Last updated: September 25, 2026
Article
Vaccines Give Bats a Wing Up Against White-Nose Syndrome on San Juan Island
NPS / Sophia Hammerle
A small, fuzzy bat squirms in a field technician’s gloved hand. Tiny but tough at only two inches tall, the bat wriggles out one delicate wing and tries to crawl free. But after a few moments, it seems to relax.
“It looks at you, and it’s like, oh, OK,” said Andrew Schwartz, a Scientists in Parks research assistant. “There’s this kind of emotional connection ... I feel, in that moment, responsible. I’m like, oh my gosh, I can help you."
The bat in Schwartz’s hand lives in a bat box at English Camp in San Juan Island National Historical Park. In the summer, hundreds of bat moms huddle together in this maternity colony to raise their newborn pups. But they aren’t alone—they roost among the spores of a deadly fungus that causes white-nose syndrome, a disease that has killed over seven million bats in North America.
After checking on this colony for a decade as the disease crept across Washington, researchers detected the fungus here last year—the first appearance on San Juan Island. Now, years of careful monitoring are culminating in a novel effort biologists hope will help these bats survive: vaccination.
NPS / Sophia Hammerle
With the bat in one hand and a pipette in the other, Schwartz draws liquid from a vial. He places the pipette tip into the bat’s open mouth and releases the fluid. This is the first colony-wide vaccination ever conducted for white-nose syndrome, reaching over 450 bats in two nights in late July. It’s the first time this many bats have been vaccinated in a single trial since field testing began in 2019.
The vaccine comes at a crucial time. Vaccinating bats shortly after the detection of the fungus has the greatest potential to help them survive, earlier trials suggest. Known as Pseudogymnoascus destructans (Pd), the fungus grows into bats’ skin during hibernation, disrupting their body’s regulated state and draining their energy. Infected bats wake more often from hibernation, finding themselves exhausted in the middle of winter with nothing to eat. Those that don’t die of starvation emerge in the spring with damaged wings, only to face the fungus again the following winter.
Left: USFWS / Marvin Moriarty; Right: NPS / Hazel Galloway
The bat swallows the vaccine. Once released, it takes off into the night to hunt moths, mosquitos, and other bugs along nearby bays and harbors. These water-loving insectivores are Yuma myotis bats (Myotis yumanensis). Like the other 13 bat species in Washington, they eat hundreds of insects each night—including bugs that could harm human health or damage crops and forests.
Another bat is handed to Schwartz within seconds. Vaccinations start shortly after sunset and continue past midnight, led by a high-spirited team of over a dozen biologists, field technicians, and volunteers from the National Park Service, USGS, US Fish and Wildlife Service, Washington Department of Fish and Wildlife, and local nonprofits.
“It was very exciting to have so many people show up,” said research biologist Dr. Rebecca McCaffery, who leads the USGS Forest and Rangeland Ecosystem Science Center’s Olympic Field Station and has been a key part of the white-nose syndrome response in Washington since the disease first appeared in the state. “Having people from the community, from the Salish Wildlife Rescue, to have state people, federal people from different agencies and the park all come together ... spoke to the fact that this was a special moment.”
NPS / Sophia Hammerle
A Slow but Steady Spread
San Juan Island NHP is the first NPS site in western Washington to test the vaccine, with a similar colony on nearby Lummi Island serving as an untreated comparison group. In the past few years, Pd detections have increased across the region, including in nearby parks. Bat guano tested positive for the fungus in North Cascades and Olympic National Parks in 2024, followed by an observation of a bat death from white-nose syndrome in Olympic in 2025. That same year, Pd was detected in bat guano in Lewis and Clark National Historical Park—the first appearance of the fungus in Oregon.
“Last year, in 2025, was when we really had that jump,” McCaffery said. “Our colleagues at the state were starting to see colonies actually start to decline. Then it became a little more real.”
White-nose syndrome leaped to Washington state in 2016, the first case on the west coast. It traveled 1,300 miles from its previous westernmost point, likely transferred by people using contaminated caving equipment. This surprise appearance fell just 30 miles north of Mount Rainier National Park. Biologists across the region quickly came together to implement disease surveillance and share data across groups.
A map of the US, Mexico, and southern Canada with colored polygons indicating the date of white-nose syndrome detection by county. A black X in Pennsylvania marks the site of first detection in February 2006, followed by spread across the mid-Atlantic and eastern US. A group of detections in western Washington mark the earliest appearance in the west in the mid-2010s, followed by recent spread across the western US.
