A spreading fungus can be deadly to snakes

One of the first hints that yet another fungal disease that could devastate wildlife was emerging in the United States came in 2006 with a report that an isolated winter den of timber rattlesnakes in New Hampshire had suffered a population crash.

Those snakes were on the far northern edge of their species’ habitat, and showed signs they had suffered from inbreeding. But they also had skin lesions, often called hibernation blisters or hibernation sores, that caught the attention of scientists.

Similar cases popped up in Massachusetts, said Jeffrey Lorch, a microbiologist at the U.S. Geological Survey’s National Wildlife Health Center in Madison, Wisconsin. Then rattlesnakes in Illinois, called massasaugas, began to suffer.

“People started being on the lookout,” he said. The health center started getting a lot of calls.

By 2009, Ophidiomyces ophidiodiicola, the fungus that causes the lesions, had been named. And it has been found to infect more than two dozen species of snakes in this country.

Sometimes the snakes recover quickly, but sometimes the fungus is fatal. “I’ve seen it go really, really rapidly,” said Frank Burbrink, a curator at the American Museum of Natural History in New York and an author of a new report on the disease published Wednesday in Science Advances.

“If it were a human, it would be one day Grandpa had a sore on his face and the next day it’s like ‘Night of the Living Dead.’”

Burbrink, Lorch and Karen Lips, a conservation biologist at the University of Maryland, collaborated on an analysis that concluded that any species of snake, anywhere, could be vulnerable.

Based on a mathematical analysis of the evolutionary relationships of 23 wild-infected species in the United States and two in Europe, the research found that nothing distinguished these species from most other snakes.

What is the trait that makes a species susceptible? “The trait is being a snake,” Burbrink said.

He described the paper as “a call to arms” for intense monitoring of an infection that has the potential to be as devastating to snakes as white nose syndrome has been to bats, and other fungal diseases to frogs and salamanders.

He emphasized that the new fungus may not be as bad as those other infections. But the potential is there, he said, and now is the time to get ahead of the disease.

“We know so little,” he said, including how severe the fungus may be, about its origins, about how it affects different snakes.

But it is already clear, he added, that this is “another emerging fungal disease that has really broad host ranges.”

Other fungal infections that have hit wildlife recently fuel the sense of urgency among snake biologists. Since 2007, white nose syndrome, a fungal disease that seems to have come from Europe, has killed millions of bats in 31 states and Canada.

Chytrid fungi have killed millions of frogs since the late 1990s, devastating some populations. And a number of salamander species have been banned from import because a chytrid fungus threatens them, as well.

The extent of the damage to snake populations so far is unclear. Burbrink and others say that’s because snakes are often hidden and not well studied, and the disease is new. Some individual snakes survive the fungus well, shedding their skin. But the fungus can get beneath the skin and become fatal.

Matthew Allender, a veterinarian and epidemiologist at the University of Illinois who has published with his colleagues more than a dozen papers on the fungal disease, said he agreed with the paper’s call for greater monitoring and study.

“I was glad to see that somebody took a new approach to quantify what we’ve been seeing in the field,” said Allender, who did not take part in the new research. “We see it in just about everything.” That includes snakes that live in all habitats, he said: on land, in water, in forests and on beaches, and even among burrowing snakes.

The history of the fungal disease is not known. “We really just don’t know the answers to many of these questions,” Lorch said.

It is likely that the fungus can live in the soil, at least for a short time, he said, and reports in the scientific literature of lesions that resemble the fungal infection go back at least to the 1950s. Evidence of the disease itself in captive snakes, he said, goes back to around 1980.

The fungus may be native to North America, but it has also been found in wild snakes in Europe.

It may be, Lorch said, “that what we’re looking at is the tip of the iceberg of this disease.” The new analysis “supports the notion that no species is safe.”

It may turn out that snakes are more resistant to this infection than bats or frogs have been to the fungal diseases that have devastated their populations. But additional monitoring of snake populations and research on the disease itself is necessary, he added.

“Let’s start doing our homework,” he said, “so if the sky does start falling, we can respond quickly.”