A mysterious and rapidly-spreading fungal disease called white nose syndrome has effectively wiped out Pennsylvania's second largest bat colony. Upon investigating an abandoned ore mine in Bucks County, Pa., researchers found that of the 10,000 bats that were hibernating in the mine, only 23 were still alive, and half of the survivors were also infected with the grim disease.

Pennsylvania Game Commission biologist Greg Turner visited the site for the first time in two years and found the colony of little brown bats (Myotis lucifugus) decimated. Including the mass deaths at the Durham mine, 98 percent of the state's cave-hibernating bats have died, Turner said in an interview with PhillyBurbs.com.

"Going to places where there used to be tens of thousands of bats hibernating, and then going in and seeing only a few bats - only a few stragglers left- that's very difficult," said Turner, who has been keeping tabs on the state's declining bat populations for years.

White nose syndrome first started to appear in hibernating bats in New York in the winter of 2006-2007. The disease is believed to have surfaced in Pennsylvania in 2008, according to the Pennsylvania Game Commission.

Signs of the disease include a white fungus that appears on the nose and wing membranes of bats. Because the fungus thrives in cold weather, it affects the bats while they are in hibernation.

The commission reports that the fungus called Geomyces destructans is the causative agent of the disease, but the specific mechanism of how it causes mortality is not completely understood. The fungus kills the bats by causing them to arouse too frequently while in hibernation, severely depleting the mammals' fat reserves.

White nose syndrome has spread rapidly throughout the eastern U.S. and into Canada, killing as many as 6.7 million bats in North America. It has been confirmed as far west as Oklahoma, according to WhiteNoseSyndrome.org.

"This is probably the most devastating wildlife disease that has ever hit North America," said an unidentified Pennsylvania Game Commission member in this documentary about the disease.

Little brown bats are the most common species of bat in North America and an intergral part of the ecosystem. They are often called "farmer's friends" because they will consume around 900,000 insects per year, according to PhillyBurbs.com.

A formal study into how the deaths of the bats will affect farmers and other parts of the food chain has yet to be conducted, however there is anecdotal evidence of increased insect numbers in the summertime in areas where the bats usually hunt, the website stated.