A Promising Potential Solution to White-Nose Syndrome

BCI is part of a network of researchers attempting to find and implement solutions that can reduce the spread of the fungus and treat bats after they’re infected. The team is using a technique that involves ribonucleic acid (abbreviated as RNA), which essentially converts information from DNA in order to carry out important cellular functions, like building proteins.

RNA interference (RNAi) technology is being used to combat Pd’s increasing prevalence. RNAi can stop cells from producing certain proteins, including ones the cell needs to survive. RNAi is already in use to treat human disease and manage agricultural pests, and the team behind the project has proven it can destroy Pd in a lab setting. Their research strongly suggests RNAi can also destroy Pd in the wild, which could mean far fewer bats infected with and killed by WNS each season.

Now all they have to do is convince people to try it.

The mechanism of RNAi was first described in 1998 by scientists Craig Mello, Ph.D., and Andrew Fire, Ph.D., who won the Nobel Prize in Physiology or Medicine for their work in 2006—but really, it’s a process as old as cells themselves.

RNAi works by taking advantage of the natural systems inside all living organisms, including Pd. When the fungus is exposed to double-stranded RNA (dsRNA) designed by the team at OSU, key sections of its genetic code are “silenced,” meaning they can no longer function. These sections are responsible for life-sustaining housekeeping activities like the production of proteins essential for a cell’s structural integrity. If these activities are thwarted, the fungus dies.

When the dsRNA is suspended in a liquid, it can be sprayed directly onto the walls of caves and other places where bats roost and Pd grows. Research shows that bats are generally exposed to the fungus while hibernating, so removing it from the places where they make their homes can prevent them from contracting and spreading WNS.

Chemical methods to remove Pd from the environment may be effective but can be indiscriminate: They kill the fungus, and much of what’s around it, too. Because many of the environments where bats hibernate are complex natural ecosystems, it’s necessary to use agents that target the Pd fungus but leave other natural biota unharmed. The specially created dsRNA that this technology relies on is tailored to Pd’s genome, so it doesn’t affect other microbiota. When the research team recently experimentally exposed bats, crickets, and other fungi to the sprayable dsRNA, they found that only the Pd fungus and its very closest relatives were affected. “You can make sure that the gene sequences are highly specific to targeting the fungus and no other species,” Dziedzic says. It also decomposes naturally within a few days.

The next step for the team is to take the dsRNA spray out of the lab and test it in the caves where bats are hibernating.

“In the lab you have a lot of things you can control but it’s pretty different once you’re outside,” Urbina says. “Being able to [test] it outside is a step for us to understand the things we need to improve and evaluate.”

While the conservation community generally agrees about the seriousness of the threat posed by WNS, not everyone sees eye to eye about how to handle the challenge.

Cheng says one of the most surprising things she’s encountered while researching RNAi’s potential for combatting WNS has nothing to do with the research itself, but she has found the technique to be controversial in the bat conservation community.

“Year after year, I continue to sit and work and talk with a lot of folks on the ground who are too afraid to do anything. They just want to sit and see what happens,” Cheng says. “Well, it’s been nearly 20 years since WNS first emerged in North America—I think we know what’s going to happen.”

The northern long-eared bat (Myotis septentrionalis) was once common throughout the northeastern U.S. and Canada. Today, up to 99% of its population in this area has been killed by WNS. The syndrome affects 12 species of hibernating bats, including three that are Endangered, and is particularly devastating for small species. In addition to decimating northern long-eared bats, it has killed 90% of the little brown bat (Myotis lucifugus) and tricolored bat (Perimyotis subflavus) populations.

“When Pd hits a site with vulnerable species, it’s only a matter of a year or two before we see epidemic levels of pathogen in the population, and then mass mortality,” Cheng says.

While it’s often frustrating, the team can also understand the hesitation. Dziedzic points out that methods with a genetic component, and those developed for agricultural purposes, can create particular distrust. Conservationists don’t want to tackle one problem only to create another—like when cane toads were introduced in Australia to combat cane beetles, only to become a destructive invasive species themselves. What’s more, although RNAi technology has been around longer than WNS has been in North America, this specific application is still new. People aren’t familiar with it, which makes them hesitant to trust it.

In order to combat this wariness, the team has embarked on what Cheng calls a “speaking tour,” working to share information, correct misconceptions, and strike just the right tone to inspire action. “We’ve been knocking on doors everywhere,” Urbina says.

And while the conservation community can be highly risk-averse, it’s also very responsive to new science. While researching Pd’s growth in different types of substrates, Urbina discovered that common practice among scientists for decontaminating their gear to prevent the spread of Pd from one environment to another was actually ineffective. She shared her findings, which has made an impact.

“This is a good community because they are supportive,” Urbina says. “When we broke that information they were like, ‘Thank you for letting us know,’ and pretty soon protocols were changed.”

Another effect of that positive community is the sheer number of WNS interventions being explored, which can make viable environments not already in use for testing hard to come by. Although the team had aimed to test RNAi in a cave, Dziedzic says a human-made roosting structure like a mine might present a more realistic option for their trial. That might take a bit of adjusting, but ultimately it would suit the team just fine. Pd may be hardy, but so are the researchers fighting it.