Increasing incidence of Geomyces destructans fungus in bats from the Czech Republic and Slovakia

Background

White-nose syndrome is a disease of hibernating insectivorous bats associated with the fungus Geomyces destructans. It first appeared in North America in 2006, where over a million bats died since then. In Europe, G. destructans was first identified in France in 2009. Its distribution, infection dynamics, and effects on hibernating bats in Europe are largely unknown.

Methodology/Principal Findings

We screened hibernacula in the Czech Republic and Slovakia for the presence of the fungus during the winter seasons of 2008/2009 and 2009/2010. In winter 2009/2010, we found infected bats in 76 out of 98 surveyed sites, in which the majority had been previously negative. A photographic record of over 6000 hibernating bats, taken since 1994, revealed bats with fungal growths since 1995; however, the incidence of such bats increased in Myotis myotis from 2% in 2007 to 14% by 2010. Microscopic, cultivation and molecular genetic evaluations confirmed the identity of the recently sampled fungus as G. destructans, and demonstrated its continuous distribution in the studied area. At the end of the hibernation season we recorded pathologic changes in the skin of the affected bats, from which the fungus was isolated. We registered no mass mortality caused by the fungus, and the recorded population decline in the last two years of the most affected species, M. myotis, is within the population trend prediction interval.

Conclusions/Significance

G. destructans was found to be widespread in the Czech Republic and Slovakia, with an epizootic incidence in bats during the most recent years. Further development of the situation urgently requires a detailed pan-European monitoring scheme.     

First isolation of Pseudogymnoascus destructans in bats from Portugal

The psychrophilic fungus Pseudogymnoascus destructans (formerly known as Geomyces destructans) is considered the etiological agent of white-nose disease (WND), an emerging disease which affects bats during their hibernation period. This disease is clinically characterized by the growth of a white fungus on muzzle, ears, and wings’ membranes of affected bats. This infection caused the death of several million bats in North America. Conversely, European bats show no evidence of significant mortality occurrences associated with P. destructans colonization. This fungus has been isolated from bats in at least 15 European countries since 2008, but was never before reported in the Iberian Peninsula. This study describes the first case report of P. destructans colonization in bats from Portugal. We isolated P. destructans from three hibernating Myotis blythii (lesser mouse-eared bat) with visual signs of P. destructans colonization, during a routine visit to a mine located in the Trás-os-Montes region, Northern Portugal. M. blythii is one of the rarest bat species in Europe, classified as critically endangered in Portugal. P. destructans was obtained from at least three different parts of the body of each specimen analyzed. The identification of the respective fungal isolates was based on the macroscopic and microscopic characterization of the cultures and confirmed by PCR-based analysis. All nucleotide sequences obtained showed 100 % identity with previous data reported for P. destructans. This new finding improves the current knowledge about the European distribution of P. destructans, which is of great interest for forthcoming studies on the fungus dispersion and impact among bat populations at regional and/or global level.     

Wing pathology of white-nose syndrome in bats suggests life-threatening disruption of physiology

White-nose syndrome (WNS) is causing unprecedented declines in several species of North American bats. The characteristic lesions of WNS are caused by the fungus Geomyces destructans, which erodes and replaces the living skin of bats while they hibernate. It is unknown how this infection kills the bats. We review here the unique physiological importance of wings to hibernating bats in relation to the damage caused by G. destructans and propose that mortality is caused by catastrophic disruption of wing-dependent physiological functions. Mechanisms of disease associated with G. destructans seem specific to hibernating bats and are most analogous to disease caused by chytrid fungus in amphibians.     

Temperature-Dependent Growth of Geomyces destructans,the Fungus That Causes Bat White-Nose Syndrome

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°C, and the upper critical temperature for growth was between 19.0 and 19.8°C. Growth rates varied across isolates, irrespective of geographic origin, and above 12°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.     

