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. 2025 Feb 5;11(2):118.
doi: 10.3390/jof11020118.

Nationwide Screening Unveils Endemic Ophidiomyces ophidiicola Presence in Northern Italy, Mainly Affecting Dice Snakes: Evidence from Contemporary and Historical Snake Samples

Matteo Riccardo Di Nicola  1   2   3 , Kevin P Mulder  1 , Elin Verbrugghe  1 , Federico Storniolo  4 , Naomi Terriere  1 , Luca Colla  5 , Roberto Sacchi  4 , Giacomo Vanzo  4 , Giovanni Zanfei  6 , Daniele Marini  7   8 , Frank Pasmans  1 , An Martel  1
Affiliations

Nationwide Screening Unveils Endemic Ophidiomyces ophidiicola Presence in Northern Italy, Mainly Affecting Dice Snakes: Evidence from Contemporary and Historical Snake Samples

Matteo Riccardo Di Nicola et al. J Fungi (Basel). .

Abstract

Ophidiomycosis, caused by the keratinophilic fungus Ophidiomyces ophidiicola (Oo), is an emerging threat to snake populations, yet its epidemiology in Europe remains underexplored. We investigated the distribution of Oo across free-ranging snake populations in Italy, integrating both recent field samples and historical museum specimens. Our survey involved 423 snakes representing 17 species from 17 regions, with Oo detected in 32 snakes from five different species. Additional molecular detection for Parananniziopsis spp. on a subset of 13 Oo-negative samples from snakes that exhibited clinical signs yielded negative results. Acknowledging the non-standardised sampling and the limited sample size, our findings highlight Oo's persistent and widespread presence across diverse ecological zones, particularly affecting semi-aquatic species like Natrix tessellata. While Oo Clade I was primarily found in museum specimens, indicating a historical presence, Clade II prevailed in recent samples. This highlights a complex epidemiological landscape where different clades may influence the current disease dynamics. Our results underscore the importance of continuous surveillance and highlight the need for standardised sampling to better understand snake fungal disease ecology and epidemiology in Italy.

Keywords: EIDs; Europe; Natrix; SFD; fungal pathogens; infectious disease; mediterranean; ophidia; ophidiomycosis; serpentes.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Number of sampled snakes (grey) and Oo-positive snakes (red) by species and region. Data from previous national studies are also included.
Figure 2
Figure 2
Proportion of Oo-positive snakes among contemporary samples, by period of the year. The x-axis shows the first (I) and second (II) halves of each month starting from February and ending in September. Data from previous national studies are also included.
Figure 3
Figure 3
Percentage of snakes with gross signs among contemporary samples, by period of the year. The x-axis shows the first (I) and second (II) halves of each month starting from February and ending in October. Data from previous national studies are also included.
Figure 4
Figure 4
(A) Distribution of Oo detection among gross signs presence/absence in contemporary samples (N = 353). (B) Distribution of Oo detection among age classes in contemporary samples (N = 444). Red indicates Oo positives, grey Oo negatives. Data from previous national studies are also included.
Figure 5
Figure 5
(A) Map of central and northern Italy showing the national distribution of Oo-positive samples and Oo clades. Map created using QGIS 3.28 with ESRI Satellite imagery. (B) Number of sampled snakes per region in order to visualise sampling effort. Data from our previous national studies are also included.
Figure 6
Figure 6
Histological images from selected Oo qPCR positive snakes. (A) Natrix tessellata (ID 360 in Table S5). Low magnification of necrotic serocellular crust with myriad fungal hyphae within the epidermal necrotic debris and inflammatory elements. (B) Hierophis viridiflavus (ID 243 in Table S5). Necrotic epidermis showing PAS-positive fungal hyphae and arthroconidial tuft at the air–lesion interface (red arrows). (C) Hierophis viridiflavus (ID 258 in Table S5). Epidermis with mild spongiosis, transmigrating heterophils (yellow arrows), and multifocal necrosis, with the presence of several hyphae and conidia (red arrow). (D) Hierophis viridiflavus (ID 258 in Table S5). Fungal hyphae (parallel walls, minimal undulation, occasional transverse septations, non-dichotomous and acute angle branching—highlighted by red arrows) within the epidermal necrotic debris.
Figure 7
Figure 7
Fixed effects of predictors on the probability of snakes testing positive for Oo infection, implemented in the first GLM. (A) The presence of gross signs was significantly correlated with a positive effect on the likelihood of positive detection in all species; the correlation was significantly higher in N. tessellata compared to other species. (B) No effect was found for the age class.
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