White nose syndrome, the deadly disease that is killing millions of North American bats, likely came from Europe, new research shows.
Named for the fuzzy fungus, Geomyces destructans, which grows on the nose, mouth, and wings of hibernating bats, the disease has killed at least 5.7 million bats in 19 states and four Canadian provinces since 2006. WNS White-nose syndrome has been documented in seven hibernating bat species, including two federally listed endangered bats, the Indiana and the gray bat.* While the fungus is found both in North America and in Europe, it hasn’t devastated bats across the pond.
One theory is that it’s an invasive species; another is that it naturally occurs in both places, but that the North American strain has recently undergone a deadly mutation.
So researchers, led by University of Winnipeg biologist Craig Willis, set out to see if the fungus is native or alien.
They collected 54 little brown bats from an uninfected cave in Manitoba and divided them into three groups: one inoculated with the European strain on the wing, another with the North American strain, and the third group wasn’t infected.
The first bat to die was from the European group, 71 days after inoculation; the rest of the bats were at the point of death by day 91. The first bat died from the North American strain on day 88, with the last bats euthanized on day 114. The control bats never got sick.
The fact that bats were susceptible to both strains of the fungus, and that the European strain was more virulent, “strongly supports the novel pathogen hypothesis that accidental introduction of Gd from Europe is responsible for the WNS-related mass mortality of bats in North America,” the authors write in Proceedings of the National Academy of Sciences.
So why aren’t European bats dying? It could be that they were exposed to the fungus long ago, and have since developed resistance to it. “Encouragingly, our findings suggest that European bats face little risk from the possible reintroduction of Gd from North America to Europe, although it would be useful to repeat our experiment with a European bat species,” they write.
The Wall Street Journal reports that, indeed, the team plans to conduct that experiment next year. In North America, meanwhile, "We are still working to understand if it is possible for bats to develop resilience or resistance to the fungus," Jeremy Coleman of the U.S. Fish and Wildlife Service who had no role in the latest work, told the newspaper.
The findings also provided further evidence that infection with the fungus causes bats to rouse more often from torpor, thus using up fat reserves too quickly and become emaciated. Why exactly they wake up more often—whether from the fungus causing a skin irritation, for instance, or because they’re dehydrated—remains uncertain.
For more information, visit the USFWS WNS site:
*This story was updated May 29, 2012 to reflect the US Fish and Wildlife Service's announcement that WNS has been documented in gray bats for the first time. Click here for the press release.