DISPERSAL HAZARDS OF PSEUDOGYMNOASCUS DESTRUCTANS BY BATS AND HUMAN ACTIVITY AT HIBERNACULA IN SUMMER

Unraveling the ancient fungal DNA from the Iceman gut

BACKGROUND

Fungal DNA is rarely reported in metagenomic studies of ancient samples. Although fungi are essential for their interactions with all kingdoms of life, limited information is available about ancient fungi. Here, we explore the possibility of the presence of ancient fungal species in the gut of Ötzi, the Iceman, a naturally mummified human found in the Tyrolean Alps (border between Italy and Austria).

METHODS

A robust bioinformatic pipeline has been developed to detect and authenticate fungal ancient DNA (aDNA) from muscle, stomach, small intestine, and large intestine samples.

RESULTS

We revealed the presence of ancient DNA associated with Pseudogymnoascus genus, with P. destructans and P. verrucosus as possible species, which were abundant in the stomach and small intestine and absent in the large intestine and muscle samples.

CONCLUSION

We suggest that Ötzi may have consumed these fungi accidentally, likely in association with other elements of his diet, and they persisted in his gut after his death due to their adaptability to harsh and cold environments. This suggests the potential co-occurrence of ancient humans with opportunistic fungal species and proposes and validates a conservative bioinformatic approach for detecting and authenticating fungal aDNA in historical metagenomic samples.

Bat white-nose disease fungus diversity in time and space

White-nose disease (WND), caused by the psychrophilic fungus Pseudogymnoascusdestructans, represents one of the greatest threats for North American hibernating bats. Research on molecular data has significantly advanced our knowledge of various aspects of the disease, yet more studies are needed regarding patterns of P.destructans genetic diversity distribution. In the present study, we investigate three sites within the native range of the fungus in detail: two natural hibernacula (karst caves) in Bulgaria, south-eastern Europe and one artificial hibernaculum (disused cellar) in Germany, northern Europe, where we conducted intensive surveys between 2014 and 2019. Using 18 microsatellite and two mating type markers, we describe how P.destructans genetic diversity is distributed between and within sites, the latter including differentiation across years and seasons of sampling; across sampling locations within the site; and between bats and hibernaculum walls. We found significant genetic differentiation between hibernacula, but we could not detect any significant differentiation within hibernacula, based on the variables examined. This indicates that most of the pathogen's movement occurs within sites. Genotypic richness of P.destructans varied between sites within the same order of magnitude, being approximately two times higher in the natural caves (Bulgaria) compared to the disused cellar (Germany). Within all sites, the pathogen's genotypic richness was higher in samples collected from hibernaculum walls than in samples collected from bats, which corresponds with the hypothesis that hibernacula walls represent the environmental reservoir of the fungus. Multiple pathogen genotypes were commonly isolated from a single bat (i.e. from the same swab sample) in all study sites, which might be important to consider when studying disease progression.

COULD WHITE-NOSE SYNDROME MANIFEST DIFFERENTLY IN MYOTIS LUCIFUGUS IN WESTERN VERSUS EASTERN REGIONS OF NORTH AMERICA? A REVIEW OF FACTORS

White-nose syndrome (WNS) has notably affected the abundance of Myotis lucifugus (little brown myotis) in North America. Thus far, substantial mortality has been restricted to the eastern part of the continent where the cause of WNS, the invasive fungus Pseudogymnoascus destructans, has infected bats since 2006. To date, the state of Washington is the only area in the Western US or Canada (the Rocky Mountains and further west in North America) with confirmed cases of WNS in bats, and there the disease has spread more slowly than it did in Eastern North America. Here, we review differences between M. lucifugus in western and eastern parts of the continent that may affect transmission, spread, and severity of WNS in the West and highlight important gaps in knowledge. We explore the hypothesis that western M. lucifugus may respond differently to WNS on the basis of different hibernation strategies, habitat use, and greater genetic structure. To document the effect of WNS on M. lucifugus in the West most effectively, we recommend focusing on maternity roosts for strategic disease surveillance and monitoring abundance. We further recommend continuing the challenging work of identifying hibernation and swarming sites to better understand the microclimates, microbial communities, and role in disease transmission of these sites, as well as the ecology and hibernation physiology of bats in noncavernous hibernacula.

