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White-Nose Syndrome (WNS)

By: Wildlife Futures Team Date: Apr 5, 2021

Cause

White-nose syndrome (WNS) is a disease of bats associated with the fungus Pseudogymnoascus destructans. WNS was first reported in the winter of 2006-2007 in a popular tourist cave near Albany, New York1. Since then, researchers have been actively gathering information to better understand this catastrophic disease. 

Significance

Since its discovery in 2006, WNS has caused unprecedented mortality in North American bat populations. Over six million bats have died from this disease in the United States and Canada2. The disease has spread rapidly and continues to spread, though the potential extent of the distribution of WNS is currently unknown. In some areas, current estimates of bat population declines are as high as 97%, with some caves losing 90 to 100% of hibernating bats1. WNS could be particularly devastating to bat species that are already considered threatened or endangered3,4. Bats are an integral part of the ecosystem and are important for insect control, pollination, and seed dispersal. If the bat populations continue to decline at this rate from WNS, it is uncertain what impact it will have on the ecosystem5.

Species Affected

WNS is known to cause disease in 12 hibernating bat species in the Eastern United States and parts of Canada: little brown, big brown, eastern small-footed, gray, northern long-eared, western long-eared, tri-colored, cave, fringed, Yuma, long-legged, and Indiana bats 6P. destructans has also been detected in eight other species with no confirmation of disease: the eastern red, southeastern, silver-haired, Rafinesque’s big-eared, Townsend’s big-eared, Ozark big-eared, Western small-footed, and Virginia big-eared bat5. The fungus is not believed to cause disease in humans. 

Distribution

WNS was originally discovered in New York in 2006 and has since spread to 33 states in the eastern, midwestern, and southern United States, and 7 Canadian provinces5. The fungus associated with WNS has also recently been isolated in bats in several countries in Europe, but the disease does not cause mortality as it has in North American bats2

Transmission

WNS is believed to be transmitted via direct contact, inhalation, and / or ingestion5. People can easily carry the fungus on their shoes, clothing, or equipment from one location to another. The disease was likely first introduced to North America by recreational cavers6,7.8. Caves and mines where many bats hibernate (hibernacula) are prime locations for the disease to spread because of the high density of bats and climatic conditions in the caves. Infected bats also can carry the fungus to previously unexposed caves2,9P. destructans is a fungus that grows best at low temperatures and high humidity10. During hibernation, bats’ body temperatures decrease, which promotes colonization of the fungus. Bats also seek out humid caves and mines for hibernation because it helps them to conserve body water10,11. Finally, bat immune systems are less active during hibernation, which likely contributes to their vulnerability to WNS at that time5

Clinical Signs

The most obvious clinical sign of WNS is the presence of the white cottony fungus on the nose, wings, and potentially other parts of the body of an infected bat. Visible white fungus is not always present on infected bats, and the fungus disappears rapidly once affected bats are removed from the moist cold environment. Bats with WNS behave abnormally during the winter, including flying outside of caves during the day and clustering at the entrances of caves and hibernation areas. Most bats that die of WNS are emaciated. The fungus invades and destroys the skin and causes particular damage to the wings5. Affected wings may adhere to themselves, tear easily, and have decreased elasticity. Wings play an important role in a bat’s water balance. The disruption of this function due to fungal damage is one theory as to why the fungus is so deadly to bats. According to this theory, bats become dehydrated as a result of water loss from their damaged wings and they arise from hibernation more often than usual to seek water. Bats use up a great deal of energy and fat reserves when they arise from hibernation, causing them to become emaciated and die5,10. The wing damage also interferes with flight. Affected bats have been observed “wing-walking” on the snow because they are unable to fly. Almost all deaths from WNS occur during the winter when bats should be hibernating.

Diagnosis

White-nose syndrome is confirmed by laboratory identification of the P. destructans fungus12. Initial screening may be possible by illumination of the wings with long-wave ultraviolet light13.

Treatment

There is currently no treatment for WNS5. However, a recent study suggests that bats may recover with supportive care and increased body temperature provided at wildlife rehabilitation facilities12.

Management

The United States Fish and Wildlife Service (USFWS) has organized a national plan to help state and federal agencies, tribes, and many other organizations and individuals to investigate and manage WNS6. Much about WNS is still unknown, so research continues to provide a more complete understanding of the disease. Management practices are being developed in hopes of preventing further spread of the disease and protecting bat populations. People can spread the fungus from bat to bat or cave to cave on their shoes and clothing, so it is important for people to take certain precautions in order to avoid this kind of spread. People should avoid direct contact with bats or contaminated surfaces. If contact is necessary, people must wear gloves and protective clothing. All potentially contaminated materials and surfaces should be disinfected7,8. Agencies are restricting public access to caves in hopes of preventing further human-facilitated spreading of the fungus5. Complete details of the USFWS WNS management plan can be found in their publication “A National Plan for Assisting States, Federal Agencies, and Tribes in Managing White-Nose Syndrome in Bats”6. Any sick bats, dead bats, or bats exhibiting abnormal behavior should be reported to local wildlife authorities. The public should also be respectful of any cave closures. 

