Top Story: July 11, 2014

Fighting Fungus with Fungus

frogs, fungus, chytrid, Bd, Dave Blackburn, amphibians

By Molly Michelson

As we reported in our video “Stopping Chytrid, Saving Frogs” earlier this year, local scientists and others are racing to find a cure to a deadly disease killing amphibians globally. Batrachochtyrium dendrobatidis, or Bd, is a chytrid fungus that spreads over amphibians’ skin that suppresses the animals’ immune system, spreading fast and often killing entire populations. Frogs are the hardest hit.

Researchers are looking at fungicides and natural occuring microbes found on the skin of frogs to fight and kill the fungus, and this week, researchers from the University of Florida suggest another option—the fungus itself.

Publishing in Nature, Jason Rohr and his team exposed frogs to Bd in the lab to attempt to build up behavioral or immunological resistance to the fungus. The team then killed the fungus on the frogs after exposure by raising the temperature of the lab. One experiment in the study revealed that after just one exposure to the chytrid fungus, frogs learned to avoid the deadly pathogen.

In subsequent experiments in which frogs could not avoid the fungus, frog immune responses improved with each fungal exposure and infection clearance, significantly reducing fungal growth and increasing the likelihood that the frogs survived subsequent chytrid infections.

Academy herpetologist Dave Blackburn, who studies frogs (and Bd, since the two go hand-in-hand) in Africa and elsewhere applauds the study. “This work from Jason Rohr and colleagues is a significant and important advance in our understanding of the interaction between the pathogenic fungus Bd and the amphibians it infects. Not only do they demonstrate that frogs can acquire resistance to Bd through repeated exposures, but they also demonstrate that frogs can acquire resistance even through exposure to dead Bd.

“This study will have important consequences to amphibian conservation, especially for captive breeding programs,” he continues. “As the authors point out, it may help to have controlled and repeated exposures to Bd in captivity before reintroducing populations to the wild so that they'll have acquired immunity before encountering it once released. We often worry about Bd infecting our captive frogs that we have for research and exhibit purposes and then decimating our living collections. Perhaps a strategy to control Bd outbreaks in captive populations would be to purposefully induce acquired immunity. It makes me think that perhaps our frogs we brought back from Cameroon last year are better off because they had been infected by Bd and then cleared of it once they came to the Academy!”

Image: Thomas Brown/Flickr

comments

  • ericmills

    Encouraging news, but a bit late for the estimated 200+ frog and other amphibian species driven to extinction worldwide in recent years by the chytrid fungus (Bd).

    What’s TRULY frustrating is the fact that the California Dept. of Fish & Wildlife refuses to cease issuing import permits for the TWO MILLION non-native American bullfrogs imported annually for the live animal food markets (found mostly in various “Chinatowns”). Recent studies have documented that the majority of the bullfrogs test positive for chytrid. Though the bullfrogs do not generally succumb to the fungus, they certainly do disperse it, while preying upon and displacing our native wildlife.

    How come? The Dept. has the authority (CCR 236), but not the backbone. Back in 2010, the Fish & Game Commission voted 5:0 to instruct the Dept. to stop the permits. Only weeks later, the Director of the Dept. announced he would continue the permits on a month-to-month basis. When challenged by an irate Commissioner Dan Richards, the Deputy Director of the Dept. (Sonke Mastrup, now Exec. Director of the Commission), weakly responded, “The Director acts at the pleasure of the Governor.” So much for the democratic process…..and common sense. Reportedly, both the European Union and Australia now allow the importation of only FROZEN frog parts for human consumption. The U.S. (and others) should follow suit, ‘ere we lose ALL our amphibians and the other species which depend upon them for their very survival. Maybe us, too. And Rome continues to burn…..

    Eric Mills, coordinator
    ACTION FOR ANIMALS
    Oakland

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