You may have heard the old adage 'feed a cold and starve a fever' ? Or you may be familiar with your own decrease in appetite or certain cravings that accompany certain illnesses? Well, it turns out that this temporary loss of appetite during illness (aka parasite-mediated anorexia) is a rather ubiquitous behavior in hosts ranging from flies to humans. Yet, we still do not understand whether this behavior benefits the host, parasite, both, or neither.
Perhaps more importantly, we do not understand the high-order consequences of altering this behavior. Nonetheless, many common biomedical and veterinary practices alter both the magnitude and duration of the anorexic symptom.
My research takes an integrative approach to understanding this ubiquitous but poorly understood component of host-parasite interactions.
For example, the ubiquity of this behavior, combined with mounting evidence that calorie restriction can improve host health, emphasizes the importance of harnessing host nutrition as a nonpharmacological strategy to combat disease.
However, these efforts overlook that within-host resources also fuel parasite traits (e.g., virulence and transmission), consequently affecting disease severity and prevalence.
Using an adaptive dynamics approach, I show that reducing within-host nutrients (via parasite-mediated anorexia or prescribed calorie restriction) can either enhance or diminish disease severity, depending on whether the host’s diet bolsters or suppresses immune function and parasite production. Subsequently, depending on dietary context, interventions that suppress anorexia (overfeed) could backfire, inadvertently selecting for more virulent parasites and larger epidemics.
A central focus of my research program is testing these predictions using detailed experiments in Daphnia, Drosophila, and longitudinal data from livestock studies.
Hite J.L. and C.E. Cressler. Parasite-mediated anorexia, dietary context, and the evolution of virulence. In review (BioRxiv) pdf
Hite J.L., A.C. Pfenning, and C.E. Cressler. The epidemiological, evolutionary, and ecological consequences of parasite-mediated anorexia: Review and Synthesis. In review.