Snake Fungal Disease in North America: 

U.S. Geological Survey Updates

By Noelle E. Thompson1, Emily W. Lankau2, and Gail Moede Rogall2

Snake fungal disease (SFD) results from a skin infection 

that has been documented only in snakes. Historically, reports 

of snakes with skin infections of unknown origin have been sporadic. Recently, the number of reported cases of skin infections 

in snakes has increased substantially. This emerging infectious 

disease, confirmed in numerous species of snakes, is caused 

by the fungus Ophidiomyces ophiodiicola. As of August 2017, 

O. ophiodiicola has been detected in at least 23 States and one

Canadian Province. However, researchers suspect that SFD may

be more widely distributed than these documented cases suggest,

because efforts to monitor the health of many snake populations

are limited. Snake fungal disease may also be underreported in

populations where it affects snakes infrequently or in species

that develop less severe illness. Signs of SFD include crusted

or ulcerated scales, nodules (that is, abnormal bumps) under the

skin, and facial disfiguration that can be quite severe, leading

to emaciation and death. Many snake populations are already

in decline due to habitat loss and dwindling prey populations,

and the recent emergence of SFD may accelerate this decline,

causing certain species to disappear entirely from some locations

(Allender and others, 2015; Lorch and others, 2016).

Snakes play a vital role in natural food webs as both prey 

and predator. Besides being an important food item for many 

mammal and bird species (Mullin and Siegel, 2009), snakes 

consume a variety of prey, including rodents that can damage 

agricultural crops or carry diseases that affect people and other 

animals. For example, snakes can reduce local incidence of 

Lyme disease by consuming rodents and other small mammals 

infested with ticks that transmit Lyme disease. Mathematical 

models suggest that a single Crotalus horridus (timber rattlesnake) reduces the number of ticks within its foraging range by 

2,500–4,500 annually; other viper species likely provide similar 

disease-control services (Kabay and others, 2013). 

Field biologists have sporadically detected skin lesions (that 

is, sores) in wild North American snakes for decades, most often 

after snakes emerge from hibernation (Lorch and others, 2016). 

These lesions were colloquially called “hibernation sores,” but 

the specific cause of these lesions was unknown until an investigation of deadly outbreaks of skin lesions in Sistrusrus catenatus

(eastern massasauga rattlesnakes) in 2008 implicated a fungal 

pathogen (Allender and others, 2011). The fungus, O. ophiodiicola (formerly Chrysosporium ophiodiicola), was later also 

isolated from a skin nodule in a captive Pantherophis alleghaniensis (eastern rat snake; previously classified as Elaphe obsoleta 

obsoleta) (Rajeev and others, 2009). Ophidiomyces ophiodiicola

was also found later during a study of archived tissue samples 

commonly associated with skin lesions in captive snakes (Sigler 

and others, 2013). After 2008, increasing numbers of snakes 

with fungal skin infections were reported, including additional 

cases in imperiled populations of eastern massasauga rattlesnakes in central Illinois and timber rattlesnakes in New England 

(Allender and others, 2015; McBride and others, 2015; fig. 1). 

These new reports caused increased concern about SFD and the 

potential for substantial declines in some snake populations, 

exacerbating risk for local extinction of both eastern massasauga 

rattlesnakes in central Illinois and timber rattlesnakes in New 

England (Allender and others, 2011, 2015).

1

University of Illinois at Urbana-Champaign.

2

U.S. Geological Survey.

Figure 1. Sistrurus catenatus (eastern massasauga rattlesnake) 

populations in the Midwestern United States have been heavily 

affected by habitat destruction and fragmentation (U.S. Fish and 

Wildlife Service, 2016) and recently, snake fungal disease. Photo

by Rori Paloski, Wisconsin Department of Natural Resources.

