White-nose syndrome, a fungus spreading like wildfire through hibernating North American bats, has just been reported in 12 European countries. But unlike the American epidemic, which typically kills 75 percent or more of exposed bats, the European infection has not been associated with mortality.
This suggests that Geomyces destructans, the fungus responsible, has been in Europe a long time, says biologist Sébastien Puechmaille of University College Dublin. “And when I say a long time, I mean thousands — if not tens of thousands — of years,” he says. “Our bats have likely coevolved with this fungus.”
White-nose syndrome first appeared four years ago in a hibernating colony of bats in New York state. Since then, it has wiped out an estimated million more at winter roosting sites across eastern Canada and the eastern United States. Tentative sightings — ones not confirmed by genetic analyses — turned up last year as far west as Missouri and Oklahoma, notes wildlife pathologist Carol Meteyer of the U.S. Geological Survey’s National Wildlife Health Center in Madison, Wis.
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Two years ago, Puechmaille’s group reported the first European sighting of G. destructans, in a French bat. Shortly thereafter, the fungus was spotted in three more countries. The new survey by Puechmaille and other European scientists in the April 27 PLoS ONE reports genetic confirmation of the infection in a total of eight countries and “compelling photographic evidence for its presence” in an additional four, including Romania and Turkey.
Infections were spotted from Denmark and the Netherlands to Estonia. The fungus’ southern range extends from western France through Germany and the Czech Republic to Ukraine. Of 107 bats examined, only two were dead. “And we’re pretty convinced that they died from completely unrelated causes,” Puechmaille says, “because we did not find the fungus in them.” Their surface infection appears to have occurred only after death.
“We have also, for the first time ever, isolated viable fungal spores from cave walls,” Puechmaille says. That suggests bats may become infected as they stir up spores while entering caves and mines for winter roosting.
In a Nov. 11 paper in BMC Biology, Meteyer and her colleagues outline how G. destructans appears to kill American bats. Although white-nose syndrome gets its name from the cottony fibers typically covering the muzzle of infected bats, the fungus can grow on any part of the animal.
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Its wings now appear to be the portal of entry. G. destructans drives through paper-thin wing tissue “like a bulldozer,” Meteyer says. The fungus digests the skin, then rootlike fungal hyphae — the active tissue — migrate in and begin replacing all bat tissue in their path. Along the way, the hyphae kill blood vessels, leading to the sudden and complete death of downstream tissues.
This wing damage probably fosters dehydration, Meteyer says, causing intensely thirsty bats to rouse from hibernation. It takes a lot of energy to wake, and hibernating bats have little to spare. Identifying why the fungus is not eating through the wings of European bats “is probably one of our best hopes to understanding the dynamics of this disease,” says Meteyer.