Since 2006, a fungal disease has wiped out millions of North American bats. It’s called white nose syndrome for the cottony-white fungi that show up on a bat’s face. The infection saps the bats’ energy as they hibernate during winter. But there may be a solution for this epidemic: bacteria.
Not just any bacteria, of course. Joseph Hoyt is an ecologist at Virginia Tech in Blacksburg. He headed a team from across the United States that is working with a bacterium known as Pseudomonas fluorescens (Su-doh-MOH-nus Flor-ESS-enz). Many bats already host these naturally antifungal bacteria. The new treatment merely boosts how many of these helpful germs a bat carries.
Hoyt’s team ran tests on two groups of bats infected with white nose syndrome. One group lived in cages inside an old mine. Another was living in the same place but could fly in and out of the mine. Half of each group was spritzed with the germ spray.
Scientists now report some limited success with squirting a liquid full of the P. fluorescens bacteria onto the bats. Nearly half of the treated animals lived through their winter hibernation. By comparison, just 8 percent of bats in the untreated groups did.
This is not the first time that such biowarfare has been used to tackle white nose syndrome. In 2015, researchers reported successfully treating small numbers of bats with gases spewed by certain bacteria. And earlier this year, scientists reported some success with an oral vaccine against the white-nose fungi.
Hoyt’s group described its promising new findings June 24 in Scientific Reports.
The white nose threat
The cold-loving fungus responsible for white nose syndrome has a very long name: Pseudogymnoascus destructans (SU-doh-jim-noh-AS-kus De-STRUK-tans). It appears to have come from Europe. There, most bats now appear able to fight off the infection. Their North American cousins have not been as successful.
Huge numbers of dying bats first showed up in New York caves. The animals had been hibernating there for the winter. Over the past dozen years, the white-nose epidemic has spread up into Canada, west through the U.S. Midwest to Washington State and then down into Texas. Millions of U.S. and Canadian bats from 12 different bat species have already died. Another 8 U.S. and Mexican species have tested positive for the fungus without yet showing white-nose symptoms.
A 2014 study found that bats can successfully fight off the fungus from about May to mid-October. But their resistance falls to near zero once the bats begin to hibernate.
The infection disrupts that winter rest, when the animals shut down their metabolism to save their energy. Each time they rouse, they start using more energy. If this happens too much, they can use up their fat stores and starve. Some will even leave their winter shelters in search of insects (which aren’t there) and risk dying of exposure in the cold. That’s why many infected bats don’t make it until spring, when bats’ body temps and immune systems ramp up. It’s also when their insect food sources again emerge.
“Bats are really difficult to work with,” says Hoyt. “So being able to pull out some meaningful results from this work was a huge win for us,” he says.
His group learned from previous efforts by scientists to study probiotics. Hoyt pointed to bacterial treatments for amphibians fighting infections of chytrid (KIH-trid) fungus.
Bacteria as medicine
Hoyt set up the outdoor experiment in a Wisconsin mine. There, he and his colleagues treated bats with a strain of Pseudomonas found on bats. In a 2015 study, he and other researchers had identified this strain as being one of the most effective at reducing tissue damage and death by P. destructans fungi.
Before starting the new experiments, the researchers also checked that P. fluorescens or closely related bacteria already had been present on 20 percent of bats in the mine. This helped assure that the research wouldn’t introduce microbes that might harm the animals’ environment.
In November 2015, the researchers caught 30 bats from the mine. They attached an identification tag to a wing of each bat. Then they sprayed the bacterial solution on the wings and tails of 16 of them.
The tags they used were special. They triggered a sensor at the mine’s entry every time one of these bats left or came back. This would let researchers know which bats had roused from their winter rest and attempted to forage (even though there were no insects around for them to eat).
Three treated bats and one untreated bat lost their tags, which removed them from the testing. In early March, the researchers found the remaining tagged bats and swabbed their wings for fungi. A few months later, the scientists collected data from the receiver that had kept tabs on the tagged activity of the supposedly hibernating bats.
The receiver’s data showed that six treated bats survived the winter. Only one of the untreated bats did.
That roughly 50 percent survival rate in the treated bats “is not stellar when you’re thinking of saving a species,” worries Jeremy Coleman. He’s a wildlife biologist who was not involved in the study. He also is the national white-nose-syndrome coordinator for the U.S. Fish and Wildlife Service in Springfield, Mass.
