Bat-Killing Disease Marches South

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Al Hicks took it hard when laboratory tests confirmed the presence of white-nose syndrome among recently killed bats in West Virginia.

It was the worst news the endangered species biologist with the New York State Department of Environmental Conservation had heard concerning bats since in January 2007, when the disease was first discovered, killing bats in Schoharie Cavern not far from Albany where he leads a national effort studying the bat die-off problem.

Hicks said white-nose syndrome is an efficient killer of cave bats, wiping out 75 to 90 percent of the individuals in the colonies where it has been detected.

And the disease — named for the white substance found on infected animals’ heads and wings — has been spreading fast. During the first year after its discovery, Hicks said white-nose syndrome spread from a few sites over a 12-mile radius to affect bats over a 124-mile range. But, this year, it leapt nearly 300 miles to infect hibernating bats from the rolling hills of New England to the jagged mountains of West Virginia.

“The disease is advancing across the country at a much faster rate than we could have imagined,” he said. And Hicks said its presence in West Virginia, home to numerous cave bat species, “leaves the entire Southeastern United States open to assault.”

David Blehert, a microbiologist specializing in fungi and a leading researcher studying white-nose with the USGS National Wildlife Health Center, is confident that by this spring, laboratory analysis will confirm that the fungal organism he isolated last fall — geomyces — is the agent responsible for the bats’ demise.

“All the evidence so far points in that direction; we’re proceeding as if geomyces is the cause,” he said, adding now is the time to act to stop its spread.

Blehert believes contact is the most likely mode of transmission of the fungus. And he said in a bat’s life there are numerous opportunities for that.

Hicks explained that although cave bats may range over 200 miles during a season, which in part accounts for the rapid spread of the disease agent, “they are largely social animals.” They engage in specific group behaviors tuned to particular phases of their life cycles. For example, after giving birth in the spring, female bats gather in clusters to generate the warmth needed to keep their pups growing and healthy.

Hicks said these maternal gatherings range in size from dozens of individuals, to nursing swarms comprising up to 20,000 bats. In another event, during the late summer, the sexes come together to mingle in large masses at cave entrances, and over the winter, hibernating bats find comfort huddled together suspended from the roofs of their caves.

To stop the spread of the disease, Hicks said, “There are basically three things you can do: Chemical treatment, biological treatment, or environmental treatment.”

Each poses significant challenges.

Take environmental treatment. Because the fungus that causes white-nose grows only under the refrigerator-like conditions that exist in the caves, Blehert said one environmental solution might involve heating the caves. But “some of these caves have 30 miles of underground passageways,” making that impractical.

Deploying chemical pesticides or fungicides against the pathogen raises another set of issues. “Caves are extremely rich in microbial life, and the microbes probably play an important role in the cave ecosystem,” Blehert said. “If we went in trying to kill one fungus, then end up killing a thousand different species of fungi, I don’t think we could begin to predict the effect that would have.”

Treating individual bats poses fundamental challenges as well. Besides the difficulty in catching them, Blehert noted that skin infections, particularly fungal ones like white-nose or athlete’s foot, can be notoriously difficult to treat. Part of the reason is that the outer layers of skin are basically dead cells and inaccessible to the circulatory system, “so there is no way for antibodies to get to the site of the infection.”

“The only tool that we have now is containment,” said Blehert. “And it’s probably already to late to contain the problem into the Northeastern U.S.”

Still, he added, “We should take a serious look at enacting policies to prevent the inadvertent movement of the fungus over greater distances, by people. … There’s not going to be that much we can do where the bats are the vector.”

Hicks is not ready to concede to the invader. “It’s going to require some fast action — I hope we can find the resources and the infrastructure to come up with a solution and implement it in time. We have a responsibility to the future generations to leave them a clean and healthy planet.”

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