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Snake Fungal Disease Spreading Rapidly Across the US

November 08, 2016

Story at-a-glance

  • Snake fungal disease often leads to skin lesions, including open wounds, crusty scabs and swelling, lethargy and increased molting
  • In some snake species, snake fungal disease may kill up to 90 percent of infected snakes
  • Snake fungal disease is caused by the fungus Ophidiomyces ophiodiicola

By Dr. Becker

Although you may not have the same warm and fuzzy feelings about snakes as you do about your pets, wild snakes have an important role in the ecosystem and serve a valuable purpose in the U.S., helping to keep rodent populations under control.

A deadly fungal disease, aptly known as snake fungal disease (SFD), has been spreading rapidly, however, and could be threatening the future of snake populations in some areas.

The fungal infections were first detected among snakes in the eastern U.S. in 2006. However, they’ve since spread across the U.S. and such infections have now been detected in 16 states, affecting 14 different snake species and spreading fast.

In 2016, for instance, researchers with the U.S. Geological Survey (USGS) found snake fungal disease in Louisiana for the first time.1 USGS Ecologist and lead study author Brad “Bones” Glorioso said in a USGS news release:

“Snakes may not be everyone’s favorite animal, but they are undeniably important in a well-balanced ecosystem … They deserve our respect and understanding … SFD is an emerging threat to wild snake populations particularly in the eastern United States …

We don’t know yet how the disease affects various species, but in at least one species, an estimated 80 to 90 percent of infected snakes die from the disease.”

Symptoms of Snake Fungal Disease

Snake fungal disease often leads to skin lesions, including open wounds, crusty scabs and swelling. There may be also be swelling of the eyes, thickened skin on the snout, abnormal scales, bumps below the skin and cloudy eyes not associated with molting.

While in some cases snake fungal disease may kill up to 90 percent of infected snakes, some do survive.

In one case followed by Northeast Partners in Amphibian and Reptile Conservation (Northeast PARC), a timber rattlesnake was diagnosed with snake fungal disease then released without any treatment and tracked.

Two years later, the snake, though disfigured on his snout as a result, had recovered and was very much alive.2

What Causes Snake Fungal Disease?

The fungus Ophidiomyces ophiodiicola has been associated with snake fungal disease, but it wasn’t until 2016 that researchers demonstrated O. ophiodiicola is, in fact, the causative agent.3

Captive-bred corn snakes infected with the fungus developed skin lesions identical to those observed in wild snakes with snake fungal disease.

In addition to the characteristic skin lesions, the infected snakes also became lethargic and lacked an appetite. They molted more often than usual and displayed unusual behaviors, such as basking in “conspicuous” areas.

Taken together, the symptoms could make infected snakes more vulnerable to predators in the wild. The researchers wrote in the journal mBio:4

“While these responses may help snakes to fight infection, they could also impact host fitness and may contribute to mortality in wild snakes with chronic O. ophiodiicola infection.”

Is Snake Fungal Disease Related to White-Nose Syndrome in Bats?

Fungal diseases seem to be an emerging threat to animals worldwide and have been implicated in extreme die-offs of certain species, including bats. White-nose syndrome in bats, caused by the fungus Pseudogymnoascus destructans, shares many similarities with snake fungal disease.5

Study author and Illinois Natural History Survey mycologist Andrew Miller said in a news release:6

“The fungus killing these snakes is remarkably similar in its basic biology to the fungus that has killed millions of bats … It occurs in the soil, seems to grow on a wide variety of substances, and it possesses many of the same enzymes that make the bat fungus so persistent.”

Pseudogymnoascus destructans (the bat fungus) can infect the muzzles, wings and ears of hibernating bats, causing the incredibly deadly white-nose syndrome.

It first appeared in New York in 2006 and has killed 6.7 million bats across the U.S. and Canada since. Although the disease originated in Europe, the bats there seem to be immune to the condition.

It’s thought that the fungus is spread from bat to bat, although they may also pick up the spores from contaminated caves (possibly contaminated by fungal spores brought in by human cave explorers). The fungus kills 70 percent to 90 percent of bats infected within a hibernating group.

It’s unknown at this time how snake fungal disease is spread, although it may be through direct contact with infected snakes or contact with another yet-unknown infected agent in the environment.

It’s possible the fungi could be spread internationally through the pet trade and may also be transferred on clothing, boots or field equipment used to handle snakes in the wild. The fungi also share similarities with chytrid fungi, which is spreading among frogs and salamanders.

Is Snake Fungal Disease Dangerous to Humans?

There have been no reports of infection with O. ophiodiicola in humans, and the fungi rarely cause disease in healthy mammals. So while this is an area that needs further exploration, it’s not thought that snake fungal disease is dangerous to humans.

If you should happen to come in contact with a potentially infected snake, wash your hands (and anything else that has touched the snake) with soap and water. Potentially contaminated objects can also be soaked for 15 minutes in a solution of bleach and water.

You should also report the sighting to your state wildlife agency so they can be alerted that snake fungal disease may be spreading in the area. The following snake species are among those that have had confirmed cases:

Northern water snake


Rat snake

Timber rattlesnake


Pygmy rattlesnake

Milk snake

Plains garter snake

Mud snake

Southern water snake

Be aware, however, that even snake species not on this list could be infected, as it’s believed the condition is rapidly spreading.

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Sources and References

  • 1, 3, 4 mBio November 17, 2015
  • 2 Northeast Partners in Amphibian and Reptile Conservation, Snake Fungal Disease
  • 5 Fungal Ecology October 2015
  • 6 Illinois News Bureau June 18, 2015
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