Environmental transmission of Pseudogymnoascus destructans to hibernating little brown bats

Pathogens with persistent environmental stages can have devastating effects on wildlife communities. White-nose syndrome (WNS), caused by the fungus Pseudogymnoascus destructans, has caused widespread declines in bat populations of North America. In 2009, during the early stages of the WNS investigation and before molecular techniques had been developed to readily detect P. destructans in environmental samples, we initiated this study to assess whether P. destructans can persist in the hibernaculum environment in the absence of its conclusive bat host and cause infections in naive bats. We transferred little brown bats (Myotis lucifugus) from an unaffected winter colony in northwest Wisconsin to two P. destructans contaminated hibernacula in Vermont where native bats had been excluded. Infection with P. destructans was apparent on some bats within 8 weeks following the introduction of unexposed bats to these environments, and mortality from WNS was confirmed by histopathology at both sites 14 weeks following introduction. These results indicate that environmental exposure to P. destructans is sufficient to cause the infection and mortality associated with WNS in naive bats, which increases the probability of winter colony extirpation and complicates conservation efforts.

Tricolored bats at a southern range edge exhibit partial migration northward in autumn

BACKGROUND

Animal migration is a widespread global adaptation by which individuals move in response to environmental conditions to reach more favorable conditions. For bats in temperate climates, migration and hibernation are often associated with each other when these bats must migrate to reach suitable overwintering sites. However, differences in movement across the geographical range of a species and the degree to which hibernation drives migratory behavior of bats in subtropical climates, where conditions may remain warm with available prey year-round, remains incomplete. Understanding the migratory strategies of subtropical bats during winter is of increasing importance as they are threatened by stressors such as disease and environmental change.

METHODS

We evaluated migration patterns of tricolored bats (Perimyotis subflavus) in Florida, USA, through analysis of stable hydrogen isotope ratios of the fur. We inferred the summer geographic origins of the fur samples and estimated the minimum distance and likely direction traveled by hibernating individuals. We used linear models to examine whether hibernation region, colony size, and an individual's sex affected the distance traveled.

RESULTS

We sampled 111 bats hibernating at 40 sites and found that more than half (54.1%) of individuals were residents of the area in which they hibernated. We found that almost half of the sampled bats (43.2%) traveled from southern Florida to overwinter in North Florida. We also documented three individuals that traveled > 100 km from northerly origins, one of which had traveled an estimated minimum distance of 1382 km. We also found that tricolored bats moved farther to reach hibernacula in Northwest Florida and hibernacula with more populous colonies, with no difference in movement between sexes.

CONCLUSIONS

Our results indicate a pattern of northward autumnal movements of tricolored bats in the subtropical southeastern portion of their range. We suggest that bats are differentially constrained at the edge of their geographical range, resulting in movement contrary to what is expected. Even though we found that few (2.7%) bats moved into Florida from farther north, those migrants can potentially transfer the fungus that causes the deadly white-nose syndrome, which does not currently occur in the state. Our results support the characterization of tricolored bats as flexible partial migrators, with a rarely exercised capacity for long-distance movements.

Spatial aggregation with respect to a population distribution: Impact on inference

Spatial aggregation with respect to a population distribution involves estimating aggregate population quantities based on observations from individuals. In this context, a geostatistical workflow must account for three major sources of aggregation error: aggregation weights, fine scale variation, and finite population variation. However, these sources of aggregation error are commonly ignored, and the population instead treated as a fixed population density surface. We improve common practice by introducing a sampling frame model allowing aggregation models to account for aggregation error simply and transparently. This preserves aggregate point estimates while increasing their uncertainties. We compare the proposed and the traditional approach using two simulation studies mimicking neonatal mortality rate (NMR) data from the 2014 Kenya Demographic and Health Survey. In the traditional approach, undercoverage/overcoverage of interval estimates depends arbitrarily on the aggregation grid resolution, while the new approach is resolution robust. Differences between the aggregation approaches increase as an area's population decreases, and are particularly large at the second administrative level and finer, but also at the first administrative level for some population quantities. These findings are consistent with those of an application to the true NMR data. We demonstrate in a sensitivity analysis that burden estimates and their uncertainties are not robust to changes in population density and census information, while prevalence estimates and uncertainties seem stable.

