White-nose syndrome was first observed in four caves centered roughly 30 km west of Albany, New York, in the winter of 2006/2007. Photographs subsequently emerged of apparently affected bats in nearby Howes Cave, New York, taken during the previous winter, providing the earliest evidence of the disease. Counts at winter colonies of all 6 hibernating bat species in New York revealed that populations had been stable or increasing in recent decades, prior to the arrival of WNS. Whereas the effects of WNS appear to vary between species and winter hibernation sites (“hibernacula”), overall colony losses at the most closely monitored sites have reached 95 percent within 2 to 3 years of initial detection. As of April 2011, WNS has been detected in 6 of the 9 species of hibernating bats that occur in the affected region (Connecticut, Delaware, Indiana, Kentucky, Maryland, Massachusetts, New Hampshire, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Tennessee, Vermont, Virginia, West Virginia, and the Canadian provinces: New Brunswick, Nova Scotia, Ontario, and Quebec). Species known to be susceptible to WNS thus far are the little brown bat (Myotis lucifugus), Indiana bat (M. sodalis), northern long-eared bat (M. septentrionalis), eastern small-footed bat (M. leibii), tricolored bat (Perimyotis subflavus), and big brown bat (Eptesicus fuscus). Three additional bat species were found in 2010 that tested positive for the presence of Geomyces destructans, the fungus associated with WNS, but not with the pathological invasion of the skin that is characteristic of the disease. These bats, the gray bat (M. grisescens), the cave myotis (M. velifer), and the southeastern myotis (M. austroriparius), were found in Missouri, Oklahoma, and Virginia, respectively, and their discovery could portend the spread of WNS into new regions of the southeastern and western U.S., and beyond, in the near future. The disease appears to affect bats most during long torpor bouts characteristic of winter hibernation. Therefore, bat species that use hibernation as a strategy for surviving the winter months, collectively called the “cave bats,” are most notably affected. It is currently not known if WNS is causing mortality in bats that use torpor during winter but do not regularly occur in caves and mines, such as the so-called migratory “tree bats” (for example, silver-haired bats [Lasionycteris noctivagans], hoary bats [Lasiurus cinereus], eastern red bats [Lasiurus borealis]).
The rapid and widespread mortality associated with WNS is unprecedented in hibernating bats; moreover, epizootic disease outbreaks such as WNS have not previously been documented in bats. Like other top mammalian predators, such as polar bear (Ursus marinus), sea otter (Enhydra lutris), and gray wolf (Canis lupus), most of the affected bat species are long lived (~5 to 15 years or more); hibernating bats typically only have one offspring per year, and population growth depends on high rates of adult survival. Therefore, naturally low reproductive rates combined with the high mortality observed in populations with WNS will likely prevent affected bat populations from recovering quickly.
White-nose syndrome was named for the visible presence of a white fungus around the muzzles, ears, and wing membranes of affected bats. Scientists recently identified a previously unknown species of cold-loving fungus (G. destructans) as a consistent pathogen causing skin infection in bats at affected sites. This fungus thrives in low temperatures (5-14º C; 40-55º F) and high levels of humidity (>90 %), conditions characteristic of many bat hibernacula. Pathologic findings thus far indicate that such fungal infections can be detected as early as October, and it is hypothesized that bats affected by WNS arouse from hibernation more frequently, and/or for longer periods than normal, and are prematurely expending the fat reserves they rely on for winter survival. Chronic disturbance of hibernating bats has been known to cause high rates of winter mortality through fat loss, and aberrant behaviors associated with WNS may cause bats to consume critical fat reserves prematurely during winter. Aberrant behaviors observed at sites affected by WNS include shifts of large numbers of bats in hibernacula to locations near the entrances or unusually cold areas; large numbers of bats dispersing during the day from hibernacula, even during mid-winter; a general unresponsiveness to human disturbance; and, on occasion, large numbers of fatalities, either inside the hibernacula, near the entrance, or in the immediate vicinity of the entrance. Additionally, recent hypotheses suggest that the characteristic wing pathology associated with WNS may cause death by disruption of important wing-dependent physiological functions, such as water balance, thermoregulation and mechanical function of the wing leading to dehydration, increased thirst-mediated arousals, increased heat loss, and inhibition of flight. Although evidence indicates that skin infection by G. destructans is the plausible primary cause of mortality associated with WNS, the exact processes by which skin infection leads to death remain undetermined, and it is unclear the extent to which other conditions may contribute to susceptibility of species or individuals to fungal infection and/or mortality.
For the purpose of implementing elements of this plan, WNS will be defined as Suspect when G. destructans DNA or characteristic conidia morphology is detected on bats in the absence of histopathologic evidence, or when field signs associated with WNS are observed in winter bat populations within a previously confirmed WNS affected state but diagnostic tests were either negative or not performed. WNS will be defined as Confirmed Positive upon histopathological characterization of skin invasion typical of G. destructans infection. Furthermore, a hibernaculum or area will be considered to be Infected if it is associated with bats that are either suspect or confirmed positive for WNS.
