Meeting Abstract
A shift in virulence, or a transition away from the outbreak phase of a disease, toward a stable co-existence of host and pathogen can occur following the emergence of highly pathogenic infectious agents. Yet the mechanisms that underpin such transitions remain obscure. We are investigating the role of evolution in both the host and the pathogen in this process by focusing on one of the most lethal diseases of vertebrate hosts available for study, amphibian chytridiomycosis. A decade ago, the fungal pathogen Batrachochytrium dendrobatidis (Bd) spread through western Panama in a wave-like pattern, causing mass mortality events, dramatic declines and even local extinction of many amphibian species. However, surviving populations of some susceptible species were recently rediscovered. Although Bd is present in these persisting populations, pathogen prevalence is surprisingly low, contrary to modeling predictions. This finding suggests that there has been a shift in host-pathogen dynamics since the initial chytridiomcyosis outbreaks occurred. We collected and cryo-archived isolates during chytridomycosis outbreaks and 8-10 years following initial outbreaks. These isolates were used in laboratory infection experiments and found to be differentially pathogenic to a susceptible amphibian species. We are also currently evaluating the effectiveness of anti-microbial peptides (a component of the amphibian immune defenses) that were collected and preserved from these two time points. Understanding evolution in host-pathogen dynamics will have far-reaching implications for understanding, predicting and controlling the spread of infectious diseases and will be integral to the conservation of amphibian biodiversity in post-epidemic disease systems.