Multifaceted DNA metabarcoding of guano to uncover multiple classes of ecological data in two different bat communities

DNA contained in animal scat provides a wealth of information about the animal, and DNA metabarcoding of scat collections can provide key information about animal populations and communities. Next-generation DNA sequencing technologies and DNA metabarcoding provide an efficient means for obtaining information available in scat samples. We used multifaceted DNA metabarcoding (MDM) of noninvasively collected bat guano pellets from a Myotis lucifugus colony on Fort Drum Military Installation, New York, USA, and from two mixed-species bat roosts on Fort Huachuca Military Installation, Arizona, USA, to identify attributes such as bat species composition, sex ratios, diet, and the presence of pathogens and parasites. We successfully identified bat species for nearly 98% of samples from Fort Drum and 90% of samples from Fort Huachuca, and identified the sex for 84% and 67% of samples from these same locations, respectively. Species and sex identification matched expectations based on prior censuses of bat populations utilizing those roosts, though samples from some species were more or less common than anticipated within Fort Huachuca roosts. Nearly 62% of guano samples from Fort Drum contained DNA from Pseudogymnoascus destructans, where bats with wing damage from White-nose Syndrome were commonly observed. Putative dietary items were detected in a majority of samples from insectivorous bats on Fort Drum (81%) and Fort Huachuca (63%). A minority of guano samples identified as the nectarivorous Leptonycteris yerbabuenae (28%) provided DNA sequences from putative forage plant species. Finally, DNA sequences from both putative ecto- and endoparasite taxa were detected in 35% and 56% of samples from Fort Drum and Fort Huachuca, respectively. This study demonstrates that the combination of noninvasive sampling, DNA metabarcoding, and sample and locus multiplexing provide a wide array of data that are otherwise difficult to obtain.

White-Nose Syndrome Pathogen Pseudogymnoascus destructans Detected in Migratory Tree-Roosting Bats

White-nose syndrome (WNS) is an emerging fungal epizootic disease that has caused large-scale mortality in several species of North American bats. The fungus that causes WNS, Pseudogymnoascus destructans (Pd), has also been detected in bat species without diagnostic signs of WNS. Although these species could play a role in WNS spread, understanding of the spatial and temporal extents of Pd occurrence on WNS-resistant species is limited. This study evaluated the presence of Pd on 272 individuals of three species of migratory tree-roosting bats: hoary (Lasiurus cinereus), eastern red (Lasiurus borealis), and silver-haired (Lasionycteris noctivagans) bats, obtained opportunistically during summer and autumn from throughout much of their ranges in North America. We also compared tissue sampling protocols (i.e., tissue swabbing, fur swabbing, and DNA extraction of excised wing tissue). We detected Pd on three eastern red bats from Illinois and Ohio, US, one silver-haired bat from West Virginia, US, and one hoary bat from New York, US, all via DNA extracted from wing tissue of carcasses. These results document the first publicly reported detections of Pd on a hoary bat and on migratory bats during the autumn migratory period, and demonstrate the potential for using carcasses salvaged at wind-energy facilities to monitor for Pd.

ROADWAY-ASSOCIATED CULVERTS MAY SERVE AS A TRANSMISSION CORRIDOR FOR PSEUDOGYMNOASCUS DESTRUCTANS AND WHITE-NOSE SYNDROME IN THE COASTAL PLAINS AND COASTAL REGION OF GEORGIA, USA

White-nose syndrome (WNS) is a disease among hibernating North American bats caused by the psychrophilic fungus Pseudogymnoascus destructans. Since its discovery in New York state, US, in 2006, and as of 2020, WNS has rapidly spread to 34 American states and seven Canadian provinces, causing precipitous declines of native bat populations across North America. The rapid spread of this fungal pathogen has been facilitated by the social behavior of bats, as well as the ability of subterranean hibernacula to support a favorable environment for P. destructans, and is probably exacerbated by anthropogenic transmission events. Although many bat species roost in natural cave environments, bats also selectively use diverse structures for hibernacula. Certain areas of the US lack caves, forcing bats to select different winter roosting environments. Bats have been observed using roadway-associated structures, such as bridges and culverts, for roosting, especially in regions that lack natural cave environments. However, the potential for P. destructans transmission in such roadway-associated structures requires further investigation. Understanding potential pathogen transmission in these widely used anthropogenic structures is crucial to disease management and preventing further declines of imperiled bat populations. Our study investigated these structures as potential pathogen transmission corridors by surveying the use of these structures by Perimyotis subflavus and other susceptible bat populations and by measuring their temperature. The results suggest the environments of roadway-associated culverts are thermally conducive to the proliferation of P. destructans-even in regions with mild winters-and the development of WNS in susceptible bat populations. It is apparent these roadway-associated structures have the potential to spread P. destructans and exacerbate the effect of WNS on susceptible bat populations.

