Following the pattern observed in neighboring states, white-nose syndrome, a disease that can be fatal to hibernating bats, has now been confirmed in six Minnesota counties, according to the Department of Natural Resources.
The disease has recently been confirmed in Becker, Dakota, Fillmore, Goodhue and Washington counties. Minnesota’s first confirmed case of WNS was in St. Louis County last March.
The disease is named for the white fungal growth observed on infected bats. It is not known to pose a threat to humans, pets, livestock or other wildlife.
The recent DNR bat surveys have recorded declines in the annual bat count ranging from 31 to 73 percent in locations where WNS has been confirmed. The 73 percent decrease was observed at Soudan Underground Mine in St. Louis County, where the disease was first confirmed in Minnesota a year ago. DNR biologists think the sharp decline there may reflect how long the disease has been present.
With WNS confirmed in Fillmore County in southeastern Minnesota, the count at Brightsdale Tunnel was down 39 percent from last year, and the count at Bat River Cave decreased 31 percent.
“While some locations are still testing negative, the results of recent surveys lead us to conclude that WNS is likely to be present anywhere bats hibernate in Minnesota,” said Ed Quinn, DNR natural resource program supervisor. “Four of Minnesota’s bat species hibernate, and four species migrate. WNS will have a substantial effect on Minnesota’s hibernating bat population. Neighboring states have reported declines of 70 to 95 percent in specific locations, as we recorded this year at Soudan Mine.”
Although the disease is transmitted primarily from bat to bat, people can inadvertently carry fungal spores to other caves on clothing and caving gear. For several years, public tours of Soudan Underground Mine and Mystery Cave have begun with a brief lesson on how to prevent the spread of WNS. Both before and after tours, visitors are required to walk across special mats designed to remove spores from footwear, and they are advised not to wear the same clothing, footwear or gear when visiting other caves or mines where bats may be present. Multiple washings in a standard washing machine will not provide sufficient decontamination.
Tours will continue at Soudan Underground Mine and Mystery Cave, where the DNR will continue to follow recommended national decontamination protocols to prevent human transport of fungal spores. The DNR urges owners of private caves to learn about WNS and take similar visitor precautions as outlined in the protocols.
The DNR is working with federal and state officials to consider a variety of treatment trials, to test new fungicides that may kill WNS spores. Treatments are unlikely to eradicate WNS, but could slow the spread and reduce the number of bat deaths.
DNR biologists conduct winter bat counts in several Minnesota hibernacula each year. “We use these counts to compare the number of bats in a site from year to year. Although we count all of the bats that we see, more are likely in areas we can’t reach,” said DNR mammalogist Gerda Nordquist.
WNS was first documented in North America in 2007 in eastern New York and has since spread to 30 states and five Canadian provinces, killing more than 5.7 million bats.
Nordquist encourages anyone who sees a sick or dead bat to submit a Bat Observation Report. DNR staff reviews these reports and additional follow-up or testing is conducted as needed.
To learn more about WNS and Minnesota’s bats, visit mndnr.gov/wns.