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Definitive diagnosis of the bat disease white-nose syndrome (WNS) requires histologic analysis to identify the cutaneous erosions caused by the fungal pathogen Pseudogymnoascus [formerly Geomyces] destructans (Pd). Gross visual inspection does not distinguish bats with or without WNS, and no nonlethal, on-site, preliminary screening methods are available for WNS in bats. We demonstrate that long-wave ultraviolet (UV) light (wavelength 366-385 nm) elicits a distinct orange-yellow fluorescence in bat-wing membranes (skin) that corresponds directly with the fungal cupping erosions in histologic sections of skin that are the current gold standard for diagnosis of WNS. Between March 2009 and April 2012, wing membranes from 168 North American bat carcasses submitted to the US Geological Survey National Wildlife Health Center were examined with the use of both UV light and histology. Comparison of these techniques showed that 98.8% of the bats with foci of orange-yellow wing fluorescence (n=80) were WNS-positive based on histologic diagnosis; bat wings that did not fluoresce under UV light (n=88) were all histologically negative for WNS lesions. Punch biopsy samples as small as 3 mm taken from areas of wing with UV fluorescence were effective for identifying lesions diagnostic for WNS by histopathology. In a nonlethal biopsy-based study of 62 bats sampled (4-mm diameter) in hibernacula of the Czech Republic during 2012, 95.5% of fluorescent (n=22) and 100% of nonfluorescent (n=40) wing samples were confirmed by histopathology to be WNS positive and negative, respectively. This evidence supports use of long-wave UV light as a nonlethal and field-applicable method to screen bats for lesions indicative of WNS. Further, UV fluorescence can be used to guide targeted, nonlethal biopsy sampling for follow-up molecular testing, fungal culture analysis, and histologic confirmation of WNS.

The emerging wildlife disease white-nose syndrome is causing widespread mortality in hibernating North American bats. White-nose syndrome occurs when the fungus Geomyces destructans infects the living skin of bats during hibernation, but links between infection and mortality are underexplored. We analyzed blood from hibernating bats and compared blood electrolyte levels to wing damage caused by the fungus. Sodium and chloride tended to decrease as wing damage increased in severity. Depletion of these electrolytes suggests that infected bats may become hypotonically dehydrated during winter. Although bats regularly arouse from hibernation to drink during winter, water available in hibernacula may not contain sufficient electrolytes to offset winter losses caused by disease. Damage to bat wings from G. destructans may cause life-threatening electrolyte imbalances.

White-nose syndrome, associated with the fungal skin infection geomycosis, caused regional population collapse in bats in North America. Our results, based on histopathology, show the presence of white-nose syndrome in Europe. Dermatohistopathology on two bats (Myotis myotis) found dead in March 2010 with geomycosis in the Czech Republic had characteristics resembling Geomyces destructans infection in bats confirmed with white-nose syndrome in US hibernacula. In addition, a live M. myotis, biopsied for histopathology during hibernation in April 2011, had typical fungal infection with cupping erosion and invasion of muzzle skin diagnostic for white-nose syndrome and conidiospores identical to G. destructans that were genetically confirmed as G. destructans.

Wing damage is not used to confirm WNS: In response to elevated prevalence of wing damage in bats near WNS-affected hibernacula in 2008, we proposed a wing damage index (WDI) to objectively monitor wing conditions of bats in the field (Reichard and Kunz, 2009). Francl et al. suggested WDI is used ‘‘...as a proxy for measuring population-level infection’’ with WNS (Francl et al., 2011), but wing damage is only one field sign associated with WNS and does not confirm WNSpositive bats. Instead, WNS is diagnosed by histopathologic confirmation of cutaneous infections attributed to a recently introduced fungus, Geomyces destructans (Meteyer et al., 2009; USGS, 2011). Thus, we argue that suggesting use of WDI as a proxy for infection is inappropriate and misleading.

Geomyces destructans produces the white fungal growth on the muzzle and the tacky white discoloration on wings and ears that characterize white-nose syndrome (WNS) in cave-hibernating bats. To test the hypothesis that postemergent WNS-infected bats recover from infection with G. destructans, 30 little brown bats (Myotis lucifugus) were collected in May 2009 from a WNS-affected hibernation site in New Jersey. All bats were confirmed to be infected with G. destructans using a noninvasive fungal tape method to identify the conidia of G. destructans and polymerase chain reaction (PCR). The bats were then held in captivity and given supportive care for 70 days. Of the 26 bats that survived and were humanely killed after 70 days, 25 showed significant improvement in the external appearance of wing membranes, had no microscopic evidence of infection by G. destructans, and had wing tissue samples that were negative for G. destructans by PCR. A subset of the bats was treated topically at the beginning of the rehabilitation study with a dilute vinegar solution, but treatment with vinegar provided no added advantage to recovery. Provision of supportive care to homeothermic bats was sufficient for full recovery from WNS. One bat at day 70 still had both gross pathology and microscopic evidence of WNS in wing membranes and was PCR-positive for G. destructans. Dense aggregates of neutrophils surrounded the hyphae that remained in the wing membrane of this bat.

Since 2009, resource management agencies throughout much of the United States have required biologists to record a wing damage index (WDI) for bats captured. Interestingly, this requirement preceded publication of the technique (Reichard and Kunz, 2009), which (when published) advocated WDI as an ‘‘important tool for assessing the spread of [white-nose syndrome, or WNS] and for establishing baseline data for unaffected bats.’’ This statement immediately found a willing audience among regulatory biologists who saw WDI scores as a potential, easy proxy for monitoring the extent of WNS across broad geographic regions. In summer 2009, we surveyed bats at 459 sites in New York, Pennsylvania, New Jersey, Virginia, and Maryland and, as required, collected WDI scores for each bat captured (Francl et al., 2011). Like many biologists, we expected to document numerous bats with severely necrotic wings. Only 4 of 3,419 bats had severe (WDI53) and 47 had moderate (WDI52) damage. Taken alone, this result indicates that either WDI did not provide the easy assessment of the occurrence and severity of WNS across the landscape for which the regulatory community had hoped or that the majority of bats we captured were healthy. In an effort to further understand the value of the WDI, we attempted to correlate WDI with body mass index (BMI), a surrogate for health in bats, and with distance from infected hibernacula. In their response, Reichard et al. (2011) correctly questioned whether we failed to find a relationship between BMI and WDI scores because our sample included bats of multiple species and bats that were heavier due to full stomachs or pregnancy. The effect of a full stomach or pregnancy might be addressed with larger sample sizes, but our data set is the largest of which we are aware. Even when we accounted for these potential interand intraspecific biases, we found no apparent patterns between BMI and WDI. This is not surprising given that Reichard and Kunz (2009) only found such effects for bats with severe wing damage, which were extremely rare in our samples. This rarity perhaps is because these bats die or do not travel far from the roost. We did, however document higher WDI scores close to infected hibernacula. To some extent, Francl et al. (2011) was obsolete before it was published. Much like Reichard and Kunz (2009), we made our results available to other biologists prior to publication. Partly in response to this effort, WDI is now used by resource agencies to identify bats that should be subjected to more invasive and expensive analyses such as genetic testing (Lorch et al., 2010) for the putative causal organism (Geomyces destructans) or histology to confirm infection (Meteyer et al., 2009). Our comments about utility of WDI only apply to its use as a proxy for studying large-scale incidence of WNS, and thus do not preclude its use in a more controlled setting or its value as part of a suite of measurements.