The Milieu Souterrain Superficiel as hibernation habitat for bats: implications for white-nose syndrome

Recent studies have revealed that western populations of little brown bats (Myotis lucifugus) in North America exhibit different hibernation behavior than their eastern counterparts. Understanding these differences is essential for assessing the risk white-nose syndrome (WNS) poses to western bat populations. We used acoustic monitoring and radiotelemetry to study the overwintering behavior of little brown bats near Juneau, Alaska during 2011-2014. Our objectives were to identify the structures they use for hibernation, measure the microclimates within those structures, and determine the timing of immergence and emergence and the length of the hibernation season. We radiotracked 10 little brown bats to underground hibernacula dispersed along two ridge systems. All hibernacula were ≤ 24.2 km from where the bats were captured. Eight bats hibernated in the "Milieu Souterrain Superficiel" (MSS), a network of air-filled underground voids between the rock fragments found in scree (talus) deposits. Two bats hibernated in holes in the soil beneath the root system of a tree or stump (rootball). At least two hibernacula in the MSS were reused in subsequent years. Average MSS and rootball temperatures were warmer and more stable than ambient temperature and were well below the optimal growth range of the fungus that causes WNS. Temperatures in the MSS dropped below freezing, but MSS temperatures increased with depth, indicating bats could avoid subfreezing temperatures by moving deeper into the MSS. Relative humidity (RH) approached 100% in the MSS and under rootballs and was more stable than ambient RH, which also was high, but dropped substantially during periods of extreme cold. Acoustic monitoring revealed that bats hibernated by late October and began emerging by the second week of April; estimates of minimum length of the hibernation season ranged from 156 to 190 days. The cold temperatures, dispersed nature of the hibernacula, and close proximity of hibernacula to summering areas may slow the spread and reduce the impacts of WNS on local populations of little brown bats.

Ten-year projection of white-nose syndrome disease dynamics at the southern leading-edge of infection in North America

Predicting the emergence and spread of infectious diseases is critical for the effective conservation of biodiversity. White-nose syndrome (WNS), an emerging infectious disease of bats, has resulted in high mortality in eastern North America. Because the fungal causative agent Pseudogymnoascus destructans is constrained by temperature and humidity, spread dynamics may vary by geography. Environmental conditions in the southern part of the continent are different than the northeast, where disease dynamics are typically studied, making it difficult to predict how the disease will manifest. Herein, we modelled WNS pathogen spread in Texas based on cave densities and average dispersal distances of hosts, projecting these results out to 10 years. We parameterized a predictive model of WNS epidemiology and its effects on bat populations with observed cave environmental data. Our model suggests that bat populations in northern Texas will be more affected by WNS mortality than southern Texas. As such, we recommend prioritizing the preservation of large overwintering colonies of bats in north Texas through management actions. Our model illustrates that infectious disease spread and infectious disease severity can become uncoupled over a gradient of environmental variation and highlight the importance of understanding host, pathogen and environmental conditions across a breadth of environments.

White-Nose Syndrome Confirmed in Italy: A Preliminary Assessment of Its Occurrence in Bat Species

Although no mass mortality has been recorded so far, the precise demographic effect of white-nose syndrome (WNS) on European bats still remains to be ascertained. Following the first isolation of P. destructans in Italy, further surveys were performed to assess the distribution of the fungus in NW Italy and its effects on bats. Data were collected from March 2019 to April 2020 at sites used for hibernation (six sites) and/or for reproduction (four sites) in Piedmont and Aosta Valley. A total of 138 bats, belonging to 10 species, were examined to identify clinical features possibly related to the fungal presence. Culture from swabs and the molecular identification of isolates confirmed the presence of P. destructans in bats from five sites, including two maternal roosts. Dermal fungal infiltration, the criterion to assess the presence of WNS, was observed in biopsies of bats belonging to Myotis blythii, M. daubentonii, M. emarginatus and M. myotis. This is the first report of the disease in Italy. The results suggest a greater susceptibility to the infection of the genus Myotis and particularly of M. emarginatus, possibly due to the long length of its hibernation period. Other fungal dermatophytes were also observed.