More than half of the 45 species of bats that occur in the U.S. rely on hibernation as a primary strategy for surviving the winter, when insect prey are not available. All four endangered species and subspecies of hibernating bats in the continental U.S. rely on undisturbed caves or mines for successful hibernation, and are at potential risk from WNS. Three of these species (Indiana, gray, and Virginia big-eared bat [Corynorhinus townsendii virginianus]) are currently within the affected area, and the remaining subspecies (Ozark big-eared bat [C. t. ingens]) will likely be at risk soon. Although the potential for WNS to continue to spread is currently unknown, the implications of its undermining the survival strategy of so many bat species are considerable. We are just beginning to appreciate the roles bats play in North American ecosystems, and the impact of WNS on bat populations has the potential to greatly impact ecosystem function. Considerable and abrupt reductions in predation pressure on insect populations, for example, could lead to increased numbers of insect pests resulting in damage to forests and agriculture, higher loads of environmental pesticides, and/or potential public health risks associated with zoonotic disease or chemical contact. As the major contributor of nutrients into many cave systems, mainly in the form of guano, bats are also an integral part of cave and karst ecosystems. The loss of bats could also, therefore, disrupt cave ecosystems and put many rare and unique cave fauna in jeopardy.
The mobility of bats, the rapid spread of WNS, the potential for human-assisted transmission, and the severity of the consequences make it imperative that a national effort on multiple scales be mounted to avert irreversible losses to bat populations, and associated ecological impacts, throughout North America. It is anticipated that WNS will continue spreading to surrounding states, and the potential exists for outbreaks due to human activities in states distant to the currently affected area.
State, Federal, and Tribal wildlife and land management agencies have statutory and regulatory authorities for managing trust wildlife species and their habitats. In exercising these authorities, agencies must comply with applicable laws. For example, Federal agencies must comply with the National Environmental Policy Act, the Endangered Species Act, and the Federal Cave Resources Protection Act, among other laws. Some of these laws provide alternative procedures to address emergency situations. The implementation of a national plan will assist State, Federal, and Tribal agencies, as well as local governments, in exercising their authorities for managing bats threatened by WNS and complying with all applicable laws. The implementation of a national plan will also help to standardize management practices, including disease surveillance and bat population monitoring, to ensure consistency in data collection and to facilitate the interpretation of results.
There is already a history of State-Federal collaboration in addressing the many challenges posed by WNS, which pre-date the formal requests for assistance made by State agents in the northeastern United States to the U.S. Fish and Wildlife Service (USFWS) and U.S. Geological Survey (USGS) in the winter of 2007/2008. It is incumbent upon wildlife management agencies to advise and consult, as appropriate, with non-government organizations and those in the scientific community with appropriate expertise and authorities to assist in mitigating this threat. Further, this collaboration should extend internationally because the risk of WNS extends across borders and these insectivorous bats are a North American resource. A national plan will serve to facilitate this collaboration.
State and Tribal agencies will largely be responsible for implementing surveillance, population monitoring, and disease management programs at the local level, based on national guidance provided by the working groups. The primary Federal role will be to provide cross-border coordination and assistance with research, surveillance, disease management, diagnostic testing, communications, information dissemination, education, and funding for State WNS programs. Federal land management agencies such as the National Park Service, U.S. Forest Service, Bureau of Land Management, National Wildlife Refuge System (USFWS), and DoD also will provide guidance and policy for addressing WNS in relation to planning and managing Federal lands under their respective jurisdictions. Federal agencies will provide tools and financial assistance, when available, to States, and help develop standardized approaches to WNS control and mitigation.
While we have gained considerable knowledge regarding WNS and the presumed etiology, there are still large gaps in our understanding. Despite this, general principles of epidemiology, ecology, and conservation biology will continue to be applied, along with expert opinion, to inform the actions outlined in this plan. As our knowledge and understanding of WNS improves, plans will be modified and adapted accordingly to ensure that the best available science is applied to addressing this issue.
The development of coordinated, science-based, response plans, tiered from the national plan but tailored individually to meet the WNS-related needs of discrete State, Tribal, and Federal agencies, is also fundamental to the success of a national plan for managing WNS, and is encouraged. Ideally, such plans would consider the needs of all stakeholders and cover multiple jurisdictions, especially when jurisdictions share an affected population. Response plans should follow a standard outline of basic components that include objectives, management tools, management of contaminated environments, results monitoring, restoration plans, and budget. Response plans will form the basis for funding, public responsibility and accountability, and measuring results. Because such coordinated response plans may be difficult to prepare in a short time frame, a process for immediate funding for initial response for newly identified outbreaks should also be made available, as well as for preparation and education in currently unaffected areas.
WNS response plans will vary depending upon such factors as length of time the disease has been present, affected species, population density, location, resources, and human dynamics. States and other entities may use different strategies in response to different combinations of these factors. One of the key challenges is to learn as quickly as possible the safety and efficacy of control or disease mitigation strategies. As research knowledge provides new diagnostic, monitoring, and management tools, the challenge will be to continually adapt and improve WNS management strategies. Oversight committees will be convened as part of the implementation strategy, composed of representatives from State, Federal, and Tribal agencies, to assist with the coordinated execution of efforts to manage WNS at the national and local level. The organizational structure of the groups and committees engaged in the national response to WNS will be made available in the forthcoming implementation plan.