A skin-eating fungus that originated in Asia millions of years ago is causing major salamander die-offs in Europe. And with the exotic pet trade, the emerging disease threatens to wipe out amphibian populations in the U.S. soon. The findings were published in Science last week.
Poor, poor amphibians. In the last 30 years or so, the deadly chytridiomycosis infection, caused by the fungal pathogen Batrachochytrium dendrobatidis, has already led to devastating declines of amphibians around the world. This new plague that’s spreading intercontinentally is caused by a closely related fungus called Batrachochytrium salamandrivorans. The pathogen rapidly invades the skin, which is critical to the amphibian respiratory system. Researchers aren’t sure how it kills the host, but B. dendrobatidis, which also infects the skin, interferes with breathing and the ability to absorb water and nutrients.
B. salamandrivorans isn’t new. It’s been present in amphibians from Thailand, Vietnam, and Japan since before 1861—but without causing disease, likely because they've evolved defenses against it. It was discovered in Europe in the last couple years by researchers investigating a major crash in the population of fire salamanders (pictured above) in the Netherlands. “First we were very happy because it is very exciting to detect a novel species of fungus,” An Martel of Ghent University tells Nature. “But then it was scary.” Only four percent of the Dutch population was still alive last year.
To see who’s susceptible, Martel and a large international collaboration exposed 35 amphibian species to the fungal spores. Turns out, it only attacks salamanders, infecting neither frogs nor the snake-looking amphibians called caecilians. Newts, a salamander subgroup, are especially vulnerable. When two common North American speciest—the Eastern red-spotted newt (pictured here) and the rough-skinned newt—were exposed in the lab, 100 percent of them died. "We have billions of these newts living in the wild all across the continent," Karen Lips from the University of Maryland says in a statement. “And because they're highly sensitive to this fungus, they could amplify it or spread it to other groups of salamanders."
To determine the fungus’s origin and reach, the team screened more than 5,000 amphibians from four continents. The fungus, they found, originated in salamanders in Asia some 30 million years ago and only recently reached Europe through trade and trafficking. "When a disease has been around for a long time, animals develop resistance to it," Martel says in a news release. "Globalization has resulted in the movement of humans and animals all across the world, bringing pathogens into contact with hosts that haven't had the opportunity to establish resistance.”
The fungus is lethal to at least a dozen European and North American salamanders. And while it hasn’t reached the Americas yet, at least 2.3 million Chinese fire-bellied newts (pictured, right) were imported to the U.S. as pets between 2001 and 2009. Even if a few of them have the fungus, it's only a matter of time before it impacts the continent.
Images: Frank Pasmans (top, bottom), Nicholas Caruso (middle)