Worry grows over white-nose syndrome’s widening reach among bats
A disease killing more than a million with a mortality rate close to 100% continues to sweep across the country. First detected in New York in 2006, it is now found in 14 states in the East and South, leaving starvation and death in its wake, and is working its way westward.
This disease affects not people but hibernating bats. White-nose syndrome, so named because of the white fungus that grows on infected bats’ noses, was discovered last month in Oklahoma, the farthest west it has been seen. Since it first appeared in a cave near Albany, N.Y., four years ago, more than a million bats have died, and its reach now extends northward to Ontario, Canada, and southward to Tennessee.
The discovery in Oklahoma is particularly worrisome because the bats there share caves with Mexican bats that migrate to and from Argentina. If the Mexican bats come in contact with the fungus, they could spread it widely.
“I’m afraid of what next year’s map is going to look like,” said biologist DeeAnn Reeder of Bucknell University in Pennsylvania, who has been researching the disease since it was discovered. “It got farther than I expected this year.”
One possible nugget of good news: The fungus that is linked to the disease grows only in cold temperatures, so bats in milder climates with shorter winters may find a reprieve. “Everyone’s crossing their fingers that there’s a climate barrier,” said Nina Fascione, executive director of the Texas-based nonprofit Bat Conservation International.
In 2008, two years after the disease was first identified, researchers linked the fungus to the syndrome, Geomyces destructans. Exactly how it kills the bats is still a mystery, although scientists know it infects the bats’ skin and appears to interfere with the animals’ hibernation patterns.
During winter, healthy hibernating bats arouse about once every two weeks and in the two hours or so that they are awake, use more calories than in the entire two weeks of hibernation. In contrast, bats with white-nose syndrome wake up as frequently as every four days, speeding the depletion of their precious energy stores and in some cases leading to starvation.
“We’ve got to connect these dots to figure out how you go from skin infection to death,” said Reeder, who conducted the hibernation study.
Though some scientists believe that the sick bats wake up more frequently because the fungus is itchy and irritating, Reeder thinks the situation is more complex. She suspects that the first time a bat wakes in the winter, the immune system — which is mostly shut down during hibernation — detects the fungus. The animal’s system then attempts to mount a protective immune response, burning calories in the process. That leaves fewer resources to help the bat last out the winter.
Part of this immune response may also include the production of chemicals that can travel to the brain and change the bat’s behavior — maybe causing it to wake up more frequently, Reeder said.
“I think this is going to end up being a sort of complicated story,” she added.
As the white-nose syndrome continues to spread, the importance of bats to the environment is coming sharply into focus.
“These bats are major regulators of ecosystems,” Reeder said. “For those million bats that are dead, 692 tons of insects are not being eaten this summer. You can put numbers on the amount of pesticides that farmers don’t have to put out because of those bats.”
Bat-lovers are particularly concerned about how this disease is affecting species whose populations were already at risk. Numbers of gray bats in the South had been recovering because of conservation efforts over the last 30 years, and the species was poised to be removed from the endangered species list.
But with the appearance of white-nose syndrome, their prognosis again looks grim. “We had people in the office literally in tears” the day the disease was found in gray bats, Fascione said.
Although many unknowns remain about this baffling syndrome, researchers continue pushing forward. “It’s probably going to make it all the way to California before we can do anything to stop the disease,” said Thomas Tomasi, a biologist at Missouri State University. “But if we can slow it down, if we can decrease the number that die from this disease, it’s worth a shot.”
In an interesting twist, the fungus that may be responsible for white-nose syndrome was also discovered in bats in France in 2009. However, it doesn’t appear to kill the bats there. Some researchers speculate that the fungus swept through Europe 100 to 200 years earlier, killing off most of the population but leaving behind a small number of bats that were genetically resistant. Those bats, the theory goes, then repopulated the region.
This suggests that, in time, the American bat population may recover as well.