Snake Fungal Disease in Tennessee
Observations of infectious diseases in wildlife populations have been increasing in recent years and impacts vary geographically and by species. In Tennessee, various species of wildlife have been impacted by multiple diseases that include, deer (epizootic hemorrhagic disease), waterfowl (avian influenza), amphibians (chytrid fungus and ranavirus), and bats (white-nose syndrome).
Impacts to these species have varied, but large declines have been observed on localized scales, or in the case of bats, declines have been observed statewide.
Snake Fungal Disease (SFD) is an emerging skin disease affecting both free-ranging and captive snake species across North America. SFD can be extremely debilitating to snakes, and in severe cases, lethal or requiring human intervention and euthanasia. In 2009, the fungus Chrysosporium ophiodiicola was described from a black rat snake (Elaphe obsoleta obsoleta) in Georgia. This individual presented symptoms of large, slow-growing facial masses.
The fungus was later re-circumscribed as Ophidiomyces ophiodiicola in the family Onygenaceae based on morphological, cultural and molecular data. The majority of disease cases reported have been restricted to the eastern United States. SFD has been confirmed in 20 U.S. states (Florida, Georgia, New Hampshire, Illinois, Massachusetts, Michigan, Louisiana, Virginia, Pennsylvania, South Carolina, Wisconsin, Kentucky, Ohio, New Jersey, New York, Alabama, Minnesota, Connecticut, Vermont, and Tennessee) and Canada. SFD has been documented in 30 species of snakes in North America and it is possible impacts may vary by species, population, and geographically. Reports and observations of SFD have increased across the eastern United States in recent years.
Snakes presenting with SFD may be observed with ulcerated and/or eroded skin, incomplete sheds, large nodules on the head or other parts of the body, severely malformed heads, appear malnourished or lethargic, and unusual behaviors, to include frequently observed in the open or basking at unusual times. O. ophiodiicola invades the superficial skin of snakes causing lesions.
These lesions swell and lead to thickening, crusting, and eventual death of the epidermis. During molting, the shedding skin bunches up, with portions adhering to one another, leading to dysecdysis (portions of the molt being retained on the new skin). After this, the crust falls off the snake, the ulcerated and eroded skin is revealed. Some scales may be smaller, deformed or depigmented as a result of these lesions. Snakes also develop dermal granulomas on the head, neck, and chin. The effects of lesions developed as the result of SFD can vary, be mild to severe or ultimately lethal. In addition, this fungus has been routinely detected in asymptomatic snakes leading researchers to question if these snakes haven’t yet developed symptoms characteristic of SFD, or alternatively if O. ophiodiicola occurs as a commensal member of the snake microbiome.
SFD was first confirmed in Tennessee during fall of 2012 in samples taken from a timber rattlesnake (Crotalus horridus) collected in Dekalb County. During the following spring, additional samples collected from both a timber rattlesnake and queen snake (Regina septemviattta) collected in Rutherford County, TN also tested positive.
It is highly likely SFD may have been present in some populations prior to these confirmations as researchers have observed snakes in other portions of the state in previous years with clinical symptoms similar to those presented above. However, these early reports of snake fungal disease in Tennessee are speculation. Since the initial SFD project was implemented in the state, over 235 samples have been collected from 20 snake species. Samples have been collected in 25 counties and O. ophiodiicola was confirmed in or present on 14 snake species across 15 Tennessee counties.
Observations of SFD
Observations of SFD can be made across the state throughout the year. Because of the geographic scope of any potential occurrence, collecting the samples necessary for testing can be problematic. However, maintaining a database of observations being made can be used to direct where sampling and monitoring can be targeted. The public is encouraged to submit records of any observations made to aid the efforts surrounding SFD. Any record submitted should contain the following information:
1. The date the observation is made
2. The exact location of the observation. GPS coordinates (dd.ddddd) must accompany any locality information submitted.
3. The species of snake observed.
4. The symptoms observed, to include unusual behavior.
5. Photographs of both the snake and symptoms, including any lesions, bumps or scabs observed.
