Amphibians acquire resistance to live and dead chytrid fungus overcoming fungal immunosuppression

Background/Question/Methods

Emerging fungal pathogens pose a greater threat to biodiversity than any other parasitic group, causing declines of many taxa, including bats, corals, bees, snakes, and amphibians. Currently, there is little evidence that wild animals can acquire resistance to these pathogens. Batrachochytrium dendrobatidis (Bd) is a pathogenic fungus implicated in recent global amphibian declines. Here, we demonstrate that amphibians can acquire immunological resistance to both live and dead Bd. We exposed frogs to either live or dead Bd, zero to four times depending on their treatment assignment, and cleared infections with heat after each exposure. 

Results/Conclusions

We found that the number of previous Bd-exposures was a negative predictor of Bd burden on frogs and Bd-induced frog mortality and was positively associated with lymphocyte abundance and proliferation. These results suggest that amphibians can acquire immunity to Bd that overcomes pathogen-induced immunosuppression and increases amphibian survival. Importantly, exposure to dead Bd induced a similar magnitude of acquired resistance as exposure to live Bd. Exposure of frogs to Bd antigens might offer a practical way to protect naïve amphibians and facilitate the reintroduction of amphibians to locations in the wild where Bd persists. Moreover, given the conserved nature of vertebrate immune responses to fungi, these results offer hope that other wild animal taxa threatened by invasive fungi might be rescued by management approaches based on ‘herd immunity.’