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 fungusimplicated 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.
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.
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.
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.
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.
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.
The plan not only includes goals for each working group—which vary from collecting basic information on the disease to coordinating a nationwide monitoring effort—but also an emergency response protocol, which can be rolled out quickly in the event of an outbreak.
The protocol has a range of scenarios, from discovering a dead salamander in the wild with signs of infection to detecting the pathogen in a captive population. And for each, there’s an algorithm, a list of steps to contain the outbreak as quickly as possible.
Say someone finds a lethargic salamander covered in ulcers, for example, and reports it to a ranger. According to the protocol, the ranger should then follow a series of steps, starting with sending the salamander to one of 11 labs in North America that are equipped to test for the fungal disease. If the test comes back positive, the ranger should, among other steps, convene an emergency meeting to determine what actions to take.
And there aren’t many. The simplest approach would be to isolate the site of infection; restrict public access and fence in the area, for example. The official could also cover the pond or water body in netting to prevent birds from tracking spores to another pond.
Depending on the level of risk, scientists may also choose to take a more dramatic approach. If a small, shallow pond is bustling with Bsal and it’s home to endangered and susceptible salamanders, such as the black-spotted newt, scientists could consider dumping in fungicides. However, this method could result in serious collateral damage, according to Bletz.
“Most antifungals are pretty broad spectrum,” she says. “Even though they are potentially going to kill Bsal or other negative pathogens, they also have the potential to kill good fungi responsible for ecosystem processes within a pond.”
It’s not just pouring fungicides into a pond that has consequences. Each action, whether it’s fencing off an area or bringing species into captivity, has a drawback. And that makes decision-making for local officials incredibly difficult—especially when there’s no time.
But members of the task force, many who are veterans from the battle against Bd, saw this coming. And so they created the decision support working group. Using simulations and models, the unit’s aim is to evaluate tradeoffs and risk for “optimal decision-making.” In other words, the group will help officials determine when drastic actions might be worth the drawbacks.
Once the course of action is clear, yet another group, management, is responsible for ensuring that there are no barriers to implementation, such as restrictions under the National Environmental Protection Act (NEPA).
“Suppose there’s an outbreak in a national park or a state forest and the animals are dying in a pond,” Harris says. “Even something as simple as putting up a fence to prevent the salamanders from traveling out would require a permit.”
And obtaining one can take months or even years.
Again taking advantage of foresight, Bletz and other researchers have been seeking “categorical exemptions” from NEPA, which would essentially grant certain actions known to slow the spread of Bsal pre-approval.
No such thing as ready
If all goes according to the strategic plan, wildlife officials will be able to make informed decisions quickly at the first sign of Bsal, slowing the fungus in its tracks. And the plan isn’t just applicable to the U.S.— Kerby says he’s coordinating with the Wildlife Health Unit of the Canadian Wildlife Service to tailor the plan to fit Canada’s needs, as well.
But here’s the bad news: no one knows how to stop it. As the plan clearly states, there’s no proven method for preventing Bsal from spreading, which is why many scientists and wildlife officials are concerned about a forthcoming invasion, even though they’ve had years to prepare.
“We feel as prepared as we can possibly be given the current state of our knowledge and the availability of control techniques,” John Jensen, a senior wildlife biologist at the Georgia Department of Natural Resources, told Mongabay. “Fungal diseases are very difficult to contain; if it arrives in the U.S. or is here already, I fear it will spread relatively unabated.”
His belief is shared by other biologists working at the state and national level. Katie Richgels of the USGS told Mongabay in September that if Bsal gets here “it’s spreading, and we’re looking at catastrophic losses of a couple of species or more.”
What’s missing, many researchers acknowledge, is a silver bullet: a vaccine or a large-scale environmental treatment that doesn’t cause so much collateral damage. The longer they can keep Bsal at bay using existing actions, the more time they’ll have to find one.
A weapon in the works
A silver bullet may take many forms, yet all of them are likely to be infinitesimally small.
One of the most promising ideas for helping salamanders cope with the pathogen is using probiotics, or bacteria that naturally attack Bsal (much in the same way that bacteria in a human stomach combat their harmful brethren).
As researchers are discovering, some salamanders are naturally immune to Bsal; put them in a pond with the frightening fungus and they walk out unscathed. These species are naturally producing probiotics on their skin, researchers believe, and perhaps that cocktail of beneficial bacteria can be replicated and passed on to the less fortunate, more susceptible species.
The Blue Ridge two-lined salamander (Eurycea wilderae) is found in the southern Appalachian Mountains. Photo by Todd W. Pierson.
At the University of Massachusetts, Bletz is exploring another kind of probiotic bacteria—one that emits Bsal-prohibiting compounds into the air. It’s like a probiotic spray (but not the kind sold at Whole Foods).
It can “actually kill the pathogen without contact,” she says. “It’s not something that’s going to eliminate the pathogen, but we could create a situation where these VOCs [volatile organic compounds] reduce the infection enough that it’s not going to reach a lethal level.”
Researchers are also exploring the possibility of using some of the world’s puniest predators to control Bsal. Small, waterborne organisms, such as certain species of copepods, like to eat fungal spores, Bletz says. In fact, lab research on Bd has shown that the presence of these micro-predators can reduce the probability of infection.
“Manipulation of micropredator communities could serve as a feasible tactic to minimize infection risk,” researchers on the task force write in the strategic plan.
Then finally, there’s talk of developing a vaccine.
“We’re trying to use the technical advances in other fields like human medicine,” Bletz says. “If we can figure out what protein from Bsal is actually associated with virulence—the reason it’s so effective at invading amphibian skin—we might be able to” develop an immune response for the hosts.
Preliminary research is promising, and it continues to race ahead. But it’s just that—preliminary. Until there’s a cure or an effective treatment that yields field-tested results, the outlook for salamanders remains unknown, if not somewhat bleak.
Whenever the pathogen arrives—whether or not a silver bullet has been found—it will be a test of how ready scientists are, Harris says, of how effective the planning process has been.
“I feel like we’ve done as best as we can with the knowledge we have,” Kerby says. “We’ve thought about a lot of scenarios and we’re equipped to deal with them effectively.
“But on the other hand we don’t know.”
This article by Benji Jones was first published on Mongabay.com on 19 Dec 2018.