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Bats with white-nose-syndrome
Bats show signs of infection by the fungus that causes white nose syndrome. (Credit: Kim Miller / USGS)

Genetic analysis has shown that the first West Coast case of white nose syndrome, a disease that’s killing millions of bats across America, was probably caused by a fungal strain that came from the eastern U.S. rather than from across the Pacific.

The findings, published today in the journal mSphere, resolve part of the mystery surrounding the case, which was reported in March in King County near North Bend, Wash. They also have implications for battling the spread of the disease.

White nose syndrome is caused by a fungus known as Pseudogymnoascus destructans, or Pd for short. The fungus grows on the nose, wings and ears of infected bats during winter hibernation, giving them a white, fuzzy appearance. When Pd invades the skin tissue, it causes extensive internal damage, disrupting hibernation and causing mass deaths.

The disease has been detected in 25 states and five Canadian provinces, but the Washington case is the only one that’s been confirmed west of the Rockies. (The fungus was later detected on a silver-haired bat collected in King County, but that bat was unaffected by the disease.)

Scientists extracted DNA from the fungus on the little brown bat that died and sequenced its genome to trace the pathogen’s origin.

One possibility is that the Pd fungus was brought in from Eurasia – perhaps by bats, people or goods that somehow made the trip eastward to the Seattle area by air or sea. The other possibility is that the fungus somehow made a long westward jump from the eastern United States.

Scientists found that the genetic signature of the fungus is more akin to strains from Wisconsin, New York and Alabama than to strains from the Czech Republic. That supports the view that Pd took the westward route.

Some researchers have suggested that the fungus was brought to North America from Europe years ago, perhaps on the clothes or boots of cave explorers. But it’s not yet clear whether the fungus was transported to Washington state by migrating bats, by humans, or by some other carrier.

White nose syndrome map
This map shows the distribution of cases of white nose syndrome on a county-by-county basis as of last month. (Credit: Lindsey Heffernan / PA Game Commission)

“Although it remains unclear how Pd reached Washington, this finding guides us to look to North America as the source,” Jonathan Sleeman, director of the U.S. Geological Survey’s National Wildlife Health Center, said in a news release. “Now that Pd has been identified in the western U.S., it’s critical to continue working with resource managers to help conserve imperiled bat species, which are worth billions of dollars per year to North American agriculture and forestry.”

White-nose syndrome is not known to pose a threat to humans, pets, livestock or wildlife other than bats.

The Washington Department of Fish and Wildlife has a list of recommendations for reducing the risk of spreading the disease, and is providing online reporting forms for sightings of sick or dead bats as well as bat colonies in general.

The authors of the mSphere study, “First Detection of Bat White-Nose Syndrome in Western North America,” include Jeffrey Lorch, Jonathan Palmer, Daniel Lindner, Anne Ballmann, Kyle George, Kathryn Griffin, Susan Knowles, John Huckabee, Katherine Haman, Christopher Anderson, Penny Becker, Joseph Buchanan, Jeffrey Foster and David Biehert.

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