A Disease That Is Wiping Out Bats Spreads Across the U.S.
A deadly fungal disease called white-nose syndrome is wreaking havoc on North American bat populations, spreading farther and faster last year than ever before, according to a new report by the U.S. Geological Survey’s National Wildlife Health Center.
The result: a severe, accelerated loss of bats in the United States, with populations in some caves falling 90 to 100 percent.
That could have significant consequences for both the United States economy and its food supply, according to David Blehert, a U.S. Geological Survey white-nose syndrome researcher based in Madison, Wisconsin.
“Bats are major predators of insects, and it has been estimated that they provide pest-control services to U.S. farmers valued at greater than $3.7 billion per year,” Blehert said. “Globally, bats are also important seed dispersers and pollinators.”
White-nose syndrome is caused by the fungus P. destructans, or Pd, and is named for the distinctive white fungus that tends to collect along infected bats’ muzzles. It has killed more than 6 million hibernating bats in North America since the winter of 2006–07, when it was first detected on a bat in a cave near Albany, New York.
White-nose syndrome has spread to 29 states—up four states since fall 2015—as well as five Canadian provinces. This year scientists have detected Pd in 32 states and five Canadian provinces and in more caves than ever.
White-nose syndrome leapfrogged to the West Coast when it was detected in a dead bat found in Washington state in March.
How is the disease spreading so far, so fast? Turns out, people might be partly to blame.
The fungus thrives in cold, damp caves, where it readily disperses spores. The spores can survive for years in soil, water, and bat guano. “If a human enters [a cave] contaminated with Pd, that individual may accumulate infectious spores on their clothing, gear, or shoes, which creates risk for transferring the fungal pathogen to new locations,” said Blehert.
Bats contract white-nose syndrome from either their environment or direct contact with other bats. That bats naturally cluster together when hibernating helps facilitate the spread of disease during the winter months they spend hanging from the ceilings of caves.
On a bat, white-nose syndrome colonizes skin tissues, causing severe skin lesions and an accumulation of snow-like white fungal fluff on the muzzle—the disease’s namesake symptom. The disease also causes bats to engage in erratic behaviors that disrupt hibernation, resulting in dehydration, starvation, and death.
The U.S. Fish and Wildlife Service recommends that anyone who spends time in caves—usually researchers and recreational cavers called spelunkers—follow the agency’s white-nose syndrome decontamination protocol. The elaborate procedure involves the washing of bodies, clothes, vehicles, and equipment. Some cavers skip it, spend less time in caves, or simply stop caving altogether, said Jennifer Foote, white-nose syndrome liaison for the National Speleological Society, a national caving association.
“A lot of us have reduced the amount of cave trips and gear we bring into caves because we have to consider the time and damage to our gear caused by decontamination,” said Foote. “It has made it more stressful than relaxing to go out and enjoy nature.”
In an effort to quell the spread of disease, the Fish and Wildlife Service, with the support of the U.S. Geological Survey and state wildlife agencies, restricts access to caves where white-nose syndrome has been detected.
Over the past seven years, scientists have made significant strides in understanding the pathology of white-nose syndrome and why North American hibernating bats are most vulnerable to disease.
Genetic research on the white-nose syndrome fungus and affected bats has played a big role in that understanding: On Wednesday, experts at the U.S. Geological Survey announced the strain of the disease found in the sick Washington state bat was genetically similar to strains found in the Eastern United States. Scientists say this could be evidence that humans spread the disease west across the continent rather than it being brought to the U.S. from Asia, another possibility they had considered.
But they haven’t been able to stop the syndrome, and the long-term effects of a massive bat die-off are not well understood. What is certain: We can’t live without these winged creatures.