White-nose syndrome

White-nose Syndrome: An Emerging Disease in Bats


Pseudogymnoascus destructans (Pd) is the causative fungal pathogen of white-nose syndrome (WNS).  WNS is named for the characteristic white fungus which appears on hibernating bats, especially the muzzle. The disease was first detected near Albany, New York in February 2006. Since initial detection more than 10 years ago, WNS has been confirmed in 33 states and 7 Canadian provinces. WNS has been confirmed in Arkansas, Pd has been detected in Mississippi and Texas, increasing the potential of spread into our state. Currently, 12 bat species in North America have been identified with diagnostic symptoms of WNS, four of these species occur in Louisiana (Table 1). Pd has been detected without diagnostic signs of WNS in 6 additional species of bats, 4 of which occur in Louisiana.  


Pd is a psychrophilic (cold-loving) fungus which infects hibernating bats during winter torpor when body temperature decreases. Optimal growth of Pd occurs in more humid environments at ambient temperatures of 0⁰ to 15⁰ C.  The fungus invades hair follicles, tissue, sebaceous and sweat glands. After invasion, ear and wing skin is eroded. Healthy wings allow bats to maintain water balance and is critical to homeostasis. As skin is eroded, individuals become dehydrated and have electrolyte imbalances. Fungal growth results in more frequent arousal, increasing animal movement during seasonal periods of food or water limitations. Additionally, unique behaviors such as flying outside during the day or clustering at hibernacula openings increases metabolic activity. The increased activity levels reduce or completely deplete fat reserves which are critical for hibernation, resulting in mortality. 


To date, the disease is responsible for more than 6 million bat deaths in United States. In some locations infection has resulted in 90% to 100% mortality in a hibernaculum. Drastic declines in bat populations threaten some species to regional extinction, such as the little brown bat (Myotis lucifugus), which was one of the most common species of bat in North America. The spread of WNS over the last decade can potentially lead to diminished ecosystem services as a result of declining population numbers. Bats aid in seed and pollen dispersal as well as insect control. Insectivorous bat species feed largely on arthropods and airborne insects. They can consume hundreds to thousands of insects per hour, many of which are known vectors of disease to humans and other mammals. Additionally, they help control agricultural crop pests and aid in ecosystem stability.


Louisiana is on the geographical leading edge of Pd disease spread. Pd was first detected in Arkansas and Mississippi in 2013-2014, and Texas in 2016-2017. Since those first detections, Pd has continued to spread closer to Louisiana boarders, increasing the potential for spread into the state. Rafinesque’s big-eared (Corynorhinus rafinesquii), big brown (Eptesicus fuscus), eastern red (Lasiurus borealis), southeastern myotis (Myotis austroriparius), northern long-eared (Myotis septentrionalis), tricolored (Perimyotis subflavus), and Mexican free-tailed (Tadarida braziliensis), Horay (Lasiurus cinereus), Silver-haired (Lasionycteris noctivagans), and Evening (Nycticeius humeralis) bats occur in Louisiana. E. fuscus, M. austroriparius, M. septentrionalis, P. subflavus have been confirmed with diagnostic symptoms of WNS in other locations. Pd has been detected but without diagnostic sign of WNS in C. rafinesquii, L. borealis, L. noctivagans, and T. braziliensis.


In Louisiana bats typically roost in culverts and man-made structures due to a lack of available cave hibernacula. The Louisiana Department of Wildlife and Fisheries is working to monitor known bat hibernaculum and roost locations. To date Pd and WNS have not been detected in Louisiana. For additional information, visit https://www.whitenosesyndrome.org/. To see current WNS and Pd detection locations, visit https://www.whitenosesyndrome.org/where-is-wns.


If you observe bats exhibiting signs of Pd or WNS please report it to Nikki Anderson (NAnderson@wlf.la.gov) or Dr. Jim LaCour (JLaCour@wlf.la.gov).


Table 1. Bat species known to occur in Louisiana.

Bat species confirmed with diagnostic symptoms of WNS

Common Name


Big brown bat

Eptesicus fuscus

Southeastern bat

Myotis austroriparius

Northern long-eared bat  (threatened)

Myotis septentrionalis

Tricolored bat 1

Perimyotis subflavus


Bat species with Pd detection but no diagnostic signs of WNS

Common Name


Rafinesque’s big-eared bat

Corynorhinus rafinesquii

Silver-haired bat

Lasionycteris noctivagans

Eastern red bat

Lasiurus borealis

Mexican free-tailed bat

Tadarida brazi


Bats species currently unaffected by WNS or Pd

Common Name


Hoary bat

Lasiurus cinereus

Northern yellow bat

Lasiurus intermedius

Seminole bat

Lasiurus seminolus

Evening bat

Nycticeius humeralis