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White-nose disease (WND), caused by the psychrophilic fungus Pseudogymnoascus destructans, 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.

Healthy wing membranes are essential for bats. They are critical for maintaining the water balance and, during hibernation, they protect the bat’s body from dehydration. Assessing the state of the membrane visually is an easy and effective way to monitor a bat’s health and discover abnormal structures and infections in wild bat populations. During pre- and post-hibernation surveys of bats’ wings, we identified the presence of skin mites, Psorergatoides kerivoulae (Fain, 1959). The parasite causes cutaneous lesions on the wing membranes of the greater moused-eared bat, Myotis myotis (Borkhausen, 1797) and the lesser moused-eared bat, Myotis blythii (Tomes, 1857). The lesser mouse-eared bat is a new host for this parasite. Our study is the first to describe the histopathology of the infection on the wings of the greater and lesser mouse-eared bats. To our knowledge, this is the southernmost record of this parasite and the first mention of the genus Psorergatoides for the Balkans.

White-Nose Disease (WND) has killed millions of hibernating bats in the US and Canada. Its causative agent, the fungus Pseudogymnoascus destructans was introduced to North America, but is native to Europe and Asia, where it is not associated with mass mortality. Although it is nearly impossible to eradicate an emerging wildlife disease, research on P. destructans spread mechanisms can aid in prevention of new introductions and development of better environmental management strategies. It is of particular importance to quantify the potential role of people visiting caves (cavers, tourists, bat researchers, etc.) whom inadvertently move P. destructans spores between sites, and to limit spread, particularly to areas where the fungus is absent. In the course of two consecutive field seasons, samples were collected from the equipment before and after work in Bulgarian caves where P. destructans is present. Viable P. destructans spores were isolated from field equipment after nearly 100% of cave visits, irrespective of the season. Results from lab experiments show the pathogen’s spores can remain viable on pieces of contaminated caving equipment under room temperature for at least 25 days, with no significant reduction in germination rates. This is concerning evidence indicating the potential for movement of viable P. destructans spores across countries and continents. Results further demonstrated that any type of regular washing can successfully remove the majority of P. destructans spores from several fabric types. Brushing complemented by washing in a ‘washing machine’ was slightly more effective than brushing alone, while a washing temperature of 50°C was more effective than temperatures of 30 and 40°C. However, none of the methods herein tested fully removed P. destructans and hence they are not a substitute for decontamination. Since many cavers forgo washing equipment after surveys, and bat workers often visit several underground sites per day during monitoring activities without cleaning equipment in between sites, it is essential to raise awareness on this subject and introduce hygienic protocols for the prevention of pathogen pollution in underground sites.

Ecological niche breadth may help explain spatial distribution patterns in animals. In this study on European bats, Alberdi et al. combine DNA metabarcoding and species distribution modelling to show that dietary niche breadth is related to hunting flexibility and broad-scale spatial patterns in species distribution.