White Nose Syndrome Spreads Through USA Bat Population

Since 2006 an epidemic has been traveling across America, and it’s not swine flu. So called White Nose Syndrome was first identified in caves near Albany, New York, three years ago. Since then it has spread across the northeast United States and has recently been identified in six more caves in Virginia.

The tell-tale white marking of the muzzles and ears of the bats may not even be the cause of the bat mortality—although 99% of affected bats die, and are found to have the fungal infestation—it still isn’t clear if the fungus causes the deaths or is simply an opportunist infestation of already ill animals.

Bat deaths cause insect populations to spiral

Little Brown Bat populations have had the highest mortality rate, but Eastern Pipistrelles and Northern Long-Eared Bats have also been affected and it’s not simply a question of bats dying. The effects on the ecosystem as a whole may be profound because less bats means more insects, as bats are the highest consumers of nocturnal insect life around and without them predating on local insect populations, both households and farmers may find that pest species become rampant.

This is likely to mean increased use of insecticides on crops and that economic and environmental cost will be carried by the consumer in the end. Two species of endangered bats live in the region where the WNS has been discovered in the past month. These are Indiana Bats and Virginia Big Eared Bats. The latter has a densely populated cave system less than five miles from one of the caves where WNS has just been found.

An epidemic without a clear cause or cure

It’s still not clear what is killing the bat populations, but what is known is that bats with WNS wake up more frequently from their winter hibernation which means they use up their fat stores, forcing them to leave the caves to seek food before the insect populations are around so that they simply starve to death. It’s also unclear how WNS spreads: some experts think it travels from bat to bat, while others suggest that disoriented and weakened bats may simply seek out the nearest cave after leaving their home community, thereby transmitting the disease or condition to a new bat colony, but others believe that humans who move from cave to cave may be transmitting the infection on their clothing and equipment. As a result, caves where WNS has been confirmed are ruled off limits to recreational cavers although there is on system in place to police the warning signs placed outside caves.

Like bees, bats are dying from unknown causes

There are interesting, and worrying, parallels with the Colony Collapse Disorder being experienced by bees: in that nobody knows the exact cause, the means of transmission or what the effect of this population loss will be on the wider environment.

There are a few reasons for optimism. First, WNS is not known to directly affect humans and second, researchers have discovered that providing a heat source to bats infected with WNS may help them conserve their body heat better, meaning that they although they wake, they return to sleep when near the heat, which might be a way of keeping some infected populations alive next winter, while a definitive cure or treatment is still being sought.

Bats courtesy of basykes at Flickr under a creative commons licence