Chytridiomycosis is an emerging infectious disease caused by the fungal pathogen, Batrachochytrium dendrobatidis (Bd), and has been implicated in amphibian extinctions and mass die-offs globally. Studies have shown there is variation in susceptibility between different amphibian species, yet the cause is unknown. Although Asia is known to harbor this deadly pathogen, there have been no records of die-offs from Bd infections. How Bd persists in Asian amphibian populations without any signs of disease is also not known. One hypothesis is that Asian amphibians have co-evolved with unique endemic strains of the Bd pathogen and have therefore developed natural immune defenses. The amphibian skin microbiome is known to play a role in susceptibility and resistance to chytridiomycosis by means of anti-fungal metabolites produced by bacteria. We aimed to determine infection prevalence and intensity across a wide range of amphibian taxa, elevation, and habitat in Taiwan, as well as investigate the bacterial communities of the microbiome. DNA was extracted from swabs collected from wild amphibians in Taiwan and assayed using qPCR. We used 16S rRNA next-generation sequencing to help describe the microbial communities living on the skin of infected and uninfected amphibians.
Results/Conclusions
Our preliminary data shows an overall infection prevalence of 10.3% and an average infection intensity of 2.57 genomic equivalents (GE) across all species. Three out of nine species (33.3%) were susceptible to infection, including an endangered and endemic salamander. All infected individuals had very low infection intensities, except for one frog (26.8 GE). These results are consistent with past surveys showing similar results suggesting that local amphibians may persist with some background level of infection. Furthermore, although Bd was found at only 20% (4/20) of our sites, they ranged in elevation from 169 to 2,951 m A.S.L. By showing widespread geographical occurrence of Bd with low levels of infection, these preliminary results lend support for the hypothesis that Asian amphibians have co-evolved with unique endemic strains. Currently, data from an Illumina Miseq is being analyzed in order to determine presence and community composition of anti-fungal bacteria living on the skin of these individuals. These upcoming results may help explain why Asian amphibians persist despite constant disease presence, shed light on why species vary in susceptibility, and therefore aid in conservation efforts aimed at populations experiencing collapse in other parts of the world.