“We’re not likely to find a single treatment that is going to solve this problem,” he admits. The new treatment could likely be tried elsewhere using different antifungal bacteria present at other sites. This should avoid 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,” says Coleman. By bottleneck, he means some condition that reduces genetic diversity. Given enough time, he and others believe, North American bats probably can evolve natural defenses to the white-nose fungus — as have bats in Europe. They just have to survive long enough for that to happen.
This video shows that despite a widespread epidemic of white nose syndrome, some seem able to survive the fungal infection.
amphibians A group of animals that includes frogs, salamanders and caecilians. Amphibians have backbones and can breathe through their skin.
antifungal Having properties that prevent or limit the growth of fungi.
bacteria (singular: bacterium) Single-celled organisms. These dwell nearly everywhere on Earth, from the bottom of the sea to inside other living organisms (such as plants and animals). Bacteria are one of the three domains of life on Earth. (adj. bacterial)
bat A type of winged mammal comprising more than 1,100 separate species — or one in every four known species of mammal.
biology The study of living things. The scientists who study them are known as biologists.
bottleneck (in biology) Also known as genetic bottleneck. This is where a large share of the population of some species dies off. There are enough individuals for the species to survive, but much of the genetic diversity in the species has been lost. This occurs when die-offs in the population were random (and not due to genetic flaws or an inability to adapt).
colleague Someone who works with another; a co-worker or team member.
defense (in biology) A natural protective action taken or chemical response that occurs when a species confront predators or agents that might harm it. (adj. defensive)
disrupt (n. disruption) To break apart something; interrupt the normal operation of something; or to throw the normal organization (or order) of something into disorder.
diversity A broad spectrum of similar items, ideas or people. (in biology) A range of different life forms.
ecology A branch of biology that deals with the relations of organisms to one another and to their physical surroundings. A scientist who works in this field is called an ecologist.
ecosystem A group of interacting living organisms — including microorganisms, plants and animals — and their physical environment within a particular climate. Examples include tropical reefs, rainforests, alpine meadows and polar tundra. The term can also be applied to elements that make up some an artificial environment, such as a company, classroom or the internet.
environment The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of things in the vicinity of an item of interest).
epidemic A widespread outbreak of an infectious disease that sickens many people (or other organisms) in a community at the same time. The term also may be applied to non-infectious diseases or conditions that have spread in a similar way.
evolve (adj. evolving) To change gradually over generations, or a long period of time. In living organisms, such an evolution usually involves random changes to genes that will then be passed along to an individual’s offspring. These can lead to new traits, such as altered coloration, new susceptibility to disease or protection from it, or different shaped features (such as legs, antennae, toes or internal organs).
forage To search for something, especially food. It’s also a term for the food eaten by grazing animals, such as cattle and horses.
fungus (plural: fungi) One of a group of single- or multiple-celled organisms that reproduce via spores and feed on living or decaying organic matter. Examples include mold, yeasts and mushrooms.
genetic diversity The range of genes types — and traits — within a population.
germ Any one-celled microorganism, such as a bacterium or fungal species, or a virus particle. Some germs cause disease. Others can promote the health of more complex organisms, including birds and mammals. The health effects of most germs, however, remain unknown.
hibernation A state of inactivity that some animals enter to save energy at certain times of year. Bears and bats, for example, may hibernate through the winter. During this time, the animal does not move very much, and the use of energy by its body slows down. This eliminates the need to feed for months at a time.
host (in biology and medicine) The organism (or environment) in which some other thing resides.
immune system The collection of cells and their responses that help the body fight off infections and deal with foreign substances that may provoke allergies.
infection A disease that can spread from one organism to another. It’s usually caused by some type of germ.
insect A type of arthropod that as an adult will have six segmented legs and three body parts: a head, thorax and abdomen. There are hundreds of thousands of insects, which include bees, beetles, flies and moths.
literally A term that the phrase that it modifies is precisely true. For instance, to say: "It's so cold that I'm literally dying," means that this person actually expects to soon be dead, the result of getting too cold.
metabolism The set of life-sustaining chemical reactions that take place inside cells and bigger structures, such as organs. These reactions enable organisms to grow, reproduce, move and otherwise respond to their environments.
microbe Short for microorganism. A living thing that is too small to see with the unaided eye, including bacteria, some fungi and many other organisms such as amoebas. Most consist of a single cell.
probiotic A beneficial bacterium that is found in food or can be added to the diet. It can fight bad germs in the body or perform functions, such as producing vitamins that support human health.
