Skin-Eating Fungus Threatens American and European Salamanders

The disease catches a ride on Asian amphibians imported as pets.

(Photo: 'The Washington Post'/Getty Images)

Oct 30, 2014· 2 MIN READ
Hannah Hoag reports on the environment, global health, science, and science policy for Nature, Discover, Wired, and others.

A lethal fungus wiping out salamanders in Europe could do the same in the United States by piggybacking on legally imported Asian amphibians popular in pet stores.

Scientists studying the newly identified fungus Batrachochytrium salamandrivorans have discovered it can kill at least a dozen European and North American—but not Asian—salamander and newt species. Although Asian salamanders can carry the fungus on their skin, they are largely resistant to the disease.

“They get sick, but they can recover,” said An Martel, a veterinarian at Ghent University in Merelbeke, Belgium. Martel has been studying the outbreak among European salamanders ever since sick and dead ones began showing up in the Netherlands several years ago.

Martel and her colleagues screened the skin swabs of nearly 5,400 amphibians collected from four continents for the presence of the chytrid fungus B. salamandrivorans, also called Bs.

Samples from the Eastern and Midwestern U.S. and Panama were free of the fungus. “That was the good news,” said Karen Lips, an ecologist at the University of Maryland in College Park, who also worked on the research.

The group has not tested salamanders from California or Mexico. “Those would be our high priorities,” said Lips.

Martel and her colleagues warn that the global movement of humans and other animals has eroded “ancient barriers to pathogen transmission, allowing the infection of hosts that have not had the opportunity to establish resistance.”

They found three captive Asian newts imported to Europe in 2010 that tested positive for the fungus.

Several Asian amphibian species carry the fungus and are resistant to it or able to tolerate the infection. The researchers believe the fungus has been present in Asia for 30 million years, and that ancient outbreaks likely led to the survival of only those species able to fight the disease.

The fungus infects the salamander’s skin, which is a key part of its respiratory system. It is related to the chytrid fungus B. dendrobatidis (Bd), which has caused extensive disease and devastated populations in a variety of frogs, toads, salamanders, newts, and caecilians. The fungus kills its hosts by infecting the skin and interfering with amphibians’ breathing and their ability to absorb water and minerals, but scientists can’t say for sure if Bs kills salamanders the same way.

Researchers studying the amphibian trade between Asia and the U.S. found that 3.6 million amphibians were exported from Hong Kong between 2006 and 2010. In 2012, they tested commercial shipments of live amphibians, finding that one in every four shipments tested positive for Bd and that the water the animals were shipped in also tested positive for it, running the risk of untreated wastewater spreading the disease.

No U.S. policy requires the testing of incoming live animal imports for pathogens or parasites. “We wouldn’t know if Bs arrived in the U.S.,” said Lips.

The global spread of Bd has led to steep declines in populations of frogs and toads and helped push some, such as the golden toad of Monteverde, into extinction. That has scientists worried that Bs could do the same to salamanders in Europe and the Americas.

“There are no natural barriers that prevent the spread of the fungus,” said Martel. “We are really afraid that it will keep on spreading and that it will affect all European salamanders.”

Martel was part of the team that identified the Bs fungus in 2013. In 2010, volunteers monitoring populations of fire salamanders in the southern Netherlands began finding sick, dying animals on forest footpaths. Within two years, the population in Bunderbos crashed to 4 percent of what it had been. Since then, the outbreak has marched south into Belgium.

In 2009, the nonprofit conservation organization Defenders of Wildlife filed petitions with the U.S. Departments of the Interior and Agriculture, urging them to regulate live amphibian imports in the pet, food, scientific, and live bait trades to block the spread of Bd. “We’re concerned and support any federal regulations that would address what scientists believe is a significant threat to amphibian salamanders here,” said Michael Senatore, vice president of conservation law at Defenders of Wildlife, in Washington, D.C.

“Even if we knew they were infected, we couldn’t prevent the spread,” said Lips. “We’re blindfolded, and our hands are tied behind our backs.”