Before its arrival on the west coast, white-nose syndrome had spread rapidly across the northeastern United States in the decade following its emergence in 2006. Jumping from bat to bat huddled together in roost sites, the previously unknown disease wiped out entire colonies. Eastern populations of northern long-eared bats, for example, declined as much as 90%—putting them at risk of extinction.
The disease has moved more slowly in Washington, likely due to regional variation in how bats hibernate. Unlike on the east coast, where bats gather by the thousands in crowded caves, many bats in the west hibernate in small groups under tree bark or in crevices near their summer roosts. These differences appear even in bat species with populations on both sides of the continental divide.
“Is the nature of how bats are inhabiting this landscape giving us a little bit of time to implement and test these vaccines?” McCaffery said.
Bats come together to raise their pups in summer maternity colonies, like the bat box at English Camp. But researchers know very little about where they hibernate in the winter—so they may not be seeing the full scale of the disease in the west. Despite a slower spread, white-nose syndrome can be just as deadly once established in a colony.
“We have seen maternity colonies collapse,” McCaffery said. “I don’t want to sugarcoat it too much. There have been maternity colonies that have dropped from dozens or hundreds of bats down to just a handful.”
The reality of these declines puts recently infected colonies at a turning point—one where vaccination could make a huge impact. Earlier trials found that vaccinated bats had lower levels of fungus on their bodies, less severe wing damage, and greater chances of returning to their roosts in subsequent years. These results come from colonies where a subset of bats were vaccinated, while others received a placebo. Now, researchers are ready for the next phase of vaccine testing: treating entire colonies. On San Juan Island, that means hundreds of bats.
Left: NPS / Sophia Hammerle; Right: NPS / Hazel Galloway
Pillowcases Full of Bats
At sunset, bats exit the box like clockwork. But instead of an open night sky, they find themselves fluttering down a plastic chute. Earlier that evening, the vaccination team taped sheets of painter’s plastic into tubes with a pillowcase at the bottom. Known as funnel traps, these contraptions harmlessly collect bats as they exit their roost.
The fabric rustles as four pillowcases fill with bats. Their chirping grows louder: they’re talking to each other. Unlike high-pitched echolocation calls, the lower-frequency chirps bats use for social communication can be heard by humans.
It’s not the first time these bats have found themselves in a pillowcase instead of out in the evening air chasing insects. Every spring for the past decade, researchers collect a subset of the colony and swab their skin for the fungus. Disease monitoring began in 2017 as part of the regional response to white-nose syndrome, a collaboration among NPS, state and federal agencies, and nonprofits.
“It really is a huge team of people working together,” McCaffery said.
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Bat Vocalizations
Yuma myotis (Myotis yumanensis) squeaking during a capture in San Juan Island National Historical Park
NPS / Sophia Hammerle
Before they could monitor bats, researchers needed to find them. They worked with maintenance staff at NPS sites to identify colonies in and around buildings. They also placed ultrasonic acoustic recorders across the landscape to capture the high-frequency calls bats use for echolocation.
Each species of bat can be identified by a distinct pattern in their calls. Not only do these calls tell researchers which bats live where, but they also reveal changes in occupancy when recorded year after year across the region. Seeing a species in fewer locations over time, for example, could be a sign of habitat loss or population decline. Coordinated by the Northwest Bat Hub as part of the North American Bat Monitoring Program (NABat), this resurgence in monitoring filled an important knowledge gap.
“We had not done any acoustic survey work for bats in our Washington parks since around 2000,” McCaffery said. “Back in those days, we were recording on cassette tapes.”
Counting bats as they leave their roosts for the night offers another way to monitor populations. At the English Camp bat box, volunteers conduct emergence counts at least once a month from March to October. These counts made the vaccine trial possible by providing population data for the colony prior to infection and treatment. When swabs returned a positive Pd detection last year, the team was ready to respond.
“The vaccine was within that first set of options,” said Claire Crawbuck, biologist at San Juan Island NHP. “That gave me a lot of ease, knowing that we had such a strong and supportive team that really wanted to try all options for our bats.”
Developing the Vaccine
A field technician reaches a gloved hand into the wriggling pillowcase and pulls out a bat. “Adult female,” she says, checking its age by holding its outstretched wing up to a headlamp to inspect the cartilage in a wing joint. A volunteer notes the age and sex of each bat on a data sheet. Female bats are a priority for vaccination because of their role in reproduction. Typically, each mother gives birth to just one pup each year. Like humans and other mammals, bats nurse their young. The slow, energy-intensive process of raising a pup makes it harder for a disease-stricken population to recover.
