Nature Today | Snake fungus discovered in wild grass snakes in the Netherlands

Distribution and symptoms

The fungus Ophidiomyces ophidiicola causes the skin disease ophidiomycosis (also called ‘snake fungal disease’) in individual snakes. To date, the fungus has been found in 62 wild snake species on three continents, as well as in various domestic and (wild) snakes in the trade.

The fungus is associated with declining populations of several North American snake species. O. ophidiicola is only found in snakes and causes a skin disease that can be limited to small sores on the skin but can also lead to a fatal fungal infection. Snakes with a heavy infection are often lethargic, sunbathe an above-average amount and show reduced flight behavior. This also makes the animals vulnerable to predation.
An infection can be recognized by abnormally colored or shaped scales, yellowish to brown crusts, ulcers, swelling of the skin, subcutaneous nodules and an increased frequency of peeling. The infection can be recognized by small scars on molted skin. It is also possible for the fungus to be present on a host without visible symptoms. The fungus seems to occur mainly in species that prefer moist habitats.

The snake fungus in the Netherlands

Although cases of ophidiomycosis have been numerous in North America over the last two decades, only a few cases have been reported in Europe. O. ophidiicola has not yet been detected in the Benelux. To monitor the situation in the Netherlands, RAVON and Ghent University have been conducting research into the fungus since 2017. Between 2017 and 2023, molts, carcasses and skin swabs of 284 wild and captive snakes from the Netherlands, belonging to 22 species, were tested for the presence of the fungus. Two molts of wild grass snakes (Natrix helvetica) in North Holland tested positive for the presence of the fungus, although both molts had no visible abnormalities consistent with the disease. However, small sores on molts can easily be missed. The presence of the fungus can only be demonstrated through genetic research. This discovery is the first description of O. ophidiicola in the Netherlands. The article describing this discovery was published in the Flemish Veterinary Journal.

Different variants

Three different variants of this fungus have been described: Clade I, II and III. In Europe, at least two different variants are present in the wild (Clade I and II). Only Clade II is known in North America. Clade III has so far only been found in snakes in Southeast Asia and in captivity. Much is still unclear about the difference between the strains, such as pathogenic potential, interplay between the strains and climatic preference. Multiple strains are known to be present in farmed animals and in the trade. It is still unknown which variants we are dealing with in the Netherlands. Spill-over of new variants in Dutch nature due to released or escaped snakes is a real risk.

Follow-up research

The current distribution in North Holland and adjacent Utrecht, but also the degree of occurrence (prevalence) of the fungus in the grass snake population where the positive samples were found, is not yet known. This is essential information to find out at what epidemiological stage the spread of the fungus is, what is necessary to formulate possible next steps.

An attempt is also being made to determine which variants are present in the Netherlands and what the impact is on the body condition of individual snakes. An investigation was started in 2024 to obtain answers to these questions. In addition, reports from other parts of the country are also very welcome.

Call: report observations

Have you found a dead snake or seen a snake with suspicious symptoms, whether or not combined with abnormal behavior? Please take good photos (including good detail shots of the affected body parts), note the exact date and location and contact Tariq Stark at RAVON.

Have you found a peeling skin? Please store each piece in a dry and dark place at room temperature in a paper envelope (not in a plastic bag) and send it to RAVON, Attn. Tariq Stark, PO Box 1413, 6501 BK Nijmegen, stating your name, location and date.

More information

Thanks
The Ministry of Agriculture, Nature and Food Quality, the ‘Van der Hucht de Beukelaar Foundation’, the European Snake Society and the Herpetofauna Foundation are thanked for their financial support for this study.

Text: Tariq Stark, Wouter Beukema, Maarten Gilbert, Edo Goverse, Richard Struijk, RAVON. Also on behalf of An Martel, Frank Pasmans and Elin Verbrugghe, Wildlife Health Ghent, Ghent University
Image: Richard Struijk; Tariq Stark; Steven Allain, Allain et al. 2024