risk The chance or mathematical likelihood that some bad thing might happen. For instance, exposure to radiation poses a risk of cancer. Or the hazard — or peril — itself. (For instance: Among cancer risks that the people faced were radiation and drinking water tainted with arsenic.)
sensor A device that picks up information on physical or chemical conditions — such as temperature, barometric pressure, salinity, humidity, pH, light intensity or radiation — and stores or broadcasts that information. Scientists and engineers often rely on sensors to inform them of conditions that may change over time or that exist far from where a researcher can measure them directly.
species A group of similar organisms capable of producing offspring that can survive and reproduce.
strain (in biology) Organisms that belong to the same species that share some small but definable characteristics. For example, biologists breed certain strains of mice that may have a particular susceptibility to disease. Certain bacteria or viruses may develop one or more mutations that turn them into a strain that is immune to the ordinarily lethal effect of one or more drugs.
symptom A physical or mental indicator generally regarded to be characteristic of a disease. Sometimes a single symptom — especially a general one, such as fever or pain — can be a sign of any of many different types of injury or disease.
syndrome Two or more symptoms that together characterize a particular disease, disorder or social condition.
tag (in conservation science) To attach some rugged band or package of instruments onto an animal. Sometimes the tag is used to give each individual a unique identification number. Once attached to the leg, ear or other part of the body of a critter, it can effectively become the animal’s “name.” In some instances, a tag can collect information from the environment around the animal or relay information about the animal to some outside sensor (receiver). This helps scientists understand both the environment and the animal’s role within it.
U.S. Fish and Wildlife Service A research agency of the U.S. Department of the Interior, it was created in 1871 as the U.S. Commission on Fish and Fisheries. Fourteen years later, it acquired an office of ornithology (the science of birds). In 1905 it was renamed the Bureau of Biological Survey. It now has authority for research on and the conservation of land-based species, of freshwater species and of migratory birds.
white nose syndrome A fungal disease affecting bats. The fungus, Pseudogymnoascus destructans, lives in caves where bats hibernate through the winter. It causes a white dusting on their noses and on other areas of the body. The fungus causes dehydration and can eat holes through bats’ wings and blood vessels. Eventually, it weakens them, leaving them unable to fly and find food.
Journal: J. Hoyt et al. Field trial of a probiotic bacteria to protect bats from white-nose syndrome. Scientific Reports. Published online June 24, 2019. doi:10.1038/s41598-019-45453-z.
Journal: T. Rocke et al. Virally-vectored vaccine candidates against white-nose syndrome induce anti-fungal immune response in little brown bats (Myotis lucifugus). Scientific Reports. Vol. 9, May 1, 2019. doi: 10.1038/s41598-019-43210-w.
News story: S. Milius. White-nose bat disease jumps the Rockies to Washington state. Science News. March 31, 2017.
Journal: J. Hoyt et al. Bacteria Isolated from bats inhibit the growth of Pseudogymnoascus destructans, the causative agent of white-nose syndrome. PLOS ONE. Published online April 8, 2015. doi: 10.1371/journal.pone.0121329.
Journal: K.E. Langwig et al. Host and pathogen ecology drive the seasonal dynamics of a fungal disease, white-nose syndrome. Proceedings of the Royal Society B: Biological Sciences. Jan. 22, 2015. doi: 10.1098/rspb.2014.2335.
News story: B. Brookshire. 'Tis the season for white-nose syndrome in bats. Science News. Dec. 9, 2014.
News story: J. Raloff. Bat-killing fungus is a European import. Science News. Vol. 181, May 19, 2012, p. 9.
Journal: Warnecke et al. Inoculation of bats with European Geomyces destructans supports the novel pathogen hypothesis for the origin of white-nose syndrome. Proceedings of the National Academy of Sciences. Vol. 109, May 1, 2012, p. 6999. doi: 10.1073/pnas.1200374109.
Journal: P.M. Cryan et al. Wing pathology of white-nose syndrome in bats suggests life-threatening disruption of physiology. BMC Biology, Vol. 8, November 11, 2010, p. 135. doi:10.1186/1741-7007-8-135.
Journal: S.J. Puechmaille et al. Pan-European distribution of white-nose syndrome fungus (Geomyces destructans) not associated with mass mortality. PLOS ONE, April 27, 2011, p. e19167. doi:10.1371/journal.pone.0019167.