Winnipeg Free Press - PRINT EDITION

Bat-killing fungus came from Europe

City researchers leading effort to battle white-nose syndrome

The fungus responsible for the deaths of millions of North American bats appears to be an invasive pathogen from Europe and not a new mutation, according to research led by University of Winnipeg biologists.

Since 2006, at least five million bats in 16 U.S. states and four Canadian provinces have succumbed to white-nose syndrome, a disease that appears to rouse hibernating bat species from their winter torpor, speed up their metabolisms and cause them to starve to death. Wildlife officials fear the disease may eventually kill off most if not all the hibernating bats in North America.

The fungus responsible has been identified as Geomyces destructans, which has been found on European bats but does not appear to kill them. Biologists feared a mutated version could be killing the North American bats and that such a mutation could spread to Europe.

But research led by the U of W's Craig Willis appears to conclude the lethal pathogen comes from Europe, which is a small bit of good news for bat biologists otherwise at a loss to do anything to stop the spread of white-nose syndrome.

In a paper published Monday in the Proceedings of the National Academy of Sciences, an academic journal, Willis and scientists from Winnipeg, Colorado, Wisconsin, Saskatchewan and Germany found North American and European varieties of the fungus both lead to the death of little brown bats hibernating in labs.

Two winters ago, the Willis-led team captured 54 bats from a Manitoba cave, took them to a laboratory in Saskatoon and infected 18 with a fungus found in a New York cave, 18 others with the same species of fungus from a German cave and left 18 as a control group.

Using infrared cameras and radio-transmitting skin-temperature monitors, the scientists found both varieties of the fungus disturbed the torpor of the infected groups of bats and led them to deplete their fat reserves and die. By the end of the winter, the control group had enough fat to keep on hibernating.

Since European bats don't seem to be affected by the fungus, the experiment suggests bats overseas have adapted or evolved some means of protecting themselves from the pathogen, Willis said.

"We really need to look at European bats and figure out what's different about them," the biologist said Monday in an interview. "If European bats mount an immune response and antibody response, we really need to know what that is."

Inoculating wild bats, however, may be practically impossible, even if a vaccine could be developed, Willis said. "Bats are difficult to deal with because they don't do what we tell them," he quipped.

The fungus appears to be spreading in North America due to bat-to-bat contact. But the pathogen's origin in Europe suggests human beings are responsible for bringing it to this continent, Willis said.

"This tells us it's probably our fault. People have an obligation to try to fix it and see if there's something we can do," he said.

One hypothesis is recreational spelunkers or biologists who visited a cave in Europe unwittingly transmitted the fungus to a cave in New York state. Cavers and biologists alike now disinfect their clothes and equipment after visiting caves -- and stay away from known bat hibernacula.

Willis said protecting remaining hibernacula from visitors is now crucial -- especially those with low humidity, as his research also suggests bat mortality is highest in humid caves.

"If humidity is playing a role here, maybe we can find a level of humidity that still allows bats to survive but is dry enough to slow down the fungus," Willis said.

The surviving bats from the experiment were removed from their chambers, anesthetized and humanely euthanized, according to the published research.

bartley.kives@freepress.mb.ca

Republished from the Winnipeg Free Press print edition April 10, 2012 A5

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