A one-time spritz with a solution of beneficial bacteria may help bats infected with white nose syndrome survive the deadly disease.
Boosting the amount of naturally antifungal Pseudomonas fluorescens bacteria that are already present on many bats’ skin allowed nearly half of the animals to live through winter, compared with only 8 percent surviving in an untreated group, a small study finds.
The cold-loving fungus responsible for white nose syndrome (Pseudogymnoascus destructans) has devastated North American bat populations. Since the disease arrived on the continent in 2006, it has wiped out more than 90 percent of most little brown bat colonies (Myotis lucifugus) in the northeastern United States, and is spreading west with infected bats (SN: 4/30/16, p. 20).
Infections disrupt the animals’ hibernation, causing them either to use up their fat stores and starve or to leave their winter shelters and die of exposure (SN Online: 1/5/15). Many infected bats don’t make it until spring, when bats’ body temperatures and immune systems ramp up again, and the animals are more able to fight off fungal infections.
“Bats are really difficult to work with, so being able to pull out some meaningful results from this work was a huge win for us,” says ecologist Joseph Hoyt, who set up the experiment in a Wisconsin mine. The researchers learned from previous efforts by scientists to study probiotic treatments for amphibians to fight chytrid fungus infections, says Hoyt, of Virginia Tech in Blacksburg.
Hoyt and colleagues used a strain of Pseudomonas found on bats that he and other researchers had identified in a 2015 study as being one of the most effective at reducing P. destructans fungi. Before starting the experiment, the team also determined that P. fluorescens or closely related bacteria were present already on 20 percent of bats in the mine — helping assure that the research wouldn’t introduce microbes that could harm the animals’ environment.
In November 2015, the researchers caught 30 bats from the cave, spraying a solution on the wings and tails of 16 of them, and attaching transponders to their wings. The transponders triggered a sensor at the mine opening to let researchers know when a bat had left or entered, and thus, was no longer hibernating and was still alive. Three treated bats and one untreated bat were eliminated from the experiment after losing their transponders. Then, in early March, the researchers swabbed the wings of the surviving bats in both the treated and untreated groups for fungi, and a few months later, collected the data from the transponder receiver.
Of the bats remaining in the experiment, six that had been treated lived through the winter, while only one of the untreated bats survived, the researchers report online June 24 in Scientific Reports.
That roughly 50 percent survival rate in the treated bats “is not stellar when you’re thinking of saving a species,” says wildlife biologist Jeremy Coleman, the national white nose syndrome coordinator for the U.S. Fish and Wildlife Service in Springfield, Mass. “But we’re not likely to find a single treatment that is going to solve this problem,” says Coleman, who was not involved in the study. The new probiotic solution could also be replicated using naturally occurring antifungal bacteria from other sites to avoid any possible impacts from introducing new types of bacteria into an ecosystem.
“Maybe using Pseudomonas with other treatments will get these animals through what we think is a bottleneck event,” which reduces genetic diversity, but doesn’t wipe a species out altogether before it can evolve natural defenses as bats in Europe have, Coleman says.