It looks somewhat like a dusting of confectioner's sugar, but the white coating that is showing up on more and more noses and wings of bats is the signature of a dire fungal disease that threatens to decimate bat colonies across the country.
From its discovery in 2006 a cave in upstate New York, "white-nose syndrome" has somewhat rapidly spread south and west. It now has been confirmed in at least 11 states and three units of the National Park System -- Delaware Water Gap National Recreation Area, Great Smoky Mountains National Park, and Ozark National Scenic Riverways. While some dead bats were discovered at the NRA, only signs of the fungus were found at the other two units.
As it continues its march westward, National Park Service officials are working to establish protocols that hopefully will both protect their bat colonies from infection and, if they are infected, try to contain it.
"Overall, I would say that the risk (of infection) is pretty high in some areas, especially where we have large numbers of hibernating bats, including certain caves at Mammoth Cave and Great Smoky Mountains national parks," says Dr. Kevin Castle, a wildlife veterinarian who is overseeing the Park Service's response to the emergence and spread of WNS. "We don't know what the impacts might be in areas where the bats don't tend to congregate in such large numbers, for example as occurs in much of the western United States.
"Nor do we know what the impact might be in areas such as Carlsbad Caverns, where there are large concentrations of non-hibernating bats."
The battle is just in its early stages, as officials aren't entirely sure what causes the disease or how to manage it. Nor do they know whether the disease originated in the United States or came over from Europe, where a similar fungus exists on bats, or whether there are pockets of naturally immune bat populations, although there is a genus of big-eared bats that have not been found with the disease, said Dr. Castle
"Carlsbad has primarily Brazilian free-tailed bats. They have other species, too," he added. "The desert Southwest is one of the hot spots for bat species, so there’s lots of them. We haven’t found the fungus associated with them yet, and no one can really say if we’re going to or not.”
While it's not considered a health threat to humans, white-nose syndrome is deadly to bats, and there are fears that entire species could be eradicated by it. As the disease spreads, its impacts could ripple through ecosystems. Not only are bats efficient predators when it comes to insect control -- some bats can eat up to 2,000 mosquito-sized insects in a single night -- but they in turn are prey for hawks, owls, and skunks, just to name some predators.
At Great Smoky Mountains, park officials shut off human access to all their caves back in April 2009. While Mammoth Cave National Park still leads about 400,000 visitors a year through about 10 miles of the nearly 400 miles of passages interlaced within the park's massive cave systems, officials have instituted procedures intended to prevent the human-introduction of WNS into the cave.
“This is an effort to screen and then intervene in terms of trying to protect the cave from getting white-nose syndrome, and also trying to think in terms of, if it should arrive, try to contain it and not spread it elsewhere," said Steve Thomas, a wildlife biologist with the Park Service's Cumberland Piedmont Network who is providing WNS technical assistance to Mammoth Cave officials.
The park's protocols range from addressing the issue on its website to discussing it with visitors before they go underground on cave tours. About 15 minutes before each tour leaves, an announcement concerning WNS is made. In it visitors are asked if they have been in a cave in the past five years and, if so, are they wearing any footwear or clothing, or carrying any items, such as a camera, that they had with them on those previous caving experiences.
"Certainly, footwear is the biggest concern, but anything that they can remember that might have been with them in the cave, those items are potentially at risk for having the (fungal) spores on them," Mr. Thomas said. "Once they say, 'Yes, my shoes were on a cave tour in West Virginia last year,' the next step is to ask them, 'Well, can you change shoes? Do you have a pair of shoes or boots in your vehicle or tent that were clean and were never in a cave or mine in the last five years?' Sometimes that’s an easy one, they say 'yep' and go change.
"If that’s not an option, another option is to try to clean or decontaminate the item," he added.
In that case, footwear are treated with a concentration of an industrially concentrated solution of Lysol that testing at Northern Kentucky University has shown to be effective at killing the fungus. In the case of items such as jewelry or cameras, Lysol wipes are used to clean the items. Jewelry also can be placed in Ziplock baggies.
Visitors who refuse to go through the process can be denied access to the cave.
The safeguards are enhanced for visitors who go on a "wild cave" tour, one that involves crawling through passages, and for researchers. On wild cave tours, the park provides the helmets, headlamps, knee pads, and overalls for participants, whose footwear go through the Lysol soak if they've previously been used caving. Each night those items are decontaminated.
"We don’t believe white-nose is here, but after they’re done with the wild cave tour, they’re not let loose to return to their vehicle," said Mr. Thomas. "They have to return everything they borrowed from the park, but then they have to have their boots cleaned again (as a precaution). If white-nose were to be here this is the procedure they’d have to follow anyway, so we decided to start early and get going on it.”
While researchers are working to devise another decontamination system for footwear, one, for instance, that might entail simply walking across a pad or mat treated with a decontaminant, a potential issue there is ensuring that none of the decontaminant is then tracked into the cave where it might kill naturally occurring organisms.
Whether the spores can be deposited from a contaminated boot onto the floor of the park's visitor center and picked up by the footwear of a visitor who has never been caving before, and so wouldn't think to go through the decontamination process, is unknown at this point.
“No one knows for sure what the spore load is, and what the risk is. There is evidence that shows these spores can be transported on gear, articles of clothing after going into an infected cave," said Mr. Thomas. "It’s potentially possible, and that’s why we want to come up with a method to treat everybody’s footwear as they leave.”
The wildlife biologist acknowledged that "there is a risk associated with people going on cave tours," but added that "the park is trying to be proactive and through these measures trying to minimize the risk as much as possible.”
At Carlsbad Caverns National Park, officials there are also developing protocols to screen visitors before they enter the caves.
"Our ongoing risk assessment has shown that most visitors pose little threat to the park's bats since their roosts are far from visitor trails, " said Carlsbad Caverns Superintendent John Benjamin. "By keeping our developed caves open where the risk of this fungus transmission is low, we will be able to continue educating the public about bats and WNS."
While the U.S. Fish and Wildlife Service has issued an advisory that caves and mines within states, and adjacent to states, where WNS has been identified be closed to the public, Park Service officials believe their approach is sufficient at the present to protect their bat colonies. Back in September the agency's Washington headquarters sent out a system-wide memo directing parks with caves or mines on their properties to develop by year's end protocols on how to address any WNS threat and to prepare risk assessments evaluating those threats.
“For the most part, caves on Park Service lands are generally closed unless you have a permit. It will vary from park to park, but that’s a general policy. And a permit can include a tour ticket," said Dr. Castle. "If the people at the park have a way to screen users for potential transmission, and can screen them and keep out gear and things that seem to potentially be a problem, then those caves ought to remain open. If we can’t screen people, then those caves should remain closed.”
The wildlife veterinarian added that by keeping its caves open, the Park Service can reach more people to educate them about WNS.
"I truly think that where we determine that risk of human transmission is low and the potential for education is high, it makes sense to do so," he said.