A gruesome and deadly skin disease threatens to wreak havoc among North America’s salamanders, researchers warn in a study published in Science today. The Asian fungus that causes the disease — called Bsal — has already reached Europe, wiping out 96 percent of fire salamanders in the Netherlands. Now, researchers have determined that the fungus will spread like wildfire if it reaches North America, and they’re calling for an immediate ban on all salamander imports.
Salamanders that are infected with Bsal develop large, bleeding lesions all over their bodies, explains Vance Vrendenburg, a biologist at San Francisco State University and a co-author of the study. "Blood just comes out, and they die sometimes within a week." Scientists believe that Bsal came to Europe two years ago by hitchhiking atop certain species of Asian salamanders that can tolerate the fungus. The disease is easily transmitted through touch; when infected salamanders are purposefully or inadvertently released from captivity, Bsal spreads to the wild population, Vredenburg says.
"Blood just comes out, and they die sometimes within a week."
Researchers don’t really know how salamanders in North America will react to Bsal. When scientists tested it on rough-skinned newts — a North American species — 100 percent of the amphibians died within a few weeks. But North America is home to 48 percent of the world’s 676 salamander species, and testing each of them to see if they die from Bsal would be costly, not to mention a huge timesuck. That’s why Vredenburg and his team decided to use existing data to find out where North America’s salamanders are most vulnerable to the Bsal fungus.
To determine areas of Bsal vulnerability, Vredenburg and his team layered maps of North American salamander species ranges on top of the best projected habitats for Bsal. They found that the southeastern US, the western US, and the highlands of central Mexico are most at risk. And that’s a big problem: San Francisco, Tampa, and Atlanta — major salamander import sites — overlap almost perfectly with areas where salamanders are most at risk for the fungus.
Salamander Bsal Vulnerability model (Yap et al. 2015)
Over the past five years, close to 800,000 salamanders entered the US through one of those sites, and 91 percent of them were relatives of two of the species that are thought to carry Bsal.
"If the trade had been taking place in where there are no native salamanders, like northern Alaska, we wouldn’t be as worried," Vredenburg says. But "what we found was that there are tens of thousands of salamanders that are coming into the US in the very worst of places."
North America is home almost half of the world’s 676 salamander species
"These findings reveal the enormous magnitude of the threat that the Bsal fungus poses to North American amphibians," says Kimberly Terrell, a wildlife biologist at Tulane University who's familiar with the study. Given how many salamanders the US imports every year through the pet trade, it’s only a matter of time before we import the fungus, if we haven’t already, she says. "Unless something changes, we’re setting the stage for a major wildlife disease outbreak."
"We’re setting the stage for a major wildlife disease outbreak."
What’s most frustrating about the threat of Bsal in North America is the accompanying sense of déjà vu, Vredenburg says. In the late ‘90s, a related fungus, called bd, spread throughout the world. At the time, scientists didn’t know why so many animals were dying, and they failed to act. As a result, more than 200 species of salamanders went extinct, or were driven to near extinction, Vredenburg says. That’s the kind of devastation that the researchers want to avoid this time around.
"I strongly support the authors’ call for an immediate ban on the importation of salamanders into the US, and an increase in Bsal research and surveillance," Terrell says. "This fungus is a ticking time bomb, and we have the rare opportunity to stop a catastrophe before it starts."