What Is White-Nose Syndrome in Bats?

White-nose syndrome (WNS) is an emerging disease affecting North American bats. The condition gets its name for the appearance of the white fungal growth found around the noses and wings of affected hibernating bats. The fungus Pseudogymnoascus destructans (Pd), formerly named Geomyces destructans, colonizes bat wing skin, leading to disease. To date, millions of bats in the United States and Canada have died from white-nose syndrome, placing some species at risk of extinction. There is no known treatment for the disorder and preventative measures to date have been ineffective.

White-Nose Bat Syndrome

The earliest documented case of white-nose syndrome comes from a photograph of a bat taken in Schoharie County, New York in 2006. By 2017, at least fifteen bat species had been affected, including four endangered or threatened species. The disease rapidly spread to 33 U.S. states and 7 Canadian provinces (2018). While most cases have been documented in eastern North America, a little brown bat was found to be infected in Washington state in 2016.

Originally, the fungal pathogen was identified as Geomyces destructans, but it was later reclassified as the related species Pseudogymnoascus destructans. The fungus is a psychrophile or cold-loving organism that prefers temperatures between 39–59 °F and stops growing when temperatures exceed 68 °F.

The fungus spreads from direct contact between bats or between bats and infected surfaces. The white growth becomes apparent late in the winter hibernation season. Pseudogymnoascus destructans infects the epidermis of the bat's wings, disrupting the animal's metabolism. Affected bats suffer dehydration, body fat loss, and wing scarring. The cause of death is usually starvation, as infection depletes a bat's winter fat reserves. Bats that survive the winter may suffer wing damage and become unable to find food.

Pseudogymnoascus destructans occurs in Europe, but European bats don't get white-nose syndrome. The fungus is an invasive species in North America, where bats have not developed an immune response. No treatment or preventative measure for white-nose syndrome has been found.

An infection decimates a colony, killing over 90% of the bats. In 2012, scientists estimated between 5.7 to 6.7 million bats had succumbed to the disease. Bat numbers have collapsed in affected areas.

Can White-Nose Syndrome Affect Humans?

Humans cannot contract white-nose syndrome and appear completely unaffected by the fungus. However, it's possible people can carry the pathogen from an infected cave on shoes, clothing, or gear. The bat disease indirectly affects people because bats are important for insect control, pollination, and seed dispersal. The collapse of bat colonies forces farmers to apply insecticides to control pests.

How to Prevent the Spread of White-Nose Syndrome

Starting in 2009, the U.S. Fish and Wildlife Service (USFWS) began closing infected caves to minimize the risk of cavers spreading the fungus. When people visit caves that may contain bats, the USFWS recommends people wear clothing and use gear that has never been in a cave. Upon leaving a cave, items may be decontaminated by immersion in hot (140 °F) water for 20 minutes. If you observe hibernating bats in a cave, the best course of action is to leave immediately. Disturbing bats, even if they are not infected, raises their metabolism and depletes fat reserves, putting them at risk of not surviving the season.

Sources

• Blehert DS, Hicks AC, Behr M, Meteyer CU, Berlowski-Zier BM, Buckles EL, Coleman JT, Darling SR, Gargas A, Niver R, Okoniewski JC, Rudd RJ, Stone WB (January 2009). "Bat white-nose syndrome: an emerging fungal pathogen?". Science. 323 (5911): 227. doi:10.1126/science.1163874
• Frick WF, Pollock JF, Hicks AC, Langwig KE, Reynolds DS, Turner GG, Butchkoski CM, Kunz TH (August 2010). "An emerging disease causes regional population collapse of a common North American bat species". Science. 329 (5992): 679–82. doi:10.1126/science.1188594
• Langwig KE, Frick WF, Bried JT, Hicks AC, Kunz TH, Kilpatrick AM (September 2012). "Sociality, density-dependence and microclimates determine the persistence of populations suffering from a novel fungal disease, white-nose syndrome". Ecology Letters. 15 (9): 1050–7. doi:10.1111/j.1461-0248.2012.01829.x
• Lindner DL, Gargas A, Lorch JM, Banik MT, Glaeser J, Kunz TH, Blehert DS (2011). "DNA-based detection of the fungal pathogen Geomyces destructans in soils from bat hibernacula". Mycologia. 103 (2): 241–6. doi:10.3852/10-262
• Warnecke L, Turner JM, Bollinger TK, Lorch JM, Misra V, Cryan PM, Wibbelt G, Blehert DS, et al. (May 2012). "Inoculation of bats with European Geomyces destructans supports the novel pathogen hypothesis for the origin of white-nose syndrome". Proceedings of the National Academy of Sciences of the United States of America. 109 (18): 6999–7003. doi:10.1073/pnas.1200374109