NWDC is in the process of updating this fact sheet.
NWDC is in the process of updating this fact sheet.
White-nose syndrome (WNS) is a newly recognized disease of bats associated with the recently identified fungus Pseudogymnoascus destructans (formerly Geomyces destructans). WNS was first reported in the winter of 2006-2007 in a popular tourist cave near Albany, New York. Since then, researchers have been actively gathering information to better understand this catastrophic disease.
Since its discovery in 2007, WNS has caused unprecedented mortality in North American bat populations. Over one million bats have died from this disease in the United States and Canada. 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 bats. WNS could be particularly devastating to bat species that are already considered threatened or endangered. 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 ecosystem.
WNS is known to affect 7 hibernating bat species in the Eastern United States and parts of Canada. Little brown, big brown, eastern small-footed, gray bat, northern long-eared, tri-colored, and Indiana bats have been confirmed to be infected with the fungus. P. destructans has also been detected in the eastern red bat, southeastern bat, silver-haired bat, Rafinesque’s big-eared bat, and the Virginia big-eared bat, but with no confirmation of observed disease. The fungus has also been isolated in numerous species of European bats, but unlike North American bats they seem to be resistant and do not die from WNS. The fungus is not believed to cause disease in humans.
WNS was originally discovered in New York in 2006 and has since spread to 25 states in the eastern, Midwestern, and southern United States, and 5 Canadian provinces. 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 bats.
WNS is believed to be transmitted via direct contact, inhalation, or ingestion. People can easily carry the fungus on their shoes or clothing from one location to another. The disease was likely first introduced to North America by recreational cavers. Caves and mines where many bats hibernate (hibernacula) are prime locations for the disease to spread because of the high density of bats. Infected bats can carry the fungus to previously unexposed caves. P. destructans is a fungus that grows best at low temperatures and high humidity. 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 water. Finally, bat immune systems are less active during hibernation, which likely contributes to their vulnerability to WNS during hibernation.
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 wings. 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 die. 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.
White-nose syndrome is confirmed by laboratory identification of the P. destructans fungus. Initial screening may be possible by illumination of the wings with long-wave ultraviolet light.
There is currently no treatment for WNS. However, a recent study suggests that bats may recover with supportive care and increased body temperature provided at wildlife rehabilitation facilities.
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 WNS. 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 disinfected. Agencies are restricting public access to caves in hopes of preventing further human facilitated spreading of the fungus. Complete details of the USFWS WNS management plan can be found in their May 2011 publication “A National Plan for Assisting States, Federal Agencies, and Tribes in Managing White-Nose Syndrome in Bats”. Any sick bats, dead bats, or bats exhibiting abnormal behavior should be reported to the local wildlife authorities. The public should also be respectful of any cave closures.