Many parasites establish infections through two different pathways: vertical transmission to offspring of infected hosts, and horizontal transmission to uninfected hosts. This study examines a key, unexplored question regarding parasite behavior: how does host aging influence parasite transmission? A mathematical model of host-parasite dynamics predicts increased horizontal transmission as host age increases and reproduction declines. Preliminary results from a model bacterial system confirm this expectation. Further experiments using this bacterial system will examine the behavior of parasites upon introduction to hosts with varying aging patterns. Initial parasite behavior in these new hosts will identify any general ability of parasites to detect and respond to differences in host aging. Laboratory evolution experiments will subsequently explore parasite behaviors that require specialization to a particular host. Taken together, these efforts explore the role of host aging in shaping parasite transmission behavior from both theoretical and empirical perspectives.
This study develops both a mathematical modeling framework and an experimental system for exploring the effects of host aging on parasite behavior. This research thus provides theoretical and experimental tools for future research on vertically transmitted parasites. This class of parasites includes agents of human disease such as AIDS and cancer, as well as infectious agents of crops and livestock. Understanding the basic behavior of such parasites will therefore assist in effectively managing organisms that detrimentally impact human health and the economy.
