Biomarker Metabolites Discriminate between Physiological States of Field, Cave and White-nose Syndrome Diseased Bats.

Lisa B. Forse,Anna C. Doty,A. Dan Wilson,Thomas S. Risch

doi:10.3390/s22031031

Abstract

Analysis of volatile organic compound (VOC) emissions using electronic-nose (e-nose) devices has shown promise for early detection of white-nose syndrome (WNS) in bats. Tricolored bats, Perimyotis subflavus, from three separate sampling groups defined by environmental conditions, levels of physical activity, and WNS-disease status were captured temporarily for collection of VOC emissions to determine relationships between these combinations of factors and physiological states, Pseudogymnoascus destructans (Pd)-infection status, and metabolic conditions. Physiologically active (non-torpid) healthy individuals were captured outside of caves in Arkansas and Louisiana. In addition, healthy and WNS-diseased torpid bats were sampled within caves in Arkansas. Whole-body VOC emissions from bats were collected using portable air-collection and sampling-chamber devices in tandem. Electronic aroma-detection data using three-dimensional Principal Component Analysis provided strong evidence that the three groups of bats had significantly different e-nose aroma signatures, indicative of different VOC profiles. This was confirmed by differences in peak numbers, peak areas, and tentative chemical identities indicated by chromatograms from dual-column GC-analyses. The numbers and quantities of VOCs present in whole-body emissions from physiologically active healthy field bats were significantly greater than those of torpid healthy and diseased cave bats. Specific VOCs were identified as chemical biomarkers of healthy and diseased states, environmental conditions (outside and inside of caves), and levels of physiological activity. These results suggest that GC/E-nose dual-technologies based on VOC-detection and analyses of physiological states, provide noninvasive alternative means for early assessments of Pd-infection, WNS-disease status, and other physiological states.

Highlights

White-nose syndrome (WNS), a necrotrophic fungal disease found primarily in cavedwelling Nearctic bats, has reduced bat populations in some eastern regions of NorthAmerica by as much as 99% [1,2,3]
The aims of this study were to (1) determine differences in volatile organic compound (VOC) composition of whole-body emissions from tricolored bats in three categories, including (a) healthy, active bats in summer; (b) healthy, torpid bats in winter, and (c) diseased, torpid bats affected by WNS; (2) identify unique chemical VOC biomarkers indicative of specific types of physiological activities and states; and (3) identify differences in overall VOC profiles of these three sample groups based on electronic-nose principal component analysis (PCA) aroma-map comparisons
The output data from the dual-technology, Heracles II GC/E-nose instrument analysis of whole-body VOC emission provided two types of chemical data that were useful in characterizing the physiological states of P. subflavus bats under different physical environments and levels of physical activity

Summary

Introduction

White-nose syndrome (WNS), a necrotrophic fungal disease found primarily in cavedwelling Nearctic bats, has reduced bat populations in some eastern regions of NorthAmerica by as much as 99% [1,2,3]. White-nose syndrome (WNS), a necrotrophic fungal disease found primarily in cavedwelling Nearctic bats, has reduced bat populations in some eastern regions of North. WNS is caused by a keratinophilic fungal pathogen, Pseudogymnoascus destructans (Pd), that develops epidermal and deep, subcutaneous skin infections in at least twelve insectivorous bat species [4,5]. The disease was first discovered in North American bat populations in 2006 (within New York caves) and is believed to have originated from Europe where bats have likely coexisted with P. destructans for millenia [6,7]. Skin-infections by P. destructans result in characteristic epidermal erosions that develop into necrotic flecks, filled with fungal hyphae on the muzzles, ears, and wings. WNS systemically disrupts the normal physiology of hibernating bats, leading to adverse physiological cascades, including chronic respiratory acidosis, frequent fat-depleting arousals causing starvation and dehydration, Immune Reconstitution Inflammatory Syndrome (IRIS) during conscious periods of euthermia (following hibernation), and death [9,10,11,12,13]

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