Field Diagnostics and Seasonality of Ophidiomyces ophiodiicola in Wild Snake Populations

McKenzie, Jennifer M.; Price, Steven J.; Fleckenstein, J. Leo; Drayer, Andrea N.; Connette, Grant M.; Bohuski, Elizabeth A.; Lorch, Jeffrey M.

doi:10.1007/s10393-018-1384-8

Cited by 41 publications

(45 citation statements)

References 22 publications

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“…It is interesting to note that in EIS, the negative predictive value of skin lesions in identifying apparent ophidiomycosis was 100%. Conversely, the positive predictive value is poor, making it difficult to use clinical signs to confirm a diagnosis of apparent ophidiomycosis [53]. This is consistent with previous literature that showed the rate of false negatives is nearly 10 times higher in animals without lesions than individuals with lesions [48].…”

Section: Discussionsupporting

confidence: 85%

Ophidiomycosis prevalence in Georgia’s Eastern Indigo Snake (Drymarchon couperi) populations

Chandler¹,

Allender

Stegenga³

et al. 2019

PLoS ONE

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Wildlife diseases have posed a significant challenge to the conservation of many species in recent years. Diseases have been implicated in population declines over large geographic areas, with severe disease outbreaks leading to either local or complete extinctions of wild populations. Ophidiomycosis, commonly known as snake fungal disease, is caused by the fungus Ophidiomyces ophiodiicola , which has been documented in snake populations across the eastern and southern United States. We collected swab samples from the federally threatened Eastern Indigo Snake ( Drymarchon couperi ) in populations across the species’ Georgia range. We used quantitative PCR to determine the presence of O . ophiodiicola DNA and also recorded skin abnormalities characteristic of ophidiomycosis. From 1 September 2016 to 4 August 2018, Eastern Indigo Snakes tested positive for O . ophiodiicola DNA on 47 of 107 occasions (43.9%) and tested negative for fungal DNA but had skin lesions consistent with ophidiomycosis on 42 occasions (39.3%). Symptomatic and qPCR positive individuals were more likely to be encountered during January and February when compared to November and December. We found no effect of sex (p = 0.517), age-class (p = 0.106), or body size (snout-vent length: p = 0.083; mass: p = 0.206; body condition: p = 0.063) on ophidiomycosis status. Over the two-year study, we encountered individuals in which infection was clearly negatively impacting overall health and also documented individuals in which infection apparently cleared from one year to the next. These results demonstrate that O . ophiodiicola and lesions characteristic of ophidiomycosis are widespread in Georgia’s Eastern Indigo Snake populations. However, there are many unanswered questions regarding this disease, including the effects of disease on populations and individuals, the presence of infection vectors, and the change in prevalence over time. More research is needed to address ophidiomycosis and understand its impacts on ongoing conservation efforts.

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Section: Discussionsupporting

confidence: 85%

Ophidiomycosis prevalence in Georgia’s Eastern Indigo Snake (Drymarchon couperi) populations

Chandler¹,

Allender

Stegenga³

et al. 2019

PLoS ONE

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“…In eastern indigo snakes alone, 83.2% of snakes had skin lesions and 43.9% of snakes tested qPCR positive 15 . Previous state-wide studies found a 12.7% prevalence of skin lesions in eastern massasauga rattlesnakes in Michigan 16 , a 51.7% prevalence of lesions in snakes in Kentucky 18 , and a 30.0% prevalence of qPCR positive snakes in Tennessee 22 . However, the prevalence of disease in eastern massasaugas in Michigan was found to vary significantly across time and space, with the prevalence of lesions varying from 0 to 61.1% and the prevalence of positive qPCR results varying from 0 to 13.3% 26 .…”

Section: Discussionmentioning

confidence: 87%

“…While informative, these studies do not provide data regarding the overall epidemiology of the disease, including the impacts of geographic, temporal, and phylogenetic factors. Such broad examinations of disease distribution are crucial for informing management decisions that may mitigate the effects of ophidiomycosis on species of conservation concern and all snake populations worldwide 18 . Previous published reports of the disease in wild-caught snakes in the state of Georgia are rare, but include a black rat snake (Pantherophis obsoletus) with swelling around the right eye 19 , a mud snake (Farancia abacura) with head swelling and dysecdysis 20 , and populations of eastern indigo snakes (Drymarchon couperi), which are a species of conservation concern 15 .…”

mentioning

confidence: 99%

Ophidiomycosis surveillance of snakes in Georgia, USA reveals new host species and taxonomic associations with disease

