Fungus is cause of bat deaths

LOS ANGELES - Researchers say they now have proof that a fungus discovered in 2007 is responsible for white-nose syndrome, the devastating infectious disease that has killed more than one million bats in North America.

The confirmation is a significant step toward developing strategies to moderate effects of the disease as it continues to move westward along migratory flyways, the researchers reported Wednesday in the online journal Nature.

"We can now focus our research on managing one pathogen as the cause of this disease and the environment that brings animals and this pathogen together - caves," said senior researcher David S. Blehert, a microbiologist at the U.S. Geological Survey's National Wildlife Health Center in Madison, Wis.

"We could pursue ways in which environments such as caves and mines can be manipulated so as to be less conducive to the fungus but not harmful to bats," Blehert said. "Vaccination is also a strategy we could pursue. Although the study of bat immune systems is still in its infancy, vaccination can control other wildlife diseases such as rabies and plague."

The role of Geomyces destructans in white-nose syndrome - which gets its name from the powdery, white substance that appears around muzzles, ears, and wings of affected bats - was uncertain because of the assumption that fungal infections in mammals are usually associated with immune-system dysfunction, according to the report.

As the disease spread, researchers learned that a similar fungal growth had long been seen in hibernating bats in Europe. But they had not experienced a large-scale die-off. That fueled speculation that unidentified factors were the primary causes of the disease.

The new findings were based on studies of little brown bats with no underlying health conditions that were intentionally infected with the fungus. Those experiments confirmed that Geomyces destructans causes white-nose syndrome and that the disease can be transmitted by animals via direct contact.

The report also suggested that white-nose syndrome may have originated in Europe, where bats evolved with the fungus, and then made its way into North America's bat population, which had no time to adapt to the threat.

Since it was first documented in 2007 in New York state's Howe Caverns, the rapidly spreading fungus has swept across 19 states as far west as Oklahoma. It has killed mostly little brown bats, which have lost an estimated 20 percent of their population in the northeastern United States.

The fungus seems to prefer the 25 species of hibernating bats. But each of the 45 species of bats in the United States and Canada may be susceptible to white-nose syndrome, according to federal wildlife biologists. A study published in Science estimates that the value of pest control provided by bats each year is at least $3.7 billion nationwide.