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White Nose Syndrome of Bats Fact Sheet

October 2014

Photo of bats hanging from cave wall exhibiting Geomyces destructans fungus on their muzzles. This is the fungus associated with WNS.
Click on photo to enlarge
Bats exhibiting Pseudogymnoascus destructans fungus on their muzzles. This fungus causes WNS in bats.
Nancy Heaslip, New York Department of Environmental Conservation
If you find 5 or more dead bats at a location or notice bats exhibiting unusual behavior such as flying outside during freezing weather, please leave a message on our Wildlife Health Hotline (800) 606-8768.
Range map for White Nose Syndrom as of November 2015
Click on map to enlarge
Range map for White Nose Syndrome.
Map: Cal Butchkoski, PA Game Commission

What is it?

White-nose Syndrome (WNS) of bats is a disease caused by the fungus Pseudogymnoascus destructans (formerly known as Geomyces destructans). The disease is estimated to have killed over six million bats in the eastern United States since 2006, and can kill up to 100 % of bats in a colony during hibernation. Although it has not been found in Washington to date, the fungus and disease are spreading across North America towards the West and into Canada.

The fungus grows on the noses, wings and ears of bats during winter hibernation, giving them a white, fuzzy appearance. The fungus invades the deep skin tissues and causes extensive damage.  Affected bats arouse more often during hibernation which causes them to burn up their crucial fat reserves needed to sustain them through hibernation, leading to starvation and death. Additional causes for mortalities may include impairment of physiological processes due to wing damage, including reduced circulatory and thermoregulatory abilities, reduced gas exchange capabilities, and dehydration.

Species Affected

To date, seven cave hibernating species of bats in eastern North America are afflicted by WNS. These include:

  • Little brown bat (Myotis lucifugus)
  • Northern long-eared bat (M. septentrionalis)
  • Eastern small-footed bat (M. leibii)
  • Indiana bat (M. sodalis; federally endangered)
  • Gray bat (M. grisescens; federally endangered)
  • Tricolored bat (Perimyotis subflavus)
  • Big brown bat (Eptesicus fuscus)

Five additional hibernating species have been found with the causative fungus on them, but have not developed the disease. Little brown bats and big brown bats occur in Washington, in addition to another 11 cave/mine-roosting species that are potentially at risk in this state. There is currently no indication that humans or other animal species are susceptible to infection with the fungus that causes WNS.

Clinical Signs in bats

Clinical signs of WNS in bats include:

  • the presence of a white powder-appearing substance on their nose, wings or ears during hibernation when their body temperatures are reduced and the environment is near freezing;
  • emaciation;
  • damaged wings; and
  • activity during winter, including flying outside during freezing temperatures.


WNS appears to spread primarily through physical bat-to-bat contact or infected environment-to-bat contact. Humans have the potential to spread the fungus to new locations when it may attach to clothing and gear used in caves, mines and roosts. Those who visit bat roosts, caves, and mines are strongly urged to decontaminate all clothing and gear afterwards by using appropriate cleaning and disinfection protocols (see US Fish and Wildlife Service Decontamination Protocol)


  • Advise the Washington Department of Fish and Wildlife or the US Fish and Wildlife Service immediately if you suspect you have seen bats with this condition, or if you see bats flying outside during freezing temperatures.
  • Do not handle animals that appear sick or are found dead. Bats should never be handled by anyone other than qualified specialists who have been vaccinated against rabies.
  • Avoid entering caves and mines for unnecessary reasons to avoid disturbing bats and potentially spreading this condition to unaffected areas.
  • People who must enter caves, mines or bat roosts are advised to decontaminate all equipment and clothing between caves, mines and bat roosts. Do not allow dogs in caves (they may act as carriers of the fungus to new sites)
Picture of researcher with dead bats infected with WNS
Greg Turner with many dead bats during winter.
PA Game Commission


Bats are valuable members of ecosystems around the world, saving farmers in the US alone over $3 billion annually in pest control services. One colony of bats can consume many tons of insects that would otherwise consume valuable crops and forests, or otherwise threaten human health and well-being. Many species of bats are also valuable for the pollination of plants and dispersal of plant seeds.

Over six million bats are estimated to have died due to this disease over the past few years in the eastern US and Canada, with as much as 100% mortality in some colonies. This disease could possibly lead to the extinction of some bat species.

Key Findings

  • White-nose Syndrome (WNS) causes very high mortality  (up to 100%) in bat colonies during hibernation.
  • The pathogen responsible for WNS is Pseudogymnoascus destructans (formerly Geomyces destructans).
  • Bat-to-bat and infected cave or mine –to-bat contact appear to be the primary transmission routes, although humans can likely transfer the fungus to new locations and thereby assist in spreading the disease.
  • The fungus and disease are spreading across North America towards the West and into Canada.
  • All species of cave-hibernating bats are potentially susceptible, currently 7 species are known to be affected.


  • Kristin Mansfield, DVM, MPVM
  • Ella Rowan, MS