Snake Fungal Disease in Georgia

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This indigo snake from southern Georgia, with a suspect scale behind the eye, was sampled for snake fungal disease.
An indigo snake from southern Georgia with a suspect scale behind the eye. This individual was sampled for snake fungal disease. – Houston Chandler
What is Snake Fungal Disease?

Wildlife diseases have come to the forefront of conservation biology in recent decades. Well-known examples of the toll that diseases can have on wildlife populations include large-scale die-offs associated white-nose syndrome in bats and chytrid fungus in amphibians. In addition to these well-publicized examples, there are a plethora of other diseases currently impacting wildlife populations to various degrees. One such disease is ophidiomycosis or snake fungal disease as it is commonly referred to. Snake fungal disease is caused by the fungal pathogen Ophidiomyces ophidiicola, which infects the skin of snakes and causes a wide range of symptoms. These symptoms can range from a few crusty or dry scales to serious lesions and eroding scales that can, in severe cases, be fatal for the infected snake.

Snake Fungal Disease Research in Georgia

We started studying snake fungal disease in Georgia’s snake populations back in 2016. Over two years, we collected swab samples from the skin of 786 snakes representing 34 species. These samples were then tested for the presence of fungal DNA and all sampled snakes were visually inspected for skin lesions that could indicate disease presence. The results of this work suggested that snake fungal disease is widespread in Georgia’s snake populations, both geographically and taxonomically (Chandler et al. 2020; Haynes et al. 2021). Just over 13% of all sampled snakes tested positive for O. ophiodiicola DNA and almost 80% of positive individuals had some type of skin lesions indicative of disease infection. However, some species appear more susceptible than others to this disease, including Eastern Indigo Snakes.

Relationships between species sampled and disease status in Georgia snakes that was reported in Haynes et al. (2021). The four categories represent disease status with lines linking to each species that fell into that category. The gray circle represents negative sampling events, the orange circle represents possible ophidiomycosis (skin lesions), the purple circle represents Ophidiomyces DNA present, and the red circle represents apparent ophidiomycosis (Ophidiomyces DNA and skin lesions). – Ellen Haynes

Since those initial surveys, we have continued to sample all indigo snakes captured during annual monitoring activities for snake fungal disease. The results from sample testing in recent years have confirmed what we already suspected – most, if not all, indigo snake populations in Georgia are being impacted by this pathogen. Rates of positive detections have been variable over time but have peaked at over 90% of individuals tested in some years.

There are still many unanswered questions about the practical impacts of snake fungal disease on indigo snake populations. While it does not appear that significant mortality events are occurring and indigo snakes have long been described as having skin lesions during the winter months, more data are needed to better understand potential sub-lethal effects that disease may have on individuals. Snake fungal disease has been shown to impact behavior in some infected individuals (Tetzlaff et al. 2017), and such effects could ultimately lower fitness or long-term reproductive success. We are planning to conduct additional research on snake fungal disease in future years that would allow us to answer some of these unknown but important questions.

Crusty skin lesions that are commonly present on indigo snakes after they have spent long periods of time in and out of Gopher Tortoises burrows during the winter months. – Houston Chandler
How to Reduce the Spread of Snake Fungal Disease

While eliminating the effects of wildlife diseases is likely impractical if not impossible, there are some common sense steps that anyone can take to mitigate disease transmission in wildlife populations. For snake fungal disease, this could be particularly important as recent research has indicated that there are multiple strains of O. ophiodiicola, which may lead to different outcomes in infected snakes (i.e., some strains may lead to more severe disease; Ladner et al. 2022).

  • Regularly clean and disinfect tools, equipment, and other surfaces that come into contact with wild snakes. Use disinfectants that have been shown to be effective against Ophidiomyces (Rzadkowska et al. 2016).
  • Reduce handling of wild snakes, when possible. Especially in cases where many snakes could be handled in short succession and across multiple locations.
  • Wild snakes should not be brought into captivity and captive snakes should not be released into the wild.
  • In Georgia, severely sick snakes can be reported to the Georgia Department of Natural Resources and/or the University of Georgia’s Southeastern Cooperative Wildlife Disease Study.

Overall, wildlife diseases will remain a key conservation challenge for many species in the coming years. Addressing these challenges will require targeted research projects to insure that we can enact appropriate management actions to minimize disease effects on wildlife populations.

Literature Cited

Chandler, H.C., M.C. Allender, B. S. Stegenga, E. Haynes, E. Ospina, and D.J. Stevenson. 2019. Ophidiomycosis prevalence in Georgia’s Eastern Indigo Snake (Drymarchon couperi) populations. PLoS ONE 14:e0218351.

Haynes, E., H.C. Chandler, B.S. Stegenga, L. Adamovicz, E. Ospina, D. Zerpacatanho, D.J. Stevenson, and M.C. Allender. 2020. Ophidiomycosis surveillance of snakes in Georgia, USA reveals new host species and taxonomic associations with disease. Scientific Reports 10:10870.

Ladner, J. T., J. M. Palmer, C. L. Ettinger, J. E. Stajich, T. M. Farrell, B. M. Glorioso, B. Lawson, S. J. Price, A. G. Stengle, D. A. Grear, and J. M. Lorch. 2022. The population genetics of the causative agent of snake fungal disease indicate recent introductions to the USA. PLOS Biology 20:e3001676.

Rzadkowska, M., M.C. Allender, M. O’Dell, and C. Maddox. 2016. Evaluation of common disinfectants effective against Ophidiomyces ophiodiicola, the causative agent of Snake Fungal Disease. Journal of Wildlife Diseases 52:759–762.

Tetzlaff, S.J., M.J. Ravesi, B.A. Degregorio, M.C. Allender, J.M. Josimovich, E.T. Carter, and B.A. Kingsbury. 2017. Snake fungal disease affects behavior of free-ranging Massasauga Rattlesnakes (Sistrurus catenatus). Herpetological Conservation and Biology 12:624–634.

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