Chytrid in the clouds: an alternative passive transport of a lethal pathogen for amphibians

Fog is an important water input in ecosystems and a carrier of microorganisms, including unicellular pathogens. The aquatic amphibian-killing fungus, Batrachochytrium dendrobatidis (Bd), has a complex transport dynamic. Understanding how the exposure of amphibians to Bd can occur is important for the development of control measurements and for preventing die-offs. Therefore, we tested if the fog water may transport Bd. We collected fog and rainwater in Brazil's Atlantic Forest and experimentally tested if Bd from artificial and natural fog exposures would infect amphibians. We report the first evidence of Bd DNA in fog and corroborate previous data documenting Bd DNA in rainwater. Furthermore, our results indicate that susceptible hosts can be infected and develop lethal chytridiomycosis through the passive transport of Bd live zoospores by the artificial fog. Our results extend the current knowledge about Bd transport pathways between environmental reservoirs. A new short- to medium-range dispersal pathway through fog may explain patterns of pathogen occurrence and opens new avenues of investigation to elucidate exposure mechanisms of direct-developing amphibians to aquatic pathogens.

Automated summary

This research provides evidence that fog water may serve as a pathway for the transmission of the amphibian-killing fungus Bd. The study shows the passive transport of live Bd zoospores through artificial fog can infect susceptible hosts and lead to lethal chytridiomycosis. These findings are important for understanding the exposure mechanisms of direct-developing amphibians to aquatic pathogens and can aid in the development of control measures.