White-nose syndrome has spread into South Carolina, wildlife authorities announced Monday, suggesting the bat-killing epidemic is still on a merciless, multipronged march across North America. It was confirmed just two weeks ago in Illinois, and its presence in South Carolina now raises the total to 21 U.S. states, plus five Canadian provinces.

The Palmetto State had seemed insulated from the fungal disease, which first appeared seven years ago in New York and has since killed about 6 million bats from Nova Scotia to the Ozarks. But in late February, a dead tri-colored bat turned up at Table Rock State Park in Pickens County, and on Monday the South Carolina Department of Natural Resources announced it tested positive for white-nose syndrome (WNS).

"We have been expecting WNS in South Carolina," state wildlife biologist Mary Bunch said in a statement. "We have watched the roll call of states and counties and Canadian provinces grow each year since the first bat deaths were noted in New York in 2007."

Park staff found the dead bat on Feb. 21 and alerted Bunch, who transported it on ice to the Southeastern Cooperative Wildlife Disease Study in Athens, Ga. Lab tests confirmed the presence of Geomyces destructans, a cave fungus that causes WNS.

The illness only affects hibernating bats, since the deep sleep lowers their body temperatures enough to give the fungus a foothold, but its mortality rate is as high as 100 percent in some colonies. Rather than killing bats directly, G. destructans wakes them up too early from hibernation, causing them to starve as they search fruitlessly for insects in winter. (The name "white-nose syndrome" comes from a white fuzz that grows on the noses, ears and wings of infected bats.)

WNS has spread quickly since its New York debut, stretching north into Canada's Prince Edward Island, west across the Mississippi River and south into the Carolinas, Tennessee and Alabama. It's transmitted mainly from bat to bat, but scientists think humans help it spread by inadvertently carrying spores on their shoes, clothes and caving equipment. In fact, most experts now believe G. destructans is an invasive species from Europe, where similar fungi seem to harmlessly co-exist with bats, possibly due to an evolved immunity.

white-nose syndrome map

The spread of white-nose syndrome since 2006. Click map to enlarge. (Image: U.S. FWS)

Cave closures and decontamination procedures are now common in white-nose country, but while such precautions may slow down the disease's spread, they've shown little ability to contain it. The tri-colored bat found at Table Rock State Park, for example, was reportedly in a remote area of the park that isn't accessible to the public.

"The news that white-nose syndrome has been confirmed in South Carolina is devastating for these very important mammals," Bunch said. "We will continue to work closely with our partners to understand the spread of this deadly disease and to help minimize its impacts to affected bat species."

As the South Carolina DNR points out, the decline of American bats poses both ecological and economic problems. Not only do they eat annoying, disease-carrying insects like flies and mosquitoes, but they're also a key regulator of agricultural pests. The roughly 1 million brown bats already killed by WNS, for example, would have eaten between 660 and 1,320 metric tons of insects annually. According to a 2011 study in the journal Science, insect-eating bats save the U.S. agricultural industry at least $3 billion every year.

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Russell McLendon ( @russmclendon ) writes about humans and other wildlife.

White-nose syndrome hits South Carolina
The deadly bat disease has officially invaded South Carolina, the 21st U.S. state in an epidemic that has already killed about 6 million North American bats.