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Diseases vary among and within species but the causes of this variation can be unclear. Immune responses are an important driver of disease variation, but mechanisms on how the body resists pathogen establishment before activation of immune responses are understudied. Skin surfaces of mammals are the first line of defense against abiotic stressors and pathogens, and skin attributes such as pH, microbiomes, and lipids influence disease outcomes. Sebaceous glands produce sebum composed of multiple types of lipids with species-specific compositions. Sebum affects skin barrier function by contributing to minimizing water loss, supporting thermoregulation, protecting against pathogens, and preventing UV-induced damage. Sebum also affects skin microbiome composition both via its antimicrobial properties, and by providing potential nutrient sources. Intra- and interspecific variation in sebum composition influences skin disease outcomes in humans and domestic mammal species but is not well-characterized in wildlife. We synthesized knowledge on sebum function in mammals in relation to skin diseases and the skin microbiome. We found that sebum composition was described for only 29 live, wild mammalian species. Sebum is important in dermatophilosis, various forms of dermatitis, demodicosis, and potentially white-nose syndrome. Sebum composition likely affects disease susceptibility, as lipid components can have antimicrobial functions against specific pathogens. It is unclear why sebum composition is species-specific, but both phylogeny and environmental effects may drive differences. Our review illustrates the role of mammal sebum function and influence on skin microbes in the context of skin diseases, providing a baseline for future studies to elucidate mechanisms of disease resistance beyond immune responses. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We document white‐nose syndrome (WNS), a lethal disease of bats caused by the fungus Pseudogymnoascus destructans (Pd), and hibernacula microclimate in New Brunswick, Canada. Our study area represents a more northern region than is common for hibernacula microclimate investigations, providing insight as to how WNS may impact bats at higher latitudes. To determine the impact of the March 2011 arrival of Pd in New Brunswick and the role of hibernacula microclimate on overwintering bat mortality, we surveyed bat numbers at hibernacula twice a year from 2009 to 2015. We also collected data from iButton temperature loggers deployed at all sites and data from HOBO temperature and humidity loggers at three sites. Bat species found in New Brunswick hibernacula include Myotis lucifugus (Little Brown Bat) and M. septentrionalis (Northern Long‐eared Bat), with small numbers of Perimyotis subflavus (Tricolored Bat). All known hibernacula in the province were Pd‐positive with WNS‐positive bats by winter 2013. A 99% decrease in the overwintering bat population in New Brunswick was observed between 2011 and 2015. We did not observe P. subflavus during surveys 2013–2015 and the species appears to be extirpated from these sites. Bats did not appear to choose hibernacula based on winter temperatures, but dark zone (zone where no light penetrates) winter temperatures did not differ among our study sites. Winter dark zone temperatures were warmer and less variable than entrance or above ground temperatures. We observed visible Pd growth on hibernating bats in New Brunswick during early winter surveys (November), even though hibernacula temperatures were colder than optimum for in vitro Pd growth. This suggests that cold hibernacula temperatures encountered near the apparent northern range limit for Pd do not sufficiently slow fungal growth to prevent the onset of WNS and associated bat mortality over the winter. [ABSTRACT FROM AUTHOR]

Skin is a key aspect of the immune system in the defence against pathogens. Skin pH regulates the activity of enzymes produced both by hosts and by microbes on host skin, thus implicating pH in disease susceptibility. Skin pH varies inter- and intra-specifically and is influenced by a variety of intrinsic and extrinsic variables. Increased skin alkalinity is associated with a predisposition to cutaneous infections in humans and dogs, and inter-specific and inter-individual variation in skin pH is implicated in differential susceptibility to some skin diseases. The cutaneous pH of bats has not been characterized but is postulated to play a role in susceptibility to white-nose syndrome (WNS), a fungal infection that has decimated several Nearctic bat species. We used non-invasive probes to measure the pH of bat flight membranes in five species with differing susceptibility to WNS. Skin pH ranged from 4.67 to 8.59 and varied among bat species, geographic locations, body parts, age classes, sexes and seasons. Wild Eptesicus fuscus were consistently more acidic than wild Myotis lucifugus, Myotis leibii and Perimyotis subflavus. Juvenile bats had more acidic skin than adults during maternity season but did not differ during swarming. Male M. lucifugus were more acidic than females during maternity season, yet this trend reversed during swarming. Bat skin was more acidic in summer compared to winter, a pattern also reported in humans. Skin pH was more acidic in captive than wild E. fuscus , suggesting environmental impacts on skin pH. The pH of roosting substrates affects skin pH in captive bats and may partially explain seasonal patterns in wild bats that use different roost types across seasons. Future research on the influence of pH on microbial pathogenic factors and skin barrier function may provide valuable insights on new therapeutic targets for treating bat skin conditions. [ABSTRACT FROM AUTHOR]

