Big brown bats ( Eptesicus fuscus ) overwintering outside the underground environment are not believed to play a role in the epidemiology of the disease white-nose syndrome (WNS), caused by the fungus Pseudogymnoascus destructans (Pd). Using quantitative real-time PCR (qPCR), we provide molecular evidence for Pd on four big brown bats overwintering in heated buildings in New Brunswick, Canada. Two of the affected individuals also had very mild, focal, pustular, fungal dermatitis identified microscopically. A third bat, which was qPCR Pd-negative, had similar fungal lesions. Despite determining that these fungal lesions were caused by a suspected ascomycete, the intralesional fungi were not confirmed to be Pd. These findings demonstrate that bats overwintering in heated buildings and other above-ground sites may have subclinical or preclinical WNS, or be contaminated with Pd, and could play a role in local dispersal of Pd. Our inability to determine if the ascomycetes causing pustular lesions were Pd highlights the need for ancillary diagnostic tests, such as in situ hybridization or immunohistochemistry, so that Pd can be detected directly within a lesion. As the host-pathogen relationship for Pd evolves, and where bat species are exposed to the fungus under varying temperature regimes, lesions may become less stereotypic and such tests could help define these changes.
Keywords: Big brown bat; Eptesicus fuscus; Pseudogymnoascus destructans; fungal infection; white-nose syndrome.