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Cardiac Arrest-Causing Fungus Eliminated in Majorcan Midwife Toads

ByAllison EckNOVA NextNOVA Next

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If you’re a pathogen, it’s not a great idea to send your host species into cardiac arrest. If that happens too many times, populations will dwindle to nothing—and you’ll be left without a home.

But a virulent fungus that’s been afflicting amphibians worldwide does just that. Scientists have known about it since 1998; finally, they may be on their way to a solution.

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A team of researchers announced that they’ve rid frogs on the Spanish island of Majorca of the pathogen Batrachochytrium dendrobatidis , also known as the chytrid fungus—or B.d. for short. Other attempts to wipe out B.d. have been successful in captivity, but this is the first time the fungus has been eradicated in the wild. Biologist Trenton Garner and his team reported the discovery in the journal Biology Letters.

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B.d. infects amphibian’s skin, causing it to thicken and disrupt the flow of electrolytes, which help maintain a number of bodily functions. Eventually, the animal goes into cardiac arrest. Amphibians suffer from myriad inflictions across the globe—but B.d. has conquered especially wide territory. So far, it’s been identified in 700 species on a total of six continents.

Garner’s team began their fungus-clearing project in 2009. Their first step was to remove tadpoles from Majorcan ponds and drain the ponds completely. Since B.d. is sensitive to temperature, they hoped that exposure to the sun would kill the fungi off. After a failed first attempt, the team tried again three years later. This time, they added small amounts of disinfectant to the pond—and three years later, the area is still fungus-free.

The experiment worked well as a proof of principle, mostly because the island of Majorca is so isolated that no other amphibian species were likely to complicate the picture. But fortunate design only goes so far; the downside to unique environmental circumstances is that replication becomes trickier.

Furthermore, some scientists may be reluctant to apply the team’s strategy elsewhere, as antifungals are controversial. Here’s Rachel Nuwer, reporting for the New York Times:

The special circumstances on the island, and the threat B.d. posed to the protected Majorcan midwife toads, justified the use of fungicides in the environment, said Deanna Olson, a research ecologist at the United States Forest Service’s Pacific Northwest Research Station, who was not involved in the work. But it’s a strategy that some other scientists see as extreme.

“That would be considered very controversial in a wider application,” Dr. Olson said. “Eradication of B.d. in the wild has been discussed, but implementation has been stalled due to the widespread effects of antifungals on an extremely important component of ecosystems: fungi.”

However, Garner’s team believes the experiment shows that there could be simpler, more creative ways of eradicating infections than we might have previously considered. Meanwhile, evolving habitats as a result of climate change add another layer to the research that needs to be done, as well.

Photo credit: Wikimedia Commons