Landscape Genetic Connectivity and Evidence for Recombination in the North American Population of the White-Nose Syndrome Pathogen, Pseudogymnoascus destructans

White-Nose Syndrome is an ongoing fungal epizootic caused by epidermal infections of the fungus, Pseudogymnoascus destructans (P. destructans), affecting hibernating bat species in North America. Emerging early in 2006 in New York State, infections of P. destructans have spread to 38 US States and seven Canadian Provinces. Since then, clonal isolates of P. destructans have accumulated genotypic and phenotypic variations in North America. Using microsatellite and single nucleotide polymorphism markers, we investigated the population structure and genetic relationships among P. destructans isolates from diverse regions in North America to understand its pattern of spread, and to test hypotheses about factors that contribute to transmission. We found limited support for genetic isolation of P. destructans populations by geographic distance, and instead identified evidence for gene flow among geographic regions. Interestingly, allelic association tests revealed evidence for recombination in the North American P. destructans population. Our landscape genetic analyses revealed that the population structure of P. destructans in North America was significantly influenced by anthropogenic impacts on the landscape. Our results have important implications for understanding the mechanism(s) of P. destructans spread.

Ecology and impacts of white-nose syndrome on bats

The recent introduction of Pseudogymnoascus destructans (the fungal pathogen that causes white-nose syndrome in bats) from Eurasia to North America has resulted in the collapse of North American bat populations and restructured species communities. The long evolutionary history between P. destructans and bats in Eurasia makes understanding host life history essential to uncovering the ecology of P. destructans. In this Review, we combine information on pathogen and host biology to understand the patterns of P. destructans spread, seasonal transmission ecology, the pathogenesis of white-nose syndrome and the cross-scale impact from individual hosts to ecosystems. Collectively, this research highlights how early pathogen detection and quantification of host impacts has accelerated the understanding of this newly emerging infectious disease.

Caver Knowledge and Biosecurity Attitudes Towards White-Nose Syndrome and Implications for Global Spread

White-nose syndrome (WNS), caused by the fungus Pseudogymnoascus destructans, has caused catastrophic declines of bat populations in North America. Risk assessment indicates that cavers could pose a risk for the spread of the fungus, however, information on cavers' knowledge of WNS and their caving and biosecurity habits is lacking. An anonymous qualitative survey was completed by delegates (n = 134) from 23 countries at an international speleological conference in Sydney, Australia. Cavers indicated that they visit caves frequently (80.6% at least bimonthly), including outside of their own country, but 20.3% of respondents did not know about WNS prior to the conference. Some respondents were incorrect, or unsure, about whether they had visited caves in countries where P. destructans occurs (26.5%) or whether their own country was free of the fungus (7.8%). Although 65.9% of respondents were aware of current decontamination protocols, only 23.9% and 31.2% (when in Australian or overseas caves, respectively) fully adhered to them. Overall, cavers showed strong willingness to help prevent further spread of this disease, but further efforts at education and targeted biosecurity activities may be urgently needed to prevent the spread of P. destructans to Australia and to other unaffected regions of the world.

Assessment of the Portable C-320 Electronic Nose for Discrimination of Nine Insectivorous Bat Species: Implications for Monitoring White-Nose Syndrome

The development of new C-320 electronic-nose (e-nose) methods for pre-symptomatic detection of White-Nose Syndrome (WNS) in bats has required efficacy studies of instrument capabilities to discriminate between major sources of volatile organic compounds (VOCs) derived from clinical samples. In this phase-2 study, we further tested this e-nose for capabilities to distinguish between bat species based on differences in whole-body VOC emissions. Live healthy individuals of nine bat species were temporarily captured outside of caves in Arkansas and Louisiana. VOC emissions from bats were collected using newly developed portable air collection and sampling-chamber devices in tandem. Sensor-array output responses to bat VOC emissions were compared to those of 22 pure VOC analytical standards from five chemical classes. Distinct smellprint signatures were produced from e-nose analyses of VOC metabolites derived from individual bat species. Smellprint patterns were analyzed using 2-dimensional and 3-dimensional Principal Component Analysis (PCA) to produce aroma map plots showing effective discrimination between bat species with high statistical significance. These results demonstrate potential instrument efficacy for distinguishing between species-specific, bat-derived VOC metabolite emissions as major components of clinical samples collected from bats in caves for disease detection prior to symptom development. This study provided additional information required to fully test the efficacy of a portable e-nose instrument for diagnostic applications in subsequent phase-3 testing of noninvasive, early WNS disease detection in intra-cave hibernating bats.

