The mysterious disease has been ravaging bat populations in the northeastern US appears to be caused by a previously undescribed species of a common fungus, according to research published today (Oct. 30) in Science.

White-nose syndrome (WNS) is a fungal infection that has killed 75% of some bat populations in Massachusetts, Vermont, New York, and Connecticut since it was first discovered in a cave in upstate New York in 2006. Though the specific cause of the mass die-offs remains unknown, the fungus is a likely suspect. "At this point, we have good circumstantial evidence that a particular fungus causes the WNS-associated skin infection," lead author and United States Geological Survey researcher David Blehert said in a Science press release. "We've shown that out of 117 bats examined, 90% of them exhibited characteristic lesions of fungal skin infection."

Researchers - among them several state and federal conservation and wildlife department scientists - took fungus samples from more than 100 bats, characterized by pale fungal patches on their noses, ears, and wing membranes, of several species that had succumbed to WNS.

They genetically analyzed the fungus and suggest that it is a member of genus Geomyces, which typically colonizes the skin of animals living in cold climates. Morphologically, however, the fungus differed from that for any other known species of Geomyces. "In the case of this fungal isolate, we are fairly confident that its genetics place it in the genus Geomyces," Blehert said, "but its conidia (asexual spores) represent a previously undescribed morphology of the genus."

Culturing the fungus in the lab, the researchers found that it grows best at colder temperatures - in the range of those that prevail in caves that bats in the Northeast frequent.