Deadly Bat Disease Linked to Cold-Loving Fungus

Brian Handwerk
for National Geographic News
October 31, 2008
Scientists have pinpointed the fungus linked to white-nose syndrome, the mysterious ailment that has wiped out large populations of bats in the northeastern United States.

The fungus, found on the wings, ears, and muzzles of infected bats, is a member of the Geomyces genus.

"It's a cold-loving fungus known to be associated with Arctic permafrost soils," said study co-author David Blehert, a microbiologist at the U.S. Geological Survey's National Wildlife Health Center in Madison, Wisconsin.

Northeastern U.S. caves maintain year-round temperatures between 35 and 59 degrees Fahrenheit (2 and 15 degrees Celsius)—well within the fungus's reproductive range.

Since the winter of 2006 to 2007, white-nose syndrome has caused 80- to 97-percent-mortality rates in some large hibernation colonies, putting some species at serious risk.

The situation has experts worried, since a single bat can eat more than its body weight in bugs each night, aiding the fight against crop damage and disease.

Why Do They Die?

Scientists don't yet know if the fungus is actually causing the bats to die.

The organism doesn't look like other known Geomyces, despite its close genetic relationship.

"In one sense it looks like it could have been a [recently] introduced fungus that's spreading," Blehert said.

On the other hand, it may simply be one of the many fungi species that scientists hadn't noticed because it had no obvious impact on bats.

"Bats have evolved to live in cool, dank environments just loaded with fungi, and this problem hasn't been reported before. They must have some mechanism that prevents them from getting moldy when hibernating," he said.

Bats are generally considered to have hardy immune systems.

"Is there something that's been perturbing the bats' immune systems?" Blehert asked.

Other pathogens or diet deficiencies—perhaps pesticide-driven—could make bats newly susceptible to even familiar fungi, scientists say.

Now that the white-nose fungus has been identified, its possible role in killing the small mammals may soon become clear.

Blehert's team will run trials to see if the fungus alone can cause the syndrome in otherwise healthy bats.

Identifying the problem represents progress toward a solution, but easy fixes may be elusive, added study co-author Al Hicks, a bat expert with New York's Department of Environmental Conservation.

"We all hope it isn't [just] the fungus," he said. "I don't believe the fungus is something that we can address very easily."

(Related: "Amphibian Bacteria Fights Off Deadly Fungus, Study Says" [May 29, 2007].)

Emaciated and Starving

John Hermanson, of Cornell University's College of Veterinary Medicine, said the fungus could prove physically devastating even if it's not highly toxic.

For one, infected bats are emaciated, dehydrated, and starving, conditions that interrupt their winter hibernation cycles. The animals also likely have only enough fat reserves to survive hibernation.

"After a bad night's sleep we feel pretty bad," said Hermanson, who was not involved in the research.

"Imagine if you were supposed to sleep for four-and-a-half months" and kept having to wake up, he said.

"If they are waking up almost daily because of [the effects of the fungus], that could really be the cause of major problems."

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