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White-Nose Syndrome (WNS)

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Checking bats for White-Nose Syndrome. Photos and video captured March 1, 2016, by Larisa Bogardus, BLM. Video produced by Larry Moore, BLM. Music by
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Bats killed by WNS
Bats killed by White-nose snydrome at Aeolus Cave in Vermont. Photo courtesy University of Tennessee

White-nose syndrome (WNS) is a fungal disease occurring in hibernating bats.  The disease has spread from the northeastern US to 28 states and five Canadian provinces and has most recently been identified in the state of Washington. Since the winter of 2006-2007, over 6 million insect-eating bats have died from the effects of this disease named for the white fungus, Pseudogymnoascus destructans, often found infecting the skin of the muzzle, ears, and wings of hibernating bats. The fungus occurs and survives in the very cool environments provided by caves and abandoned mines, which is the preferred habitats of hibernating bats in winter. WNS is not known to infect or cause disease in humans, pets, livestock or other wildlife.

To determine if bats are affected by white-nose syndrome, scientists look for characteristic visible signs such as white fungal growth on the bat’s wings or muzzle, however the fungus can also be found microscopically when it is not easily visible to the eye. The fungus invades the bats’ skin and infects delicate wing tissue, and causes physiologic imbalances that can lead to disturbed hibernation, depleted fat reserves, dehydration and death. Many of the diagnoses involving infected bats has started with the discovery of dead bats in winter hibernation caves (hibernaculum) or a display of abnormal behaviors during the bats hibernation such as daytime flights during winter. Bats flying during winter when no food is available will contribute to the consumption of stored fat reserves causing emaciation, starvation, and ultimately death from WNS.  The recent finding near North Bend, Washington involved an infected bat that likely had been roused from hibernation and was attempting to feed when insects were not available.

Bat population declines in the northeastern US since the emergence of WNS is thought to be as high as 80%.  Not all species of bats are susceptible to WNS as some bat species live more solitary and roost in trees.  However, those that congregate in groups and hibernate in caves during winter are presently the most affected by WNS and these populations cannot recover quickly because most bats have only a single pup per year.

The true ecological consequences of large-scale population reductions currently under way among hibernating bats are not yet known. In Oregon and throughout the Pacific Northwest bats are important primary consumers of insects and a recent economic analysis indicated that the value provided by bats to U.S. agriculture is between 4 to 50 billion dollars per year because of a decreased need to use pesticides on crops.

Due the difficulty in containing a disease infecting a group of animals that flies, migrates, and lives in habitats that can be hard to locate or access, WNS has not been contained in its western spread across the US. The Oregon Department of Fish and Wildlife, along with federal partners at the USGS National Wildlife Health Center (NWHC), U.S. Fish and Wildlife Service, and biologists with the US Forest Service and Bureau of Land Management, play a primary role in WNS surveillance, management and research. ODFW biologists and veterinarians, with our federal partners, have been surveying caves for the disease over the previous 2 years with no positive indications that the disease is presently in Oregon bat populations. We currently conduct surveillance and management activities with state funding and a grant provided by the USFWS.

ODFW veterinarians advise against handling sick or dead animals. If you find a dead bat or observe bats flying outside during the day or during freezing weather, please report your observation online or contact the ODFW Wildlife Health Hotline at (866) 968-2600.

To learn more about WNS visit

White-nose Syndrome FAQ (pdf)


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