Post-brumation yeast mycobiota in Vipera berus (European adder): clinically relevant Candida parapsilosis oral dominance and diverse fecal communities compared with warmer-region snakes.

Snakes may harbor clinically relevant yeasts, yet the culturable yeast mycobiota of temperate snake species remains poorly characterized. We surveyed culturable yeasts from 17 fecal samples and 5 oral swab samples of Vipera berus (European adder) collected in European Russia immediately after spring emergence from brumation. Yeasts were isolated by culturing at multiple incubation temperatures and identified by conventional phenotyping and ITS region sequencing (ITS1–5.8S–ITS2). In total, 16 yeast species were recovered. Alpha diversity was significantly higher in fecal samples (median richness = 11.0; Shannon H′ = 2.32; Simpson’s index of diversity (1 − D) = 0.91) than in oral samples (median richness = 2.0; H′ = 0.46; (1 − D) = 0.22; Mann–Whitney U test, p < 0.001). Oral communities were dominated by Candida parapsilosis (mean relative abundance ~ 84%), whereas fecal samples showed greater compositional diversity, with Aureobasidium pullulans, Debaryomyces fabryi, and Tausonia pullulans among the most abundant taxa. Beta diversity analyses indicated differentiation between compartments (Bray–Curtis PERMANOVA pseudo-F = 71.01, R² = 0.78, p < 0.001; ANOSIM R = 1.00, p < 0.001), and this pattern was not explained by differences in dispersion (PERMDISP p = 0.49). Psychrotolerant yeasts (e.g., Aureobasidium subglaciale, Leucosporidium yakuticum, T. pullulans) were detected in post-brumation samples. Aggregated presence/absence comparisons with published snake datasets indicated region-specific differences in culturable yeast assemblages. Overall, V. berus may carry the clinically relevant species C. parapsilosis in temperate environments; however, determining whether this constitutes a true ecological reservoir requires evidence of long-term maintenance and transmission, which was not assessed in this study. These findings support further One Health-focused studies on exposure routes and transmission context.