MILWAUKEE — When bats in northeastern America began dying off in alarming numbers a few years ago, wildlife ecologists were perplexed.
They named the disease white-nose syndrome, but until now authorities had no idea what caused the fatal ailment.
Researchers in Wisconsin have discovered the culprit is a fungus that’s common in Europe but wasn’t seen in the United States until five years ago. Now that the cause has been determined, officials can turn their attention to stopping the spread of the disease.
In research published online Wednesday in the journal Nature, scientists from the University of Wisconsin-Madison, U.S. Geological Survey National Wildlife Health Center in Madison and other institutions determined that the fungus Geomyces destructans causes white-nose syndrome.
“We need to know what we’re up against, what we’re fighting,” said David Redell, a Wisconsin Department of Natural Resources bat ecologist and a co-author of the study.
An estimated 2 million bats in North America have already died of the disease since 2006. The threat from white-nose syndrome is so dire that scientists say little brown bats have a 99 percent chance of regional extinction in the Northeast within a decade.
Because bats consume so many insects that spread West Nile virus and other illnesses, they’re a vital part of the ecosystem. Without them farmers would need more pesticides for their crops.
Researchers in Wisconsin collected about 100 healthy little brown bats three years ago from a hibernaculum in the state and transported them to the Madison research lab in a cool environment so they did not wake from their hibernation. The fungus was spread in liquid form on their nose and wing membranes.
Scientists also transported bats already infected with white-nose syndrome in New York and placed them in a controlled setting with healthy bats at the Madison facility.
In each of the experiments, the healthy little brown bats succumbed to white-nose syndrome, named for the white fungus on bat muzzles. The fungus attacks their delicate skin, eating holes in wings during hibernation when they’re most vulnerable. In the study where the fungus was spread on their wings, every bat contracted white-nose syndrome and died. In the other test, almost 90 percent of healthy bats that came in contact with the infected bats became ill and died.
David Blehert, the senior author of the study, said that once the disease infects the bat population it’s very difficult, if not impossible, to stop it in its tracks.
“There is still not a magic bullet to deploy,” said Blehert, a microbiologist at the U.S. Geological Survey National Wildlife Health Center.
Now that the cause has been determined, the next step is to learn exactly how and why the fungus kills bats. That will help wildlife officials come up with a strategy to prevent the disease from spreading.
A bat immunology study is starting soon with the aim of seeing whether vaccines could be administered. Also, researchers are looking at whether slight changes in hibernaculum conditions, such as temperature and humidity in the caves and mines where bats spend the winter, might make a difference in spreading white-nose syndrome, Blehert said.
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