Imported pet salamanders carry killer fungus

The new fungus "is an imminent threat, and a place where policy could have a very positive effect," says Vance Vredenburg. "We actually have a decent chance of preventing a major catastrophe." Above, a red-spotted newt, a native of the Eastern US. (Credit: iStockphoto)

Five amphibian experts are urging the US Fish and Wildlife Service to immediately stop salamander imports.

They warn that a recently discovered fungus already devastating salamanders in Europe could imperil American salamanders.

Ensatia salamanders
The Ensatina salamander (Ensatina eschscholtzii), a lungless salamander common along the west coast of the US, is one of hundreds of species of salamanders endemic to North America threatened by an emerging infectious pathogen. (Credit: Tiffany Yap)

Salamanders are an important part of forest ecosystems but also a popular pet worldwide. Nearly three quarters of a million salamanders were imported into the US between 2010 and 2014, 99 percent of them from Asia, where the fungus likely originated.

Because of this, the scientists and other herpetologists worry that the fungus could spread from Asia, where the salamanders seem to tolerate the fungus, to more vulnerable parts of the globe. Since it was first recognized in 2013, the fungus has caused a 96 percent fatality rate among the European salamander species that it infected.

Why a ban is urgent

What makes a US ban urgent is that a recent study showed that two common American salamanders—the rough-skinned newt found all over the Pacific Coast and the iconic Eastern newt of the Eastern US—are highly susceptible to the fungus.

The fungus, called Batrachochytrium salamandrivorans (Bsal), is related to another fungus—Batrachochytrium dendrobatidis (Bd), or chytrid—that has already severely impacted frog and salamander populations around the globe.

The infection “just turns them into little masses of slime in three to four days”

“This fungus is much worse than the chytrid fungus, which is more like a lingering disease that affects the skin and puts stress on the salamander until it dies,” says David Wake, a professor in the graduate school at University of California, Berkeley and the director and founder of AmphibiaWeb, an online database of information on amphibian biology.

“Bsal is an acute infection that just turns them into little masses of slime in three to four days.”

The federal government has been slow to act despite support for the ban by key scientists and an online petition initiated by the Center of Biological Diversity in May.

“There is a lot at stake here if the US Fish and Wildlife Service doesn’t stop imports now to prevent the introduction of this devastating pathogen to North America,” says coauthor Michelle Koo, a UC Berkeley researcher in the Museum of Vertebrate Zoology and associate director of AmphibiaWeb, an online database of information on amphibian biology.

A paper describing the potential effects of the fungus on US and Mexican salamanders appears today in the journal Science.

Tracking Bsal

Koo and first author Tiffany Yap, a UCLA graduate student working in the museum, created a model to identify vulnerable salamander populations in Canada, the US, and Mexico. After pinpointing North American areas similar to the native habitat of the Asian fungus, they assessed the salamander populations in those areas and their proximity to ports of entry for the salamander trade.

The model produced a map of salamander populations at highest risk of declines and extinctions from the fungus, with hotspots in the southeastern United States, particularly the southern extent of the Appalachian Mountain range and its southern neighboring region; the Pacific Northwest and the Sierra Nevada; and the central highlands of Mexico.

Through AmphibiaWeb, Koo is working with the US Forest Service to create an online portal where biologists can record occurrences of Bsal infection, in order to track the spread of the fungus. Koo will discuss the Bsal vulnerability model and centralized database this week during the meeting of the Society for the Study of Amphibians and Reptiles, held July 30-August 3 at the University of Kansas.

Dying animals

Coauthor Vance Vredenburg, who has studied the chytrid or Bd fungus for more than a decade, notes that more than 200 species of amphibians have gone extinct or are near to extinction as a result of infection, making it the most devastating infectious wildlife disease ever recorded.

“I have seen the effects of Bd on frogs, to the point where I’ve seen tens of thousands of animals die in the wild in pristine areas, here in California, right in front of my eyes,” says Vredenburg, an associate professor of biology at San Francisco State University.

The new fungus, he says, “is an imminent threat, and a place where policy could have a very positive effect. We actually have a decent chance of preventing a major catastrophe.”

Salamanders are one of the most abundant vertebrate animals in many North American ecosystems and play a number of key ecological roles, Koo said.

“Because salamanders are small, often nocturnal and live underground, they are an often overlooked but integral part of the ecosystem,” she says. “They’re frequently the top predator and can make up the majority of the animal biomass of a forest. This fungus puts at risk an important part of a healthy forest.”

One of the European salamanders shown to be highly susceptible to the fungus is a member of the plethodontid family, which has its greatest biodiversity in the US Nearly two-thirds of the 675 salamander species are plethodontids, including the familiar California slender salamander, and they make up the majority of salamanders in the US

“California salamander populations are already way down because of the drought,” Wake says. “We need a ban now to head off this new fungus; otherwise, we will have to spend a lot of money to eradicate it.”

Richard Ambrose of UCLA is also a coauthor of the paper.

Source: UC Berkeley