Snake Fungal Disease Hits U.S.
A fungal outbreak in the eastern and Midwestern United States is infecting some populations of wild snakes. Snake Fungal Disease (SFD), a fungal dermatitis consistently associated with the fungus Ophidiomyces ophiodiicola, is showing recent spikes in occurrence according to the U.S. Geological Survey's National Wildlife Health Center (NWHC) and other diagnostic laboratories.
So far, the diseased snakes submitted by Wildlife Monitors to the NWHC are attributed to wild populations from nine states, including Florida, Massachusetts, New York, New Jersey, Tennessee, Illinois, Minnesota, Ohio, and Wisconsin.
Snakes diagnosed with SFD include the northern water snake (Nerodia sipedon), eastern racer (Coluber constrictor), rat snake (Pantherophis obsoletus species complex), timber rattlesnake (Crotalus horridus), massasauga (Sistrurus catenatus), pygmy rattlesnake (Sistrurus miliarius), and milk snake (Lampropeltis triangulum).
The snakes share common clinical symptoms of snake fungal disease such as scabbed scales, opaque cloudiness of the eyes, thickening and crusting of the skin, and swelling of the face. Other symptoms including skin ulcers and lesions have also been documented. The severity of clinical signs may vary from snake to snake and specific criteria to determine the influence of this disease has yet to be established by scientists.
Research involving SFD, however, suggests that human activity significantly influences the result of the disease's emergence by transporting the disease to unaffected areas, much like fungal diseases that have devastated amphibian and bat population recently.
"The main way that humans facilitate the emergence of novel pathogens in wildlife is by transporting disease agents to new areas," says Dr. Jeff Lorch, Research Associate for the Department of Pathobiological Sciences and School of Veterinary Medicine at the University of Wisconsin-Madison. "In their native range, these pathogens may not cause significant disease because the host and pathogen have evolved alongside each other. In other words, the host often has some sort of resistance that may prevent the pathogen from causing severe disease."
This is similar to the Columbian Exchange; the 1492 event brought upon by Christopher Columbus when he and his small army of voyaging Spanish conquistadors landed in what is now the Americas. The Spanish and the natives not only exchanged cultural ideas, animals, and plants, but the contact created widespread infectious diseases ultimately killing off huge populations of humans.
While conducting research on SFD in collaboration with the U.S. Geological Survey - National Wildlife Health Center, Lorch explains that "these naive hosts may lack any sort of defense against the pathogen and thus can be highly susceptible to infection and/or exhibit higher mortality rates in response to infection."
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Northern water snake image via Shutterstock.