Pseudogymnoascus destructans is the causal agent of bat white-nose syndrome (WNS), which is devastating some North American bat populations. Previous transcriptome studies provided insight regarding the molecular mechanisms involved in WNS; however, it is unclear how different environmental parameters could influence pathogenicity. This information could be useful in developing management strategies to mitigate the negative impacts of P. destructans on bats. We cultured three P. destructans isolates from Atlantic Canada on two growth media (potato dextrose agar and Sabouraud dextrose agar) that differ in their nitrogen source, and at two separate incubation temperatures (4 C and 15 C) that approximate the temperature range of bat hibernacula during the winter and a temperature within its optimal mycelial growth range. We conducted RNA sequencing to determine transcript levels in each sample and performed differential gene expression (DGE) analyses to test the influence of growth medium and incubation temperature on gene expression. We also compared our in vitro results with previous RNA-sequencing data sets generated from P. destructans growing on the wings of a susceptible host, Myotis lucifugus. Our findings point to a critical role for substrate and incubation temperature in influencing the P. destructans transcriptome. DGE analyses suggested that growth medium plays a larger role than temperature in determining P. destructans gene expression and that although the psychrophilic fungus responds to different nitrogen sources, it may have evolved for continued growth at a broad range of low temperatures. Further, our data suggest that down-regulation of the RNA-interference pathway and increased fatty acid metabolism are involved in the P. destructans-bat interaction. Finally, we speculate that to reduce the activation of host defense responses, P. destructans minimizes changes in the expression of genes encoding secreted proteins during bat colonization. [ABSTRACT FROM AUTHOR]

With the exception of recent work on bats, no reports on the fungi present on live mammals in underground habitats have been published. We cultured psychrotolerant fungi from the external surface and faeces of live Deer Mice (Peromyscus maniculatus), and from the intestinal contents of a single freshly killed P. maniculatus, overwintering in a white-nose syndrome positive bat hibemaculum and from adjacent summer forest in eastern Canada. A low diversity of psychrotolerant fungi was cultured from P. maniculatus compared with that found in previous studies of the mycoflora of bats and arthropods occupying bat hibernacula in the region. Although the grooming habits of P. maniculatus may reduce the accumulation of a diverse psychrotolerant fungal assemblage on their external surface, we demonstrate that active euthermic mammals in underground habitats can carry viable spores of psychrotolerant fungi, both externally and internally. Small rodents using cave habitats may also play a role in dispersing psychrotolerant fungi between caves and suitable low-temperature habitats (i.e., burrows) in adjacent forest. [ABSTRACT FROM AUTHOR]

White-nose syndrome is one of the most lethal wildlife diseases, killing over 5 million North American bats since it was first reported in 2006. The causal agent of the disease is a psychrophilic filamentous fungus, Pseudogymnoascus destructans. The fungus is widely distributed in North America and Europe and has recently been found in some parts of Asia, but interestingly, no mass mortality is observed in European or Asian bats. Here we report a novel double-stranded RNA virus found in North American isolates of the fungus and show that the virus can be used as a tool to study the epidemiology of White-nose syndrome. The virus, termed Pseudogymnoascus destructans partitivirus-pa, contains 2 genomic segments, dsRNA 1 and dsRNA 2 of 1.76 kbp and 1.59 kbp respectively, each possessing a single open reading frame, and forms isometric particles approximately 30 nm in diameter, characteristic of the genus Gammapartitivirus in the family Partitiviridae. Phylogenetic analysis revealed that the virus is closely related to Penicillium stoloniferum virus S. We were able to cure P. destructans of the virus by treating fungal cultures with polyethylene glycol. Examination of 62 isolates of P. destructans including 35 from United States, 10 from Canada and 17 from Europe showed virus infection only in North American isolates of the fungus. Bayesian phylogenetic analysis using nucleotide sequences of the viral coat protein geographically clustered North American isolates indicating fungal spread followed by local adaptation of P. destructans in different regions of the United States and Canada. This is the first demonstration that a mycovirus potentially can be used to study fungal disease epidemiology. [ABSTRACT FROM AUTHOR]

Big brown bats ( Eptesicus fuscus) overwintering outside the underground environment are not believed to play a role in the epidemiology of the disease white-nose syndrome (WNS), caused by the fungus Pseudogymnoascus destructans ( Pd). Using quantitative real-time PCR (qPCR), we provide molecular evidence for Pd on four big brown bats overwintering in heated buildings in New Brunswick, Canada. Two of the affected individuals also had very mild, focal, pustular, fungal dermatitis identified microscopically. A third bat, which was qPCR Pd-negative, had similar fungal lesions. Despite determining that these fungal lesions were caused by a suspected ascomycete, the intralesional fungi were not confirmed to be Pd. These findings demonstrate that bats overwintering in heated buildings and other above-ground sites may have subclinical or preclinical WNS, or be contaminated with Pd, and could play a role in local dispersal of Pd. Our inability to determine if the ascomycetes causing pustular lesions were Pd highlights the need for ancillary diagnostic tests, such as in situ hybridization or immunohistochemistry, so that Pd can be detected directly within a lesion. As the host-pathogen relationship for Pd evolves, and where bat species are exposed to the fungus under varying temperature regimes, lesions may become less stereotypic and such tests could help define these changes. [ABSTRACT FROM AUTHOR]

