Ophidiomycosis, or snake fungal disease, is an emerging wildlife disease caused by the Ophidiomyces ophiodiicola fungus. The fungus can result in high mortality rates among infected snakes and has been documented across much of the eastern US, including southern Georgia. However, little is known about ophidiomycosis in northern Georgia. We surveyed wild snake populations in five counties of northern Georgia between March 2019 and March 2020 and swabbed captured snakes (n=27) for the presence of O. ophiodiicola DNA. We followed similar sampling protocols with a group of captive snakes (n=6) at the Elachee Nature Center in Hall County, Georgia. Quantitative PCR confirmed the presence of O. ophiodiicola DNA in 33% (11/33) of snakes. Eight of the confirmed positive samples were collected from wild snakes (30%, 8/27) across our sample region, while three were from our captive group (50%, 3/6). Our results indicated that O. ophiodiicola is present in wild snake populations in northern Georgia, and the pathogen is present in seemingly healthy captive snakes. This knowledge is critical for conservation and management efforts, but more research is needed to fully understand ophidiomycosis and its effect on snake populations in the region.

Wildlife diseases can threaten biodiversity and drive population declines across a variety of taxonomic groups (Daszak et al. 2000). For example, population declines have been documented due to chytridiomycosis in amphibians (Daszak et al. 1999), white nose syndrome in bats (Frick et al. 2010), chronic wasting disease in cervids (Rivera et al. 2019), and whirling disease in salmonid fish (Gilbert and Granath 2003). In 2006, a skin disease was discovered in a population of timber rattlesnakes (Crotalus horridus) in the northeastern US (Clark et al. 2011). The disease caused a population decline and was later identified as ophidiomycosis, or snake fungal disease. Ophidiomycosis often presents as ulcers or discolored and crusted scales on the head and along the body, with severe lesions most often being associated with the face (Baker et al. 2019). However, snakes can also carry the fungal pathogen on their skin asymptomatically (Thompson et al. 2018). By 2015, ophidiomycosis had been documented in wild snakes throughout most of the eastern US (Lorch et al. 2016), and substantial efforts to document the distribution and prevalence of the causative fungal pathogen in southeastern Georgia have been successful (Haynes 2020). Data from northern Georgia is lacking; therefore, we initiated sampling efforts to detect O. ophiodiicola among wild snake populations in northern Georgia. We also sampled a group of captive snakes to determine if any were asymptomatically carrying the fungus. We used observational data of clinical signs to contribute additional information.

We surveyed wild snake populations between March 2019 and March 2020 throughout five counties in northern Georgia: Lumpkin, Hall, Dawson, Murray, and White (Fig. 1). We conducted surveys by walking transects through public and private lands and visually searching for snakes. Upon capture, we measured snout-vent length, determined mass (g), conducted a visual inspection for skin lesions (crusted scales, discoloration, ulcerations, etc.), and determined general disposition (i.e., lethargic, active, or deceased). For snakes without visible skin lesions, we collected a single swab sample from the snake's head, as this region is most likely to show clinical signs of ophidiomycosis (Allender et al. 2011) and harbor the fungus. We gently applied firm pressure with the swab while rubbing the labial scales, nostrils, eyes, and jaw using sterile handling procedures. If an individual had skin lesions resembling those of ophidiomycosis, we collected an additional swab directly from the affected areas. All snakes were released near the point of capture immediately after sample collection. We placed all swab samples in dry, 2.0-mL Eppendorf tubes stored on ice in coolers in the field and then frozen at –20 C until shipping for analysis. We also sampled a group of captive snakes at Elachee Nature Center in Hall County, Georgia using the same protocol. All captive snakes were held in individual enclosures and did not come in contact with other snakes. The frozen samples were shipped overnight on ice in a cooler and analyzed by the University of Illinois Veterinary Diagnostic Laboratory, College of Veterinary Medicine using DNA extraction and quantitative PCR amplification to detect the number of copies of O. ophiodiicola per ng total of DNA (copies/ng DNA).

Figure 1

Georgia, USA, counties where we surveyed wild snake populations for Ophidiomyces ophiodiicola, including the location at which we tested captive snakes (Elachee Nature Center, Hall County, Georgia, USA).

Figure 1

Georgia, USA, counties where we surveyed wild snake populations for Ophidiomyces ophiodiicola, including the location at which we tested captive snakes (Elachee Nature Center, Hall County, Georgia, USA).