Psychrophilic and Psychrotolerant Fungi on Bats and the Presence of Geomyces spp. on Bat Wings Prior to the Arrival of White Nose Syndrome

Since 2006, Geomyces destructans, the causative agent of white nose syndrome (WNS), has killed over 5.7 million bats in North America. The current hypothesis suggests that this novel fungus is an invasive species from Europe, but little is known about the diversity within the genus Geomyces and its distribution on bats in the United States. We documented the psychrophilic and psychrotolerant fungal flora of hibernating bats prior to the arrival of WNS using culture-based techniques. A total of 149 cultures, which were obtained from 30 bats in five bat hibernacula located in four caves and one mine, were sequenced for the entire internal transcribed spacer (ITS) nuclear ribosomal DNA (nrDNA) region. Approximately 53 operational taxonomic units (OTUs) at 97% similarity were recovered from bat wings, with the community dominated by fungi within the genera Cladosporium, Fusarium, Geomyces, Mortierella, Penicillium, and Trichosporon. Eleven Geomyces isolates were obtained and placed in at least seven distinct Geomyces clades based on maximum-likelihood phylogenetic analyses. Temperature experiments revealed that all Geomyces strains isolated are psychrotolerant, unlike G. destructans, which is a true psychrophile. Our results confirm that a large diversity of fungi, including several Geomyces isolates, occurs on bats prior to the arrival of WNS. Most of these isolates were obtained from damaged wings. Additional studies need to be conducted to determine potential ecological roles of these abundant Geomyces strains isolated from bats.     

Hibernating Little Brown Myotis (Myotis lucifugus) Show Variable Immunological Responses to White-Nose Syndrome

White-nose syndrome (WNS) is an emerging infectious disease devastating hibernating North American bat populations that is caused by the psychrophilic fungus Geomyces destructans. Previous histopathological analysis demonstrated little evidence of inflammatory responses in infected bats, however few studies have compared other aspects of immune function between WNS-affected and unaffected bats. We collected bats from confirmed WNS-affected and unaffected sites during the winter of 2008–2009 and compared estimates of their circulating levels of total leukocytes, total immunoglobulins, cytokines and total antioxidants. Bats from affected and unaffected sites did not differ in their total circulating immunoglobulin levels, but significantly higher leukocyte counts were observed in bats from affected sites and particularly in affected bats with elevated body temperatures (above 20°C). Bats from WNS-affected sites exhibited significantly lower antioxidant activity and levels of interleukin-4 (IL-4), a cytokine that induces T cell differentiation. Within affected sites only, bats exhibiting visible fungal infections had significantly lower antioxidant activity and levels of IL-4 compared to bats without visible fungal infections. Overall, bats hibernating in WNS-affected sites showed immunological changes that may be evident of attempted defense against G. destructans. Observed changes, specifically elevated circulating leukocytes, may also be related to the documented changes in thermoregulatory behaviors of affected bats (i.e. increased frequencies in arousal from torpor). Alterations in immune function may reflect expensive energetic costs associated with these processes and intrinsic qualities of the immunocapability of hibernating bats to clear fungal infections. Additionally, lowered antioxidant activity indicates a possible imbalance in the pro- versus antioxidant system, may reflect oxidative tissue damage, and should be investigated as a contributor to WNS-associated morbidity and mortality.     

Pathophysiology of white-nose syndrome in bats: a mechanistic model linking wing damage to mortality

White-nose syndrome is devastating North American bat populations but we lack basic information on disease mechanisms. Altered blood physiology owing to epidermal invasion by the fungal pathogen Geomyces destructans (Gd) has been hypothesized as a cause of disrupted torpor patterns of affected hibernating bats, leading to mortality. Here, we present data on blood electrolyte concentration, haematology and acid–base balance of hibernating little brown bats, Myotis lucifugus, following experimental inoculation with Gd. Compared with controls, infected bats showed electrolyte depletion (i.e. lower plasma sodium), changes in haematology (i.e. increased haematocrit and decreased glucose) and disrupted acid–base balance (i.e. lower CO₂ partial pressure and bicarbonate). These findings indicate hypotonic dehydration, hypovolaemia and metabolic acidosis. We propose a mechanistic model linking tissue damage to altered homeostasis and morbidity/mortality.     