Experimental evaluation of genomic DNA degradation rates for the pathogen Pseudogymnoascus destructans (Pd) in bat guano

Pseudogymnoascus destructans (Pd), the causative agent of white-nose syndrome in bats (WNS), has led to dramatic declines of bat populations in eastern North America. In the spring of 2016, WNS was first detected at several locations in Washington State, USA, which has prompted the need for large scale surveillance efforts to monitor the spread of Pd. Pd is typically detected in bats using invasive methods requiring capturing and swabbing individual bats. However, Pd can also be detected in guano, which may provide an efficient, affordable, and noninvasive means to monitor Pd in bats across North America. The widespread implementation of Pd surveillance in guano is hindered by substantial uncertainty about the probability of detecting Pd when present, and how this probability is influenced by the time since defecation, local environmental conditions, the amount of guano sampled, and the original concentration of DNA shed in the guano. In addition, the expected degradation rate of Pd DNA depends on whether the Pd DNA found in guano represents extracellular DNA fragments, intracellular DNA from dead Pd fungal cells, or from intracellular and viable Pd cells. While this is currently unknown, it has been posited that most environmental DNA, such as Pd found in guano long after defecation, is fragmented extracellular DNA. Using non-viable isolated DNA at precise quantities, we experimentally characterized the degradation rates of Pd DNA in guano samples. We spiked 450 guano samples with Pd gDNA in a 10-fold dilution series from 1 million to 1,000 fg and placed them in variable environmental conditions at five sites at Mount Rainier National Park in Washington State, which is a priority location for Pd surveillance. We evaluated DNA degradation over 70 days by quantifying the amount of DNA in samples collected every 14 days using real-time quantitative PCR (qPCR). Our sampling period was from July 10th to September 17th 2018 which overlaps with bat movement between summer roosts as well as movement from maternity colonies fall swarms. We detected Pd DNA in guano 56 and 70 days after inoculation with 1 million and 100,000 fg respectively, while the lowest quantity (1,000 fg) was detected until 42 days. Detection probability was variable among sites and lower where samples were left exposed without overhead cover. If Pd is shed as extracellular DNA in guano at quantities above 1,000 fg, then guano collection is likely to provide an effective tool for environmental screening of Pd that can be employed in an early detection and rapid response framework throughout Washington and other regions where this disease is rapidly emerging.

Multiscale model of regional population decline in little brown bats due to white-nose syndrome

The introduced fungal pathogen Pseudogymnoascus destructans is causing decline of several species of bats in North America, with some even at risk of extinction or extirpation. The severity of the epidemic of white-nose syndrome caused by P. destructans has prompted investigation of the transmission and virulence of infection at multiple scales, but linking these scales is necessary to quantify the mechanisms of transmission and assess population-scale declines.We built a model connecting within-hibernaculum disease dynamics of little brown bats to regional-scale dispersal, reproduction, and disease spread, including multiple plausible mechanisms of transmission.We parameterized the model using the approach of plausible parameter sets, by comparing stochastic simulation results to statistical probes from empirical data on within-hibernaculum prevalence and survival, as well as among-hibernacula spread across a region.Our results are consistent with frequency-dependent transmission between bats, support an important role of environmental transmission, and show very little effect of dispersal among colonies on metapopulation survival.The results help identify the influential parameters and largest sources of uncertainty. The model also offers a generalizable method to assess hypotheses about hibernaculum-to-hibernaculum transmission and to identify gaps in knowledge about key processes, and could be expanded to include additional mechanisms or bat species.

Detection of Pseudogymnoascus destructans on Wisconsin Bats During Summer

White-nose syndrome (WNS) affects bats primarily in winter, with Pseudogymnoascus destructans, the fungus that causes WNS, growing on bats in colder climates as they are hibernating. As a result, nearly all disease investigations have been conducted on bats in the winter or as they are emerging in spring. Although P. destructans has been detected on bats during the summer season, the seasonal dynamics of infection during this period remain poorly understood. To test for the presence of P. destructans during the summer season, we sampled bats that were free flying from June 2017 to September 2017 and also sampled bats from a maternity roost in August and outside a known hibernaculum in September. We collected skin swabs from the muzzle and forearm of bats, and using real-time PCR methods, we detected P. destructans DNA on 16% (12/76) of bats sampled in Wisconsin, US, including juvenile little brown bats (Myotis lucifugus) from bat house maternity roosts, and free-flying adult bats of two species captured in June, the little brown bat and the migratory eastern red bat (Lasiurus borealis). These data illustrated the potential for P. destructans to be transferred and dispersed among bats during the summer and highlighted the complex seasonal dynamics associated with this pathogen.