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2017–3064

January 2018
U.S. Geological Survey (USGS) scientists at the National 

Wildlife Health Center (https://www.nwhc.usgs.gov/) and the 

Wetland Aquatic Research Center (https://www.usgs.gov/warc) 

have worked closely with government, nonprofit, and academic 

partners to understand SFD and develop strategies to mitigate 

its effects on snake populations. Together, these scientists have 

advanced basic understanding of the cause, number of cases, and 

geographic distribution of SFD in several ways, including associating physical signs of fungal infection with a diagnosis (Sigler 

and others, 2013; Allender and others 2015; Lorch and others, 

2016); experimentally demonstrating that the fungus O. ophiodiicola is the cause of SFD (Allender and others, 2015; Lorch 

and others, 2016); and establishing surveillance and monitoring 

systems to determine which snake species are infected by SFD in 

different regions (Lorch and others, 2016).

Physical signs and severity of SFD appear to vary among 

snake species and individuals, although factors contributing to 

this variability are poorly understood (Lorch and others, 2016). 

Visible signs of SFD may include scabs, skin ulcers or nodules, 

crusted scales, discolored scales, cloudy eyes, and a swollen or 

disfigured face (fig. 2). Snakes with SFD experience abnormal 

molting, and the upper layer of infected skin may be shed repeatedly in an effort to eliminate the fungus (Lorch and others, 2015). 

Affected snakes are often emaciated, possibly due to decreased 

ability to capture prey (Lorch and others, 2016). Additionally, 

they often rest in open, unprotected areas, exposing themselves to 

adverse weather and predators (Lorch and others 2015; McBride 

and others, 2015). 

Ophidiomyces ophiodiicola can survive in a relatively wide 

range of pH and temperature conditions; however, growth of 

this fungus is inhibited by high air temperatures of more than 

100 degrees Fahrenheit and moderately cold temperatures of less 

than 50 degrees Fahrenheit (Rajeev and others, 2009; Sigler and 

others, 2013; Allender and others, 2015). Ophidiomyces ophiodiicola can be transmitted by snake-to-snake contact and may persist in 

the environment without a snake host (Allender and others, 2015). 

Broken skin facilitates infection of snakes, but skin abrasions are 

not necessary for a snake to become infected (Lorch and others, 

2015). Snakes can also carry O. ophiodiicola on their skin without 

exhibiting signs of infection (Paré and others, 2013; Bohuski and 

others, 2015). Thus, detection of the fungus alone is insufficient 

evidence to document that a snake has SFD.

Figure 2. An Elaphe vulpine ( western foxsnake) captured 

in Wisconsin presenting signs of snake fungal disease 

including A (top left), skin ulcers on the nose and near the 

eyes and B (bottom left), discolored, crusted scales on the 

body. Photos by Stephanie Steinfeldt, U.S. Geological Survey.

A

B

Figure 3 (above). National Wildlife Health Center 

pathologist Susan Knowles obtains a skin biopsy for analysis 

under a microscope from a Coluber constrictor (North 

American racer) submitted for diagnostic testing. Photo by 

Jennifer Swan, U.S. Geological Survey.
Although O. ophiodiicola can be detected using laboratory techniques, microscopic examination of a biopsy, a piece of 

skin and underlying tissues, is required to confirm a diagnosis 

of SFD (fig. 3) through identification of inflammation and other 

signs of the invasive fungal infection. This serves to differentiate 

mere presence of the fungus on the skin of an otherwise-healthy 

animal from a skin infection characteristic of SFD.

It is unclear when or why O. ophiodiicola emerged as a 

fungal pathogen that harms snakes. Ophidiomyces ophiodiicola 

has been found throughout the eastern United States and may be 

native to this region. However, severe outbreaks of SFD have 

been documented in only a few locations throughout the country. 

Scientists hypothesize that environmental and climatic changes 

such as habitat destruction and fragmentation, increasing average 

temperatures, and cooler, wetter springs may be contributing to 

the recent emergence of this disease (Lorch and others, 2016). 

Concern about SFD has resulted in enhanced monitoring of 

snake populations across the United States, which could 

also contribute to documenting apparent trends of increasing 

frequency or severity of SFD as a result of increased awareness 

and surveillance.

The public can help with monitoring 

and response to SFD by reporting sightings 

of snakes with skin sores or abnormal 

behavior to a local or state wildlife agency. 

However, members of the general public 

should avoid disturbing wild snakes. 