Prevalence and phenology of white-nose syndrome fungus Pseudogymnoascus destructans in bats from Poland

Pseudogymnoascus destructans (Pd), a parasitic fungus (being responsible for a disease known as white-nose syndrome, WNS) that caused mass mortality of cave-dwelling, hibernating bats in North America, appears to be native of Europe, where it also occurs on wintering bats, but no similar outbreaks of WNS have been recorded. Herein, we provide the first account on prevalence and phenology of P. destructans in Poland. Bats were counted once per month, from October or January to May (2010-2013), in an abandoned ore mine in southern Poland. Presence of P. destructans in two samples was confirmed by sequencing of isolated fungal DNA. Observations of phenotypically identical mycosis on bats hibernating at this site in March 2006 are likely to be the first known records of P. destructans from Poland. All Pd-suspected individuals were Myotis myotis with an exception of one Myotis daubentonii. The first Pd-suspected bats were noted in mid-February, but their number was the highest in March, what overlapped with maximum numbers of hibernating M. myotis. The prevalence in March was 7%–27% of M. myotis individuals. No mass mortality of bats was observed in the mine, with only three dead individuals found in the hibernaculum which hosted up to 130 bats, representing 6–7 species.     

Geomyces destructans associated with bat disease WNS detected in Slovakia

The paper describes macro- and micromorphological features of Geomyces destructans, the fungus which is associated with the white-nose syndrome (WNS) bat disease in North America. This species was isolated from hibernating Myotis myotis at two sites in Malé Karpaty Mts (the old mine Pod medveđou skalou and the Zbojnícka Cave) in Western Slovakia. Besides Geomyces destructans, the species Isaria farinosa, Cladosporium macrocarpum and Alternaria tenuissima were isolated, too. All strains are deposed at the Department of Soil Science, Comenius University in Bratislava (Slovakia) and in CMF at Institute of Soil Biology in Českějovice (Czech Republic).     

Phylogenetic evaluation of Geomyces and allies reveals no close relatives of Pseudogymnoascus destructans, comb. nov., in bat hibernacula of eastern North America

White-nose syndrome (WNS)  of bats, caused by the fungus previously known as Geomyces destructans, has decimated populations of insectivorous bats in eastern North America. Recent work on fungi associated with bat hibernacula uncovered a large number of species of Geomyces and allies, far exceeding the number of described species. Communication about these species has been hindered by the lack of a modern taxonomic evaluation, and a phylogenetic framework of the group is needed to understand the origin of G. destructans and to target closely related species and their genomes for the purposes of understanding mechanisms of pathogenicity. We addressed these issues by generating DNA sequence data for the internal transcribed spacer (ITS) region, nuclear large subunit (LSU) rDNA, MCM7, RPB2, and TEF1 from a diverse array of Geomyces and allies that included isolates recovered from bat hibernacula as well as those that represent important type species. Phylogenetic analyses indicate Geomyces and allies should be classified in the family Pseudeurotiaceae, and the genera Geomyces, Gymnostellatospora, and Pseudogymnoascus should be recognized as distinct. True Geomyces are restricted to a basal lineage based on phylogenetic placement of the type species, Geomyces auratus. Thus, G. destructans is placed in genus Pseudogymnoascus. The closest relatives of Pseudogymnoascus destructans are members of the Pseudogymnoascus roseus species complex, however, the isolated and long branch of P. destructans indicates that none of the species included in this study are closely related, thus providing further support to the hypothesis that this pathogen is non-native and invasive in eastern North America. Several conidia-producing isolates from bat hibernacula previously identified as members of Pseudeurotium are determined to belong to the genus Leuconeurospora, which is widespread, especially in colder regions. Teberdinia hygrophila is transferred to Pseudeurotium as Pseudeurotium hygrophilum, comb. nov., in accordance with the one name per fungus system of classification, and two additional combinations are made in Pseudogymnoascus including Pseudogymnoascus carnis and Pseudogymnoascus pannorum. Additional sampling from other regions of the world is needed to better understand the evolution and biogeography of this important and diverse group of fungi.     

Nonlinear Distribution Pattern of Hibernating Bats in Caves along an Elevational Gradient in Mountain (Carpathians,Southern Poland)

Background

Thermal gradients along changes in elevation in mountainous environments are reflected by different biotas. Although there have been studies of elevation variation in bat assemblages in summer, winter changes in the same gradients remain unknown.