Does the fungus causing white-nose syndrome pose a significant risk to Australian bats?

Abstract ContextPseudogymnoascus destructans is the fungus responsible for white-nose syndrome (WNS), which has killed millions of hibernating bats in North America, but also occurs in bats in Europe and China without causing large-scale population effects. This is likely to be due to differences in species susceptibility and behaviour, and environmental factors, such as temperature and humidity. Pseudogymnoascus destructans is currently believed to be absent from Australia. AimsTo ascertain the level of risk that white-nose syndrome poses for Australian bats. Methods This risk analysis examines the likelihood that P. destructans enters Australia, the likelihood of the fungus coming in contact with native bats on successful entry, and the potential consequences should this occur. Key results This risk assessment concluded that it is very likely to almost certain that P. destructans will enter Australia, and it is likely that bats will be exposed to the fungus over the next 10 years. Eight cave-dwelling bat species from southern Australia are the ones most likely to be affected. ConclusionsThe risk was assessed as medium for the critically endangered southern bent-winged bat (Miniopterus orianae bassanii), because any increase in mortality could affect its long-term survival. The risk to other species was deemed to range from low to very low, owing to their wider distribution, which extends beyond the P. destructans risk zone. Implications Although Australia’s milder climate may preclude the large mortality events seen in North America, the fungus could still significantly affect Australian bat populations, particularly bent-winged bats. Active surveillance is required to confirm Australia’s continuing WNS-free status, and to detect the presence of P. destructans should it enter the country. Although White-nose Syndrome Response Guidelines have been developed by Wildlife Health Australia to assist response agencies in the event of an incursion of WNS into bats in Australia, these guidelines would be strengthened by further research to characterise Australian cave temperatures and hibernating bat biology, such as length of torpor bouts and movement over winter. Risk-mitigation strategies should focus on education programs that target cavers, show-cave managers and tourists, particularly those who have visited regions where WNS is known to occur.

Challenges and Opportunities Developing Mathematical Models of Shared Pathogens of Domestic and Wild Animals

Diseases that affect both wild and domestic animals can be particularly difficult to prevent, predict, mitigate, and control. Such multi-host diseases can have devastating economic impacts on domestic animal producers and can present significant challenges to wildlife populations, particularly for populations of conservation concern. Few mathematical models exist that capture the complexities of these multi-host pathogens, yet the development of such models would allow us to estimate and compare the potential effectiveness of management actions for mitigating or suppressing disease in wildlife and/or livestock host populations. We conducted a workshop in March 2014 to identify the challenges associated with developing models of pathogen transmission across the wildlife-livestock interface. The development of mathematical models of pathogen transmission at this interface is hampered by the difficulties associated with describing the host-pathogen systems, including: (1) the identity of wildlife hosts, their distributions, and movement patterns; (2) the pathogen transmission pathways between wildlife and domestic animals; (3) the effects of the disease and concomitant mitigation efforts on wild and domestic animal populations; and (4) barriers to communication between sectors. To promote the development of mathematical models of transmission at this interface, we recommend further integration of modern quantitative techniques and improvement of communication among wildlife biologists, mathematical modelers, veterinary medicine professionals, producers, and other stakeholders concerned with the consequences of pathogen transmission at this important, yet poorly understood, interface.

Phenotypic Divergence along Geographic Gradients Reveals Potential for Rapid Adaptation of the White-Nose Syndrome Pathogen, Pseudogymnoascus destructans, in North America

