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Amphibian resistance to chytridiomycosis increases following low virulence chytrid fungal infection or drug-mediated clearance

Citation

Waddle, Anthony (2022), Amphibian resistance to chytridiomycosis increases following low virulence chytrid fungal infection or drug-mediated clearance , Dryad, Dataset, https://doi.org/10.5061/dryad.83bk3j9rw

Abstract

Amphibian biodiversity is experiencing ongoing declines due in part to the infectious disease, chytridiomycosis. Efforts to mitigate the effects of the causal agent of chytridiomycosis, Batrachochytrium dendrobatidis (Bd), in the wild have not been wholly effective. Translocations are an important management tool for amphibians, and immunizations represent a possible strategy for preparing amphibians for release across a landscape where Bd exists.

We evaluated the utility of using an isolate of Bd that was shown to be hypovirulent to the relict leopard frog (Rana onca) as a transmissible inoculum for promoting chytridiomycosis-resistance. We conducted a cohousing experiment to determine if the isolate we used could be passed between R. onca without increasing in virulence. We then  followed with an experiment where frogs that were exposed to the hypovirulent isolate were then challenged with a virulent Bd isolate. In other experiments, we evaluated whether Bd infections followed by clearance with itraconazole (an antifungal) could increase resistance to chytridiomycosis in R. onca and Rana pipiens (northern leopard frog).

We found that our hypovirulent Bd inoculation was transmissible between hosts, did not cause chytridiomycosis, and was effective at increasing chytridiomycosis-resistance. Rana onca inoculated with the hypovirulent Bd isolate had lower pathogen burdens and were 55 times more likely to survive infections by a virulent Bd isolate than non-inoculated frogs.

For both species, prior exposure to Bd followed by infection clearance with itraconazole resulted in significantly increased survivorship and lower pathogen burdens as compared to controls that had no prior Bd exposure. Rana onca that were previously exposed to Bd were more than 15 times more likely to survive infections. Previously exposed R. pipiens survived in higher proportions than controls, but with weaker statistical support.  

Methods

The data is predominately qPCR data generated from skin swabs collected weekly during our challenge studies. Outputs are measured in zoospore equivalents (ZE). This is a measure we have determined using DNA standards of a known amount of Bd zoospores. We also have some ancillary data included in these files (mass, SVL, and survivorship).

Usage Notes

All missing values are frogs that had developed fatal disease and thus no longer contributed data to the experiment. These are noted as "null" in each dataset.

Funding

U.S. Bureau of Land Management, Award: L16AC00149