Histopathology of tri-colored bats (Perimyotis subflavus) exposed to the fungus Pseudogymnoascus destructans under varying temperature and humidity conditions

This work is part of an experimental trial investigating the effects of microclimate conditions of temperature and humidity on a fungal pathogen, Pseudogymnoascus destructans (Pd), that causes white-nose syndrome (WNS) disease in hibernating bats. As part of the trial, tri-colored bats (Perimyotis subflavus) were exposed to Pseudogymnoascus destructans (Pd) and allowed to hibernate in chambers with a variety of temperature and humidity conditions. Bats were euthanized after 83 days. A portion of the wing was rolled around dental wax dowels, fixed in 10% neutral buffered formalin, processed and stained with periodic acid-Schiff, and assessed by light microscopy for evidence of fungal infection. Three types of cutaneous infection were described histologically, including characteristic WNS cupping erosions, neutrophilic pustules with fungal hyphae, and fungal hyphae in the stratum corneum with dermal necrosis. Bats with any of these three conditions were scored as WNS-positive by histology. Only 11% (10/95) of bats scored as positive by histology. Of the 10 bats scored as positive, 3 bats had cupping erosions containing fungal hyphae and 7 bats had either neutrophilic pustules containing fungal hyphae, dermal necrosis associated with intra-epidermal fungal hyphae, or both. Overall, lack of infection and disease outcomes in this experiment limited our ability to make robust conclusions about the influence of microclimates on the development of WNS in bats.