Deadly white-nose syndrome attacks bats with no end in sight

— -- A plague killing bats nationwide shows no sign of slowing, say biologists whose winter cave surveys indicate the "white-nose syndrome" that decimates bat populations is still spreading.

Starting from one cave in New York state in 2006, the fungal infection that preys on hibernating bats, has killed more than 5.5 million bats in 19 states. The bat deaths could cost farmers $3.7 billion in losses, biologists estimate, given the flying mammals eat insect crop pests, such as beetles, and pollinate plants.

Until recently, most of the losses took place in Northeastern states and eastern Canadian provinces. But over the winter, the syndrome struck bats in Missouri, as far west as it has been documented, and in Alabama, as far south. Two weeks ago, wildlife officials announced that signs of the fungus had turned up in a cave in a new state: Iowa.

"Epidemics are hard to predict, but we would certainly expect it to spread farther," says Jonathan Sleeman of the U.S. Geological Survey's National Wildlife Health Center, speaking at a now-annual symposium on white-nose syndrome held this month in Madison, Wis. "We are definitely seeing the syndrome in new states, and new (bat) species."

In May, U.S. Fish and Wildlife Service biologists announced the seventh kind of bat spotted with the fungus: gray bats, an endangered species found in Tennessee caves.

Another endangered bat, the Indiana bat, has suffered large losses in previous years. There are 25 hibernating U.S. bat species, four of them endangered, and all likely susceptible to the syndrome.

White-nose syndrome gets its name from the white fungus that grows on the face, wings and bodies of hibernating bats. Afflicted bats lose fat stores and behave oddly, flying outside caves during winter hibernation months in search of food, and clustering near cold cave and mine entrances.

Over the past winter, wildlife experts reported from the symposium, more points about the syndrome have become clear:

•The fungus appears identical to one seen on bats in much smaller colonies found in Europe, and spreads bat-to-bat during hibernation.

•Some bats, banded in studies, survive several years after an infection, raising hopes that the syndrome isn't inevitably deadly.

•A few bat species, such as Virginia Big-Eared bats, appear not to decline in great numbers despite infections.

"We know the disease is quickly spreading," USGS biologist David Blehert says. "The question is how will the disease manifest itself in bats as it spreads to new areas."

So far, cases in Alabama, Indiana, Kentucky, Tennessee and Missouri have not been attended by the huge die-offs of bat colonies (around 90%), for example, that have occurred in some cases in Northeastern caves. One area of research, Blehert says, is into whether different cave humidity levels, or simply fewer bat hibernation months, prevent the fungus from wreaking as much havoc on bats in more temperate states.

"We're seeing colonies in Northeastern states where the fungus is endemic (common), with much fewer bats now, similar to Europe," says Jeremy Coleman of the U.S. Fish and Wildlife Service. "One question is whether they will stay at those low levels, or could we see a large population rebound?" His response to his own question: "Certainly not in our lifetime," because of low reproduction rates in bats.

More likely, the fungus has wiped out some of North America's signature huge bat colonies forever, Blehert suggests. "I don't think we are going to see them develop some sort of immune system defense against the fungus." Instead, bats in small colonies, as in Europe, seem not to suffer its ravages. Their small numbers don't provide the fungus enough sustenance to ramp up its attacks as it does feeding off tens of thousands of bats in larger colonies, he says.

Where will the spread of the syndrome end? Likely at the Pacific Ocean, Blehert says. "These are flying mammals that meet in the wild and return to different caves. They fly over rivers and they fly over mountains," he says.