Citations

  1. Frick, W.F., Pollock, J.F., Hicks, A.C., Langwig, K.E., Reynolds, D.S., Turner, G.G., Butchkoski, C.M. and Kunz, T.H., 2010. An emerging disease causes regional population collapse of a common North American bat species. Science329(5992), pp.679-682.
  2. Frick, W. F., Puechmaille, S. J., Hoyt, J. R., Nickel, B. A., Langwig, K. E., Foster, J. T., Barlow, K. E., Bartonička, T. š., Feller, D., Haarsma, A.-J., Herzog, C., Horáček, I., van der Kooij, J., Mulkens, B., Petrov, B., Reynolds, R., Rodrigues, L., Stihler, C. W., Turner, G. G., & Kilpatrick, A. M. (2015). Disease alters macroecological patterns of North American bats. Global Ecology and Biogeography, 24(7), 741–749.
  3. Vonhof, M.J., Amelon, S.K., Currie, R.R. and McCracken, G.F., 2016. Genetic structure of winter populations of the endangered Indiana bat (Myotis sodalis) prior to the white nose syndrome epidemic: implications for the risk of disease spread. Conservation Genetics17(5), pp.1025-1040.
  4. Ingersoll, T.E., Sewall, B.J. and Amelon, S.K., 2016. Effects of white‐nose syndrome on regional population patterns of 3 hibernating bat species. Conservation Biology30(5), pp.1048-1059.
  5. Voigt, C.C. and Kingston, T., 2016. Bats in the Anthropocene: conservation of bats in a changing world. Springer Nature.
  6. U.S. Fish and Wildlife Service (2021).  White-nose Syndrome Response Team [online]. Available from: https://www.whitenosesyndrome.org/ (Accessed 30 March 2021).
  7. Leopardi, S., Blake, D. and Puechmaille, S.J., 2015. White-nose syndrome fungus introduced from Europe to North America. Current Biology25(6), pp.R217-R219.
  8. Ballmann, A.E., Torkelson, M.R., Bohuski, E.A., Russell, R.E. and Blehert, D.S., 2017. Dispersal hazards of Pseudogymnoascus destructans by bats and human activity at hibernacula in summer. Journal of Wildlife Diseases53(4), pp.725-735.
  9. Neubaum, D.J. and Siemers, J.L., 2021. Bat swarming behavior among sites and its potential for spreading white‐nose syndrome. Ecology, p.e03325.
  10. Langwig, K.E., Frick, W.F., Bried, J.T., Hicks, A.C., Kunz, T.H. and Marm Kilpatrick, A., 2012. Sociality, density‐dependence and microclimates determine the persistence of populations suffering from a novel fungal disease, white‐nose syndrome. Ecology letters15(9), pp.1050-1057.
  11. Haase, C.G., Fuller, N.W., Dzal, Y.A., Hranac, C.R., Hayman, D.T., Lausen, C.L., Silas, K.A., Olson, S.H. and Plowright, R.K., 2020. Body mass and hibernation microclimate may predict bat susceptibility to white‐nose syndrome. Ecology and evolution.
  12. Meteyer, C.U., Valent, M., Kashmer, J., Buckles, E.L., Lorch, J.M., Blehert, D.S., Lollar, A., Berndt, D., Wheeler, E., White, C.L. and Ballmann, A.E., 2011. Recovery of little brown bats (Myotis lucifugus) from natural infection with Geomyces destructans, white-nose syndrome. Journal of Wildlife Diseases47(3), pp.618-626.
  13. Turner, G.G., Meteyer, C.U., Barton, H., Gumbs, J.F., Reeder, D.M., Overton, B., Bandouchova, H., Bartonička, T., Martínková, N., Pikula, J. and Zukal, J., 2014. Nonlethal screening of bat-wing skin with the use of ultraviolet fluorescence to detect lesions indicative of white-nose syndrome. Journal of Wildlife Diseases50(3), pp.566-573.

Further reading

  1. White Nose Syndrome Response Team – U.S. Fish and Wildlife Service
  2. White-Nose Syndrome (USGS.gov)
  3. White-nose Syndrome - Bat Conservation International