Evolution of parasite life history strategies in a changing environment
As all other organisms, parasites experience trade-offs between life history traits, including growth, reproduction and survival. Natural selection will shape life history strategies to maximize fitness in a particular environment and when the environment changes, organisms are selected to alter life history strategies in response. Parasites can adapt to environmental changes by facultative (within infection) changes to life-history strategies as well as by longer-term evolutionary changes.
When parasitic diseases are important to humans (plant, animal and human diseases) we use interventions to control disease, including chemical treatment like fungicides or antibiotics. Such interventions change the environment for parasites and will affect their life-history strategies.
Evolution of parasite virulence and transmission in response to drug treatment
Natural selection solves the trade-off between rate and duration of transmission, which is mediated by virulence, to maximise lifetime transmission success (fitness). Theory predicts that, under conditions of drug treatment that fails to clear all parasites from infections (suboptimal treatment), fitness is maximised at higher virulence levels and thus, more virulent parasites are favoured by natural selection. Understanding how virulence and ultimately, transmission success of parasites is shaped by human-induced selection pressures is important for the development of disease control policies.
Malaria parasites offer a unique opportunity to address our research questions, are one the most medically and economically important group of parasites and are frequently exposed to low levels of antimalarial drugs. We use a mouse malaria model (Plasmodium chabaudi) to test how, why and when suboptimal treatment shapes selection on virulence and will quantify the downstream effects this has on transmission success. We will integrate our in vivo results by translating key results to in vitro experiments with human malaria parasites (P. falciparum).
We will quantify and test whether (1) drug sensitivity is linked to virulence-related traits; (2) parasites alter their virulence in response to suboptimal drug treatment, using experimental evolution to test for facultative and evolved changes; and (3) fitness consequences result from drug-induced changes to virulence.