DISSERTATION RESEARCH: Ecologically variable immunity and its consequences for parasite dynamics

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An important goal of researchers who predict disease epidemics is to know how the parasites that cause them move through a population of hosts. In making predictions about epidemics, people consider how and when susceptible and infected hosts come into contact with one another, but they generally do not consider what happens after the parasite gets inside its host. However, the within-host battles between host and parasite could also be important for disease spread. These within-host battles happen because a host's body is constantly resisting and defending against parasites. It is important to consider these dynamics in predicting disease dynamics because not all hosts are equally equipped to fend off parasites and diseases. Ultimately, hosts that have lower immunity are more likely to allow parasites to spread. In this project, the researcher will focus on populations of an invertebrate that lives in lakes in which they experience large parasite epidemics every year. The researcher will improve our understanding of disease spread by incorporating information about how variability in immunity affects it with host-to-host contact information. The results of this project will help scientists better understand the importance of immune defenses when parasites infect humans, farm animals, and wildlife populations. It will also enable the training of a graduate student, and support projects aimed at encouraging underrepresented minority, female and low-income undergraduate and grade school students to be involved in science.Our understanding of how ecological and immunological factors interact in natural populations to determine both an individual's probability of infection and the subsequent overall disease prevalence remains limited. Working with a model host-parasite system (Daphnia host and fungal parasite), this research examines the mechanisms underlying immune function, as well as the consequences of variable immunity for parasite transmission. Specifically, the researcher will examine how environmental stressors (e.g. resource quality and availability) shape natural Daphnia populations' mean levels of and variation in immune function. The establishment and spread of the highly virulent parasite within these populations will then be quantified, while tracking each population's levels of exposure and infection success through time. The research relies on tools from multiple disciplines, including ecology, quantitative biology, transcriptomics, and immunology. Moreover, the project integrates theories from disease ecology and ecological immunology to examine disease processes across scales: from the genome, to the individual, to the population and community.