Idaho Detects White Nose Syndrome Fungus That Has Killed Millions Of Bats In North America; Economic, Ecological Implications

Idaho Fish and Game has received confirmation that six bats tested positive for a fungus that leads to a deadly disease known as “white-nose syndrome.” The bats were located in Minnetonka Cave in Bear Lake County, and it’s the first case of the fungus ever being detected in Idaho after a decade of testing.

The potential loss of bats has important economic and ecological implications for Idaho, and conserving bats is important to the state’s economy. Bats are voracious predators of insects, including many crop and forest pests, which makes them valuable to Idaho’s agricultural industry.

“We’re extremely concerned, but not surprised by this discovery,” said Rita Dixon, Idaho Fish and Game’s State Wildlife Action Plan Coordinator.” The fungus known as Pseudogymnoascus destructans, or Pd, and white-nose syndrome are found in neighboring states, and despite our best efforts to keep it out of Idaho, the fungus is now here.”

Dixon added only the fungus has been detected, not bats with white-nose syndrome, and no evidence exists that the fungus affects humans, pets, livestock, or other wildlife. Although no bats have been confirmed with the disease, discovery of the fungus is typically a precursor to bats eventually getting it.

Test results from Minnetonka Cave showed six of 33 bats swabbed in October 2021 tested positive for Pd. Samples were collected from individual bats emerging from the cave during a fall capture event led by Fish and Game, US Forest Service, and USGS National Wildlife Health Center.

Minnetonka Cave serves as a winter roost for at least seven bat species, and it is one of the largest and most species-rich bat habitats in the state. The six bats that tested positive for Pd included three species, Little Brown Myotis, Long-legged Myotis, and Yuma Myotis, all of which are known to be susceptible to white-nose syndrome. Testing was conducted at the USGS National Wildlife Health Center in Madison, Wisconsin.

The goal going forward, Dixon said, is to minimize the decline of resident bat populations should the fungus become established, and to reduce the likelihood of transmission to other sites.

Minnetonka Cave and adjacent lands are managed by the Caribou–Targhee National Forest. Fish and Game and the Forest Service have worked since 2012 to minimize the possibility of Pd introduction at Minnetonka Cave.

White-nose syndrome has been known to exist in the West since 2016 after being detected in Washington, and also confirmed in Montana and Wyoming. It is a deadly disease to hibernating bats spread primarily through bat-to-bat transmission, but possibly human-assisted transmission, such as clothing or equipment exposed to the fungus.

Since first detected in North America in 2006, white-nose syndrome has killed millions of bats and caused declines up to 90% to 100% at some sites. Because most bat species only produce one to two pups per year, it can take decades or longer for their populations to recover.

People can assist in the efforts to identify any bats in the state that may have white-nose syndrome by reporting more than five dead or sick bats at one location at the same time (within a week). Signs of white-nose syndrome include white or gray powdery fungus seen around the muzzle, ears, wings/limbs, or tail, and they are typically only seen November through May.

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