...Title Should Read DEADLY FUNGUS OUTLIVES BATS
The deadly fungus decimating bat populations across a growing swath of North America appears to be a more hardy foe than previously thought, able to live in the soil of caves long after all of the bats have died, according to a new study by Wisconsin researchers.
The disease caused by the fungus, white-nose syndrome, has killed an estimated 5.5 million bats in the eastern United States since it was identified in the winter of 2006-'07.
While the disease does not appear able to spread to humans, it has strong implications for agriculture. Bats are prolific consumers of insects that damage crops. A single little brown bat can consume 1,000 insects in a single night.
A 2011 study found that the bat die-offs due to white-nose syndrome could cost American agriculture anywhere from $3.7 billion to $53 billion a year. The U.S. Geological Survey has estimated that bats provide an annual benefit to Wisconsin agriculture of between $658 million and $1.5 billion.
White-nose syndrome causes hibernating bats to wake up much more frequently than they should, causing them to burn through fat reserves and eventually starve to death.
The new research, published last week in the journal Applied and Environmental Microbiology, deals a blow to the theory that after the disease has killed off its hosts, bats might be able to recolonize the same caves and rebuild their populations.
"This is going to be a lot harder a disease to deal with than maybe we had hoped," said Jeffrey M. Lorch, one of the study's authors and a research associate in the Department of Forest and Wildlife Ecology at the University of Wisconsin-Madison.
Lorch and his colleagues examined 14 bat hibernation sites inside the areas where the disease has been found. The fungus, known as Geomyces destructans, was found in 11 of the 14 locations; in at least two of the caves where it was discovered, bats were no longer present.
"We know it can survive at least two years without a bat," Lorch said.
The finding is important because it may influence the regulations states impose to prevent the spread of the disease. Already some caves have been closed to prevent humans from aiding the spread of the disease.
There is evidence that the disease spread from one bat to another. So far there is no proof that humans have helped the disease migrate, but there is concern that humans could get the fungus on clothing and transport it hundreds of miles to states that have so far remained untouched.
The disease has yet to appear in Wisconsin, but DNA from the fungus has been found a little more than 30 miles from the state, in a state park in eastern Iowa.
Other fungal pathogens, including some that afflict trees, are also able to survive in soil.
Lorch said there is mounting evidence that white-nose syndrome was introduced to North America from Europe. However, the fungus has been found on bats in Europe that don't appear to be sick. This may be a sign that European bats have developed some level of resistance to the fungus.