White-nose syndrome comes to the West
Researchers race to find solutions for deadly bat disease.
The disease that’s wiped out at least 7 million bats in the East and Midwest has now jumped to the West. Hikers in Washington, 30 miles east of Seattle, found a sick little brown bat on March 11 and took it to a wildlife sanctuary, where it died a few days later. The USGS National Wildlife Health Center analyzed the remains and announced that it had white-nose syndrome, a fungal infection that irritates bats and rouses them from hibernation in the dead of winter. They leave their caves to forage, but soon starve from lack of insects. Once the infection gains a foothold in a bat colony, the mortality rate can reach 99 percent.
The deadly disease has jumped more than 1,300 miles from where it was last detected, in Nebraska and Minnesota. “This news is extremely disappointing and unnerving,” says Jeremy Coleman, national white-nose syndrome coordinator for the U.S. Fish and Wildlife Service, adding that it’s probably been spreading in Washington, and perhaps other parts of the Northwest, for a while. "Researchers in Eastern caves have found that it can take a few years for fungal loads to build up to the point of causing disease in bats," says Coleman, "so it may be that the fungus has been in the area for a few years already and is widespread.”
As to how white-nose syndrome reached Washington in the first place, the most likely explanation is that a caver visited an infected cave in the East, then carried spores on gear or clothing to the Cascades. The stricken bat seems to be a Western subspecies of little brown bat, Coleman says, so it probably wasn’t a bat from back East that somehow got translocated. Another possible, but unlikely, route for transmission could have been a shipping container from Asia or Europe that came into Seattle or Vancouver carrying an infected bat. State and federal researchers will be combing the area where the bat was found to try to locate other sick bats, and the public is also requested to notify the Washington Department of Fish and Wildlife about any bats they find dead or see flying in the daytime — usually an indication of illness.
Because white-nose syndrome requires cold and humidity to thrive, it’s not clear yet how the disease might affect the West’s bat populations. Some Southwestern species, like Mexican free-tailed bats, don’t hibernate and hence may not be affected by the pathogen. Other species that do hibernate in chilly, higher-altitude caves, like little brown bats, are vulnerable, but perhaps less so than in the East, where bats congregate for the winter in immense numbers. “We don’t know if it will rip through populations here like it did in the East, or whether it will kill fewer because they don’t hibernate in such big groups,” says Marm Kilpatrick, an associate professor in the Department of Ecology & Evolutionary Biology at the University of California, Santa Cruz.
The Fish and Wildlife Service released an updated “cave access advisory" in March to try to lessen disturbance of hibernating bats and slow the disease’s spread; it calls for precautions such as cave and mine closures and decontamination procedures. The Forest Service, Bureau of Land Management, National Park Service and other federal agencies will decide how to implement its recommendations. In certain areas, like the Rocky Mountain Region of the Forest Service, some requirements are already in place, such as registration before entering caves, seasonal cave closures and decontamination protocols.
Meanwhile, researchers are scrambling to find tools and treatments, but the wide variety of habitats and behaviors among bat species mean that no single solution will work. “We’re really trying to develop a broad toolbox,” says Coleman, “treatments that can be deployed in advance of the fungus, as well as treatments that improve the ability of bats to survive. We need things that can be used without a lot of hands-on effort, and can scale up easily.”
The tools being investigated include probiotic treatments, substances with antifungal properties (like chitosan and even other fungi species), and possible vaccines.
Researchers, including Tina Cheng and Joe Hoyt at UC Santa Cruz, have been studying bacteria that have antifungal properties (see our story, “Crisis biology: can bacteria save bats and frogs from deadly disease?”), which could be incorporated into a spray to be used on bats or on the cave itself. According to Kilpatrick, at least three possibilities are in the lab trial stage, and one could be used in field tests as early as this fall.
A chemical cleaning compound is also showing promise as a way to reduce fungal contamination in caves, says Kilpatrick. Within two years of the fungus’s first appearance in a cave, it typically has spread to at least a third of the cave surfaces, making it much more likely that bats will come in contact with it. “We want to push back the date of first infection by reducing cave contamination,” he says. Bats that contract white nose syndrome typically live about three months, so if they get infected early in the winter, they die. But if they get infected later, their odds are much better. If they emerge from hibernation in spring, when there are enough insects to eat, the bats gain strength and can actually clear the infection on their own over the summer.
The caveat, though, is that the chemical might also affect other forms of cave life, so it can be used only in artificial habitats, like abandoned mines. “Most of us would be happy to even have tools that just worked in manmade habitats,” Kilpatrick says, because it could help keep bat species from completely blinking out. At least one Eastern bat, the northern long-eared, is now close to extinction thanks to the disease. Such a treatment could help scientists maintain small populations of vanishing bat species while longer-term solutions are developed.
And if you’re wondering what the West, and the rest of the world, would be like without bats, check out this video, by John Hoekstra, chief scientist of the World Wildlife Fund. A few hints: No brazil nuts. More mosquitoes. And another billion dollars of pesticides applied to crops every year.
Jodi Peterson is a senior editor with High Country News. Follow @Peterson_Jodi
