How to Vaccinate Bats Living Deep in Caves and Stop Disease Outbreaks in Wild Animals
October 27, 2023 at 6:30 a.m. EDT
A scientist releases a bat Sept. 29 at Minnetonka Cave in Idaho as a team of researchers undertakes a vaccination expedition. (Jared Ragland for The Washington Post)
MINNETONKA CAVE, IDAHO — In the depths of darkness, a deadly menace lurks. Like a nocturnal predator, it silently stalks its victims in their slumber, invading their bodies until they succumb — and perish.
A fatal fungus has been ravaging hibernating bats across North America, decimating millions of these flying mammals.
Under the glow of a full moon on a crisp fall evening, a group of about a dozen scientists gathered at the entrance of a colossal limestone cave, armed with a groundbreaking solution: a revolutionary vaccine designed specifically for bats.
One by one, the researchers, dressed in protective masks and white Tyvek jumpsuits, ascended from the cave with brown paper bags containing bats that struggled and squeaked for freedom. In a remote area of southeastern Idaho, at a row of tables set up in the wilderness, Rita Dixon from the Idaho Department of Fish and Game delicately extended the translucent wing of a bat under the illumination of headlamps, carefully swabbing for the invisible killer.
Passing the bat to her colleague Tonie Rocke, an epidemiologist from the U.S. Geological Survey, the most crucial step began: administering a lifesaving vaccine through a pipette into the bat’s mouth.
One bat down. Rocke expressed her desire to vaccinate around 150 bats that night. However, the task ahead was daunting, as there are millions more bats across the country that need protection.
Some speculate that bats may be the source of the virus responsible for the emergence of COVID-19. Now, a coalition of federal and state agencies is leveraging the same technology used to develop coronavirus vaccines to combat the deadly disease outbreaks affecting bats.
While the research is groundbreaking, the question remains: How do you vaccinate bats residing deep in caves or prevent disease outbreaks in wild animals?
This conundrum does not have simple answers, yet it is a challenge we are increasingly confronted with. The ease of global travel enables diseases, once confined to specific regions, to spread rapidly across continents. Humans have already experienced this harsh reality with COVID-19, but many animal species are silently facing their own epidemics as wildlife pathogens hitch a ride on airplanes and ships.
Birds succumbing to avian flu. Starfish disintegrating into a viscous substance. Frogs falling victim to infections inducing heart attacks. Wildlife diseases are not only costing governments and farmers significant resources, but they are also exacerbating the ongoing global extinction crisis, which threatens to wipe out millions of species.
For a dozen bat species in North America, the lethal disease is known as white-nose syndrome — a threat so severe that researchers are compelled to employ an all-encompassing approach to combat it. If these nocturnal hunters were to disappear, farmers would lose a vital pest control resource, and ecosystems would be disrupted.
In Idaho, this translates to working in the dead of night, capturing bats, and conducting vaccine trials, all with the hope of developing a more efficient method to immunize bats in the future.
“We need to find a way to do this without any direct contact,” Rocke emphasized.
The crisis first surfaced nearly 2,000 miles away in Upstate New York. Researchers stumbled upon a cave in 2007 littered with bat corpses, their noses covered in white powder resembling cocaine. It was a sight to behold.
Bats possess powerful immune systems, allowing them to carry numerous pathogens without falling ill. However, tests conducted at the National Wildlife Health Center, where Rocke operates, unveiled an unknown culprit.
The fungus, which thrives in cold temperatures, attacks bats during their vulnerable hibernation period. It spreads from bat to bat as they nestle together, seeking warmth. This pathogen likely originated in Europe or Asia, hitching a ride across the Atlantic on an unwitting spelunker’s shoe. Bats in other regions seem to have developed immunity, but their North American counterparts have limited defenses.
Contrary to its name, white-nose syndrome affects more than just the bats’ noses. It eats away at their ears and wings, rousing the hibernators prematurely, depleting their fat reserves, and triggering chaotic immune responses. Consequently, the infected bats succumb to dehydration and starvation.
This fungus has evolved to exploit the bats when they are at their weakest — during the hibernation season, as Jonathan Reichard, the national assistant coordinator for white-nose syndrome at the U.S. Fish and Wildlife Service, explains.
In slightly over a decade, this devastating disease has spread across at least 40 states, stretching from Maine to Washington. It is estimated to have claimed the lives of over 5 million bats in North America. Multiple species have experienced population declines of over 90%.
“It was alarming,” Reichard confessed. Initially, he feared that all the bats would perish, spelling the end for hibernating bats. However, this mass extinction did not occur. Nevertheless, the early years brought immense shock and concern.
Once the disease was detected, Dixon became worried about Minnetonka Cave. During the warmer months, over 40,000 visitors flock to witness the majestic limestone formations and dripping stalactites that have formed over countless generations. However, in winter, the cave transforms into a sanctuary for bats. It is closed to the public as hundreds of bats from at least seven different species cling to the ceiling, seeking refuge from the biting cold.
“We expected this cave to be our first detection site in Idaho,” Dixon expressed. Consequently, officials established a boot-washing station at the entrance to prevent the pathogen from hitching a ride on visitors’ shoes, clothes, or gear — or from being inadvertently transported by a bat.
Dixon approached Rocke, who was already researching a vaccine, to propose running trials in the cave. With its diverse bat population, Minnetonka Cave was the ideal location to test the vaccine’s effectiveness. “Minnetonka Cave is truly special,” Rocke affirmed.
In 2022, their fears were confirmed: the fungus had arrived.
For now, the bats inhabiting Minnetonka Cave appear to be in good health. Since the fungus has only recently emerged, the cave provides an opportune environment for testing the efficacy of the vaccine.
David Dressel from the Idaho Department of Fish and Game expressed relief as the team descended a vertical array of wires positioned at the cave entrance. “This looks promising,” he remarked, strumming the strings of a harp trap, a device designed to capture bats without causing harm. When bats fly into these wires, they fall into a basket where scientists can collect and vaccinate them.
Rocke has dedicated most of her career to devising ways to vaccinate wild animals. Based in Madison, Wisconsin, she boasts nearly four decades of experience at the National Wildlife Health Center, the primary federal laboratory focused on studying wildlife diseases.
However, inoculating animals is no easy task. Traditional vaccination methods used on humans, such as injections, are often unfeasible for the animal kingdom. “We can’t rely on capturing animals and injecting them,” Rocke acknowledged. “It’s too challenging for the animals — and the people involved.”
Hence, Rocke’s team must devise innovative solutions. “While we develop vaccines,” Rocke explained, “we simultaneously explore novel delivery methods.”
For instance, in the case of black-footed ferrets, their solution was peanut butter. Following a plague outbreak that affected North America’s only native ferret species, Rocke and her team integrated the plague vaccine into prairie dogs, the ferrets’ primary prey, using peanut butter-flavored bait. Through this method, the predators could acquire immunity by consuming their prey.
“They absolutely love it,” Rocke revealed, regarding the ferrets’ fondness for the bait.
When it comes to honeybees, the U.S. government granted approval this year for the first-ever vaccine designed for an insect. The distribution method involves targeting the queen bee. By incorporating a vaccine for a bacterial disease called foulbrood into the queen’s food, the vaccine ultimately reaches her offspring, granting them immunity.
For bats, Rocke’s team took a cue from Johnson & Johnson and other vaccine manufacturers by genetically modifying a virus to express fungal antigens. This prompts the bats’ immune systems to produce a response against the fungus.
Rocke now aims to exploit the congregational behavior of bats, which contributes to the rapid spread of white-nose syndrome. Her team is contemplating the development of a spray or paste that bats can transport back to their roosts…
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