Meeting Abstract
How do epidemics end? A transition away from the outbreak phase of a disease can occur following the emergence of highly pathogenic infectious agents. Yet the mechanisms that underpin such transitions remain obscure. We have been investigating shifts in disease dynamics in the lethal disease amphibian chytridiomycosis by focusing on host recoveries in the amphibian assemblages of Panama. The fungal pathogen that causes chytridiomycosis, Batrachochytrium dendrobatidis (Bd), spread through Panama in a wave-like pattern, causing mass mortality events and declines in many amphibian species over a decade ago. However, some host populations that survived initial outbreaks are rebounding despite Bd infection. We have found that Bd prevalence is now low, but the pathogenicity of Bd isolates collected from these populations is still high, causing 100% mortality in naive hosts. This finding suggests that shifts in host resistance to infection may be important for amphibian recoveries. We collected samples of host skin secretions containing anti-Bd peptides from multiple species, naive and infected populations, and at numerous time points to test their effectiveness at limiting Bd growth. We found that there is wide variation in peptide effectiveness among and within species, as well as in samples collected from numerous time points. We suggest that persisting and recovering populations may have improved innate immune defenses that help protect amphibian hosts against chytridiomycosis.
