Explaining the complex lives of parasites: within-host dynamics, parasite plasticity, and life history evolution

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Despite centuries of research into infectious diseases, there are no satisfying answers to important ecological and evolutionary questions, such as: Which factors have shaped the evolution of parasite traits that determine harm caused to hosts and infectiousness? How and why do interactions between parasites and hosts differ across parasite species, i.e., why are some diseases severe and others less so? How might drugs or vaccines affect parasite traits and their interactions with hosts? Global disease statistics highlight the importance of answering these questions: infectious diseases currently account for 1 in 6 deaths worldwide, and 1 in 2 deaths in developing regions (WHO). Further, in Canada we are confronted with an ever-increasing threat from drug resistant bacteria (e.g., MRSA), which are a consequence of ecological interactions and evolutionary responses. Developing a better understanding of parasite evolutionary ecology is therefore critical to designing effective treatment and control strategies. A key insight from evolutionary ecology is that parasites are more sophisticated organisms than they tend to be given credit for - they are able to detect changes in their environment and adjust their strategies accordingly. By integrating mathematical modeling with experimental data, my research program investigates the causes, consequences, and limits of this 'phenotypic plasticity'. Over the next five years, my group will determine (1) what impact changes in parasite traits have on patterns of disease within hosts and whether they contribute to the variation observed across parasite strains, (2) whether these changes help parasites deal with a variable environment (i.e., whether this plasticity is adaptive), and (3) what the potential is for this plasticity to erode disease control efforts. This research will train graduate and undergraduate students in mathematical and statistical techniques that are applicable to industry, biomedicine, government, and academia. While the focus of much of our research effort will be on malaria parasites, the evolutionary principles we uncover will have far reaching implications, improving understanding of disease and offering new insight to biomedicine.