The introduction of Pseudogymnoascus destructans (Pd) to North America, agent of white-nose syndrome in hibernating bats, has increased interest in fungi from underground habitats. While bats are assumed to be the main vector transmitting Pd cave-to-cave, the role of other fauna is unexplored. We documented the fungi associated with over-wintering arthropods in Pd-positive hibernacula, including sites where bats had been recently extirpated or near-extirpated, to determine if arthropods carried Pd, and to compare fungal assemblages on arthropods to bats. We isolated 87 fungal taxa in 64 genera from arthropods. Viable Pd was cultured from 15.3% of arthropods, most frequently from harvestmen (Nelima elegans). Fungal assemblages on arthropods were similar to those on bats. The different fungal assemblages documented among arthropods may be due to divergent patterns of movement, aggregation, feeding, or other factors. While it is unlikely that arthropods play a major role in the transmission dynamics of Pd, we demonstrate that arthropods may carry viable Pd spores and therefore have the potential to transport Pd, either naturally or anthropogenically, within or among hibernacula. This underlines the need for those entering hibernacula to observe decontamination procedures and for such procedures to evolve as our understanding of potential mechanisms of Pd dispersal improve. [ABSTRACT FROM AUTHOR]

The introduction of the fungal pathogen Pseudogymnoascus destructans (Pd) to North America has stimulated research on the poorly known mycology of caves. It is possible that the introduction of Pd reduces the diversity of fungi associated with bats hibernating in caves. To test this hypothesis we examined the fungal assemblages associated with hibernating bats (Myotis spp.) pre- and post- white-nose syndrome (WNS) infection in eastern Canada using culture-dependent methods. We found the mean number of fungal taxa isolated from bats/ hibernaculum was not significantly different between pre-infection (29.6 ± 6.1SD) and postinfection with WNS (32.4 ± 4.3). Although the number of fungal taxa per bat was significantly higher on Myotis lucifugus vs. M. septentrionalis, evidence suggests that this is a reflection of environmental features of individual hibernacula, rather than any biological difference between bat species. The composition and number of the most common and widespread fungal taxa on hibernating Myotis spp. did not change with the introduction of Pd to hibernacula. We found no evidence to suggest that Pd interacts with other fungi on the external surface of bats in hibernacula, even among fungal species of the same genus. However, our data do suggest that environmental characteristics of individual caves can have a significant influence on the fungal assemblages cultured from hibernating bats at specific hibernacula. Following the mortality of thousands of WNS-infected Myotis spp. in one hibernacula, we found that those fungal taxa growing on dead bats were cultured with increased frequency from live bats. This suggests that fungal assemblages on live bats may be sensitive to sporadic introductions of new fungal substrates to hibernacula. [ABSTRACT FROM AUTHOR]

The tricolored bat (Perimyotis subflavus) is threatened by white-nose syndrome (WNS), a fungal disease caused by Pseudogymnoascus destructans (Pd) and was recently ranked as endangered under the Canadian Species-at-Risk Act. There have been few prior studies on the fungi associated with over-wintering bats. Such information is important in assessing overall fungal diversity within the cave habitat, in determining the ecological role that bats may play as dispersers of fungi, and in the identification of fungal species potentially antagonistic to Pd. We swabbed twenty-two P. subflavus overwintering in caves and mines in New Brunswick, Canada, in 2012 and 2013. This produced 408 isolates comprising 60 taxa in 49 fungal genera with an average of 10.2 ± 3.9SD fungal taxa recorded per bat. We found fungal assemblages on P. subflavus (post- WNS) very similar to those we cultured previously from Myotis spp. (pre-WNS) at the same sites. We suggest that the variation in fungal assemblages observed from site-to-site on hibernating P. subflavus is largely due to environmental and ecological characteristics of individual caves, rather than the presence of Pd or roosting habits. [ABSTRACT FROM AUTHOR]

