Can UV lights help stop the spread of white-nose syndrome in bats?

White-nose syndrome (WNS) has nearly wiped out some species of bats in the U.S. since it was first discovered in New York state in 2006. Five of Michigan's nine bat species are susceptible to it; eight years after WNS turned up in the state, it's devastated populations of little brown bats and northern long-eared bats.

Maarten Vonhof is a biology professor at Western Michigan University. Vonhof said researchers discovered a few years ago that a certain kind of ultraviolet light kills the fungus that causes WNS.

“They did a little test in the lab where they shone UV light on a variety of different fungi. And lo and behold, it killed the fungus that causes white-nose syndrome, but didn't kill some of these other fungi," he said.

Vonhof, along with researchers from Rutgers University and Ball State University, are building on that research and bringing UV lights to the caves and mines where bats live.

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WMU biologist, Maarten Vonhof (standing) with researchers, state biologists and graduate students in a New York mine, Spring 2023. The group is swabbing a sampling bats to assess how much fungus that causes white-nose syndrome is on their wings. UV pictures are taken to quantify how much of each bat’s wing is covered by fungus.

Tim Carter / Ball State University

2 of 3  — Bat wing under an ultraviolet light

The fungus that causes white-nose syndrome fluoresces under UV light on this bat's wing. The bat was tested while it was hibernating over winter in an old mine in Michigan's Upper Peninsula.

Maarten Vonhof / Western Michigan University

3 of 3  — Researcher swabs a bat for white-nose syndrome.

A researcher swabs a bat for white-nose syndrome in an old mine in Michigan's Upper Peninsula.

Maarten Vonhof / Western Michigan University

“We go to the hibernation sites when the bats aren't present. So, we go during the summertime, and we use these whole-room ultraviolet light sanitizers that are used in hospitals to sanitize them from bacteria and fungi.”

They follow that up with handheld ultraviolet lights to shine into cracks and crevices. When the bats return in the fall to hibernate, Vonhof hopes they are returning to safer environment.

To confirm that, researchers return in early spring while the flying mammals are still hibernating. On this visit, they swab a sampling of bats and study the wing under ultraviolet light, to see if the experiment is working.

This is Vonhof’s second summer treating nine caves in Michigan, New York and New Jersey with ultraviolet light. The project is funded by a grant from the National Fish and Wildlife Foundation (NFWF). He said he expects to know this spring whether the UV treatment of caves is helping to reduce the fungus.

Jonathan Reichard is with the White-Nose Syndrome Response Team. It’s part of the U.S. Fish and Wildlife Service, and works with the NFWF. Reichard said the UV research Vonhof is doing is promising.

In the meantime, Reichard said there are positive signs in Michigan.

“There are some glimmers, or indications, that they (bats) are still around and in some cases even doing better than we would have expected them to be 10 years ago, when they were in the middle of the big invasion," he said.