A deadly fungus called Bsal decimated salamander populations in Europe, and scientists are very worried that it will soon invade North America.North America – and the U.S. in particular – is the world’s hotspot of salamander diversity, hosting about a third of all species. Researchers think half of U.S. species may be susceptible to Bsal.Scientists say it may be only a matter of time before Bsal gets to North America. And when it does, they warn that it could mean devastation for salamanders and even drive some species to extinction.In an effort to head off the threat, scientists and government officials created the Bsal Task Force in 2015. Next month they intend to release their strategic plan, the culmination of years of collaboration and research, which provides a roadmap for what to do in the event Bsal is detected in North America. Any day now. That’s when Batrachochytrium salamandrivorans (Bsal), the “salamander-eating” fungus, is expected to arrive in the United States, home to more than a third of the world’s species of these slippery amphibians. It all began in 2008, when Bsal traveledsome through the pet trade from Asia to northern Europe. There, it escaped into the wild and decimated the local population of fire salamanders. And now it’s only a matter of time before it sneaks across the U.S. border, scientists say. But for years, they’ve been preparing for that day. In 2015, a group of amphibian researchers came together to establish the Bsal Task Force, a volunteer-led organization dedicated to mitigating the domestic threat. Over the years, it has coordinated research and monitoring efforts, and released a number of reports. And next month, the task force plans to release a nearly 100-page national strategic plan, a culmination of its work to preemptively thwart the pathogen. In the world of wildlife diseases, the plan is unprecedented. Never before have scientists and wildlife officials been so prepared for a disease—certainly not for Bd, a related chytrid fungus implicated in the decline of some 200 species of frogs, and certainly not for white-nose syndrome, a fungus that has obliterated bats. “I think we’re in an unprecedented position to be able to control an outbreak,” says Reid Harris, the former task force chair and director of international disease mitigation at Amphibian Survival Alliance. “I’m cautiously optimistic.” But not everyone is. Among amphibian academics familiar with the pathogen, hope is hard to come by. There’s no such thing as ready, many say—short of developing a vaccine or a treatment for large habitats, neither of which are on the horizon. Ground zero Sometime around 2008, bright yellow and black salamanders began dying in the Netherlands. At first, scientists suspected Bd, known as chytrid fungus, a pathogen that infects more than 700 species of amphibian worldwide with the deadly disease chytridiomycosis. Yet the tests came back negative. Bsal has decimated fire salamander (Salamandra salamandra) populations in western Europe. Photo by Christian Jansky via Wikimedia Commons (CC BY-SA 1.0) With more and more salamanders dying each week, Reptile, Amphibian & Fish Conservation Netherlands, a local nonprofit, hustled 39 of them into captivity. But there they continued to fall ill, developing lesions all over their bodies. Unsure what to do, the nonprofit brought one of the sick salamanders to nearby Ghent University for testing, where veterinarians swabbed its skin and created a fungal culture that promised to reveal the culprit. As they suspected, it wasn’t Bd, but they saw something similar. It was a species of fungus in the same genus that the vets named Batrachochytrium salamandrivorans, or literally “salamander-eating” chytrid fungus. And it, too, was capable of causing the deadly disease chytridiomycosis—this time, in salamanders. A pernicious pathogen Since Bsal was described in 2013, it wiped out 99 percent of fire salamanders in the Netherlands. And now, it’s spreading in Northern Europe, threatening species in neighboring Germany and Belgium. But in that time, researchers have also come to better understand the pathology of the disease—knowledge, they hope, that can be used against it. Like Bd, microscopic spores of the Bsal fungus latch onto the moist skin of an amphibian host. Then they get to work, using resources from the animal’s flesh to construct “mother cells,” essentially becoming small factories that generate more and more spores. The green salamander (Aneides aeneus) is a member of the Plethodontidae family of salamanders that scientists believe are particularly susceptible to Bsal. Like other plethodontids, green salamanders don’t have lungs, breathing instead through their skin and vascularized tissue in their mouths. Image by Todd W. Pierson. As the fungal society advances, susceptible salamanders develop lesions on their skin that look like cigarette burns. That’s bad news for amphibians, many of which use their epidermis to absorb oxygen, water, and nutrients from the environment. “It’s death by a thousand holes,” says Molly Bletz, a disease ecologist at the University of Massachusetts. “It sears holes into the skin of the amphibian and may actually inhibit the animal’s immune system.” And without a properly functioning immune system, a salamander can’t fight back. Bsal is not just a capable killer; it’s also highly mobile, scientists say, perhaps even more so than Bd (which has conquered much of the planet over the last two decades). Both fungi produce swimming spores, which don’t last long without a host. But Bsal generates another, much hardier spore that floats on the water’s surface. There, it waits to adhere to an unsuspecting salamander or to the feet of waterfowl, which can easily transport the pathogen between distant water bodies. Inevitable arrival If Bsal is a perfect pathogen, than the U.S. might be the perfect host country. It has the highest diversity of salamanders in the world, and more than half of them may be susceptible to chytridiomycosis. Without a doubt, the most effective tactic for thwarting a Bsal crisis is to prevent the fungus from arriving stateside in the first place. To that end, the U.S. Fish and Wildlife Service placed an import ban on 201 salamander species in 2016; to this day, it’s illegal to ship any of those salamanders into the country, as pet-friendly as they may be. Heat map of the U.S. showing the total relative risk of Bsal to native U.S. salamanders based on the introduction and consequences assessment published in the journal Royal Society. Figure from Richgels, et al., 2016, via CC BY 4.0 But while the ban may be delaying the pathogen’s arrival, it’s not a failsafe. In fact, there are known Bsal carriers absent from that list like the highly traded Asian salamander Pachytriton. And according to one study, up to 66,000 salamanders infected with Bsal could have entered the U.S. in the last decade, not to mention frogs, which account for 94 percent of all imported amphibians and can also harbor Bsal. “With the current trade laws that we have, it does look like some like Bsal will find its way here,” says, Jake Kerby, the task force chair and biologist at the University of South Dakota. “It’s just the way wildlife diseases work.” Readying a response With so much to lose, scientists refuse to be caught off guard. Instead, they’re taking advantage of a rare opportunity within the field of wildlife disease to be proactive, to prepare a counterattack. According to the strategic plan, the task force has organized itself into several different battalions: research, diagnostic, surveillance, response, decision support, management, and communication and outreach. Each of them is responsible for a different angle of the disease’s takedown. “The research working group focuses on testing possible disease management options, the decision working group helps biologists decide upon a course of action given likelihood of success, and the management working group assists biologists with implementing management strategies,” they write in the strategic plan.
