Examining Cytokine Biomarkers in Fecal Samples vs. Wing Tissue in Little Brown Bats Recovering from White Nose Syndrome

Over the past 18 years White Nose Syndrome (WNS)- the disease caused by the fungus Pseudogymnascus destructans ( Pd )- has been causing devastating population loss across 12 species of North American bats. Little brown bats ( Myotis lucifigus ) have been among the hardest hit species and up to 90% population loss within colonies has been observed, prompting the need for increased pathogen surveillance and study of disease progression to manage WNS in little brown bats as naive colonies are exposed to Pd. Assessing cytokines as a biomarker for disease severity, as well as to better understand the health of individual bats within colonies that are currently affected or recovering from Pd, will aid in a greater project developing a non-invasive colony assessment tool to determine the likelihood and degree of colony recovery. The host’s inflammatory responses, measured by mRNA expression of cytokines known to respond to Pd infection in Myotis (IL-6, IL-17α, IL-1β), were assayed in non-invasively collected sample (guano, n=431) and a minimally invasive biosample (wing biopsy, n=81 paired samples) to detect differential expression across individual bats of varying wing scores (a categorical descriptor of disease progression) and across colonies with varied responses to the Pd pathogen. We were particularly interested in testing the hypothesis that guano samples would be valuable as a non-invasive measure of host inflammatory status. Host mRNA was recovered in 378 of 431 samples from Myotis guano and all 81 skin biopsies. In both guano and wing tissue, there were significant correlations in expression of three biomarker cytokines after normalization for amount of RNA recovered (all p<0.0001), indicating that when host mRNA was detectable, any assayed cytokine could prove a useful indicator of host status. We did not detect any differences in the expression of IL-6 or IL-17α between early (responding) and late (healing) stages of the disease in skin biopsy samples, but noted a 33% decline in IL-1β mRNA expression between early and late disease stages (T=1.98, df=31, p=0.057). Significant differences in the relative expression of IL-17α (F7,275=2.494, p=0.017) and IL-1β (F7,288=2.278, p=0.03), but not IL-6 (F7,293=1.166, p=0.322), were detected across colonies in the guano samples using one-way ANOVA. Wing biopsy and guano mRNA expression were not correlated. Because high cytokine mRNA expression was found in wing biopsies, dose dependent lipopolysaccharide immune challenges were performed on little brown bat fibroblasts to better understand the extent of their cytokine expression. We found high cytokine expression in wing biopsies across individual bats of varying wing scores and across colonies of varying growth rates. U.S. Fish and Wildlife Service This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.