The work presented in this dissertation explores contemporary disease ecology questions framed by the looming amphibian disease, chytridiomycosis. How do skin microbiota and defense peptides, components of host innate immunity, interact on amphibian skin to provide protection from infection? Can a probiotic strategy be designed to successfully ameliorate the effects of chytridiomycosis? The focus of these studies is on a highly susceptible Discoglossid host, the midwife toad, Alytes obstetricans.
A complex interplay of interactions between the etiological disease agent, Batrachochytrium dendrobatidis (Bd) and components of innate immunity are elucidated by sampling hosts in their natural habitat and testing the effects of these isolated immune components under controlled laboratory conditions and semi-natural mesocosms. An innate immunity profile of the host is first characterized and individual components screened in vitro to identify candidates with beneficial probiotic agents (Chapter 1). Beneficial traits of a probiotic for treating Bd-infected hosts include the ability to inhibit pathogen growth while simultaneously persisting in the presence of the host’s defense components at the skin surface. How the selected probiotics influence the established microbial communities of naturally Bd-infected tadpoles was evaluated in vivo with bioaugmentative therapeutic treatments in semi-natural mesocosms (Chapter 2) to improve host survival outcomes post- metamorphosis (Chapter 3).