influence host and parasite densities, traits, and resource availability, all with cascading effects on disease transmission. Understanding this community ecology of disease for any given host-parasite system is key to creating better transmission models and parsing unexplained heterogeneity in observed transmission dynamics. Here, I investigate driving forces in schistosome transmission from the individual to the community level, and how ecological interactions may feedback on a crucial host trait, body size. Schistosomiasis is a Neglected Tropical disease that impacts over 200 million people globally and is caused by parasitic flatworms, schistosomes, that obligately cycle between human and snail hosts. I quantified the impact that body size has on both exposure and susceptibility of host snails to parasites, and built a size-explicit transmission model to better model transmission dynamics in size-structured populations. Scaling up from the individual level, I used experimental communities of host and non-host snails to investigate the role they play in host snail abundance, body size, and shedding of cercariae, the life stage of schistosomes that is infectious to people. I demonstrated that while one non-host species is a weak resource competitor that can decrease cercarial output but not host snail abundance, the other species I tested acts as an intraguild predator of host snail eggs, resulting in an unexpected release from intraspecific competition that results in increased cercarial shedding. Finally, I characterized the community of macroinvertebrate competitors and predators of host snails in the endemic region of Mwanza, Tanzania and established how community composition may influence schistosome prevalence. Overall, my work demonstrates how key ecological interactions between non-hosts, hosts, and parasites may result in unanticipated transmission dynamics, and therefore the importance of investigating the mechanisms driving the patterns we observe in host-parasite systems.
Table of Contents
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File download under embargo until 16 August 2029 | 2023-08-11 08:12:10 -0400 | File download under embargo until 16 August 2029 |
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