Methodology/Principal Findings

The objective of this study was to document changes in the species composition of bats hibernating in caves along a temperate elevational gradient. We studied 70 caves between from 300 m to 1,930 m altitude along a slope of the Carpathian Mountains in southern Poland. We recorded changes in bats, including species richness, abundance, altitudinal distribution and dominance during consecutive winters between 2003 and 2009. Similarity of dominance of faunal structure was assessed by using the Bray-Curtis similarity index. We used the generalised additive model and rarefaction to study the variation in species richness, and generalized additive mixed models to examine the effect of abiotic factors on the qualitative and quantitative structure of bat assemblages. During 351 surveys we recorded 13,856 hibernating bats from 15 species. Species richness peaked around mid-elevation (1,100–1,400 m a.s.l.) with richness declining at both higher and lower elevations. Based on the results of a cluster analysis, we could distinguish among four altitudinal zones that differed in species richness and dominance structure.

Conclusions/Significance

This is the first study documenting changes in species richness and variation of structure of bats hibernating in caves along an elevational gradient. The most surprising and key finding is the fact that changes in the structure of assemblages of hibernating bats along the altitudinal gradient occurred in jumps, forming zones similar to those observed in the vegetation zones. Moreover, species richness and dominance structure of assemblages of hibernating bats in the mountains depended not only on location above sea level, but also on local geomorphologic conditions which strongly affected the microclimate of the caves.     

DNA-based detection of the fungal pathogen Geomyces destructans in soils from bat hibernacula

White-nose syndrome (WNS) is an emerging disease causing unprecedented morbidity and mortality among bats in eastern North America. The disease is characterized by cutaneous infection of hibernating bats by the psychrophilic fungus Geomyces destructans. Detection of G. destructans in environments occupied by bats will be critical for WNS surveillance, management and characterization of the fungal lifecycle. We initiated an rRNA gene region-based molecular survey to characterize the distribution of G. destructans in soil samples collected from bat hibernacula in the eastern United States with an existing PCR test. Although this test did not specifically detect G. destructans in soil samples based on a presence/absence metric, it did favor amplification of DNA from putative Geomyces species. Cloning and sequencing of PCR products amplified from 24 soil samples revealed 74 unique sequence variants representing 12 clades. Clones with exact sequence matches to G. destructans were identified in three of 19 soil samples from hibernacula in states where WNS is known to occur. Geomyces destructans was not identified in an additional five samples collected outside the region where WNS has been documented. This study highlights the diversity of putative Geomyces spp. in soil from bat hibernacula and indicates that further research is needed to better define the taxonomy of this genus and to develop enhanced diagnostic tests for rapid and specific detection of G. destructans in environmental samples.     

High diversity of rabies viruses associated with insectivorous bats in Argentina: presence of several independent enzootics

Background

Rabies is a fatal infection of the central nervous system primarily transmitted by rabid animal bites. Rabies virus (RABV) circulates through two different epidemiological cycles: terrestrial and aerial, where dogs, foxes or skunks and bats, respectively, act as the most relevant reservoirs and/or vectors. It is widely accepted that insectivorous bats are not important vectors of RABV in Argentina despite the great diversity of bat species and the extensive Argentinean territory.

Methods

We studied the positivity rate of RABV detection in different areas of the country, and the antigenic and genetic diversity of 99 rabies virus (RABV) strains obtained from 14 species of insectivorous bats collected in Argentina between 1991 and 2008.

Results

Based on the analysis of bats received for RABV analysis by the National Rabies system of surveillance, the positivity rate of RABV in insectivorous bats ranged from 3.1 to 5.4%, depending on the geographic location. The findings were distributed among an extensive area of the Argentinean territory. The 99 strains of insectivorous bat-related sequences were divided into six distinct lineages associated with Tadarida brasiliensis, Myotis spp, Eptesicus spp, Histiotus montanus, Lasiurus blosseviilli and Lasiurus cinereus. Comparison with RABV sequences obtained from insectivorous bats of the Americas revealed co-circulation of similar genetic variants in several countries. Finally, inter-species transmission, mostly related with Lasiurus species, was demonstrated in 11.8% of the samples.

Conclusions

This study demonstrates the presence of several independent enzootics of rabies in insectivorous bats of Argentina. This information is relevant to identify potential areas at risk for human and animal infection.     

