Discuss as:

Disease wiping out bats hits new species, spreads west

Cory Holliday / Fish & Wildlife Service

White-nose syndrome is seen around the nose of a gray bat inside a cave in Montgomery County, Tenn.

A mysterious bat-plaguing disease has shown up in a seventh species, the U.S. reported Tuesday, and said even more could succumb as white-nose syndrome makes its way across the nation from the East Coast. That's particularly bad news for farmers who benefit from bat colonies that can devour a ton of insects in a single serving.

Gray bats, a vulnerable species that's been federally protected since 1976, are the latest to get hit, with infections of the white fungus found on bats in two Tennessee counties, the U.S. Fish & Wildlife Service announced

If trends continue, the syndrome "is likely to continue to spread west and it is probable that other bat species will be impacted," Paul McKenzie, a service staffer who works on endangered species issues, told msnbc.com. 

The 26 species of hibernating bats across the U.S. are the ones at risk, since the disease thrives in the cool temperatures of caves and mines where those species spend their winters. 

The concern is not just about protecting bats for their sake, or even the ecosystems they create inside caves, but their contribution as a natural pest control saves farmers billions of dollars a year and means fewer chemicals used on our foods. 

"Gray bats eat a lot of moths, beetles, flies" and other insects, Ann Froschauer, a spokeswoman for the service's White-Nose Syndrome program, told msnbc.com. "A colony of 250,000 gray bats can eat about one ton of insects in a night."

Fish & Wildlife Service

"There aren't other animals that can step in and take the place of bats in terms of these pest control services," she added. 

Year after year "gray bats probably consume over a trillion insects" across their Southeast and Midwest habitats, added McKenzie. "The economic impact to agriculture and forestry could be astronomical" if the disease starts a mass die-off.

The disease was first detected in 2006 in New York state. Thought to have come from Europe, it has since spread to 19 states and four Canadian provinces -- killing some 6 million bats.

In some areas, entire colonies have been wiped out.

A recently discovered fungus, Geomyces destructans, is now known to cause the syndrome, but scientists still don't know how to combat the disease. Some bats survive, but others die after losing their fat reserves or leaving their caves before winter is over. 

In the case of gray bats, which number around 4 million, no deaths have been reported. But they are particularly vulnerable to disease because they hang out in dense colonies that can number in the hundreds of thousands.

The species was "well on the way to recovery" before the disease hit, McKenzie noted, but now the fear is it will "expand exponentially" across the bats' habitat.

More content from msnbc.com and NBC News:

Follow US News on msnbc.com on Twitter and Facebook