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The pathogenic fungusBatrachochytrium dendrobatidis(Bd)is associated with drastic global amphibian declines. Prophylactic exposure to killed zoospores and the soluble chemicals they produce (Bdmetabolites) can induce acquired resistance toBdin adult Cuban treefrogsOsteopilus septentrionalis. Here, we exposed metamorphic frogs of a second species, the Pacific chorus frogPseudacris regilla, to one of 2 prophylactic treatments prior to liveBdexposures: killedBdzoospores with metabolites, killed zoospores alone, or a water control. Prior exposure to killedBdzoospores with metabolites reducedBdinfection intensity in metamorphic Pacific chorus frogs by 60.4% compared to control frogs. Interestingly,Bdintensity in metamorphs previously exposed to killed zoospores alone did not differ in magnitude relative to the control metamorphs, nor to those treated with killed zoospores plus metabolites. Previous work indicated thatBdmetabolites alone can induce acquired resistance in tadpoles, and so these findings together indicate that it is possible that the solubleBdmetabolites may contain immunomodulatory components that drive this resistance phenotype. Our results expand the generality of this prophylaxis work by identifying a second amphibian species (Pacific chorus frog) and an additional amphibian life stage (metamorphic frog) that can acquire resistance toBdafter metabolite exposure. This work increases hopes that aBd-metabolite prophylaxis might be widely effective across amphibian species and life stages.
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This content will become publicly available on November 11, 2025
Efficacy of Bd metabolite prophylaxis dose and duration on host defence against the deadly chytrid fungus Batrachochytrium dendrobatidis
Abstract Batrachochytrium dendrobatidis(Bd), an aquatic pathogenic fungus, is responsible for the decline of hundreds of amphibian species worldwide and negatively impacts biodiversity globally. Prophylactic exposure to the metabolites produced by Bd can provide protection for naïve tree frogs and reduce subsequent Bd infection intensity.Here, we used a response surface design crossing Bd metabolite prophylaxis concentration and exposure duration to determine how these factors modulate prophylactic protection against Bd in Pacific chorus frog (Pseudacris regilla) tadpoles (5 × 5 surface design) and metamorphs (3 × 3 surface design). We exposed individuals every weekday to one of five Bd metabolite concentrations or a water control for 1–5 weeks, after which all animals were challenged with live Bd to evaluate their susceptibility.Exposure to the Bd metabolite prophylaxis reduced Bd load and prevalence compared to the control for both the tadpoles and metamorphs. Increasing Bd metabolite prophylaxis concentration did not confer additional protection for either life stage, but increasing duration of exposure did benefit metamorphs by decreasing Bd prevalence but not Bd load.On average, control tadpoles and metamorphs had 66.2% and 99.4% higher Bd loads, respectively, than tadpoles and metamorphs exposed to any Bd metabolite prophylaxis.Additionally, Bd metabolite prophylaxis reduced Bd prevalence relative to controls in both tadpoles (20.5% vs. 56.3%, respectively) and metamorphs (21.9% vs. 87.5%, respectively).Synthesis and applications: The efficacy of short‐term exposures of relatively low concentrations of Bd metabolites at reducing Bd infections suggests that this approach has the potential to be scaled up to field use to aid in disease mitigation and conservation. Our results, combined with additional research on Bd metabolite prophylaxis for other amphibian species, suggest that this strategy may represent a broadly useful tool to protect at‐risk amphibian populations.
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- PAR ID:
- 10581649
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Applied Ecology
- Volume:
- 61
- Issue:
- 12
- ISSN:
- 0021-8901
- Format(s):
- Medium: X Size: p. 3139-3147
- Size(s):
- p. 3139-3147
- Sponsoring Org:
- National Science Foundation
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