Direct Detection of Fungal Siderophores on Bats with White-Nose Syndrome via Fluorescence Microscopy-Guided Ambient Ionization Mass Spectrometry

White-nose syndrome (WNS) caused by the pathogenic fungus Pseudogymnoascus destructans is decimating the populations of several hibernating North American bat species. Little is known about the molecular interplay between pathogen and host in this disease. Fluorescence microscopy ambient ionization mass spectrometry was used to generate metabolic profiles from the wings of both healthy and diseased bats of the genus Myotis. Fungal siderophores, molecules that scavenge iron from the environment, were detected on the wings of bats with WNS, but not on healthy bats. This work is among the first examples in which microbial molecules are directly detected from an infected host and highlights the ability of atmospheric ionization methodologies to provide direct molecular insight into infection.     

Bacteria Isolated from Bats Inhibit the Growth of Pseudogymnoascus destructans,the Causative Agent of White-Nose Syndrome

Emerging infectious diseases are a key threat to wildlife. Several fungal skin pathogens have recently emerged and caused widespread mortality in several vertebrate groups, including amphibians, bats, rattlesnakes and humans. White-nose syndrome, caused by the fungal skin pathogen Pseudogymnoascus destructans, threatens several hibernating bat species with extinction and there are few effective treatment strategies. The skin microbiome is increasingly understood to play a large role in determining disease outcome. We isolated bacteria from the skin of four bat species, and co-cultured these isolates with P. destructans to identify bacteria that might inhibit or kill P. destructans. We then conducted two reciprocal challenge experiments in vitro with six bacterial isolates (all in the genus Pseudomonas) to quantify the effect of these bacteria on the growth of P. destructans. All six Pseudomonas isolates significantly inhibited growth of P. destructans compared to non-inhibitory control bacteria, and two isolates performed significantly better than others in suppressing P. destructans growth for at least 35 days. In both challenge experiments, the extent of suppression of P. destructans growth was dependent on the initial concentration of P. destructans and the initial concentration of the bacterial isolate. These results show that bacteria found naturally occurring on bats can inhibit the growth of P. destructans in vitro and should be studied further as a possible probiotic to protect bats from white-nose syndrome. In addition, the presence of these bacteria may influence disease outcomes among individuals, populations, and species.     

Rapid Real-Time PCR Assay for Culture and Tissue Identification of <Emphasis Type="Italic">Geomyces destructans</Emphasis>: the Etiologic Agent of Bat Geomycosis (White Nose Syndrome)

Geomyces destructans is the etiologic agent of bat geomycosis, commonly referred to as white nose syndrome (WNS). This infection has caused severe morbidity and mortality in little brown bats (Myotis lucifugus) and has also spread to other bat species with significant decline in the populations. Currently, G. destructans infection is identified by culture, ITS–PCR, and histopathology. We hypothesized that a real-time PCR assay would considerably improve detection of G. destructans in bats. The 100 bp sequence of the Alpha-L-Rhamnosidase gene was validated as a target for real-time PCR. The assay sensitivity was determined from serial dilution of DNA extracted from G. destructans conidia (5 × 10⁻¹–5 × 10⁷), and the specificity was tested using DNA from 30 closely and distantly related fungi and 5 common bacterial pathogens. The real-time PCR assay was highly sensitive with detection limit of two G. destructans conidia per reaction at 40 PCR cycles. The assay was also highly specific as none of the other fungal or bacterial DNA cross-reacted in the real-time PCR assay. One hundred and forty-seven bat tissue samples, suspected of infection with G. destructans, were used to compare the real-time PCR assay to other methods employed for the detection of G. destructans. Real-time PCR was highly sensitive with 80 of 147 (55%) samples testing positive for G. destructans DNA. In comparison, histopathology examination revealed 64/147 (44%) positive samples. The internal transcribed spacer (ITS)–PCR yielded positive amplicon for G. destructans from 37 tissue samples (25%). The least sensitive assay was the fungal culture with only 17 tissue samples (12%) yielding G. destructans in culture. The data suggested that the real-time PCR assay is highly promising for rapid, sensitive, and specific identification of G. destructans. Further trials and inter-laboratory comparisons of this novel assay are recommended to improve the diagnosis of bat geomycosis.     

