White-Nose Syndrome in Bats - Frequently Asked Questions
What is white-nose syndrome?
White-nose syndrome (WNS) was first documented in bats in New York in winter 2006-2007. The syndrome was named for the white fungus that sometimes develops on the muzzle of the bat, giving the appearance of a white nose. The fungus has been identified as a new species named Geomyces destructans. Places where bats hibernate, such as caves or underground mines (known as 'hibernacula'), are ideal environments for this fungus, as it thrives in cold, damp conditions. It is unclear if the fungus is the cause of disease or an abnormal growth of a naturally occurring fungus resulting from infection with some other pathogen. Not all bats affected by the disease have white muzzles, and the fungus often grows on the naked wing and tail membrane as well.
What does WNS do to bats?
WNS primarily affects bats during hibernation. Many insect-eating bats survive winter by going into hibernation, during which their body temperatures are lowered and fat deposits collected during summer months are utilized. WNS is believed to disrupt this cycle, causing bats to prematurely and repeatedly awaken from hibernation, quickly depleting their fat reserves and losing body condition. Bats weakened by the loss of fat reserves are unable to replenish them due to lack of food (insects) in winter and die before spring. Bats with WNS often exhibit unusual behavior, such as flying during daylight hours or gathering outside of caves in cold weather. To date over one million bats have died from WNS. Some bat colonies in the northeast U.S. have experienced die-offs in excess of 90 percent. Entire populations and endangered species of bats are at risk. Scientists across the country are working vigorously to understand more about this disease.
Is WNS in Michigan?
Yes, WNS has been identified in Michigan. DNR staff members are collaborating with other state, federal and local government officials, as well as university researchers and bat conservation groups to minimize its impact.
How is WNS spread?
Transmission of the fungus associated with WNS is believed to occur in two ways: 1) through bat-to-bat contact and 2) by humans visiting caves and mines. Bat-to-bat contact occurs during pre-hibernation movements, while in hibernacula and in maternal colonies. Conditions in hibernacula make it an ideal place for the spread of the fungus, as temperature and humidity are optimal and high densities of bats are gathered in one location. There is also evidence that the fungus is inadvertently spread by humans. Cavers (spelunkers) may transfer the causative agent on their clothing, shoes and gear between caves. Evidence of WNS has been documented in caves absent of bats, and many states have restricted access to caves to prevent further spread by humans.
How do we prevent and control WNS?
Many questions about WNS remain unanswered, and there are currently no effective or practical treatment options available. Some states have restricted access to caves and mines to prevent humans from spreading the fungus from cave to cave. At present, the best and most practical WNS control strategy is preventing humans from spreading the disease to uninfected areas (by staying out of unsupervised caves and abandoned mines), and conserving infected populations by minimizing human disturbance of the caves and mines in which they hibernate.
Why is WNS a significant threat to bats?
Conserving bats is important. Bats make up one-fourth of the world's mammalian species. They consume large amounts of insects and are one of the primary nighttime predators of insects. As WNS continues to spread throughout the US, we are at risk of losing entire bat species. Endangered species of bats, such as the Indiana bat, are threatened with potential extinction by WNS. In addition, prolonged die-offs of currently common species, such as the little brown bat, could force wildlife managers to list those species as endangered too. Those listings could result in additional economic costs for activities as diverse as timber sales and bridge construction.
Can WNS affect humans?
There is no evidence that WNS is infectious to humans. The fungus does not grow at temperatures above 68 degrees Fahrenheit, which is much lower than human body temperature. The loss of large numbers of bats may have an indirect impact on human health. Bats are a primary predator of nighttime insects, and large-scale losses of bats may lead to an increase in insect populations. These increases may result in damage to crops, which may lead to an increase in pesticide use and application that can impact the environment. Some insects act as vectors of zoonotic diseases, and an increase in insect populations may lead to an increase in the spread of such diseases.
Although most bats are not rabid, bats are the primary rabies-positive animal in Michigan, and exposure to a live bat should be avoided. A dead bat should be handled only with a protected (gloved) hand. If there is a potential exposure to a bat (touching a bat with an unprotected hand, waking up with a bat in the room, or a bat found in a room with a child or impaired individual), it should be tested for rabies. Contact your local health department for procedures to follow to submit the animal for testing.
What symptoms should I look for, and where do I report my sightings?
Please use the online reporting form at www.michigan.gov/emergingdiseases if you observe bats displaying any of the following:
- flying during the daytime in the winter;
- difficulty flying;
- large numbers (six or more) of dying or dead bats, especially at the opening of a cave or mine;
- hibernating bats with white fungus on the face or wings observed during winter (fungus on the body of bats has not been observed at any other time of year, although wing scarring from the fungus may be visible year-round).