Snake Fungal Disease

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Snake fungal disease is an emerging infectious disease, confirmed in numerous species of snakes, caused by the fungus Ophidiomyces ophiodiicola.

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. As of August 2017, the fungus Ophidiomyces ophiodiicola has been detected in at least 23 States and one Canadian Province. However, researchers suspect that snake fungal disease (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 localized thickening or crusting of the skin, ulcerated skin, nodules (that is, abnormal bumps) under the skin, abnormal molting, white opaque cloudiness of the eyes (not associated with molting), and facial disfiguration that can be quite severe, leading to emaciation and death.  Many snake populations are already in decline and the recent emergence of SFD may accelerate this decline, causing certain species to disappear entirely from some locations.

In 2016 scientists from the National Wildlife Health Center (NWHC) published a study demonstrating that SFD is widespread in eastern North America, has a broad host range among snakes, and is the predominant cause of skin infections in wild snakes. The study also showed that O. ophiodiicola frequently causes non-lethal infections in snakes and that environmental changes are likely causing the recent emergence of severe and fatal infections in some snake populations. The NWHC has continued to participate in collaborative projects with multiple state natural resource agencies aimed at better understanding SFD and its potential impacts on snake populations. In support of this effort, the NWHC has analyzed samples from over 100 whole carcasses and biopsies from snakes exhibiting clinical signs consistent with SFD. The NWHC is working with researchers to better understand the epidemiology of SFD in different snake populations in North America and abroad. The intent of this research is to determine the spatial extent and severity of this disease in wild populations to determine if intervention is needed to reduce its impacts on sensitive populations.

We encourage conservation agencies and natural resource managers to contact the NWHC if snakes with clinical signs consistent with SFD are encountered.

For more information on snake fungal disease, see the USGS Fact Sheet: Snake fungal disease in North America: U.S. Geological Survey updates.