A horrifying fungus invasion is headed for the U.S., but for the first time, there’s a chance that we can stop it. The pathogen Batrachochytrium salamandrivorans (Bsal) infects salamanders only, causing lesions and killing them within a week. "It’s really nasty," San Francisco State’s Vance Vredenburg tells IFLScience. "It’s like Ebola for salamanders."
Identified in 2013 and described in 2014, Bsal likely originated in Asia, where the salamanders seem to have tolerated it since the 1800s. But with the international trade of these cute, charismatic critters, the highly virulent pathogen has spread through direct contact to wild European fire salamanders, causing mass die-offs in the Netherlands. The fatality rate is 96%, and Bsal is already making its way to Belgium. While there’s no effective way of controlling the fungus after it infects wild populations, it’s possible to avert a North American crisis.
Using information from the online database AmphibiaWeb, UCLA’s Tiffany Yap and colleagues created a map of suitable Bsal habitats in North America based on locations of its Asian carriers. When they overlapped this with a map of salamander-rich areas, they developed a predictive model of where wild salamanders are the most vulnerable. Three high-risk zones were identified: southeastern U.S. where the Appalachian Mountains end, the Pacific Northwest and Sierra Nevada mountain range, and the highlands of central Mexico.
They also found that the five most active U.S. ports – Los Angeles, Tampa, New York, Atlanta, and San Francisco – are all within or near these vulnerability zones. Between 2010 and 2014 alone, 779,002 salamanders came through these ports, and 99% of them were from Asia. Bsal hasn’t arrived yet, but the risk of an introduction is high. Their findings are published in Science this week.
Salamander Bsal vulnerability model. Black squares are major ports for salamander imports. Port 6 represents Mexico City. Yap et al., 2015 Science.
The continent is home to nearly half of all 676 salamander species. "Because salamanders are small, often nocturnal and live underground, they are an often overlooked but integral part of the ecosystem," Michelle Koo of UC Berkeley says in a statement. "They're frequently the top predator and can make up the majority of the animal biomass of a forest."
Researchers previously identified three main Bsal carriers: blue-tailed fire-bellied newt (Cynops cyanurus), Japanese fire-bellied newt (Cynops pyrrhogaster), and Tam Dao salamander (Paramesotriton deloustali). And 91% of salamanders imported to North America come from these two genera.
So, the team calls for an immediate ban on live salamander imports until protocols to stop Bsal spread are established. "This is an imminent threat, and a place where policy could have a very positive effect," Vredenburg says in a statement. "We actually have a decent chance of preventing a major catastrophe." A detection test for Bsal already exists.
We’ve seen something like this before. The related fungal pathogen Batrachochytrium dendrobatidis (Bd) has caused the collapse or extinction of over 200 amphibian species, salamanders and frogs alike. "This fungus is much worse," UC Berkeley’s David Wake says. While Bd is a lingering disease, "Bsal is an acute infection that just turns them into little masses of slime in three to four days." But, as Vredenburg adds: "What's encouraging about this time, with Bsal, is that the scientific community figured it out really quickly, and we can learn a lesson from the past."
Third image: A red-bellied newt (Taricha rivularis). Common along the coast in northern California, they migrate from upland areas to breed in streams in the spring. Emanuele Biggi.