The same fungal species wiping out hibernating American bats also strikes their European kin — although it doesn’t kill them. But that’s not because the European strain of the fungus that causes white-nose syndrome is less virulent, a new study finds.
“The European version is even nastier than the North American one,” says Craig Willis, a wildlife biologist at the University of Winnipeg in Manitoba. The surprise finding emerged from a trial in which he and his colleagues infected 36 healthy Canadian little brown bats with the fungus Geomyces destructans.
Half of the animals got fungus isolated from North America, the others fungus from Europe. All animals quickly developed white-nose syndrome, a disease named for the telltale mask of threadlike fungal growths it leaves on bat faces. Harder to see but more devastating, G. destructans eats through the skin of a bat’s wings and begins digesting inner tissue.
Bats receiving the European strain of the fungus died about a month sooner than those infected with the American strain, Willis and his colleagues report online April 9 in the Proceedings of the National Academy of Sciences. These findings suggest the American strain is a recent immigrant from Europe, Willis says. Because the naïve populations the strain encounters in North America die so easily from infection, he suspects that the American strain of the fungus has evolved to be less deadly.
Jeff Foster, a wildlife disease ecologist at Northern Arizona University in Flagstaff, agrees. His team recently compared the entire genetic blueprint of G. destructans from both continents, confirming they are nearly identical. But slight genetic variability showed up among strains from throughout Europe, he notes, “whereas those from North America showed none.” That suggests the fungus only recently arrived in America.
Periodically, hibernating bats rouse, burning fat to briefly bring their temperature up to normal. Willis’s new study found that compared to healthy bats in the lab, those infected with the American fungal strain roused three times as frequently — and those with the European strain four times as often — during hibernation.
This explains why white-nose victims became emaciated, Willis says, with some too weak to rouse at all: “They just run out of fuel.” Uninfected bats, by contrast, remained relatively fat and healthy throughout the trial.
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Up to nearly 7 million North American bats have succumbed to white-nose syndrome since late 2005, the U.S. Fish and Wildlife Service estimated in January. And the disease continues to spread.
On April 2, the Missouri Department of Conservation announced the disease had hit its state, the first time it has crossed the Mississippi River. The infected animals were sick but still alive, says pathologist Carol Meteyer of the National Wildlife Health Center in Madison, Wisc.
Petitions to list three bat species — including the little browns — for protection under the Endangered Species Act are now under consideration, says national white-nose syndrome coordinator Jeremy Coleman of the FWS in Hadley, Mass. On April 6, his agency issued $1.4 million in contracts to Willis and others to further study the disease. “We need to know what the post–white-nose world means and what the prognosis is for the future,” Coleman says.