Snake Fungal Disease (SFD) is a fungal infection in the skin of snakes. This disease is though to be caused by a fungus, Ophidiomyces ophiodiicola, that can survive at a wide range of temperatures and pH’s. O. ophiodiicola typically is found living on a variety of materials, but can also survive in the epidermal and, in some severe cases, dermal layers of snake skin. With such a wide range of suitable conditions, it is no surprise that this fungus has spread rapidly across eastern and midwestern U.S. There is, however, little known about the actual cause of SFD and more research is needed to be sure that O. ophiodiicola is the true cause of SFD. In any case, SFD may play a large role in decreasing the number of free-ranging snakes across the U.S. Although only found in snakes, it has infected a variety of species, making this especially problematic for endangered or threatened species.
Mechanism for Infection
The fungus seems to infect snakes by two methods. The first is a substrate to skin contact, where the snake’s epidermis or an abrasion on the epidermis (the outermost layer of the skin) permits direct contact with the fungus that is living on detritus. The second is through snake to snake contact, where an infected snake has direct contact with a healthy snake. Although thought to be solitary animals, snakes will congregate to reproduce and hibernate (in some cases) allowing easy transmission. Both modes result in a launched immune response and ultimately in a crusty, thickened lesion on the snake’s skin.
- Scabs/crusty scales
- Skin nodules (tumor-like lesions)
- Premature molting/shedding
- Cloudy eyes
- Localized crusting or thickening of the skin
- Ulcers, swelling or deep tissue nodules in the head
SFD has been documented in free-ranging snakes from Canada to Louisiana, indicating a wide-spread case of infectious disease. Recorded instances are concentrated at the eastern and midwestern parts of the country, but it is thought that the actual range might be larger and expanding.
Very little is known about O. ophiodiicola and what its exact relationship with SFD is. Scientists do not know if this fungus is invasive or a naturally occurring but uncontrolled pathogen. Many species of snakes are effected by this, some of which are listed as “at risk”. Because so little is known about the fungus and how it effects these species, other variables such as climate change and habitat loss only complicate the matter further. Some species appear to be handling the disease well with minimal effects, but others have been severely impacted. High infection rates, high variability in effects and little understanding of SFD and O. ophiodiicola makes for a concerning concoction that may have drastic effects we have yet to see.
NWHC. (2016, May 19). Snake Fungal Disease. Retrieved April 18, 2017, from https://www.nwhc.usgs.gov/disease_information/other_diseases/snake_fungal_disease.jsp
Lorch JM et al. 2016 Snake fungal disease: an emerging threat to wild snakes. Phil. Trans. R. Soc. B 371: 20150457. https://pdfs.semanticscholar.org/27e2/a971b5ecfebaffc363c242c3986e2ed270c5.pdf
CWHC. (n.d.). Snake Fungal Disease. Retrieved April 18, 2017, from http://www.cwhc-rcsf.ca/docs/fact_sheets/SFD_FactSheet.pdf
Tetzlaff, S., Allender, M., Ravesi, M., Smith, J., & Kingsbury, B. (2015). First report of snake fungal disease from Michigan, USA involving Massasaugas, Sistrurus catenatus (Rafinesque 1818). Herpetology Notes, 8, 31-33. Retrieved April 18, 2017, from https://www.researchgate.net/profile/Sasha_Tetzlaff/publication/280134562_First_report_of_snake_fungal_disease_from_Michigan_USA_involving_Massasaugas_Sistrurus_catenatus_Rafinesque_1818/links/55ac3bd008aea3d08685ebb6.pdf.
Glorioso, B. M., Waddle, J. H., Green, D. E., & Lorch, J. M. (2016). First Documented Case of Snake Fungal Disease in a Free-Ranging Wild Snake in Louisiana [Abstract]. Southeastern Naturalist, 16(1), N4-N6. Retrieved April 18, 2017, from http://www.bioone.org/doi/abs/10.1656/058.015.0111