Experimental inoculation trial to determine the effects of temperature and humidity on White-nose Syndrome in hibernating bats

Winifred F. Frick,Julia S. Lankton,Jeffrey T. Foster,Emily Johnson,Robin Warne,Tina L. Cheng,Jason Dallas,Justin G. Boyles,Katy L. Parise,Liam P. McGuire

doi:10.1038/s41598-022-04965-x

Abstract

Disease results from interactions among the host, pathogen, and environment. Inoculation trials can quantify interactions among these players and explain aspects of disease ecology to inform management in variable and dynamic natural environments. White-nose Syndrome, a disease caused by the fungal pathogen, Pseudogymnoascus destructans (Pd), has caused severe population declines of several bat species in North America. We conducted the first experimental infection trial on the tri-colored bat, Perimyotis subflavus, to test the effect of temperature and humidity on disease severity. We also tested the effects of temperature and humidity on fungal growth and persistence on substrates. Unexpectedly, only 37% (35/95) of bats experimentally inoculated with Pd at the start of the experiment showed any infection response or disease symptoms after 83 days of captive hibernation. There was no evidence that temperature or humidity influenced infection response. Temperature had a strong effect on fungal growth on media plates, but the influence of humidity was more variable and uncertain. Designing laboratory studies to maximize research outcomes would be beneficial given the high costs of such efforts and potential for unexpected outcomes. Understanding the influence of microclimates on host–pathogen interactions remains an important consideration for managing wildlife diseases, particularly in variable environments.

Highlights

Disease results from interactions among the host, pathogen, and environment
White-nose Syndrome (WNS) is an infectious disease of hibernating bats caused by a fungal pathogen (Pseudogymnoascus destructans; Pd)[6,7,8,9] that was first detected in eastern North America in 200610 and has caused rapid and extreme population declines of several species of hibernating bats[11,12,13,14]
In areas where Pd has established in North America, fungal loads are positively correlated with roosting temperatures of hibernating species, such that species that tend to roost at relatively warmer temperatures tend to have higher loads and in turn higher mortality from WNS24

Summary

Introduction

Inoculation trials can quantify interactions among these players and explain aspects of disease ecology to inform management in variable and dynamic natural environments. Experimental inoculation trials in laboratory settings provide the advantage of controlling and randomly assigning specific conditions of interest to enable causal inference and determine disease susceptibility These inferences can be used to explain key aspects of disease ecology and inform management actions taking place in variable and dynamic natural environments[4]. White-nose Syndrome (WNS) is an infectious disease of hibernating bats caused by a fungal pathogen (Pseudogymnoascus destructans; Pd)[6,7,8,9] that was first detected in eastern North America in 200610 and has caused rapid and extreme population declines of several species of hibernating bats[11,12,13,14]. Humidity can influence Pd growth[28], but has been harder to study in situ due to the difficulty of reliably measuring humidity in natural hibernacula[29]

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