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New tools in the fight against frog-killing fungus available online

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As the deadly chytrid fungus (Batrachochytrium dendrobatidis, or Bd ) continues its spread around the globe, putting thousands of amphibian species at risk of extinction, scientists are taking a few steps to control it, or at least understand it better.

First, researchers led by Jamie Voyles of James Cook University in Townsville, Australia, believe they have finally figured out how the chytrid fungus kills. Writing in the October 23 Science, Voyles and her team report that the fungus changes the electrolyte balance in frogs and other amphibians, sending them into fatal cardiac arrests.

The team’s findings come from observations of the green tree frogs (Litoria caerulea ) infected with Bd. The frogs suffered a drop inelectrolyte transport across the epidermis that exceeded 50 percent, as well as reductions in plasma sodium and potassium. Such electrolyte imbalances can disrupt heart rhythms, thereby leading to cardiac arrest.

Although Voyles’s team could not save any of the frogs infected with Bd, they did find that providing drugs to restore electrolyte balance did give the subjects a little bit more time before they succumbed.

Knowing how the chytrid fungus kills is important, but identifying it before it spreads to new populations is even more vital. Early identification is key. Kerry Kriger, founder of the Save the Frogs Foundation, recently conducted a course at the Smithsonian Tropical Research Institute in Panama, which presented a method to detect and quantify the number of Bd zoospores present on frogs’ skins. He has also made the information available for free online.

The highly detailed protocol, the first of its kind that has been made publicly available, uses quantitative (real-time) polymerase chain reaction (qPCR) to identify the fungus and its concentration on a frog. The protocol also provides examples of how to properly swab frogs of various sizes to obtain samples for testing.

“There are only a handful of laboratories and scientists in the world knowledgeable in qPCR chytrid-detection techniques, which is a major hindrance to amphibian disease research,” Kriger says. “By making this protocol publicly available in a format in which any moderately skilled scientist can learn the basic skills needed to perform qPCR in their own laboratory, [we have] contributed significantly to the scientific community’s ability to manage chytridiomycosis,” the technical term for the fungal infection.

The protocol will soon be translated from English into Spanish and other languages. Since the protocol was put online October 14, scientists from 16 countries have signed up with Save the Frogs to receive updates, Kriger says.

Once chytrid fungus is identified, its spread must be stopped. Save the Frogs recommends several steps, including removing frog legs from restaurant menus and lobbying for rules to control the pet industry. “The pet and food trade are significant contributors to the amphibian disease problem by transporting millions of amphibians around the world each year,” Kriger says. The group also wants test frogs before they can infect other populations. “We will be working with government agencies to ensure that proper disease testing regulations are put in place,” he adds.

Since it was first observed in 1999 chytrid fungus has been found on all six continents with amphibian populations. According to Amphibian Ark, after the fungus hits a community, 50 percent of amphibian species and 80 percent of individuals can be expected to disappear within one year. So far, no cure or prevention for the fungus exists.

 

Image: Swabbing a Litoria wilcoxii frog to test for the chytrid fungus. Courtesy of Save the Frogs Foundation, used with permission.





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