The continued spread of a mysterious disease that has killed thousands of bats in the Northeast United States may have a surprising human cause.

Scientists are suggesting that cavers may be inadvertently transporting fungal spores on their clothing or gear and contributing to the deadly march of White Nose Syndrome (WNS), named for the downy coat of fungus covering the muzzles of its victims.

Little brown bats with WNS

"It appears that there's been a significant tracking via cavers," DeeAnn Reeder, a Bucknell University biologist who has been tracking the spread of WNS through Pennsylvania bat populations, told The Scientist.

She cited fresh data that shows WNS hopping from state to state, first appearing in caves popular among cavers and the general public that Reeder called "new little ground zeroes" for the spread of the disease. If the disease was spreading through migrating bats alone, she said, it would likely spread more steadily east-to-west. "There have been some bigger jumps."

Reeder noted that established caving groups such as the National Speleological Society (NSS) have been very helpful in studying WNS and have worked with scientists to adopt methods for decontaminating gear and clothing that could possibly spread fungal spores. The real problem, she said, is amateur cavers, especially people who purposefully enter caves that are off limits.

Peter Youngbaer, a member of the NSS, president of Vermont's caving association, and a liaison between these groups and the research and management communities, said that responsible cavers have been adhering to decontamination guidelines put forth by the US Fish and Wildlife Service for nearly a year. These include thoroughly washing and disinfecting clothing and equipment and using different sets of gear for different caves. "Those [protocols] are very very tedious and thorough and they're a complete annoyance for cavers and a complete annoyance for researchers going in," he said. "It's a drag."

Youngbaer added that the caves owned by the NSS in the Northeast have been closed to cavers while bats are present. Several states, including West Virginia, New York, Pennsylvania, and most recently Virginia, have enacted a voluntary moratorium on caving where hibernating bats are present in winter months.

Reeder, who follows the same federal guidelines on decontaminating caving gear as she conducts field studies, said that the moratorium should possibly be extended nationally until researchers have better a understanding of WNS and how the disease spreads. "We'd like to see some regulation coming from the federal level," she said. "Until we have a better handle on this, we need a moratorium on caving in bat sites."

David Blehert, a microbiologist at the US Geological Survey's Wildlife Health Center, is one researcher who is close to uncovering key clues about WNS. Blehert told The Scientist that experiments he has underway will determine whether the characteristic fungus is the causative agent of the disease or an opportunistic infection showing up in weakened bats. The results should be in by the end of the year, he added. "Right now the fungus is the only concrete piece of evidence we have for a causative agent," he said. "We don't yet know for certain that this fungus is causative, but I think all the evidence is pointing in that direction."

Blehert noted that the fungus (Geomyces sp.) may remain viable for two weeks or longer outside of its host, depending on the environmental conditions. "If the spores could persist on clothing or gear for two weeks, you create a risk of vectoring it," he said. "If the pathogen does indeed turn out to be this fungus, then I think we have a greater concern with regard to human-to-environment spread than we would if it were some other pathogen with less of a tendency towards environmental persistence in the absence of a host."

But Youngbaer, who is collaborating with Blehert on a separate study to determine the prevalence of fungal spores in the soil of caves throughout the Northeast, said while he is happy to conform to existing precautions and protocols, a widespread moratorium on caving is premature, given the lack of science's understanding of WNS. "I think we should assist in these precautions, but when they go beyond that and say, 'Let's have a national moratorium and not go into caves in the summer,' there's just too many questions there," he said. "It's a fair discussion to have, but it's very premature."

With WNS spreading beyond Northeastern states and more and more bats succumbing to the mysterious disease, such a moratorium may have little effect, said Blehert. "I might argue that at least in the Northeast US, it's too late," he said. "It seems like the cat's out of the bag in the Northeast US."


Related stories:

White noses hit PA brown bats
[29th January 2009]

Deadly bat fungus fingered
[30th October 2008]

Nabbing bats' nemesis
[October 2008]

Photo courtesy of New York Department of Environmental Conservation