Browsing by Author "Rudolf, Volker H.W."

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    The impact of within-host interactions and priority effects on disease dynamics in coinfected populations
    (2019-03-21) Clay, Patrick A; Rudolf, Volker H.W.
    Multiple parasite strains and species generally coinfect host populations. These coinfections matter because parasites interact within shared hosts. For instance- parasites can compete for shared resources, interfere with one another directly, or trigger apparent competition through the immune system. These interactions alter parasite fitness within hosts, and in doing so, scale up to alter disease patterns such as epidemic severity. However, within-host interactions are highly context-dependent. Specifically, the timing and order of infections in coinfected hosts can determine the strength of within-host interactions and whether they are positive or negative. Thus, we ask how these within-host priority effects scale up to alter disease patterns such as parasite coexistence, parasite prevalence, and our ability to predict epidemic severity. We answer these questions by measuring within-host priority effects in a coinfected zooplankton system, using those measurements to parameterize mechanistic epidemic models, and comparing model predictions to experimental multi-pathogen epidemics. We first found that within-host priority effect can foster or prevent coexistence, depending on whether parasites have a higher fitness when arriving first or second in coinfected hosts (Chapter 1). In Chapter 2, we showed that parasite prevalence relationships (the change in the prevalence of a parasite in response to changing prevalence of coinfecting parasites) are monotonically positive or negative in the absence of within-host priority effects, but humped or u-shaped if within-host priority effects are present. The results of the first two chapters are largely driven by priority effect mediated frequency dependence. In chapter 3, we demonstrated that measuring within-host priority effects vastly improves our ability to predict the severity of multi-pathogen epidemics. Finally, in chapter four, we demonstrate that a variety of within-host interactions alter parasite evolution by changing the prevalence of coinfection in a host population. Ultimately, this research identifies novel ways in which within-host pathogen dynamics scale up to alter disease patterns at the host-population scale, and will help us predict and respond to the spread of pathogens in coinfected systems.