Haynes

Chandler²,

Stegenga³

et al. 2020

Sci Rep

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Ophidiomycosis (snake fungal disease) is caused by the fungus Ophidiomyces ophiodiicola and threatens snake health worldwide. It has been documented throughout the eastern United States and severe cases have recently been reported in Georgia, USA. To evaluate disease distribution and prevalence in this state, 786 free-ranging snakes were examined for skin lesions consistent with ophidiomycosis and swabbed to detect O. ophiodiicola DNA using qPCR. Sampled snakes represented 34 species and 4 families; 27.5% had skin lesions, 13.3% were positive for O. ophiodiicola DNA, and 77.8% of the qPCR positive individuals had skin lesions. This is the first report of O. ophiodiicola in five of the 22 species that were qPCR positive. Multinomial logistic regression modeling indicated that Drymarchon couperi had a higher relative risk of apparent ophidiomycosis (lesions present and qPCR positive), and the best models predicting qPCR result and ophidiomycosis category included individual factors and excluded temporal and spatial factors. Phylogeny-based bipartite network analysis showed that Nerodia erythrogaster, Nerodia taxispilota, and D. couperi had the highest prevalence of apparent ophidiomycosis; this category was more prevalent in the subfamily Colubrinae and less prevalent in Natricinae. These results provide important information about ophidiomycosis epidemiology, which has implications for snake conservation.

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“…North American crotalids and Nerodia species have previously been shown to have a high prevalence of ophidiomycosis and may be uniquely sensitive to infection due to their environment ( Nerodia ) or morphology (pits in crotalids) [ 24 , 28 , 39 , 53 ]. Recent studies in aquatic snakes in Kentucky have highlighted that aquatic snake susceptibility is under-represented in the literature and warrants careful investigation [ 39 ]. It is possible that the perceived increase in susceptibility of crotalids represents a sampling bias in which more crotalids are sampled historically.…”

Section: Discussionmentioning

confidence: 99%

Ophidiomycosis, an emerging fungal disease of snakes: Targeted surveillance on military lands and detection in the western US and Puerto Rico

et al. 2020

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Wildlife disease surveillance and pathogen detection are fundamental for conservation, population sustainability, and public health. Detection of pathogens in snakes is often overlooked despite their essential roles as both predators and prey within their communities. Ophidiomycosis (formerly referred to as Snake Fungal Disease, SFD), an emergent disease on the North American landscape caused by the fungus Ophidiomyces ophiodiicola , poses a threat to snake population health and stability. We tested 657 individual snakes representing 58 species in 31 states from 56 military bases in the continental US and Puerto Rico for O . ophiodiicola . Ophidiomyces ophiodiicola DNA was detected in samples from 113 snakes for a prevalence of 17.2% (95% CI: 14.4–20.3%), representing 25 species from 19 states/territories, including the first reports of the pathogen in snakes in Idaho, Oklahoma, and Puerto Rico. Most animals were ophidiomycosis negative (n = 462), with Ophidiomyces detected by qPCR (n = 64), possible ophidiomycosis (n = 82), and apparent ophidiomycosis (n = 49) occurring less frequently. Adults had 2.38 times greater odds than juveniles of being diagnosed with ophidiomycosis. Snakes from Georgia, Massachusetts, Pennsylvania, and Virginia all had greater odds of ophidiomycosis diagnosis, while snakes from Idaho were less likely to be diagnosed with ophidiomycosis. The results of this survey indicate that this pathogen is endemic in the eastern US and identified new sites that could represent emergence or improved detection of endemic sites. The direct mortality of snakes with ophidiomycosis is unknown from this study, but the presence of numerous individuals with clinical disease warrants further investigation and possible conservation action.

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Field Diagnostics and Seasonality of Ophidiomyces ophiodiicola in Wild Snake Populations

Cited by 41 publications

References 22 publications

Ophidiomycosis prevalence in Georgia’s Eastern Indigo Snake (Drymarchon couperi) populations

Ophidiomycosis prevalence in Georgia’s Eastern Indigo Snake (Drymarchon couperi) populations

Ophidiomycosis surveillance of snakes in Georgia, USA reveals new host species and taxonomic associations with disease

Ophidiomycosis, an emerging fungal disease of snakes: Targeted surveillance on military lands and detection in the western US and Puerto Rico

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