Infected bats can recover . . . with lots of help
Unfortunately, there aren’t enough people to nurse more than a tiny number back to health.
A paper published October 26 in Nature confirms what everyone had come to assume: that a fungus is responsible for killing vast numbers of North American bats. (Proving the link took some fancy lab work to nail down). But that’s not the only bat news. Some authors of the new report also reported data today establishing that with enough coddling, many heavily infected bats can recover.
The rub: Federal scientists pointed out that there really aren’t sufficient resources to save more than a handful of bats this way.
Their marginally encouraging news emerges from a study of 30 little brown bats, all of whom bore visual evidence of a severe white-nose infection. Those new data show that if infected bats are provided warmth, food and water, “they actually can mount a rapid recovery,” notes David Blehert of the U.S. Geological Survey’s National Wildlife Health Center in Madison, Wisc. He’s an author of the study.
Science News headlines, in your inbox
Headlines and summaries of the latest Science News articles, delivered to your email inbox every Thursday.
Thank you for signing up!
There was a problem signing you up.
These were bats that had recently — and naturally — emerged from winter hibernation, explains his colleague, wildlife pathologist Carol Meteyer; she also works at the Madison center. The animals had been traveling in and out of caves during late spring and were captured by hand in May and then transported by car to a rehabilitation facility run by Bat World New Jersey.
Nurtured in the lab, the animals’ immune systems — which basically turn off during hibernation — revved up again. The first seven weeks of protective custody proved critical. During that time, the bats were individually taught to eat lab-administered meal worms. The researchers also treated visibly infected wing tissue on two-thirds of the bats using a dilute vinegar solution. In the end, that acid test offered no additional advantage.
Twenty-six of the animals survived 70 days (at which point they were sacrificed for further study). By that time, all had recovered and their wings were fungus-free. Meteyer and her team detail their findings in the current (July) issue of the Journal of Wildlife Diseases.
As the bats’ immunity moved into full gear, wing lesions where the fungus had been eating through the animals’ skin, began to scab over. Their bodies “tend to wall off that fungus and lift it away from the bat wing,” Meteyer says. “I call it ‘bat magic.’”
Subscribe to Science News
Get great science journalism, from the most trusted source, delivered to your doorstep.
Eventually, the wings (which are the structures most vulnerable to white-nose syndrome) “look entirely normal,” she says — both to the naked eye and upon microscopic investigation. Somehow, wings regenerate fungus-savaged tissue to the point that recovered bats cannot be distinguished from uninfected ones, she says.
That’s the good news. The bad: More than one million bats have succumbed to white nose syndrome in the past five years and there’s no sign this infection is slowing. It’s actually continuing to radiate throughout North America. And insect-eating bats aren’t interested in the idea of a lab rehab. Most don’t cotton to eating the meal worms they’re offered and may need to be painstakingly and individually coerced before they readily eat this grub.
Meteyer says only a few Northeast facilities have been licensed to treat wild bats. Offering palliative care to affected bats can require round-the-clock attention and tends to evolve into a labor of love. Clearly, she observes, the logistics of trying to gear this up for widescale nursing of sick bats “isn’t feasible at this point.”
Adds Blehert, once a site where bats congregate for hibernation becomes infected with the white-nose pathogen (Geomyces destructans), viable fungus can persist on the walls and floors — ready to claim a new host.
Some people have been investigating a possible vaccine for white nose syndrome, but Meteyer is dubious about its potential.
The vaccine might be functional during the summer, she says, when the animals’ immune system is up and running. But “that’s not when this fungus is most infectious,” she explains. It loves the near-freezing cold of the caves where northern bats hibernate. So it’s likely that any vaccine-triggered immunity would take a hiatus along with the rest of the animals’ infection-fighting apparatus during hibernations — precisely when bats are most likely to encounter the pathogen.
For now, “there’s no magic bullet,” says Jeremy Coleman, a U.S. Fish and Wildlife Service biologist in Cortland, N.Y., and coordinator of white-nose syndrome programs for his agency. That’s why the Fish and Wildlife Service has started contemplating a new captive management strategy, he says.
“It doesn’t include rehabilitation,” he told reporters during a briefing, “and [Meteyer] indicated how difficult a large-scale rehab would be.” But the Fish and Wildlife Service has begun working with experts internationally to explore possible options for eight species of North American bats being hammered by white nose syndrome. A report detailing potential recommendations should be out by New Year’s, Coleman says. “We’re looking at the potential for a full-on captive propagation program similar to what has been done successfully with the black-footed ferret and California condor.”
But make no mistake, bat biologists warn: Captive rearing is easier to contemplate than to accomplish. “So far as I know, there are no sustaining populations of insectivorous bats in captivity,” says Alison Robbins of the Cummings School of Veterinary Medicine at Tufts University in North Grafton, Mass. Various research groups have maintained such bats in captivity, she notes — “but not to the point where they can properly reproduce.”
She knows the pitfalls well. Robbins took in 120 infected little-brown bats last year for a treatment trial. Each was hand fed for two weeks before they began chowing down on meal worms without assistance. But within three months, every one had died. Her suspicion: The stress of handling did them in.