A generalized pollination system in the tropics: bats, birds and Aphelandra acanthus

Background and Aims

A number of different types of flower-visiting animals coexist in any given habitat. What evolutionary and ecological factors influence the subset of these that a given plant relies on for its pollination? Addressing this question requires a mechanistic understanding of the importance of different potential pollinators in terms of visitation rate (pollinator ‘quantity’) and effectiveness at transferring pollen (pollinator ‘quality’) is required. While bat-pollinated plants typically are highly specialized to bats, there are some instances of bat-pollinated plants that use other pollinators as well. These generalized exceptions tend to occur in habitats where bat ‘quantity’ is poor due to low or fluctuating bat densities.

Methods

Aphelandra acanthus occurs in tropical cloud forests with relatively high densities of bat visitors, yet displays a mix of floral syndrome characteristics, suggesting adaptation to multiple types of pollinators. To understand its pollination system better, aspects of its floral phenology and the ‘quantity’ and ‘quality’ components of pollination by its floral visitors are studied here.

Key Results

Flowers were found to open and senesce throughout the day and night, although anther dehiscence was restricted to the late afternoon and night. Videotaping reveals that flowers are visited nocturnally by bats and moths, and diurnally by hummingbirds. Analysis of pollen deposition shows that bats regularly transfer large amounts of conspecific pollen, while hummingbirds occasionally transfer some pollen, and moths rarely do so.

Conclusions

Hummingbirds and bats were comparable in terms of pollination ‘quantity’, while bats were the most effective in terms of ‘quality’. Considering these components together, bats are responsible for approx. 70 % of A. acanthus pollination. However, bats also transferred remarkably large amounts of foreign pollen along with the conspecific grains (three of four grains were foreign). It is suggested that the negative effects of interspecific pollen transfer may decrease bat ‘quality’ for A. acanthus, and thus select for generalization on multiple pollinators instead of specialization on bats.Key words: Specialization, generalization, pollinator effectiveness, hummingbirds, floral syndrome, bat pollination, chiropterophily, ornithophily, cloud forest, heterospecific pollen transfer     

White-nose syndrome: is this emerging disease a threat to European bats?

White-nose syndrome (WNS) is a newly emergent disease that potentially threatens all temperate bat species. A recently identified fungus, Geomyces destructans, is the most likely causative agent of this disease. Until 2009, WNS and G. destructans were exclusively known from North America, but recent studies have confirmed this fungus is also present in Europe. We assembled an international WNS consortium of 67 scientists from 29 countries and identified the most important research and conservation priorities to assess the risk of WNS to European bats. Here, we review what is known about WNS and G. destructans and detail the conservation and research recommendations aimed at understanding and containing this emerging infectious disease.     

Diseases and causes of death in European bats: dynamics in disease susceptibility and infection rates

Background

Bats receive increasing attention in infectious disease studies, because of their well recognized status as reservoir species for various infectious agents. This is even more important, as bats with their capability of long distance dispersal and complex social structures are unique in the way microbes could be spread by these mammalian species. Nevertheless, infection studies in bats are predominantly limited to the identification of specific pathogens presenting a potential health threat to humans. But the impact of infectious agents on the individual host and their importance on bat mortality is largely unknown and has been neglected in most studies published to date.

Methodology/Principal Findings

Between 2002 and 2009, 486 deceased bats of 19 European species (family Vespertilionidae) were collected in different geographic regions in Germany. Most animals represented individual cases that have been incidentally found close to roosting sites or near human habitation in urban and urban-like environments. The bat carcasses were subjected to a post-mortem examination and investigated histo-pathologically, bacteriologically and virologically. Trauma and disease represented the most important causes of death in these bats. Comparative analysis of pathological findings and microbiological results show that microbial agents indeed have an impact on bats succumbing to infectious diseases, with fatal bacterial, viral and parasitic infections found in at least 12% of the bats investigated.

Conclusions/Significance

Our data demonstrate the importance of diseases and infectious agents as cause of death in European bat species. The clear seasonal and individual variations in disease prevalence and infection rates indicate that maternity colonies are more susceptible to infectious agents, underlining the possible important role of host physiology, immunity and roosting behavior as risk factors for infection of bats.