North American bats have experienced catastrophic population declines from white-nose syndrome (WNS), a fungal disease caused by Pseudogymnoascus destructans (Pd). Although Pd can infect many hibernating bat species, population-level impacts of WNS vary by host species. Microbial skin assemblages, including the fungal component (mycobiome), can influence host resistance to infectious diseases; however, little is known about the influence the skin mycobiome of bats may have on susceptibility to WNS. We sampled ten bat species in the eastern United States that are known to be either susceptible, tolerant, or resistant to WNS by swabbing their wing skin. We then cultured fungi from the swabs, isolated morphologically distinct colonies of fungi, and identified the fungi through DNA sequencing. Using this culture-based approach, we compared skin mycobiome characteristics. The mycobiomes of WNS-susceptible bat species had significantly lower alpha diversity and abundance compared to WNS-tolerant species. Overall mycobiome structure did not vary based on WNS-susceptibility, but several yeast species were differentially abundant on WNS-tolerant bat species. Multi-locus phylogenies and scanning electron microscopy suggest that some yeasts likely represent novel taxa which may be adapted to colonizing bat skin. Further exploration of interactions between Pd and components of the mycobiome may prove useful for predicting susceptibility of bat populations and for developing effective mitigation strategies for WNS.

White-nose syndrome (WNS) is an emergent disease estimated to have killed over five million North American bats. Caused by the psychrophilic fungus Geomyces destructans, WNS specifically affects bats during hibernation. We describe temperature-dependent growth performance and morphology for six independent isolates of G. destructans from North America and Europe. Thermal performance curves for all isolates displayed an intermediate peak with rapid decline in performance above the peak. Optimal temperatures for growth were between 12.5 and 15.8 degrees C, and the upper critical temperature for growth was between 19.0 and 19.8 degrees C. Growth rates varied across isolates, irrespective of geographic origin, and above 12 degrees C all isolates displayed atypical morphology that may have implications for proliferation of the fungus. This study demonstrates that small variations in temperature, consistent with those inherent of bat hibernacula, affect growth performance and physiology of G. destructans, which may influence temperature-dependent progression and severity of WNS in wild bats.

White-nose syndrome (WNS) is an emergent disease estimated to have killed over five million North American bats. Caused by the psychrophilic fungus Geomyces destructans, WNS specifically affects bats during hibernation. We describe temperature-dependent growth performance and morphology for six independent isolates of G. destructans from North America and Europe. Thermal performance curves for all isolates displayed an intermediate peak with rapid decline in performance above the peak. Optimal temperatures for growth were between 12.5 and 15.8 degrees C, and the upper critical temperature for growth was between 19.0 and 19.8 degrees C. Growth rates varied across isolates, irrespective of geographic origin, and above 12 degrees C all isolates displayed atypical morphology that may have implications for proliferation of the fungus. This study demonstrates that small variations in temperature, consistent with those inherent of bat hibernacula, affect growth performance and physiology of G. destructans, which may influence temperature-dependent progression and severity of WNS in wild bats.

This work is part of a study investigating the movement of microcystin from aquatic to terrestrial ecosystems via trophic transfer. Little brown bats (Myotis lucifugus), feeding opportunistically on aquatic insects including Hexagenia mayflies, were collected from a maternity roost near Little Traverse Lake (Leelanau County, Michigan, USA). Bats and fecal samples were collected for dietary analysis, quantification of microcystin in livers and feces, and histopathological evaluation of the liver. Liver was collected in RNAlater and stored frozen. Livers from three bats with the highest microcystin levels by ELISA were thawed, washed with PBS, fixed in 10% neutral buffered formalin, processed routinely for histopathology, and assessed by light microscopy. Microscopic lesions included centrilobular congestion, periportal to midzonal hepatocellular vacuolation, and low numbers of portal inflammatory cells. These changes are non-specific; no evidence of acute microcystin toxicosis was present. Results suggest that despite the detection of microcystin in bat feces from the site, there is no evidence of acute clinical toxicity in the bats collected.