White-nose syndrome (WNS) is an ongoing epizootic affecting multiple species of North American bats, caused by epidermal infections of the psychrophilic filamentous fungus Pseudogymnoascus destructans Since its introduction from Europe, WNS has spread rapidly across eastern North America and resulted in high mortality rates in bats. At present, the mechanisms behind its spread and the extent of its adaptation to different geographic and ecological niches remain unknown. The objective of this study was to examine the geographic patterns of phenotypic variation and the potential evidence for adaptation among strains representing broad geographic locations in eastern North America. The morphological features of these strains were evaluated on artificial medium, and the viability of asexual arthroconidia of representative strains was investigated after storage at high (23°C), moderate (14°C), and low (4°C) temperatures at different lengths of time. Our analyses identified evidence for a geographic pattern of colony morphology changes among the clonal descendants of the fungus, with trait values correlated with increased distance from the epicenter of WNS. Our genomic comparisons of three representative isolates revealed novel genetic polymorphisms and suggested potential candidate mutations that might be related to some of the phenotypic changes. These results show that even though this pathogen arrived in North America only recently and reproduces asexually, there has been substantial evolution and phenotypic diversification during its rapid clonal expansion.IMPORTANCE The causal agent of white-nose syndrome in bats is Pseudogymnoascus destructans, a filamentous fungus recently introduced from its native range in Europe. Infections caused by P. destructans have progressed across the eastern parts of Canada and the United States over the last 10 years. It is not clear how the disease is spread, as the pathogen is unable to grow above 23°C and ambient temperature can act as a barrier when hosts disperse. Here, we explore the patterns of phenotypic diversity and the germination of the fungal asexual spores, arthroconidia, from strains across a sizeable area of the epizootic range. Our analyses revealed evidence of adaptation along geographic gradients during its expansion. The results have implications for understanding the diversification of P. destructans and the limits of WNS spread in North America. Given the rapidly expanding distribution of WNS, a detailed understanding of the genetic bases for phenotypic variations in growth, reproduction, and dispersal of P. destructans is urgently needed to help control this disease.

Observed Resiliency of Little Brown Myotis to Long-Term White-Nose Syndrome Exposure

White-nose syndrome (WNS) is a disease that has killed millions of bats in eastern North America and has steadily been spreading across the continent. Little brown myotis Myotis lucifugus populations have experienced extensive declines; however, some localized populations have remained resilient, with bats surviving multiple years past initial WNS exposure. These persistent populations may be critical to species recovery, and understanding mechanisms leading to this long-term survival and persistence may provide insight into overall bat and disease management. We monitored a maternity colony of little brown myotis on Fort Drum Military Installation in northern New York between 2006 and 2017 to determine basic demographic parameters and find evidence of what may be leading to resiliency and persistence at this site. Total colony size declined by approximately 88% from 2008 to 2010 due primarily to impacts of WNS. Counts of all adults returning to the colony stabilized during 2010–2014 (mean = 94, range 84–101) and increased after 2014 (mean = 132, range = 108–166). We captured 727 little brown myotis (575 females, 152 males) and banded 534 individuals (389 females, 145 males) at the colony. The majority of sampled bats showed evidence of recent past WNS infection and exposure to Pseudogymnoascus destructans, and we documented pervasive presence and limited viability of the fungus within the colony's main roosting structure. We recaptured 98 individually marked females in years after initial banding, and some individuals survived at least 6 y. Ninety-one percent of all adult females, 93% of recaptured bats, and 90% of 1-y-old females (i.e., bats recaptured the first year after initial capture as juveniles) showed evidence of reproduction during the monitoring period. Using mark–recapture models, we estimated annual survival rates of juvenile and adult little brown myotis during 2009–2016 and examined whether reproductive condition or evidence of recent infection of WNS had any effect on survival. Annual survival rates were similar between juveniles and adults, but highly variable, ranging from 41.0 to 86.5%. Models indicated that neither evidence of recent past exposure to WNS nor reproductive status were related to survival. No one parameter stood out as being responsible for this colony's continued existence, and it is likely that many interwoven factors were responsible for the observed resilience. Although relatively high reproductive effort from all females (i.e., both1-y-old and >1-y-old ) and intermittently suitable survival rates have led to the continued persistence of, and population increases in, this summer colony, mortality from WNS and inherently low reproductive potential still seemed to be limiting population growth. Until there is a better understanding of this overall potential resiliency in little brown myotis, we recommend considering minimizing disturbance and direct human involvement within these persisting populations to allow whatever natural recovery that may be occurring to evolve uninterrupted.

Chiroptera

With over 1200 species identified, bats represent almost one quarter of the world’s mammals. Bats provide crucial environmental services, such as insect control and pollination, and inhabit a wide variety of ecological niches on all continents except Antarctica. Despite their ubiquity and ecological importance, relatively little has been published on diseases of bats, while much has been written on bats’ role as reservoirs in disease transmission. This chapter will focus on diseases and pathologic processes most commonly reported in captive and free-ranging bats. Unique anatomical and histological features and common infectious and non-infectious diseases will be discussed. As recognition of both the importance and vulnerability of bats grows, particularly following population declines in North America due to the introduction of the fungal disease white-nose syndrome, efforts should be made to better understand threats to the health of this unique group of mammals.