White-Nose Syndrome Disease Severity and a Comparison of Diagnostic Methods
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White-nose syndrome is caused by the fungus Pseudogymnoascus destructans and has killed millions of hibernating bats in North America but the pathophysiology of the disease remains poorly understood. Our objectives were to (1) assess non-destructive diagnostic methods for P. destructans infection compared to histopathology, the current gold-standard, and (2) to evaluate potential metrics of disease severity. We used data from three captive inoculation experiments involving 181 little brown bats (Myotis lucifugus) to compare histopathology, quantitative PCR (qPCR), and ultraviolet fluorescence as diagnostic methods of P. destructans infection. To assess disease severity, we considered two histology metrics (wing area with fungal hyphae, area of dermal necrosis), P. destructans fungal load (qPCR), ultraviolet fluorescence, and blood chemistry (hematocrit, sodium, glucose, pCO2, and bicarbonate). Quantitative PCR was most effective for early detection of P. destructans, while all three methods were comparable in severe infections. Correlations among hyphae and necrosis scores, qPCR, ultraviolet fluorescence, blood chemistry, and hibernation duration indicate a multi-stage pattern of disease. Disruptions of homeostasis occurred rapidly in late hibernation. Our results provide valuable information about the use of non-destructive techniques for monitoring, and provide novel insight into the pathophysiology of white-nose syndrome, with implications for developing and implementing potential mitigation strategies.
Keywordsblood chemistry histopathology Myotis lucifugus non-destructive methods PCR Pseudogymnoascus destructans ultraviolet fluorescence
We thank the animal care staff (Monique Burmester, Paula Mason, Melanie Weiss), imaging specialists (Ian Shirley, Chris Stuart), and necropsy team (Marnie Zimmer, Crystal Rainbow) at the Western College of Veterinary Medicine for their support and technical expertise throughout these studies. We also thank Katy Parise, Nicolette Janke, and Kevin Drees at the Center for Microbial Genetics and Genomics at Northern Arizona State University for molecular diagnostics. Funding was provided by the United States Fish and Wildlife Service, Canada Foundation for Innovation, Manitoba Research and Innovation Fund, Natural Sciences and Engineering Research Council of Canada, the German Academic Exchange Service (DAAD), and NSF grant DEB-1115895.
All applicable institutional and/or national guidelines for the care and use of animals were followed. Collection of wild bats was approved under permits from Manitoba Conservation (Permits WB11145 and WB13148) and experiments were approved by the University of Saskatchewan Committee on Animal Care and Supply (Protocol #20100120).
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