This fact sheet was updated on 12/16/20.
This fact sheet was updated on 12/16/20.
White-nose syndrome (WNS) was first recognized as a disease of bats in 2006-7 and is caused by the fungus Pseudogymnoascus destructans (Pd; formerly Geomyces destructans), which infects the skin of the muzzle, ears and wings of bats. 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, WNS has caused unprecedented mortality in North American bat populations. Between 2006 and 2012, an estimated 6 million bats died from this disease in the United States and Canada. The disease has spread rapidly and continues to spread west, 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. In spite of guarded optimism about recovering species WNS has been devastating to bat species that are already considered threatened or endangered. Indeed states and federal agencies periodically conduct status review of the little brown, tricolored, and northern long-eared bat populations for listing under the federal Endangered Species Act.
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.
Currently, WNS is known to affect 12 hibernating bat species in North America, including two federally endangered species and one federally threatened species. Little brown, big brown, cave, eastern small-footed, fringed, gray, long-legged, northern long-eared, western long-eared, tri-colored, Yuma and Indiana bats have been confirmed to be infected with the fungus.
Pd has also been detected in six other bat species, including two endangered species, without observed disease. These include the eastern red, Mexican free-tailed, southeastern, silver-haired, Rafinesque’s big-eared, Townsend’s big eared, Ozark big-eared and the Virginia big-eared bats.
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. Pd is not believed to cause disease in humans.
Since its original discovery WNS has since spread to 35 states and seven Canadian provinces. The fungus associated with WNS has also recently been newly isolated in bats in several countries in Europe and Asia, but there the disease does not cause mortality as it has in North American bats.
Pd is believed to be transmitted via direct bat to bat contact or indirectly through a contaminated environment or fomites. The fungus grows best in cold (41-68F), dark, and humid conditions and spores can survive a long period of time on surfaces including clothes, shoes and outdoor gear. People can easily and unknowingly carry the fungus from one location to another.
During hibernation, a bats’ body temperature decreases, 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. Therefore, 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 also carry the fungus to previously unexposed caves. The fungus can survive for many years even when bats are extirpated from the site.
The most obvious clinical sign of WNS is the presence of the white cotton-like 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. Several bat species have tested positive for Pd but do not show overt clinical signs of the disease.
The fungus can be particularly damaging to bat wings. Affected wings may adhere to themselves, tear easily, and have decreased elasticity. These changes can interfere with flight. Affected bats have been observed “wing-walking” on the snow because they are unable to fly. Bat wings also play a role in water balance and when damaged result in loss of fluid and electroyles. This phenomenon causes bats to arouse from hibernation more often and earlier than normal to seek water. Bats with WNS are often observed flying outside of caves during the day and clustering at the entrances of caves and hibernation areas. Bats consume a great deal of energy and fat reserves when they are aroused from hibernation. It is the dehydration and starvation that causes most bats to die of WNS. The number of bats dying in the spring are much more difficult to measure but is thought to be an additional source of mortality.
Groups of dead or dying bats should raise suspicion of WNS and although the majority of deaths occur during winter when bats should be hibernating, deaths can occur year around.
White-nose syndrome is confirmed by laboratory identification of Pd via PCR or fungal culture of a swab from an animal or the environment or via a microscopic examination of a tissue sample. Initial screening may be possible by long-wave ultraviolet light illumination of bat skin. While UV light does not definitely diagnose WNS, the presence of orange fluorescence can indicate the presence of Pd and guide further sampling efforts.
There is currently no treatment for WNS. However, supportive care and increased body temperature provided at wildlife rehabilitation facilities may help bats to recover. Experimental treatments, such as vaccines, UV light, anti-fungal and biological sprays are also being studied and evaluated for effectiveness.
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. People can spread the fungus from bat to bat or cave to cave on their shoes and clothing, so it is important for individuals to take precautions 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 according to the latest decontamination guidance, available at Whitenosesyndrome.org. Agencies are restricting public access to caves in hopes of preventing further human facilitated spreading of the fungus. Current details about local initiatives and species’ status is best obtained from the state wildlife management agency biologists. 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. Management practices are being developed in hopes of preventing further spread of the disease, protecting bat populations, and increasing bat health.