Science: Researchers Identify Fungus Implicated in Bat White-Nose Syndrome

Little brown bat with fungus on muzzle

Image courtesy of Al Hicks, NY DEC

It's Halloween season, and we'll see plenty of bat decorations and bat-inspired costumes. In some regions in the northeastern United States, however, bats themselves will be in short supply.

In the last two years, bat populations have been disappearing in some areas across Connecticut, Massachusetts, New York and Vermont, dropping by more than 75% in some caves and mines. The cause of the die-offs is a mystery, but many of the dead bats are found with a white fungus on their muzzles, ears and wings, prompting researchers to name the phenomenon "white-nose syndrome."

David Blehert, a diagnostic microbiologist at the United States Geological Survey's National Wildlife Health Center in Madison, Wisconsin, and his colleagues examined this fungus and determined that it is a cold-loving species that likely belongs to the genus Geomyces, which includes other species that colonize the skin of animals in cold climates.

These findings, described in a Brevium appearing online today at Science Express, are consistent with the possibility that the fungus is at least partially responsible for the bats' deaths, though more research will be necessary before scientists truly know what's causing white-nose syndrome.

The die-offs are curious because bats are fairly tough immunologically, carrying diseases like rabies, and the implications are particularly troubling since bats play important roles in insect control, plant pollination and seed dissemination.

"A single bat can eat up to 100% or more of its body weight in bugs each night, which can translate to over 3,000 mosquitoes per night," Blehert said. "Decreased bat numbers could lead to dramatic increases in insect populations leading to crop damage, tree defoliation, and perhaps increased incidence of vector borne diseases, such as West Nile Virus."

In their study, Blehert and colleagues took samples of fungus from over 100 bats, of several species, afflicted with white-nose syndrome. By culturing the fungus in the lab, the researchers discovered it prefers to grow at cold temperatures; warmer temperatures inhibit the infection. A genetic analysis suggested that the fungus belongs to the Geomyces genus, although the fungus' physical appearance is different from that of other Geomyces fungi.

The study authors see a possible parallel between this fungus and the lethal fungal skin infection that has caused a dramatic decline in global amphibian populations. They hope that a better understanding of what causes bat white-nose syndrome and how the disease develops will allow researchers and wildlife managers develop an effective strategy to protect the bats of the northeastern United States.

Kathleen Wren

30 October 2008