NPS / Eliza Goode
The field technician hands the bat to those delivering the vaccine. Among these is Dr. Tonie Rocke, research epidemiologist at the USGS National Wildlife Health Center. Rocke leads field trials of the vaccine and has spearheaded its development since the project began in 2015.
“At the time, nobody thought that a vaccine would really work. It’s a fungus. Few scientists have attempted to develop fungal vaccines,” Rocke said.
Fungal vaccines pose a challenge to develop because fungi are closely related to animals. Their cells are more similar to those of humans—and bats—than to the viruses typically targeted by a vaccine. There are still no approved fungal vaccines for humans. But for bats? In the face of this disease, researchers tried something few thought possible.
NPS / Sophia Hammerle
A vaccine emerged out of collaboration between the USGS National Wildlife Health Center and scientists at the University of Wisconsin. Researchers identified two antigens from Pd that prompt bats’ immune systems to fight the fungus.
Antigens are molecules on the surface of a cell that act like labels, telling an organism’s immune system whether a particle belongs to self or other. When Pd infects a bat, the bat's immune cells detect an unfamiliar antigen and produce antibodies to destroy the intruder. If a bat’s immune system can glimpse these antigens without the fungus attached, it can get a head start in developing an immune response.
To put bats one step ahead of the fungus, researchers modified a racoonpox virus to act as a harmless carrier of these antigens. Other wildlife vaccines have used the same approach, taking advantage of the virus’ ability to enter cells but modifying it so that it does not produce illness. Instead, the virus works as a messenger, carrying antigens into cells to prime a bat’s immune response. Later, when Pd infects the bat, the bat’s immune system will recognize those same antigens and have antibodies ready to respond.
“Right from the beginning we saw positive effects both in laboratory studies and field studies,” Rocke said. "Now we’re to this point where we’re testing it at a population level.”
The vaccine is one of several efforts to give bats a wing up against white-nose syndrome. Other experimental treatments include sanitizing roost sites with UV-C light and developing a probiotic to strengthen bats’ microbiome and slow fungal growth. Three treatment sites in Washington received the probiotic as part of an ongoing university study collaborating with the Washington Department of Fish and Wildlife. Early results show a correlation between greater probiotic presence at roost sites and lower levels of the fungus.
Next to Bat
Following the vaccinations on San Juan Island, several other sites in the western United States began colony-wide vaccination trials this year, including another site in Washington and one in California near where the fungus first appeared in the state. A trial in Montana vaccinated nearly 900 bats.
“We are part of a much bigger effort across the west,” McCaffery said.
A colony in North Cascades and one in Olympic will receive the vaccination next year. On San Juan Island, the English Camp bats will find themselves in pillowcases once more as the young of the year get vaccinated. Volunteers and researchers will continue to monitor the population using emergence counts, acoustic monitoring, and disease sampling, comparing these numbers to the control colony on Lummi Island over the next few years.
"What we hope is that vaccinated colonies will survive in the face of white-nose syndrome,” Rocke said. “That they’ll continue to persist and thrive.”
NPS / Hazel Galloway
As the vaccine trials unfold in coming years, ongoing research continues to examine how bats use the landscape across elevations and seasons. McCaffery emphasized how much there is to learn.
“It’s hard to know what we’re tackling in terms of the population,” she said. "Working in these bat boxes, or in the attic of a ranger station, feels like a real tip of the iceberg moment—both for tracking disease spread and also for thinking about a management action. How many bats are there in Washington state? ... How many maternity colonies are out there in people’s attics and garages and old snags deep in the forest that nobody’s ever going to know about?”
At the English Camp bat box, bat after newly vaccinated bat takes off into the night. They will hunt insects. They will hibernate in a crevice somewhere unseen. They will return in the spring to birth and nurse their pups. And they will keep doing this, year after year, if they can survive the fungus. Vaccines are, hopefully, a step in that direction.
“It was really something to have these little critters in my hand and be able to be part of this team administering vaccine,” McCaffery said. “It’s exciting to do something that’s bigger than yourself.”
For research assistant Andrew Schwartz, the moment gave new meaning to his work with bats.
“Being able to have that bat in my hand and give it something that is very likely to help it persist in the landscape was an amazing feeling,” he said. “It brings me hope. I don’t have to continue watching their demise.... Let’s get these out there. Let’s see these numbers change.”
NPS / Hazel Galloway