Snake Fungal Disease

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Cause

Snake fungal disease (SFD) is believed to be caused by the fungus Ophidiomyces ophiodiicola (formerly known as Chrysosporium ophiodiicola). Different species of fungi have also been isolated from infected snakes, so at this time it cannot be concluded definitively that only O. ophiodiicola causes SFD. Scientists are unsure if O. ophiodiicola was recently introduced to the United States, has mutated from a different fungi and is now causing more severe disease, or if the fungi has always been present and other factors such as climate change, loss of genetic diversity, or other diseases have amplified the affects of the fungi on wild snakes.

Significance

Snake fungal disease is a newly emerging disease affecting wild snakes in the Midwestern and eastern regions of the United States. Though fungal infections were occasionally seen in snakes before 2006, the incidence of SFD has been steadily increasing over the last few years. While snake fungal disease is capable of causing mortality in snake, the overall population affects of the disease are currently unknown. 

Species Affected

Currently, snake fungal disease is only known to infect wild snakes. Snake species with confirmed diagnosis of SFD include the northern water snake, the eastern racer, the rat snake, the timber rattlesnake, the massasauga, the pygmy rattlesnake, and the milk snake, though it is likely that the disease can affect most species of snakes. SFD is not known to affect humans. 

Distribution

SFD is currently affecting wild snakes in the Midwestern and eastern parts of the United States. To date, the disease has been confirmed in snakes in Illinois, Florida, Massachusetts, Minnesota, New Jersey, New York, Ohio, Tennessee, and Wisconsin, though it is believed to be much more widespread. In 2006-2007 a population of timber rattlesnakes in New Hampshire suffered a drastic population decline from a disease with similar clinical signs to snake fungal disease. However at the time the disease was not affirmatively diagnosed as SFD. 

Transmission

At this time, it is not known how snake fungal disease is spread. It is likely that the disease is spread either through direct contact with other infected snakes or from the natural presence of O. ophiodiicola in the environment. 

Clinical Signs

Clinical signs of SFD and the severity of disease varies by species. The most common clinical signs include white opaque cloudiness in the eyes, crusty and/or thickening of the scales or skin, scabs, subcutaneous nodules, and abnormal molting. Facial swelling, skin ulcers, and nodules in the tissues of the head have also been noted.

Diagnosis

Laboratory tests are used to isolate the Ophidiomyces ophiodiicola fungi. The identification of this fungus along with the presence of the above mentioned characteristic legions are used to diagnose SFD. 

Treatment

Snakes may be treated with antifungal, thermal, and nutritional supportive therapy, though treatment is not likely possible for large snake populations in the wild. 

Management

At this time, it is not known how snake fungal disease is affecting or will affect snake populations. It is also very difficult to assess changing snake populations because of the solitary nature of snakes and the absence of long-term monitoring data. Any sightings of snakes with suspected SFD infection should be reported to the National Wildlife Health Center 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 sanitized to prevent spreading the fungus to other snakes. Wild snakes should not be relocated to new areas to prevent potentially bringing the disease to an unaffected area.

Suggested Reading

Images

Eastern racer showing signs of fungal skin infection.Eastern racer showing signs of fungal skin infection.
Northern water snake with crusty and thickened scales.Northern water snake with crusty and thickened scales.