cottonmouth snake

Snake Fungal Disease (Ophidiomycosis)

Cause of Snake Fungal Disease / Ophidiomycosis

Ophidiomycosis, formerly referred to as Snake Fungal Disease (SFD), is caused by the fungus Ophidiomyces ophiodiicola. This fungus is thought to be an emergent pathogen in North America and poses a significant threat to snake health and population sustainability. To date, O. ophiodiicola has been documented in over 15 types of wild and captive snakes.

Significance of Snake Fungal Disease / Ophidiomycosis

Ophidiomycosis is an emerging disease that affects wild and captive snakes across North America. The incidence of Ophidiomycosis has steadily increased over the last few years, specifically documented in California, Oklahoma, Puerto Rico, and Idaho.

Species Affected by Snake Fungal Disease / Ophidiomycosis

Ophidiomycosis can infect wild or captive snakes and is the predominant cause of skin infections in wild snakes. It has been documented in over 15 types of wild and captive snakes. Species confirmed with diagnosis of Ophidiomycosis include— the eastern indigo snake, the northern water snake, the eastern racer, the rat snake, the timber rattlesnake, the massasauga, the pygmy rattlesnake, garter snakes, cottonmouth snakes, the milk snake, queensnake, and eastern fox snake. The fungus causing Ophidiomycosis is not known to affect humans.

Distribution of Snake Fungal Disease / Ophidiomycosis

As of November 2019, the fungus O. ophiodiicola has been found in at least 38 states, including recent findings in California, Idaho, Oklahoma. It is also present in one U.S. territory (Puerto Rico) and one Canadian Providence (Ontario). In some species (i.e., Eastern Massasauga) the mortality rate may be over 90% in the Eastern US.

Transmission of Snake Fungal Disease / Ophidiomycosis

At this time, it is not well understood how the fungus causing Ophidiomycosis is spread. It is likely that the pathogen is shed into the environment by infected snakes and spread from the environment to other snakes (i.e., snakes that share dens). O. ophiodiicola may be spread via vertical transmission (i.e., from dam to offspring). There is no evidence of horizontal transmission (i.e., snake-to-snake transmission) of O. ophiodiicola. Host and environmental factors that lead to disease remain largely unknown. For example, it is thought that Timber rattlesnake populations are at higher risk of Ophidiomycosis in years with higher rainfall.

Clinical Signs of Snake Fungal Disease / Ophidiomycosis

Clinical signs of SFD and the severity of the disease may vary by species. The most common clinical signs include accelerated ecdysis cycles, flaking and crusting of the scales/epidermis, displaced or discolored scales, granulomas, nodules, swelling or disfiguration of infected tissues. The disease may progress internally (via the eyes, throat, and/or lungs) and cause eye infections or pneumonia.

Diagnosis of Snake Fungal Disease / Ophidiomycosis

Ophidiomycosis is diagnosed by identification of the classic clinical signs in combination with either molecular detection (PCR or qPCR) of the fungus, histopathology, and/or a positive fungal culture.

It must be noted that there may be difficulty in sampling for and detecting (by PCR/qPCR) O. ophiodiicola by skin/epidermal swabs (i.e., low DNA quantity on the skin or the fungi are deep within the epidermis). Therefore, hesitation should be taken in assigning causation to O. ophiodiicola to animals with skin lesions that are qPCR negative in the presence of skin lesions. There are numerous causes of skin lesions in wild snakes (i.e., trauma, another pathogen causing skin lesions, etc). Conversely, the absence of clinical signs of ophidiomycosis is more reliable to eliminate a diagnosis of apparent ophidiomycosis.

Treatment of Snake Fungal Disease / Ophidiomycosis

Treatment with an antifungal, Terbinafine, either by a slow-release, long-lasting implant or nebulization has been found to reach therapeutic levels in cottonmouth snakes; methods and doses for treatment are thus based on these findings. Other treatment options include thermal and nutritional supportive therapy.

Management of Snake Fungal Disease / Ophidiomycosis

Ophidiomycosis appears to be negatively impacting several species and populations of snakes across North America. However, its long-term impact remains unknown. It is also very difficult to assess changing snake populations because of the solitary nature of many snakes and, importantly, the absence of long-term monitoring data for most species of snake. Any sightings of snakes with suspected SFD infection should be reported to the Northeast Wildlife Disease Cooperative and/or DTT Herp Disease Alert System for further investigation. Wildlife specialists, veterinarians, and any other individuals who routinely come in contact with wild snakes should keep gear, snake holding containers, and clothes clean and disinfected to prevent spreading the fungus to other snakes.


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Small Animal Care

Tread Lightly: Snake Season & Pet Safety

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With summer in full swing, snake bites are on the rise—but understanding the reptiles’ behavior can help people and pets stay safe.

Cases of snake bites in emergency rooms are on the rise, and it will only become more prevalent as the season progresses. Snakes’ seasonal behavior is down to physiology. Like other reptiles, snakes depend on their environment to regulate their body temperature.

In the spring and fall, snakes are most active during the heat of the day. In the heat of the summer, however, they are going to be active during twilight and overnight hours, but will seek out shade and water to cool off during the daytime. Because of this, there is no time that is off limits to when your pet may encounter a snake. Weather is just one piece of the equation. With more free time and time spent outdoors in the summer, there are more opportunities for interactions.

While not all snakes are venomous, even nonvenomous snakes can bite when provoked.

Err on the side of caution. When we see a snake, we tend to be distracted or find difficulty in identifying the animal. It’s better to be safe than sorry. To minimize the chances of a snake encounter, it is important to understand what attracts snakes in the first place and what motivates them to bite.

Identifying snakes in Florida

There are several resources for identifying the common and uncommon snakes of Florida.

What attracts snakes?

Anywhere that has ample food (small rodents, birds, bugs, other reptiles), shade, and places to hide are likely going to have snakes. They try very hard to stay away from us, and only bite when they feel threatened.

Keeping Pets Safe From Snakes

When it comes to pets, the issue is that dogs and even cats tend to be curious about snakes—from cats swatting at a snake to dogs putting their faces a little too close— all of which can lead to a bite. Consistent precautions can help keep pets out of harm’s way.

Turn on flood lights, make some noise, and supervise your pets when they are let outside in the yard (especially at night). When taking your pets for a walk on a leash, keep them away from shrubbery, landscaping timbers, and vehicles parked on grass.

We do not suggest the aid of snake repellents, but rather make ones’ property less hospitable to snakes by clearing shrubs, brush, leaves, as well as removing hiding spots like wood piles or cars that have been sitting awhile.

When You Are Face to Face with a Snake

Snakes play a larger role in our ecosystem. Realize that they are not looking for a fight with humans. Without snakes, we would have an abundance of small rodents and other pests. Do not kill the snake!

Snake bites occur when people fail to keep their distance. Rather than approaching or attacking a snake, contact animal control for assistance. Animal control officers can safely capture and contain a snake before moving it to a safe habitat away from humans.

So what can YOU do? Simply keep an eye on the snake, so that you are able to help animal control locate the animal.

Did you know even a dead snake could present a threat? Although not common, it is still possible for some snakes to deliver their venom even after they have died. If you believe the snake to be dead, leave it alone for an hour and then use a tool like a shovel or a broom handle for removal.

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Removal Resources

Bradenton Wildlife Control:

(941) 404-8859

Sarasota Wildlife Control and Nuisance Wildlife Removal:

(866) 263-9453

Manatee County Animal Services:

(941) 742-5933


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Related: We have more information under our cat health + dog health + client care categories.