This work is part of an experimental trial investigating the effects of microclimate conditions of temperature and humidity on a fungal pathogen, Pseudogymnoascus destructans (Pd), that causes white-nose syndrome (WNS) disease in hibernating bats. As part of the trial, tri-colored bats (Perimyotis subflavus) were exposed to Pseudogymnoascus destructans (Pd) and allowed to hibernate in chambers with a variety of temperature and humidity conditions. Bats were euthanized after 83 days. A portion of the wing was rolled around dental wax dowels, fixed in 10% neutral buffered formalin, processed and stained with periodic acid-Schiff, and assessed by light microscopy for evidence of fungal infection. Three types of cutaneous infection were described histologically, including characteristic WNS cupping erosions, neutrophilic pustules with fungal hyphae, and fungal hyphae in the stratum corneum with dermal necrosis. Bats with any of these three conditions were scored as WNS-positive by histology. Only 11% (10/95) of bats scored as positive by histology. Of the 10 bats scored as positive, 3 bats had cupping erosions containing fungal hyphae and 7 bats had either neutrophilic pustules containing fungal hyphae, dermal necrosis associated with intra-epidermal fungal hyphae, or both. Overall, lack of infection and disease outcomes in this experiment limited our ability to make robust conclusions about the influence of microclimates on the development of WNS in bats.

This work is part of an experimental trial investigating the effects of microclimate conditions of temperature and humidity on a fungal pathogen, Pseudogymnoascus destructans (Pd), that causes white-nose syndrome (WNS) disease in hibernating bats. As part of the trial, tri-colored bats (Perimyotis subflavus) were exposed to Pseudogymnoascus destructans (Pd) and allowed to hibernate in chambers with a variety of temperature and humidity conditions. Bats were euthanized after 83 days. A portion of the wing was rolled around dental wax dowels, fixed in 10% neutral buffered formalin, processed and stained with periodic acid-Schiff, and assessed by light microscopy for evidence of fungal infection. Three types of cutaneous infection were described histologically, including characteristic WNS cupping erosions, neutrophilic pustules with fungal hyphae, and fungal hyphae in the stratum corneum with dermal necrosis. Bats with any of these three conditions were scored as WNS-positive by histology. Only 11% (10/95) of bats scored as positive by histology. Of the 10 bats scored as positive, 3 bats had cupping erosions containing fungal hyphae and 7 bats had either neutrophilic pustules containing fungal hyphae, dermal necrosis associated with intra-epidermal fungal hyphae, or both. Overall, lack of infection and disease outcomes in this experiment limited our ability to make robust conclusions about the influence of microclimates on the development of WNS in bats.

Through the North American Bat Monitoring Program, Bat Conservation International and U.S Geological Survey (USGS) provided technical and science support to assistance in U.S. Fish and Wildlife Service Species Status Assessment (“SSA”) for the northern long-eared bat (Myotis septentrionalis), little brown bat (Myotis lucifugus), and tri-colored bat (Perimyotis subflavus). USGS facilitated the SSA data call providing data archival for repeatable and transparent analyses, provided statistical support to assess the historical, current, an future population status for each of the three species, and developed a demographic projection tool to evaluate future viability of each species under multiple threat scenarios. We assessed population trends from count surveys of wintering colonies at hibernacula for these three bat species. Winter colony counts were downloaded from the database of the North American Bat Monitoring Program (U.S. Geological Survey North American Bat Monitoring Program. Accessed 2020-12-01. NABat Request Number 12. Database Version v5.4.0).

This dataset includes data used to summarize trends and identify best-fit models to explain patterns in presence-absence and abundance of Pseudogymnoascus destructans (Pd) in environmental substrates and on bats within six bat hibernacula at different stages of white-nose syndrome (WNS). Data relating to environmental substrates include: dates and relative spatial locations of samples collected within study hibernacula, presence and quantity of Pd in samples based on qPCR analysis, and daily temperature parameters at each sample location on the days samples were collected. Data relating to bats include: dates and relative spatial locations of hibernating bats that were sampled, species, sex, weight(g), forearm length(mm), body mass index (weight/forearm), proportion of the wing with visible fungus or fluorescence characteristic of WNS under hand-held UVA light and presence and quantity of Pd in wing-skin swab samples based on qPCR analysis. Measures of time since first detection of WNS at each study hibernaculum are also included in the dataset.