For salamanders, the fungal disease known as "Bsal" is hell.
Spores of the fungus travel through water, and when they find their intended host — the slippery skin of a salamander — they burrow in. There, they grow and reproduce, spreading their spindly thalli (stem-like structures) through the skin.
It isn't pretty. "When we take a cross section of the skin, it looks like somebody took a shotgun and shot the salamander," says Matt Gray, a professor of wildlife ecology at the University of Tennessee. "It literally creates these ulcers that are tunnels right through the skin of the amphibian."
That's a huge problem. For amphibians like frogs and salamanders, skin acts as more than just a protective covering. It's their respiratory system. It's their excretory system too. A Bsal infection is the equivalent of a disease in humans that took out the lungs, kidneys, and skin in one shot. "Also, you could imagine, if you had a bunch of little holes in your skin, it could increase your likelihood of secondary infection from other pathogens," Gray says.
Salamanders infected with Bsal become lethargic, their skin sheds excessively, and they stop eating. Then they die.
Bsal, which is believed to be native to Asia, has already wiped out entire populations of salamander communities in Europe, where the animals have no natural immunity to it.
The good news is that Bsal (short for Batrachochytrium salamandrivorans; we'll stick with Bsal) has not yet been discovered in the United States.
And the US is taking action. The US Fish and Wildlife Service, under the authority off the Lacey Act, has issued an interim rule prohibiting the trade of 201 salamander species "because of the devastating effect that we expect the fungus will have on native U.S. [species]," the wildlife department states. The rule, which goes into effect January 28, makes it illegal to import the salamanders from foreign countries or move them across state lines. (Wildlife is taking public comments for 60 days, and then will finalize the rule.)
But if Bsal ever did come here, the stakes would be even higher than they are in Europe. Fifty percent of all salamander species in the world are found in North America. In the Great Smoky Mountains, for instance, "if you take the bears, the raccoons, the birds — per a unit of area — and you put them on a scale," Gray says, "the salamanders can outweigh them."
And many of these species could be defenseless against Bsal. "When you have pathogens that move from one geographic area of the world to another," Gray says, "it's got all the machinery to devastate a host, but the host's immune system can't respond."
It's a recipe for extinction. Bsal hasn't yet reached our shores, but there's a real risk it could. We've seen it happen before: In the 1990s a similar fungus called Bd (Batrachochytrium dendrobatidis) ran laps around the world, killing off whole species of amphibians. "We are at a critical time of action to protect global amphibian biodiversity," Gray and colleagues write in a call to action in the journal PLOS Pathogens.
The scientists are worried the United States is not entirely prepared to prevent a salamandergeddon. But the outlook isn't entirely bleak. Most of all, Gray and his colleagues want the world to know this: We don't have to allow North American salamanders to die on our watch.
Why an America without salamanders would stink
Due to their large numbers — and huge appetites — salamanders are the keystone of many forests' food chains.
"Think of them as an energy conduit from bugs to birds," Dede Olson, a research ecologist with the US Forest Service, says. "If you take that middle cog out, then the whole machine stops." If all the salamanders in American forests were to die," she says, "that would change the way we understand our forests."
Aside from ecological collapse, scientists would also be missing out on potential medical discoveries. Salamanders are famous for being able to regenerate limbs and even regrow critical organs like the heart. Salamander skin also hosts an array of chemicals with potential medical importance. "Those could be used for painkillers," Gray says.
Salamanders also play an important role in trapping excess carbon from entering the atmosphere. Salamanders eat invertebrates that shred through foreign forest leaves, releasing the carbon dioxide trapped in the leaves back into the atmosphere.
In 2014, a group of scientist conducted a test on two garden plots, one with salamanders and the other without. "In the plots with no salamanders there were more shredders, and they consumed about 13 percent more of the leaf litter," the New York Times reported on the study. "Almost half of that lost weight was carbon, released into the atmosphere."
How to save the salamanders
The problem with Bsal — like so many other foreign, infectious diseases that appear out of nowhere — is that ecologists and biologists know so little about it. It was identified in 2013, and science proceeds slowly. "There's about three papers. Maybe four. And that's the total of what we know about it," Karen Lips, a conservation biologist at the University of Maryland, says.
Not all salamanders appear to succumb to it. Scientists in Europe have been testing species one by one. Those tests are not comprehensive (there are more than 400 species of salamander worldwide), but they identified some North American varieties as being vulnerable. "Even if it [Bsal] were selective and not hitting everything but hitting some species, it would be a wave of disruption," Olson says.
Gray and Olson are co-authors on the essay published in PLOS Pathogens, calling for action on the Bsal threat. They say a first step to protecting American salamanders from harm is banning international trade, which the US just did. (Gray says that even though the US has tons of salamanders, foreign ones can often be "flashy." Salamanders account for 5.5 percent of amphibian imports.)
But they also warn that the Fish and Wildlife Service has no ability to stop the import of particular disease, just the animals that carry them. So further research is needed to identify more species (perhaps even some frogs) that may be able to carry Bsal. And while the US Department of Agriculture requires shipments of domesticated animals to be certified as disease free, "evidence of pathogen-free shipments is not required for imported wildlife," Gray and his co-authors write. "These policy gaps have created challenges in efforts to reduce the risk of Bsal introduction."
And despite import bans, there's no guarantee that in an interconnected world, the fungus wouldn't find its way here.
In November, the Pet Industry Joint Advisory Council issued a recommendation to stop the import of two newt species and that "all non-retail businesses engaged in the salamander trade regularly sanitize their facilities as a prophylactic measure, as treatments are developed, out of an abundance of caution."
Once diseases like Bsal are in the wild, "there's no vaccine, no secret treatment," Lips said. In small-scale settings, Lips says, a solution that has worked for the treatment of Bd has been to kill off all infected creatures in an area and then replace them with healthy ones. "It's essentially taking a bucket of bleach, bleaching your backyard, and then adding all the animals back," she says. "Most places, that's not going to be useful."
Less drastic measures can prevent the need: Gray, Olson, and their colleagues also call for increased surveillance in pet stores and in zoos, identifying more possible routes of entry into the US, and a national response system to deal with a positive diagnosis if it were to occur.
"There are a lot of us who would like to implement something for conservation, and it’s just so hard — there are so many species, so many habitats, there’s so much, you just get numb to it," Olson says. "But here’s something that we can be effective on: We can forestall a potential disaster."