Host resistance and tolerance to parasitism: importance of behaviour and habitat in a changing world

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Emerging and re-emerging infectious diseases are a major concern for the health of humans, domestic animals, and wildlife. Effective disease management requires an intimate understanding of how hosts resist and tolerate parasitism, including how these abilities are affected by their environment. Given current and projected world-wide environmental changes, it is imperative to examine links between host habitat and parasitism and an essential next step for the development of better predictive tools is to identify underlying mechanisms. Using amphibians and their helminth parasites as a model system, my laboratory will use a suite of novel interdisciplinary tools and collaborations to mechanistically study host resistance and tolerance through three specific related themes that link interactions among hosts, parasites, and their environment: 1) the role of host behaviour, 2) the influence of habitat complexity, and 3) the impacts of multiple stressors. Behavioural defences may play a major role as it should be less costly to simply avoid infections, and hosts can also mitigate the impacts of infection through behavioural means. By investigating behaviour as a means to resist and tolerate parasitism, this work will improve our general understanding of host defences. Host infections are not just determined by their response to pathogens, but also by their frequency of exposure to infectious stages. Our second theme will help in predicting how habitat alterations influence disease patterns by considering how within-site conditions affect host exposure. It is now widely recognized that multiple stressors can affect organisms in unexpected ways, thus separate examinations do not accurately reflect most natural processes and can generate misleading conclusions. However, few studies have considered parasite infection as a stressor in conjunction with others. Consequently, our third theme will contribute to a more comprehensive view regarding the costs and implications of parasitism. Because amphibians are the most imperiled group of vertebrates worldwide, with diseases contributing to their decline, our results will produce novel findings regarding drivers of host resistance and tolerance to parasitism that aid in formulating conservation and management strategies to contribute towards a better understanding of wildlife diseases as a whole. The study of amphibian parasitism will also generate findings applicable to other freshwater organisms of conservation, cultural, and economic importance.