A study published in the journal Nature purports to prove the Geomyces destructans fungus is causing a deadly illness responsible for catastrophic die offs among multiple bat species in eastern North America.
Little brown bat with fungus on its muzzle
Courtesy of Al Hicks/New York Department of Environmental Conservation
The investigation led by the U.S. Geological Survey is offered as the first direct evidence that G destructans is behind white-nose syndrome in bats.
Since the disease was first reported in January 2007 in New York state, the white-nose syndrome outbreak has spread to hibernating bats in more than a dozen states and four Canadian provinces. Biologists estimate more than a million bats have died of white-nose syndrome, making it the worst wildlife health crisis in memory, according to the U.S. Fish and Wildlife Service.
"By identifying what causes WNS, this study will greatly enhance the ability of decision makers to develop management strategies to preserve vulnerable bat populations and the ecosystem services that they provide in the U.S. and Canada," said Anne Kinsinger, USGS associate director of ecosystems.
White-nose syndrome has been diagnosed in nine species of bats hibernating in eastern North America. Species known to be susceptible to the disease are the little brown bat (Myotis lucifugus), Indiana bat (M sodalis), northern long-eared bat (M septentrionalis), eastern small-footed bat (M leibii), tricolored bat (Perimyotis subflavus), and big brown bat (Eptesicus fuscus).
Insect-eating bats are estimated to save the U.S. agricultural industry nearly $4 billion annually in pest-control expenses. Earlier this year, the USFWS rolled out a national management plan addressing the threat posed by white-nose syndrome (see JAVMA, July 15, 2011, page 169).
More than 100 state and federal agencies, tribes, organizations, and individuals are trying to contain the disease outbreak, the first epizootic ever documented in bats. Over the past several years, the Department of the Interior has invested close to $11 million in the effort, including more than $3 million for ongoing research looking for methods to control or cure the disease.
Debate over the role of G destructans in the WNS outbreak stems in part from an assumption that fungal infections in mammals are typically associated with immune system dysfunction. Moreover, G destructans was recently found to commonly colonize the skin of bats in Europe, where no unusually high bat mortality incidents have been reported. These factors have fueled speculation that the fungus is an opportunistic pathogen and that North American bats are dying as a result of unidentified factors.
Researchers at the USGS National Wildlife Health Center in Madison, Wis., exposed captive, healthy little brown bats to pure cultures of G destructans while the animals were hibernating. All the bats subsequently developed white-nose syndrome. Researchers also demonstrated the fungus can spread through contact between individual bats.
"While our study confirmed that G destructans is spread bat to bat, it is also important to note that virtually all pathogens, especially spore-producing fungi, are spread by multiple routes," said USGS microbiologist and study author David Blehert, PhD.
The study was conducted by scientists from the USGS, University of Wisconsin-Madison, Wisconsin Veterinary Diagnostic Laboratory, University of Tennessee-Knoxville, New York Department of Environmental Conservation, USFWS, Wisconsin Department of Natural Resources, and Bucknell University.
The Nature article, "Experimental infection of bats with Geomyces destructans causes white-nose syndrome," was published online Oct. 26 at www.nature.com. More information about WNS is available on the websites of the USGS National Wildlife Health Center (www.nwhc.usgs.gov) and USFWS (www.fws.gov).