American Bat Epidemic Jumps the Rockies

A sick bat found near Seattle is the first known case of white-nose syndrome west of the Rocky Mountains, U.S. officials confirmed Thursday. Not only that, but it's 1,300 miles beyond the epidemic's previous western front — a huge leap for a disease that has already killed about 7 million bats since it came out of nowhere 10 years ago.

White-nose syndrome (WNS) first appeared at a New York cave in February 2006, kicking off a historic epidemic that has stubbornly pushed west through the U.S. and Canada. It has obliterated bat populations along the way, with a nearly 100 percent mortality rate in some colonies. By February 2016, the disease had been confirmed at bat hibernacula in 27 U.S. states and five Canadian provinces.

But on March 11, hikers found a sick bat near North Bend in Washington state, about 30 miles east of Seattle. They took it to Progressive Animal Welfare Society (PAWS) in hopes it could recover, but the bat died two days later. It had visible symptoms of a skin infection common in bats with WNS, so PAWS submitted it for testing to the U.S. National Wildlife Health Center, which confirmed those suspicions.

"We are extremely concerned about the confirmation of WNS in Washington state, about 1,300 miles from the previous westernmost detection of the fungus that causes the disease," U.S. Fish and Wildlife Service (FWS) Director Dan Ashe says in a statement. Until now, the fungus's western frontier had been in Nebraska:

This map shows the spread of white-nose syndrome across North America since 2006. (Map: whitenosesyndrome.org)

Although this is the first sign of WNS west of the Rockies, experts say it could have been hiding out west earlier than anyone realized. "That does suggest that the fungus has probably been present," Jeremy Coleman, WNS coordinator for FWS, tells Earthfix. "Based on our experience in Eastern North America, bats don't succumb to that level of disease until the fungus has been present for multiple years."

A fungus among us

WNS is named after an odd white fuzz that grows on the noses, ears and wings of infected bats. It's caused by a previously unknown fungus, Pseudogymnoascus destructans, that infiltrates bats' bodies as they hibernate. Warm-blooded mammals would normally be safe from a cold-loving cave fungus like this, but hibernation reduces bats' body temperatures enough to give P. destructans a foothold.

The fungus doesn't seem to hurt any animal aside from hibernating bats, and it doesn't even kill them directly. Instead, it makes them wake up too early from hibernation and search fruitlessly for insects during winter. Dead bats with WNS often have empty stomachs, suggesting they starved to death.

P. destructans was new to science in 2006, and began decimating bat colonies across the Eastern U.S. and Canada before anyone knew what was going on. Scientists later found the same fungus in European caves, where native bats don't seem to die from it. That suggests it's an invasive Old World pathogen preying on defenseless New World hosts. Recent research has found the fungus in China, too, where native bats also show "strong resistance" compared with their North American counterparts.

From bat to worse

As with many invasive species, P. destructans most likely hitched a ride to North America with unsuspecting humans. Spores of the fungus can stick to shoes, clothing and equipment used by spelunkers, who then inadvertently carry them to new caves. And while the disease can also spread from bat to bat, big leaps like the 1,300-mile spread to Washington state point to people as a probable culprit.

"Such a massive jump in geographical location leads us to believe that we humans are most likely responsible for its most recent spread," says Katie Gillies, imperiled-species director for Bat Conservation International (BCI). Little brown bat populations have already fallen up to 98 percent in some Eastern states where WNS is prevalent, and the species is now under review by the FWS for listing as an endangered species.

Not only is this bad news for West Coast little brown bats, Gillies adds, but also many other western bat populations that had been insulated from WNS until now.

"This is a terrible new chapter in the fight against WNS," Gillies says. "We have as many as 16 western bat species that are now at risk. We have always feared a human-assisted jump to a western state. Unfortunately, our fears have been realized, and western North America — a bastion of bat biodiversity — may now expect impacts like we have seen in the East."

Losing any native species is bad, but bats are especially beneficial to humans. One little brown bat can eat hundreds of mosquitoes per hour on summer nights, and insect-eating bats overall save U.S. farmers roughly $23 billion per year by eating crop pests. Many insects simply avoid areas where they hear bat calls.

A wing and a prayer

This disease is undeniably horrible, and its emergence on the West Coast opens a new front in its war on American bats. Yet some hints of hope have emerged in recent years, raising the chance that we can at least do something to help bats.

In Vermont, for example, a cave that has been ravaged by WNS since 2008 abruptly began showing signs of improvement in 2014. Higher survival rates suggested bats may be developing resistance, but scientists were quick to keep expectations low. Other researchers have found promising treatments for WNS in bacteria, including a common North American soil bacterium — Rhodococcus rhodochrous (strain DAP-96253) — that was used to successfully treat WNS-infected bats last year.

"We are very, very optimistic" about the new treatment, U.S. Forest Service researcher Sybill Amelon told MNN at the time, after several dozen treated bats were released in Missouri. "Cautious, but optimistic."

Still, scientists say any significant rebound is likely decades away at best. The focus for now is on containing the spread of WNS, both by closing public caves and making sure spelunkers take proper precautions.

"Bats are a crucial part of our ecology and provide essential pest control for farmers, foresters and city residents, so it is important that we stay focused on stopping the spread of this fungus," Ashe says. "People can help by following decontamination guidance to reduce the risk of accidentally transporting the fungus."