Causes and consequences of variation in parasite traits

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Understanding the evolutionary ecology of parasites is important for explaining clinical outcomes and predicting how parasites will respond to medical and public health interventions. Achieving this understanding requires identifying traits that underlie the ability of parasites to cause disease and get transmitted, and explaining variation in those traits across parasite species or genotypes. The lives of parasites are increasingly recognized as complex: many parasites spend time in multiple environments, including diverse host and vector species, and are faced with a variety of challenges like competitors within a host or changing availability of vectors. All of this means that determining why parasite traits “are the way they are” may require thinking outside of the direct interactions between parasites and humans. As one illustrative example, some antibiotic resistance genes in bacteria predate the advent of antibiotics by several millennia, owing to the fact that bacteria use chemically similar compounds in competition with each other in the external environment. An important aim of investigating parasite traits is therefore predicting which traits, that already exist and appear to serve some other purpose, will coincidentally allow parasites to mitigate the effects of our control efforts on very short timescales. This grant seeks a holistic understanding of the evolutionary ecology of malaria parasites by addressing three fundamental questions: 1) does life in a mosquito vector alter the evolution of malaria parasite traits that are expressed in a host? 2) In high-transmission settings, where malaria parasites frequently share their host with other genotypes, is there evidence that these parasites have evolved to be more virulent (a standard prediction of evolutionary theory)? And 3) what parasite traits explain observed variation in sensitivity to drugs and the evolution of vaccine-escape in experimental rodent malaria infections? While the focus of this proposal is on malaria parasites, the evolutionary and ecological principles we uncover will have wider implications, improving understanding of disease and offering new insight to biomedicine. This research will also provide high caliber students and postdoctoral fellows with broad training in ecology and evolutionary biology, as well mathematical, statistical, and computational techniques that are applicable to industry, biomedicine, government, and academia.