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We collected 35 swab samples from 27 wild snakes of eight species (Table 1). Five of the 27 snakes had lesions consistent with ophidiomycosis. Eight individuals, of five species, tested positive for the presence of O. ophiodiicola DNA (30%). One individual, a gray rat snake (Pantherophis spiloides) that exhibited lesions (Fig. 2), was swabbed upon capture and then moved into captivity. The snake tested positive with a high fungal load (70 copies/ng DNA) and died approximately 1 mo after swabbing. There was no consistent trend in geographic distribution for positive snakes. Positive samples were collected in March (n=1), April (n=1), May (n=3), and September (n=3). The reported copy number from these wild snakes ranged from 0.2–70 copies/ng DNA (Table 1). A result above 0.0 copies/ng DNA only indicates presence of the DNA. However, a result above 0.0 copies/ng DNA with clinical signs indicates a strong association with ophidiomycosis.

Table 1

Ophidiomyces ophiodiicola presence in wild snake populations in northern counties of Georgia, USA, with copies of O. ophiodiicola DNA/ng reported. Snakes positive for O. ophiodiicola are in bold.

Ophidiomyces ophiodiicola presence in wild snake populations in northern counties of Georgia, USA, with copies of O. ophiodiicola DNA/ng reported. Snakes positive for O. ophiodiicola are in bold.
Ophidiomyces ophiodiicola presence in wild snake populations in northern counties of Georgia, USA, with copies of O. ophiodiicola DNA/ng reported. Snakes positive for O. ophiodiicola are in bold.
Figure 2

Skin lesions including edema on the face, dermal crustiness, and missing scales on a wild Pantherophis spiloides (gray rat snake) that tested positive for Ophidiomyces ophiodiicola, with a high fungal load of 70 copies of DNA/ng based on quantitative PCR amplification.

Figure 2

Skin lesions including edema on the face, dermal crustiness, and missing scales on a wild Pantherophis spiloides (gray rat snake) that tested positive for Ophidiomyces ophiodiicola, with a high fungal load of 70 copies of DNA/ng based on quantitative PCR amplification.

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We collected 31 swab samples from six captive snakes of six different species (Table 2) at the Elachee Nature Center, swabbing each snake four times through the year. Three individuals tested positive for the presence of O. ophiodiicola when swabbed in November 2019. No snakes exhibited signs of lethargy or skin lesions. Snakes that were positive for O. ophiodiicola were swabbed again in January and February 2020 and results were negative. The copy number for all positive samples ranged from 0.8–5 copies/ng DNA.

Table 2

Ophidiomyces ophiodiicola presence in Elachee Nature Center (Hall County, Georgia, USA) captive snakes with copies of O. ophiodiicola DNA/ng reported. Snakes positive for O. ophiodiicola are in bold.

Ophidiomyces ophiodiicola presence in Elachee Nature Center (Hall County, Georgia, USA) captive snakes with copies of O. ophiodiicola DNA/ng reported. Snakes positive for O. ophiodiicola are in bold.
Ophidiomyces ophiodiicola presence in Elachee Nature Center (Hall County, Georgia, USA) captive snakes with copies of O. ophiodiicola DNA/ng reported. Snakes positive for O. ophiodiicola are in bold.

Our results confirmed the presence of O. ophiodiicola in several snake species and indicate that the fungal pathogen is distributed across several counties in this region. Previously, O. ophiodiicola has only been reported in southern Georgia (Haynes et al. 2020); our results bridged the gap in data coverage across the state and suggested widespread occurrence of the fungal pathogen. Although O. ophiodiicola was not detected in samples from White County, additional sampling may confirm its presence in most, if not all, counties in northern Georgia. The normal behavior exhibited by all sampled snakes upon capture, and apparent elimination of O. ophiodiicola in captive snakes, was encouraging. However, more data are needed to determine the factors contributing to the spread of O. ophiodiicola and to estimate the detrimental effects it could have on snake populations in northern Georgia.

The presence of O. ophiodiicola was confirmed in multiple individuals with no clinical signs, similar to other studies (McKenzie et al. 2019). We found that 38% (3/8) of wild individuals and 100% (6/6) of captive individuals testing positive for copies of the pathogen were asymptomatic. This suggested that the prevalence and distribution of the pathogen in Georgia may be underreported if only symptomatic individuals with obvious lesions are sampled. Lorch et al. (2015) noted behavioral changes of increased basking and increased molting by infected individuals in a laboratory setting. More data are required to understand if behavioral signs of infection manifest before external clinical signs and if infected individuals without typical skin lesions are more likely to be sampled than are uninfected individuals because of their altered behaviors. Continued sampling in northern Georgia is needed to document the distribution of the fungal pathogen in the region, host snake species, factors that contribute to the spread and impact of ophidiomycosis, and management options to mitigate any negative effects associated with the disease.

We would like to thank the University of North Georgia (UNG) Office of Research and Engagement for funding this research along with the UNG Biology Department. Thank you to John Leyba and Nancy Dalman for continued support during the project and the UNG SCALE Lab students who assisted in fieldwork. Finally, we thank the Elachee Nature Center for their participation in our research and Houston Chandler, John Jensen, and Bryan Hudson for helpful conversations during the project.

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