Little Brown Myotis with white-nose syndrome © Jonathan Mays / Maine Department of Inland Fisheries and Wildlife

Preventing white-nose syndrome in bats

White-nose syndrome (WNS) is a devastating disease affecting North American bat populations.

What is WNS?

Starting in 2007, biologists discovered piles of dying, hibernating bats in eastern US caves and mines, associated with a white fungal growth on bats' noses. WNS has now spread west and north, threatening the rich diversity of bats living in western Canada.

The disease is caused by the fungus Pseudogymnoascus destructans (Pd) that kills bats while they hibernate in winter. The fungus grows on bats’ skin causing irritation and skin damage. Disturbing bats’ hibernation during winter to fight off this fungus (e.g., grooming, jump-starting their dormant immune systems) can burn through precious stored fat and the bat may starve before the winter ends, or die of extreme electrolyte imbalances.

The WNS Probiotics Project

Western Canada has a unique challenge. We do not know where bats hibernate, which precludes the use of any treatments designed to be sprayed onto infected hibernating bats. In response, the WCS Canada Western Bat Program, led by Dr. Cori Lausen, partnered with Thompson Rivers University (Dr. N. Cheeptham Lab)and McMaster University (Dr. J.P. Xu Lab)to develop and test a potential disease management tool. We have successfully developed a summer-applied probiotic cocktail that boosts bats’ natural first line of defence – the wing microbiome.

Our promising approach

The skin of any animal houses natural microbes that protect the animal against disease. We identified a combination of four strains of naturally-occurring beneficial bacteria – found on some bats’ wings in Western Canada – that may be able to help bats survive WNS.

These bacteria inhibit the growth of the fungus that causes the WNS disease. By applying a cocktail of these beneficial bacteria onto roosting surfaces like bat boxes (focussing on maternity colonies where hundreds of adult females often roost together), bats pick up microbes on their wings.

Armed with these beneficial bacteria, bats leave their summer roosts to winter hibernacula and are potentially less susceptible to WNS.

The probiotic advantage

Our probiotic solution offers unique advantages when compared to other treatments, such as the Pd vaccine. A summer-applied probiotic is a preventative strategy aiming to protect bats before they enter hibernation.

Although our most recent lab findings (C. Insuk and JP Xu, McMaster University, unpublished data) suggest that the probiotics cocktail might also be capable of treating the disease by killing an active infection of Pd, the goal remains to proactively bolster bats’ abilities to fend off the Pd fungus to reduce mortalities before disease sets in. This is in large part because in British Columbia we know of no places where WNS-susceptible bat species congregate in large numbers for the winter. In Alberta and Northwest Territories we know of a few cave hibernacula where WNS is found on colonies of bats which could potentially be protected with direct intervention.

There are approximately double the number of bat species in the west compared to eastern Canada. While we aim to protect large maternity colonies of bats roosting in bat boxes and/or building roosts, by applying probiotics on general roosting surfaces such as under concrete bridges, multiple species may receive probiotics.

A little goes a long way

Even small numbers of probiotics bacteria on bat wings can amplify during winter to provide protection, something that happens while the bat is dormant. This differs from other approaches such as the Pd vaccine which requires an immune response by the bat to fight infection. Much like the disease itself, this disturbs the bat during hiberation to warm up its body, which uses stored body fat.

And because wing bacteria seem to transfer among individuals, our probiotics approach amplifies protection beyond the treatment roost, suggesting this could be a highly efficient disease management tool. Even if a small number of bats arrive at a hibernaculum with probiotics, these bacteria may transfer among individuals during fall mating and may transfer to hibernation surfaces.

Our results so far

We have demonstrated that spraying probiotics onto roosting surfaces is a successful method of transferring beneficial bacteria to bats’ wings. Bacteria then incorporate into their wing microbiomes.

Based on our field results in Washington state, where we started applying probiotics to bat roosts in 2023, we have determined that bat wings and roost surfaces covered in probiotics have less or no Pd fungus.

In our Washington study sites, where Washington Dept. of Fish and Wildlife have been monitoring maternity colony numbers for many years, we have determined that bats survive winter better if they have roosted in treated roosts the previous summer.

Little Brown Myotis © Charles Francis

What's next?

The Pd fungus is now found throughout much of Alberta, and WNS has been reported at hibernacula in both Alberta and NWT. We have already seen mortalities from WNS at both summer maternity and winter hibernation roosts in Alberta and NWT, creating urgency to expand the experimental use of probiotics from Alberta across the west.

While WNS has yet to be detected in British Columbia, the Pd fungus, typically seen just prior to the arrival of the disease, is now found in some locations in southern BC. There is still time for protective actions to be taken, but the window is closing rapidly.

We have the opportunity to act before the catastrophic declines seen in eastern North America occur in the west. As we deploy our probiotics in an increasing number of locations, we are continuing to learn about the efficacy of our potential disease management tool in new climates, on different bat species, and in different use scenarios (e.g., with plans to potentially treat bats in cave hibernacula).

Acknowledgements

Our work would not be possible without the contributions of our primary partners, including Thompson Rivers University, McMaster University and the Washington Department of Fish and Wildlife. Additional support is provided by a wide variety of provincial, territorial, and individual collaborators, volunteers and donors across Canada, We are hugely thankful for your support, time, and generosity.