Title
Probiotic Prophylaxis for White-Nose Syndrome: Testing Use of a Probiotic to Reduce Bat Mortality Caused by White-Nose Syndrome
Author(s)
Chadabhorn Insuk, Adrian Forsythe, Nick Fontaine, Chris Currie, Aimee Mitchell, Maleen Mund, Abigail Tobin, Heather Yoell, Naowarat Cheeptham, Cori L. Lausen, and Jianping Xu
Published
2025
Abstract
White-nose syndrome (WNS) is a disease of bats caused by Pseudogymnoascus destructans (Pd), affecting bats while they hibernate in winter in conditions conducive to fungal growth. Because the locations of winter bat roosts in western North America are poorly known, our goal was to develop a prophylaxis that could be applied during summer to reduce fungal activity on bats wings in winter and ultimately prevent or reduce the likelihood of disease development. The project originated in 2017 as a collaboration among Thompson Rivers University (Dr. Naowarat Cheeptham, cave microbiologist), McMaster University (Dr. Jianping Xu, fungal specialist), and Wildlife Conservation Society Canada (Dr. Cori Lausen, bat specialist). In 2022 the Washington Department of Fish and Wildlife (Abigail Tobin, WNS Coordinator) joined the team. We developed a topical mixture of four probiotic bacterial strains demonstrating complementary effects in inhibiting Pd in vitro. Sourced from natural skin microbiomes of healthy bats in western Canada, we successfully safety-tested this bacterial cocktail on captive bats, then applied the cocktail directly to summer nursery roost substrates of wild bats in Washington state (WA, USA), and British Columbia (Canada) at a total of 6 treatment sites (paired with 5 control sites where probiotics were not applied). Swab samples from bat wings, obtained through harp-trap captures and from roost substrates, collected by rubbing wooden surfaces inside bat boxes and building roosts, confirm long-term survival of probiotics on roost substrates and their successful transfer to bat wings. Among Pd-infected bats, we discovered the lowest concentrations of Pd on individuals with the highest concentrations of probiotics. The increasing detection of multiple probiotic strains on bats across all 11 study sites, including all Control sites, suggests that these bacteria are spread from bat-to-bat outside the summer season, facilitating regional-scale amplification well beyond sites of inoculation. In this Synthesis, we present a summary of all major milestones associated with the WNS Probiotics Project, beginning with a brief history of the development of the 4-strain probiotic cocktail consisting of bacteria sourced from BC bats, followed by a summary of the safety-testing on captive bats, and field-testing results in WA where Pd occurs and WNS is causing bat mortality. Because monitoring is key to understanding probiotic effectiveness, disease detection, and quantifying disease impacts, we provide a summary of all monitoring completed in both BC (5 study sites) and WA (6 study sites) between 2019 – present. Annually, we are applying probiotics bacteria to summer roost substrates of bats at 6 maternity colonies (3 in each of BC and WA). We swab bats in summer at regular intervals to test for the presence of, and quantify concentrations of, Pd and probiotic bacteria. We also swab-sample roost substrates periodically throughout the year to quantify probiotic bacterial reservoirs across seasons. While handling bats, we assess bat health for signs of WNS disease and insert Passive Integrated Transponder (PIT) chips for individual identification of bats and automated tracking or roost occupancy. Through PIT tag read data, we are establishing baselines for, and monitoring changes in, overwinter return rates (i.e., survival rates). These metrics are being used to evaluate the efficacy of our disease management tool and require ongoing monitoring of sentinel sites- selected on the criteria of large, stable colonies for which long-term datasets serve as a benchmark for bat populations in a region. Baseline data (natural return/survival rates, colony sizes, microbiome composition) at these sites will provide invaluable data upon which to gauge WNS impacts and disease mitigation efforts. With the observation of sharp declines observed in one of the first WNS-positive Alberta bat colonies, the Alberta Government initiated plans to apply probiotic treatments at some bat colonies in July 2025. This geographic expansion of probiotics use followed confirmation from McMaster University that the Pseudomonas strains in our probiotics had been detected in some baseline wing swabs from Alberta, ensuring that no new microbes would be introduced to this province’s bat populations.
Keywords
white-nose syndrome; bats
Full Citation
Insuk, C., A. Forsythe, N. Fontaine, C. Currie, A. Mitchell, M. Mund, A. Tobin, H. Yoell, N. Cheeptham, C.L. Lausen, and J. Xu (2025). Probiotic Prophylaxis for White-Nose Syndrome: Testing Use of a Probiotic to Reduce Bat Mortality Caused by White-Nose Syndrome. Toronto, Canada: Thompson Rivers University, McMaster University, and Wildlife Conservation Society, Canada, 1-25.