It's official: the cold-loving fungus Geomyces destructans is, in fact, the cause of White-nose Syndrome – the fast-spreading wildlife disease that has devastated bat populations through eastern North America.
The fungus was confirmed as the WNS culprit in a study by the U.S. Geological Survey's National Wildlife Health Center and its partners. Results were reported this week in the journal Nature.
Scientists have strongly suspected the fungus, which was new to science, since it was isolated from WNS-ravaged bats at the Wildlife Health Center in 2008. G. destructans was often referred to as the "putative cause" of the disease. This study, however, provides the first direct evidence that the fungus causes WNS.
"With every new disease, determining its cause is a major milestone, so we are very pleased at this news," said Nina Fascione, Executive Director of Bat Conservation International. "This confirmation gives scientists a powerful tool in their efforts to solve this deadly wildlife emergency."
White-nose Syndrome is named for the white fungus found on the muzzles (and often wings, ears and tails) of many infected bats, including those in a February 2006 photo – the first known evidence of WNS – at Howes Cave near Albany, New York. The disease attacks hibernating bats, with mortality rates approaching 100 percent at some sites. Well over a million bats of six species have been killed by this disease since the first outbreak at Howes Cave. WNS or G. destructans has now been found in 19 states and four Canadian provinces – and it shows no sign of slowing its spread.
Until now, the Nature report said, "evidence to implicate the fungus as the primary cause of this disease [was] lacking." It was unclear whether G. destructans was the actual cause of the disease, or just an "opportunistic pathogen" that took advantage of animals already weakened from some other cause.
The researchers treated 29 healthy little brown bats, which were housed in a laboratory under hibernation conditions, with spores of the Geomyces destructans fungus. All of them tested positive for WNS within 102 days. A control group of 34 bats kept in identical condition but not exposed to the fungus remained disease-free.
The study also demonstrated that the fungus can be spread through contact between individual bats.
USGS microbiologist David Blehert, an author of the study, said that while the research confirmed bat-to-bat transmission, it's also important to note that "virtually all pathogens ... are spread by multiple routes." That, he said, justifies such precautions "as limiting human access to sensitive environments occupied by bats, decontaminating equipment and clothing moved between these environments, and restricting the movement of equipment between sites."
The research team included scientists from the USGS, University of Wisconsin-Madison, Wisconsin Veterinary Diagnostic Laboratory, University of Tennessee-Knoxville, New York Department of Environmental Conservation, the U.S. Fish and Wildlife Service, Wisconsin Department of Natural Resources, and Bucknell University.
You can help scientists build on this important accomplishment by supporting Bat Conservation International's WNS Emergency Response Fund and other critical bat-conservation programs. Visit www.batcon.org/wnsdonate