To avoid inadvertent spread of pathogens, 

researchers and other wildlife professionals 

should observe universal precautions by 

thoroughly cleaning and sanitizing clothing 

and equipment that has been in contact 

with wild snakes, and by releasing 

rehabilitated snakes to as near the site of 

capture as possible. 

Lampropeltis getula (eastern king snake), photo by Keith Ramos, 

U.S. Fish and Wildlife Service.

Host Range of Ophidiomyces ophiodiicola (as of January 2018)

In North America, O. ophiodiicola has been detected on the 

skin of captive and free-ranging snake species representing 

12 genera within 2 families (Lorch and others, 2016), and 

including 2 species designated as threatened, Nerodia clarkia 

taeniata (Atlantic saltmarsh watersnakes) and Sistrurus 

catenatus (eastern massasauga rattlesnake), and one endangered species, Pituophis ruthveni (Louisiana pinesnake). 

Although presence of O. ophiodiicola has been documented 

in many specimens, not all have been sufficiently examined 

to characterize their susceptibility to infection by this fungus 

or the severity of disease that may result following infection. 

Ophidiomyces ophiodiicola, in conjunction with characteristic 

signs of SFD, have been detected on snakes in the following 

groups:

Family: Colubridae

•	 Coluber (racers)

•	 Farancia (mudsnakes)

•	 Lampropeltis (kingsnakes and milksnakes)

•	 Nerodia (watersnakes)

•	 Pantherophis (foxsnakes and ratsnakes)

•	 Pituophis (pinesnakes and bull snakes)

•	 Regina (crayfish snakes)

•	 Thamnophis (gartersnakes and ribbonsnakes)

•	 Virginia (earthsnakes)

Family: Viperidae

•	 Agkistrodon (copperheads and cottonmouths)

•	 Crotalus (rattlesnakes)

•	 Sistrurus (massasaugas and pigmy rattlesnakes)

 Coluber constrictor (North American racer). Photo by Jeffrey M. Lorch, U. S. Geological Survey.
U.S. Geological Survey Contributions to 

Understanding Snake Fungal Disease 

Scientists at the USGS are recognized leaders in 

advancing understanding of SFD. Specific contributions 

by USGS researchers include: 

• Establishing that O. ophiodiicola is the cause of SFD;

• Developing laboratory methods to detect 

O. ophiodiicola;

• Studying the development and disease progression 

of SFD in captive snakes;

• Diagnosing SFD in snakes submitted by partner 

agencies to the National Wildlife Health Center;

• Coordinating field surveillance to monitor SFD 

infections in new populations or species;

• Establishing the past extent and geographic distribution 

of SFD and projecting its future course;

• Identifying other fungi, bacteria, or viruses that may 

independently cause skin infections in snakes or 

contribute to development of SFD; and

• Examining how SFD alters the behavior and survival

of infected snakes to better understand the how the 

disease affects populations.

References Cited

Allender, M.C., Dreslik, Michael, Wylie, Sarah, Phillips, Christopher, Wylie, D.B., Maddox, Carol, Delaney, M.A., Kinsel, 

M.J., 2011, Chrysosporium sp. infection in Eastern Massasauga rattlesnakes: Emerging Infectious Diseases, v. 17, 

no. 12, p. 2383–2384, accessed July 28, 2017, at https://doi.

org/10.3201/eid1712.110240. 

Allender, M.C., Raudabaugh, D.B., Gleason, F.H., Miller, 

A.N., 2015, The natural history, ecology, and epidemiology of Ophidiomyces ophiodiicola and its potential impact 

on free-ranging snake populations: Fungal Ecology, v. 17, 

p. 187–196, accessed July 28, 2017, at http://doi.org/10.1016/j.

funeco.2015.05.003. 

Bohuski, E., Lorch, J.M., Griffin, K.M., Blehert, D.S., 2015, 

TaqMan real-time polymerase chain reaction for detection 

of Ophidiomyces ophiodiicola, the fungus associated with 

snake fungal disease: BMC Veterinary Research, v. 11, no. 95, 

accessed July 28, 2017, at http://doi.org/10.1186/s12917-015-

0407-8. 

