This 2008 file photo shows a little brown bat suffering from white-nose syndrome found in a New York cave. Credit: New York Department of Environmental Conservation

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A devastating fungus that kills hibernating bats has been found for the first time in Wisconsin in an abandoned mine in Grant County, state officials announced Thursday.

White-nose syndrome was discovered in bats last month while Department of Natural Resources personnel were inspecting an old mine site in southwestern Wisconsin, the agency said.

The finding has wide-ranging implications, especially for agriculture, because of bats' voracious insect-eating ability. A single little brown bat can consume 600 mosquitoes in an hour.

Wisconsin officials say the state has one of the largest populations of hibernating bats in the Midwest. An estimated 350,000 to 500,000 bats use caves and mines before dispersing in the spring to Illinois, Indiana, Minnesota, Iowa and Michigan.

A 2011 study examined the economic impact of bat populations and concluded that in Wisconsin alone bats provided an annual economic benefit ranging between $658million and $1.5 billion.

The fungus causes bats to awake while hibernating. Flying and other movements deplete energy stores and causes dehydration before spring.

White-nose syndrome poses no health threat to humans, the DNR said.

A few hours after the Wisconsin DNR's announcement, the Michigan Department of Natural Resources said white-nose syndrome had been discovered in three counties — Dickinson and Mackinac counties in the Upper Peninsula and Alpena in lower Michigan. Dickinson County borders Florence and Marinette counties in Wisconsin.

The announcements bring to 24 the number of states with the disease.

White-nose syndrome has killed more than 5.7 million bats in the United States and eastern Canada, according to estimates. It was first found in New York in 2006.

"A day we had long dreaded has arrived," DNR Secretary Cathy Stepp told agency personnel in an email Thursday morning.

She said the finding appeared to be an isolated incident, but experts believe once the fungus is detected, bat mortality will grow. Mortality in caves in other states has reached 95%, she told employees.

The DNR has been conducting winter surveillance to look for evidence of the disease. It was wrapping up a sweep of 85 hibernacula when employees found telltale evidence of the disease in 11 bats in the Grant County cave. White fungus was found on the muzzle of the bats and other body parts.

Laboratory results confirmed the disease in two species — little brown and northern long-eared bats.

The same site was inspected last year, but revealed no sign of the disease, according to Erin Crain, director of the state Bureau of Natural Heritage Conservation. An estimated 700 bats were hibernating there. Most were little brown bats.

The disease is transmitted when bats come into contact with the fungus or an infected bat.

"We're not surprised," Crain said. "We knew this was coming."

Crain said she expected bat populations to decline beginning in 2015.

David Blehert, a microbiologist with the federal National Wildlife Health Center in Madison, said the trend in other states has been higher bat mortality in the second and third years after detection.

The Grant County mine is within flying distance for bats from a site in Illinois where white-nose syndrome had been confirmed in 2012. The fungus, Pseudogymnoascus destructans, was discovered on a bat in Iowa's Maquoketa Caves State Park, 30 miles from Dubuque, in 2012.

The DNR is awaiting test results from 19 other caves and mines from its winter surveillance.

Officials also plan to return to Wisconsin's largest hibernaculum, the Neda mine in Dodge County.

As white-nose syndrome began to spread, Wisconsin in 2011 added the little brown, northern long-eared, eastern pipistrelle and big brown bats to its list of threatened species.

The DNR is not identifying the location of the Grant County cave, other than to say it is on private property in a region with numerous caves and old mining sites. The 2011 protections adding the bats to the state's natural heritage inventory of rare or threatened species permits authorities to keep locations private.

About 100 cave and mine owners in Grant County are being notified of the discovery.

Blehert said scientists have found that while the fungus thrives in relatively cool temperatures, it might not be as lethal when temperatures dip to freezing or below.

That could mean bats inhabiting a home attic might have less of a chance of an infection than cave-dwelling bats, where temperatures are somewhat warmer.

Larger big brown bats seem to be more resistant to white-nose syndrome than smaller bat species, Blehert said.

Scientists at the National Wildlife Health Center are investigating whether the disease acts differently in the bat populations in different parts of the country.

"We still don't know if the outcome of the disease will be the same in every location as the environment changes," Blehert said.

He said scientists also are studying whether a vaccine — not individual injections but introduced to hibernacula — could be one strategy to control the spread of the disease.

The DNR has collaborated with commercial cave operators and others to limit the spread of the fungus. One common practice is making sure those who visit a cave are not wearing the same clothing where the fungus has been found.

Most Wisconsin caves that house bats in the winter have been closed to the public during hibernation, the DNR said.

The DNR says the public should report dead or sick bats and avoid disturbing them, especially during hibernation.