Skip to main content

White-nose syndrome in bats

White-nose syndrome (WNS) is a disease of bats that hibernate in caves, mines, and other suitable hibernacula. It is caused by the fungus Pseudogymnoascus destructans (Pd). It was first identified in North America in 2007 in bats in a cave in New York. The fungus gradually spread across the United States and was eventually discovered in Wisconsin bats in 2014. All four of Wisconsin’s cave bats – tricolored bat, northern long-eared bat, big brown bat, little brown bat – are susceptible to Pd fungal infection. Additionally, they are two tree bat species in Wisconsin on which Pd has been detected, but no diagnostic sign of WNS has been documented: silver-haired bat and eastern red bat.


The fungus thrives in cold, dark damp caves where bats hibernate and overwinter. It spreads from bat to bat or onto bats that touch contaminated surfaces. The fungus survives a long time on shoes, clothes and other gear and people can unknowingly move it to new areas.


Hibernating bats will have a visible fuzzy white growth on the face or wings. The fungus causes changes in the bats that cause them to be abnormally active in the winter, including flying outside the cave in cold weather. This makes the bats use up the stored fat that they need to survive the winter. Infected bats lose weight and become dehydrated. The fungus can also cause damage to its wings.


There is currently no known treatment for the disease. Management focuses on preventing or minimizing the spread of the fungus. Visitors to caves and mines where bats hibernate are restricted or limited. Wisconsin has Decontamination Protocols for Preventing the Spread of White-Nose Syndrome in Bats [PDF]. Many organizations and agencies are researching to find a treatment, including vaccine trials. Citizens can help by reporting sick or dead bats to the WDNR's Wisconsin Bat Program.


The fungus does not infect people or pets.


White-nose Syndrome Response Team: current map of the occurrence of WNS [exit DNR]
USGS National Wildlife Health Center: White-nose Syndrome [exit DNR]
More information on bats in Wisconsin can be found on the department’s webpage: Saving Wisconsin's Bats