Kabay, E., Caruso, N.M., and Lips, K., 2013, Timber rattlesnakes 

may reduce incidence of Lyme disease in the Northeastern 

United States: Ecological Society of America Annual Conference, 98th, Minneapolis, Minnesota, August 4–9, 2013.

Lorch, J.M., Knowles, Susan, Lankton, J.S., Michell, Kathy, 

Edwards, J.L., Kapfer, M.J., Staffen, R.A., Wild, E.R., 

Schmidt, K.Z., Ballmann, A.E., Blodgett, Doug, Farrell, T.M., 

Glorioso, B.M., Last, L.A., Price, S.J., Schuler, K.L., Smith, 

C.E., Wellehan, J.F.X., Blehert, D.S., 2016, Snake fungal disease: an emerging threat to wild snakes: Philosophical Transactions of the Royal Society B, v. 371, no. 1709, accessed 

July 28, 2017, at https://doi.org/10.1098/rstb.2015.0457. 

Lorch, J.M., Lankton, J.S., Werner, Katrien, Falendysz, E.A., 

McCurley, K., Blehert, D.S., 2015, Experimental infection of 

snakes with Ophidiomyces ophiodiicola causes pathological 

changes that typify snake fungal disease: mBio, v. 6, no. 6, 

e01534–15, accessed July 28, 2017, at http://doi.org/10.1128/

mBio.01534-15. 

McBride, M.P., Wojick, K.B., Georoff, T.A., Kimbro, Jason, 

Garner, M.M., Wang, Xiaoling, Childress, A.L., Wellehan, 

J.F.X., Jr., 2015, Ophidiomyces ophiodiicola dermatitis in 

eight free-ranging timber rattlesnakes (Crotalus horridus) 

from Massachusetts: Journal of Zoo and Wildlife Medicine, 

v. 46, no. 1, p. 86–94, accessed July 28, 2017, at http://doi.

org/10.1638/2012-0248R2.1. 

Mullin, S.J., Seigel, R.A., 2009, Snakes: Ecology and conservation: Ithaca, New York: Cornell University Press, 384 p.

Paré, J.A., Sigler, Lynne, Rypien, K.L., Gibas, C.C., 2003, 

Cutaneous mycobiota of captive squamate reptiles with notes 

on the scarcity of Chrysosporium anamorph of Nannizziopsis 

vriesii: Journal of Herpetological Medicine, and Surgery, 

v. 13, p. 10–15.

Rajeev, S., Sutton, D.A., Wickes, B.L., Miller, D.L., Giri, D., 

Van Meter, M., Thompson, E.H., Rinaldi, M.G., Romanelli, 

A.M., Cano, J.F., Guarro, J., 2009, Isolation and characterization of a new fungal species, Chrysosporium ophidiicolo, 

from a mycotic granuloma of a black rat snake (Elaphe 

obsoleta obsoleta): Journal of Clinical Microbiology, v. 47, 

no. 4, p. 1264–1268, accessed July 28, 2017, at http://doi.

org/10.1128/JCM.01751-08. 

Sigler, Lynne, Hambleton, Sarah, Paré, J.A., 2013, Molecular characterization of reptile pathogens currently known 

as members of the Chrysosporium anamorph of Nannizziopsis vriesii complex and relationship with some humanassociated isolates: Journal of Clinical Microbiology, v. 51, 

no. 10, p. 3338–3357, accessed July 28, 2017, at http://doi.

org/10.1128/JCM.01465-13. 

U.S. Fish and Wildlife Service, 2016, Eastern massasauga 

(Sistrurus catenatus) fact sheet, accessed July 28, 2017, at 

https://www.fws.gov/midwest/endangered/reptiles/eama/

eama-fct-sht.html.

For additional information contact:

Director, National Wildlife Health Center

U.S. Geological Survey

6006 Schroeder Road

Madison, WI 53711-6223

Banner image (page 1): Thamnophis sirtalis (common gartersnake). Photo by Jeffrey M. Lorch, U. S. Geological Survey.

ISSN 2327-6916 (print)

ISSN 2327-6932 (online)

https://doi.org/10.3133/fs20173064