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Emerging infectious diseases may become serious threats to wildlife, a prominent example being the white-nose disease (WND). In case of WND, the cold-loving fungus Pseudogymnoascus destructans colonizes bats during hibernation, invades the skin and has already lead to the death of millions of bats in North America. P. destructans most likely originated from Europe, where it also causes lesions but without associated mortalities. However, it is still unclear how European bats cope with the fungus. Hence, it is important to have tools that precisely characterise disease progression. Because hibernation is a physiological state during which bats are vulnerable to disturbance, in-situ assessments of the clinical status should be carried out minimal-invasively to avoid detrimental impacts on bats. However, currently available disease assessment methods require handling/touching bats and are therefore invasive: i) UV-light trans-illumination of wing membranes to detect lesions and ii) a qPCR-based quantification of fungal material from wing membrane swabs. Since P. destructans ('Pd') becomes visible on all furless skin with distinct distribution patterns, we investigated the use of visible symptoms to assess levels of infections without handling/touching bats. We introduce a technique which we termed 'Visual Pd-score' (a visual classification scheme), which can be applied without disturbing the animals. To assess its reliability, we used P. destructans infected greater mouse-eared bats (Myotis myotis) to compare the novel method with the two existing golden-standard techniques. Our results show that infection levels obtained from all three techniques are correlated. Importantly, the information carried by the Visual Pd-score is most similar to a composite index combining the information from the qPCR-based and UV-light quantification methods. We conclude that the Visual Pd-score represents a promising index to better characterise disease severity as it is simultaneously representative for fungal colonization and wing damage. We discuss advantages and disadvantages of the applied techniques and conclude that the Visual Pd-score is particularly useful for routine hibernacula counts or large-scale P. destructans-surveillance. In combination with the lesion detection technique the new method is also applicable to immunological studies where both fungal colonization and associated damage have to be investigated, while qPCRs from swabs of all body parts are especially useful if it is necessary to detect cryptic infections, e.g. during the early hibernation period. [ABSTRACT FROM AUTHOR]

Emerging fungal diseases have become challenges for wildlife health and conservation. North American hibernating bat species are threatened by the psychrophilic fungus Pseudogymnoascus destructans (Pd) causing the disease called white‐nose syndrome (WNS) with unprecedented mortality rates. The fungus is widespread in North America and Europe, however, disease is not manifested in European bats. Differences in epidemiology and pathology indicate an evolution of resistance or tolerance mechanisms towards Pd in European bats. We compared the proteomic profile of blood plasma in healthy and Pd‐colonized European Myotis myotis and North American Myotis lucifugus in order to identify pathophysiological changes associated with Pd colonization, which might also explain the differences in bat survival. Expression analyses of plasma proteins revealed differences in healthy and Pd‐colonized M. lucifugus, but not in M. myotis. We identified differentially expressed proteins for acute phase response, constitutive and adaptive immunity, oxidative stress defence, metabolism and structural proteins of exosomes and desmosomes, suggesting a systemic response against Pd in North American M. lucifugus but not European M. myotis. The differences in plasma proteomic profiles between European and North American bat species colonized by Pd suggest European bats have evolved tolerance mechanisms towards Pd infection. [ABSTRACT FROM AUTHOR]

Pseudogymnoascus destructans (Pd) , the causative agent of white-nose syndrome in North America, has decimated bat populations within a decade. The fungus impacts bats during hibernation when physiological functions, including immune responses, are down-regulated. Studies have shown that Pd is native to Europe, where it is not associated with mass mortalities. Moreover, genomic and proteomic studies indicated that European bats may have evolved an effective immune defence, which is lacking in North American bats. However, it is still unclear which defence strategy enables European bats to cope with the pathogen. Here, we analyzed selected physiological and immunological parameters in torpid, Pd infected European greater mouse-eared bats (Myotis myotis) showing three different levels of infection (asymptomatic, mild and severe symptoms). From a subset of the studied bats we tracked skin temperatures during one month of hibernation. Contrasting North American bats, arousal patterns remained unaffected by Pd infections in M. myotis. In general, heavier M. myotis aroused more often from hibernation and showed less severe disease symptoms than lean individuals; most likely because heavy bats were capable of reducing the Pd load more effectively than lean individuals. In the blood of severely infected bats, we found higher gene expression levels of an inflammatory cytokine (IL-1β), but lower levels of an acute phase protein (haptoglobin), reactive oxygen metabolites (ROMs) and plasma non-enzymatic antioxidant capacity (OXY) compared to conspecifics with lower levels of infection. We conclude that M. myotis , and possibly also other European bat species, tolerate Pd infections during torpor by using selected acute phase response parameters at baseline levels, yet without arousing from torpor and without synthesizing additional immune molecules. • Hibernating European bats infected with the fungal pathogen Pseudogymnoascus destructans do not interrupt the torpor state due to the infection • European bats induce an immune response during torpor and use baseline levels of immune effectors in their blood circulation • Individuals with higher energy storage generally arouse more often from torpor and show less disease symptoms compared to lean conspecifics [ABSTRACT FROM AUTHOR]