White-Nose Syndrome

White-nose syndrome (WNS) is a disease that began spreading to hibernating bats in North America at a high rate since its discovery in New York in the winter of 2006. Since then, the disease has killed about seven million bats in the United States and Canada. The disease gets its name from the white fungus, Pseudogymnoascus destructans, that infects the bats’ muzzle, ears, and wings. The disease first strikes when bats are hibernating; they often display abnormal behavior before eventually dying.

Scientists at the US Geological Survey National Wildlife Health Center and the US Fish and Wildlife Service have been studying the disease and its ecological consequences since its discovery. They estimate that the decline in the bat population of some species in the northeastern United States between the arrival of WNS in 2006 and 2021 was approximately 90 percent. Hundreds of agencies have since collaborated to study WNS and to limit access to areas afflicted with the disease.

Brief History

White-nose syndrome (WNS) was first observed in February 2006 in four caves in Albany, New York. In January 2007, biologists officially documented the disease as white-nose syndrome. Affected bats were then observed and photographed in Howes Cave, New York. Prior to the arrival of WNS, studies showed that all six species of hibernating bats in New York were displaying population stability or increase. After the spread of the disease, colonies of hibernating bats that lived in affected caves and mines were reduced to 100 percent in some cases.

Since 2006, WNS has rapidly spread through the eastern United States and was most prevalent in the northeast, as well as in Canada. WNS spread in 2009 from the New England region into West Virginia and Virginia, where many endangered bat species reside. While scientists believe WNS is primarily transmitted from bat to bat, they think it is possible that human beings who are hiking may inadvertently spread the fungus, which may be on clothing or gear, when they venture from cave to cave. Since 2006, WNS has killed bats in forty states and eight Canadian provinces. WNS is thought to have originated in Europe, where many bat species have been infected with P. destructans, though they lack the high mortality rates of their North American counterparts. A study published in 2021 in Conservation Biology indicated that scientists have found genetic differences between bats killed by WNS and bats that survive. They believe that the survivors quickly evolved to resist the disease.

In 2009 and 2010, the US Fish and Wildlife Service helped develop a national management plan that addressed the threat of WNS facing hibernating bats. This plan established a framework for organizing the national research and response to WNS. In May 2011, the National Plan for Assisting States, Federal Agencies, and Tribes in Managing White-Nose Syndrome in Bats was finalized, which provides a general strategy for researching WNS’s causes and how to manage it.

As of 2021, nearly seven million bats were estimated to have died of WNS. In some colonies, the disease carried a 100-percent mortality rate. Seven species of bats are known to be susceptible, although scientists believe all species of cave-hibernating bats could be potentially threatened by WNS. According to Conservation Biology in 2021, WNS has killed more than 90 percent of the populations of northern long-eared, little brown, and tri-colored bats. The findings included data from more than two hundred populations in twenty-seven states and two Canadian provinces.

Overview

Species of bat that have been affected by the disease include the little brown bat, the northern long-eared bat, the tri-colored bat, the big brown bat, the eastern small-footed bat, the gray bat (endangered), and the Indiana bat (endangered). These species have low potential for population growth, since they tend to have one offspring per year. Because of this, researchers believe the bats affected by WNS will not be able to recover quickly from the dramatic loss in population.

The fungus that causes WNS, P. destructans, flourishes in dark, cold environments with high humidity, making bats that hibernate in caves and mines prime targets. The fungus typically appears on their nose as well as other hairless areas of their bodies, including their wings. It infects the bat once the animal’s body temperature has dropped into the 35- to 50-degree Fahrenheit range. While the implications for human health are unknown, as of 2021 there was no indication that the fungus affected humans or other animals, even after they have been exposed to it. Regardless of this, the US Fish and Wildlife Service requested that cavers avoid locations with hibernating bats.

During winter, bats that are infected with the fungus can exhibit erratic behavior that includes flying outside during the day and huddling together near the mouth of caves. Hibernating bats wake up a few times during the winter months to warm up, drink, urinate, and recharge their immune systems. When affected by the fungus, bats wake up more frequently, rapidly using up their valuable body fat, which then causes them to become emaciated and freeze to death. Mortality differs by location and species of bat. Scientists believe that the fungus is transmitted from bat to bat, but they also speculate that humans can carry the fungus on their clothes and cave gear, which could be transmitted to the bats when they enter caves.

To help find a cure for WNS and prevent further bat populations from dying off, many state and federal agencies are working together. They are exploring the causes, sources, and the transmission of the disease. Management strategies have also been created to minimize the impact of WNS. The caving community has also gotten involved, helping to take surveys and develop protective plans for sites.

More than half of the forty-seven species of bats in the United States and Canada rely on hibernation as a survival strategy during the winter months, when insects are not available for consumption. Because of this, the ecological significance of WNS could be devastating for hibernating bat species. A 2023 article in Animal Conservation noted that scientists may have discovered a way to prevent the spread of WNS in some bat species. Scientists conducted a study in which they used Polyethylene Glycol 8000 (PEG), a compound derived from petroleum, to roost bats in the summer prior to hibernation to disrupt the transmission of the disease in early winter. The application of PEG seemed to block the transmission of the WNS in the bats in the study.

While scientists are unsure of the disease’s potential to spread beyond the United States and Canada, they agree that WNS could have an enormous impact on bat populations throughout the world. With no bats, the insect populations would swell in number, leading to damage in forests and agriculture. Many also believe that the loss of bats could damage cave ecosystems, where rare cave fauna receives nutrients from bat droppings.

Bibliography

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Cheng, Tina L. et al. "The Scope and Severity of White Nose Syndrome in Hibernating Bats in North America." Conservation Biology, 20 Apr. 2021, doi.org/10.1111/cobi.13739. Accessed 24 Nov. 2024.

Coleman, Jeremy, et al. A National Plan for Assisting States, Federal Agencies, and Tribes in Managing White-Nose Syndrome in Bats. Hadley: US Fish and Wildlife Service, May 2011. PDF file.

Communications and Publishing. "White-Nose Syndrome Killed over 90% of Three North American Bat Species." US Geological Survey, 4 Apr. 2021, www.usgs.gov/news/national-news-release/white-nose-syndrome-killed-over-90-three-north-american-bat-species. Accessed 16 Feb. 2023.

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Pearson, Gwen. "The Secret Bataclysm: White Nose Syndrome and Extinction." Wired. Condé Nast, 12 Aug. 2014. Web. 1 Dec. 2014.

Schweber, Nate. "A Bat Fungus on the March." New York Times. New York Times, 13 Feb. 2013. Web. 1 Dec. 2014.

Sewell, B.J. et al. "Environmental Control Reduces White Nose Syndrome Infection in Hibernating Bats." Animal Conservation, 23 Feb. 2023, doi.org/10.1111/acv.12852. Accessed 24 Nov. 2024.