SAN FRANCISCO — Over the past four years, a mysterious white-nose fungus has struck hibernating North American bats. Populations in affected caves and mines can experience death rates of more than 80 percent over a winter. In desperation, an informal interagency task force of scientists from state and federal agencies has just launched an experimental program to fight the plague. Their weapon: a drug ordinarily used to treat athlete’s foot.
John Eisemann of the Agriculture Department’s Animal and Plant Health Inspection Service, better known as APHIS, in Fort Collins, Colo., mentioned the new program during his talk, here, at the American Chemical Society’s spring national meeting. He was describing legal tactics by which wildlife officials can thwart invasive vertebrate species with off-the-shelf chemicals.
He noted, for instance, how scientists have used a contraceptive vaccine — one designed to control white-tail deer populations — on rodents. It offered a nonlethal approach to reining in the population explosion of non-native fox squirrels on a University of California campus. In another instance, wildlife managers employed a cholesterol inhibiting drug to reduce sex hormone levels — and the urge to reproduce — among invasive monk parakeets. And on Guam, Eisemann’s team designed special traps baited with neonatal mouse carcasses. Each bait had been implanted with a child’s dose of acetaminophen, the active ingredient in Tylenol. It proved amazingly effective in strategically poisoning a major scourge, invasive brown treesnakes — and only that species.
The bat task force enlisted Eisemann’s help to make sure that whatever they tried would be legal. He’s the go-to guy for identifying what permissions, waivers or requests are required before wildlife managers can apply poisons or anti-fertility drugs. The Food and Drug Administration allows for some off-label use of an existing drug as a veterinary prescription. And that’s the tactic he arranged for the task force to use with the athlete’s foot drug .
Theoretically, Eisemann says, it should have been possible for scientists to apply to get the chemical officially registered — as in approved — for use on bats. But with the disease spreading like wildfire and the potential market for a white-nose therapeutic tiny, the time and expense didn’t seem feasible.
Afraid of upsetting the ecological balance of endemic fungi in caves, the scientists decided to pilot test the program in already perturbed and disturbed environments — two mines in upstate New York. In February, the researchers applied the antifungal medicine onto the noses of several hundred bats. It killed the fungus, Eisemann says. At least in test-tube studies with the fungus. Now the goal is to see if and how it might have affected the treated colonies’ die-off rate, since only a small share of any population had their noses rubbed with the antifungal drug.
Indeed, the scientists are hoping they might not need to treat the entire colony. “If there’s enough communal grooming,” Eisemann said, “they may only need to treat a certain percentage of the bats.”