While disease outbreaks are receiving increased public attention, especially in humans and endangered or economically important species, our knowledge of the factors controlling parasitic disease in nature remains woefully incomplete. The idea that selective culling of infected animals by predators can decrease parasitism is not new, yet there have been no large-scale, controlled experiments testing the effects of selective predation on parasitism. Further, the effect of predation is not always straightforward: in many cases, a predator can also facilitate parasite transmission by dispersing eggs or spores of the parasite throughout the environment. In these cases, the combined effects of predation on parasitism are unclear. I have developed an epidemiological model that incorporates selective predation of infected animals as well as survival of parasite spores, which are released back into the environment. The proposed research will test the predictions of this model using fungus-infected zooplankton and fish predators as a model system. This will provide the first experimental test of the effects of predation on parasitism. Rates of parasitism are predicted to increase in the near future as a result of anthropogenic environmental stresses; however, this prediction is based on incomplete knowledge of the factors controlling parasitism. Contributing to this knowledge is an important broader impact of this proposal. Additional broader impacts include training a graduate student and an undergraduate at the interface of mathematical and experimental field ecology, and the dissemination of project results on the internet.