The emergence of the fungal disease white-nose syndrome (WNS) among hibernating bats in North America and its causative pathogen, Geomyces destructans, underscores how little is known about fungi associated with bats and their subterranean environments. Investigating 8 caves and mines in New Brunswick, Canada, we cultured a diverse array of fungi from the fur and skin of apparently healthy, hibernating Myotis lucifugus (Little Brown Bat) and M. septentrionalis (Northern Long-eared Bat) in the year prior to the emergence of WNS in the province. Among the 117 isolated fungal taxa, we found an array of psychrophilic, psychrotrophic, keratinolytic, coprophilous, and saprobic fungi. The most common taxa were Geomycespannorum sensu lato, Penicillium spp., Mortierella spp., Mucor spp., Cephalotrichum stemonitis, Leuconeurospora spp., Penicillium solitum, Cladosporium spp., and Trichosporon dulcitum. Each bat hosted 6.9 ± 3 (SD) fungal taxa, and 30.8 ± 5 taxa were isolated per hibernaculum. Number bftaxa isolated per bat was positively correlated with mean and minimum winter temperatures in the dark zones of hibernacula. Forty-seven of the taxa have never been reported in caves, and an additional 31 taxa are new records for North American caves. The presence of Geomyces pannorum sensu lato on 70% of hibernating bats may complicate results of diagnostic techniques used for identifying G. destructans. Bats hibernating in eastern Canada harbor a rich reservoir of fungal species and probably play a role in moving fungal spores into and between hibernacula, as well as onto the landscape. [ABSTRACT FROM AUTHOR]

Information on bat populations and hibernacula is important for understanding the impacts of white-nose syndrome (WNS), a fatal fungal disease of bats. Estimates of bat populations prior to the outbreak of white-nose syndrome are presented for 2009-2011 for the most significant bat hibernacula known in New Brunswick. At one of these sites we recorded a major mortality event from white-nose syndrome, the first in the Maritime provinces, late in the winter of 2011. Winter surveys of hibernating bats suggest that a minimum of 7 000 bats overwintered in these hibernacula prior to the outbreak of white-nose syndrome in New Brunswick. The majority of hibernating bats in New Brunswick caves are Myotis lucifugus (Little Brown Myotis) and M. septentrionalis (Northern Myotis), with low numbers of Perimyotis subflavus (Tricolored Bat). The New Brunswick hibernacula that support the greatest numbers of overwintering bats have little temperature variation, winter dark zone temperatures averaging 4--5°C, and minimum dark zone temperatures dropping to no lower than 3.1°C. New Brunswick caves with these temperature patterns characteristically have >140 m of main passage and lack both running water and multiple entrances. Few cave sites in the province meet these criteria, and the known winter bat population appears to be smaller than the summer population. Many bats present during the summer in New Brunswick either hibernate in unknown locations in the province or migrate out of the province to locate suitable hibernacula. Such movements may have hastened the arrival of white-nose syndrome in New Brunswick. [ABSTRACT FROM AUTHOR]

Across their range, Raccoons (Procyon lotor) will opportunistically exploit bats (Chiroptera) roosting in caves as a source of food. During a significant mortality event associated with white-nose syndrome (WNS) at a cave in eastern Canada, we estimate that Raccoons consumed 3 169-3827 dead and dying Little Brown Bats (Myotis lucifugus) and Northern Long-eared Bats (M. septentrionalis) infected with white-nose syndrome, equivalent to 62.0-74.9% of the total bat mortality at this site. However, the generally small dispersal distances of Raccoons and their reduced activity during the period when bats are hibernating suggest that Raccoons are likely not a significant vector for moving the fungus associated with white-nose syndrome, Geoniyces destructans, between most caves at this latitude. Nevertheless, since we show that significant numbers of bats can be consumed in hibernacula through opportunistic feeding by Raccoons, estimates of in-cave mortality due to white-nose syndronie should incorporate any evidence of consumption of bats by Raccoons and other predators. [ABSTRACT FROM AUTHOR]

Studies of fungi in caves have become increasingly important with the advent of white-nose syndrome (WNS), a disease caused by the invasive fungus Pseudogymnoascus destructans (Pd) that has killed an estimated 6.5 million North American bats. We swabbed cave walls in New Brunswick, Canada, in 2012 and 2015 to determine whether the culturable fungal assemblage on cave walls changed after the introduction of Pd and subsequent decrease in hibernating bat populations. We also compared fungal assemblages on cave walls to previous studies on the fungal assemblages of arthropods and hibernating bats in the same sites. The fungal diversity of bats and cave walls was more similar than on arthropods. The diversity and composition of fungal assemblages on cave walls was significantly different among media types and sites but did not differ over time. Therefore, no change in the culturable fungal assemblage present on cave walls was detected with the introduction of Pd and subsequent disappearance of the hibernating bat population over a 3-year period. This suggests that fungi documented in caves in the region prior to the outbreak of Pd do not require regular transmission of spores by bats to maintain fungal diversity at these sites. [ABSTRACT FROM AUTHOR]