(Updates with fungus origin being unclear in the sixth paragraph.)
Oct. 26 (Bloomberg) -- A fungus is at fault for the deaths of 1 million North American bats, according to a study that’s the first to pinpoint the cause for a phenomenon that scientists say may spur agricultural losses of $3.7 billion a year.
The next question is how to attack it, said researchers at the U.S. Geological Survey in Madison, Wisconsin, who identified the Geomyces destructans fungus in a report today in the journal Nature. The flying mammals eat as much as two-thirds of their own weight in bugs nightly, including mosquitoes, grasshoppers, locusts and moths that can spread disease and devastate crops.
“There’s no magic bullet I could deploy tomorrow to cure this,” said David Blehert, a study author and a researcher at the geological survey in Madison, Wisconsin, in a telephone interview. The finding “gives us epidemiology and can help in the development of a strategy.”
A May 2010 report from the U.S. Fish and Wildlife Service identified the number of bats killed, and a study in the journal Science in April said the animals eating habits are worth about $74 an acre in helping farmers suppress pests.
The fungus caused the disorder known as white-nose syndrome. In the study in Nature, 29 healthy little brown bats exposed to the fungus culture got the syndrome. They also observed that sick bats could infect healthy ones.
Researchers have been chasing a cause for the killer illness since 2006 when it was first noted in a photograph taken by a recreational spelunker in New York, said Blehert said. The scientists said it’s unclear where the fungus came from. The bats catch the illness through physical contact, and the disease isn’t spread through the air.
In 2007, state biologists noticed their bat hibernation count was unusually low and, in 2008, other organizations joined the investigation, including the U.S. Fish and Wildlife Service, the Vermont Fish and Wildlife Department, the Northeast Cave Conservancy, and the National Speleological Society.
The disease only affects hibernating bat species, which account for a little over half of the 45 varieties in North America. Nine species are known to be affected and some are now threatened with extinction, the 2010 Fish and Wildlife report said. Bats are vulnerable to fungal infection during hibernation because they congregate in large numbers in caves, sometimes packed so densely it’s difficult to see the wall behind them.
“So it’s like little children who go to a large daycare center, they bring home more colds,” Blehert said.
The bats’ immune systems may also be suppressed as they hibernate, in order to help the animals conserve energy.
Most pathogens hibernate in colder weather, along with their hosts. If G. destructans reproduces in cooler temperatures, it may be able to outwit a hibernating immune system, causing the die-off, Blehert speculated.
While lesions caused by white nose syndromes can be detected in late September, bat die-offs don’t start until the end of January and peak during March.
Preliminary data shows that if infected bats are removed from hibernation, warmed, and given food and water, they can recover from white nose syndrome, Blehert said. That may suggest one strategy for maintaining bat populations.
--Editors: Reg Gale, Bruce Rule
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