Ultraviolet fluorescence as a field-applicable screening tool for lesions consistent with ophidiomycosis in lake erie watersnakes (Nerodia sipedon insularum)

Ophidiomycosis, commonly called snake fungal disease, has been linked to significant morbidity of free-ranging snakes in North America and Europe. Diagnosis of ophidiomyco-sis currently requires detection of skin lesions via physical exam or characteristic histopathology as well as detection of the causative agent, Ophidio-myces ophidiicola, through quantitative (q)PCR or fungal culture of a skin swab or tissue sample. While reliable, these methods require specialized training, invasive procedures (e.g., biopsy), and several days or weeks to receive results. Addition-ally, screening entire populations can quickly become costly. A fast, easy-to-use, cost-efficient, and sensitive screening tool is needed to optimize conservation strategies and treatment interven-tion. Our objective was to investigate the association between skin fluorescence under long-wave ultraviolet (UV) light (365 nm) and the detection of Ophidiomyces ophidiicola DNA using qPCR. Fifty-eight Lake Erie watersnakes (Nerodia sipe-don insularum) collected in June of 2018 and 2019 from islands in western Lake Erie, Ottawa County, Ohio, US were visually inspected for skin lesions, photographed under natural light and UV light, and swabbed for qPCR analysis. Fluorescence was highly associated with the presence of skin lesions, and the presence of at least one fluorescent skin lesion was 86% sensitive and 100% specific for identifying animals with appar-ent ophidiomycosis, with a positive predictive value of 100%. While we recommend performing standard diagnostics along with fluorescence, our study supports the use of visual UV fluorescence identification as a preliminary, affordable, nonin-vasive, and field-applicable method to screen populations for ophidiomycosis.