Conference Paper

Timber Rattlesnakes may reduce incidence of Lyme disease in the Northeastern United States

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Background/Question/Methods The role of biodiversity in regulating Lyme disease has been much debated, with empirical data and modeling showing that the diversity of host species and their identity can increase or decrease disease prevalence. We explored the role of snakes as predators on small mammals and modeled how that might affect the incidence of Lyme disease. We modeled timber rattlesnake (Crotalus horridus) prey consumption based on published snake gut contents for four localities in the northeastern United States. We determined the number of infected ticks removed from each location based on reported species-specific tick burdens. We used published energetic models and diet composition data of C. horridus to quantify annual prey consumption in adult male C. horridus diets and determined how changes in prey community composition affected the total number of ticks removed by snakes annually. In addition to quantifying the number of ticks removed from each of the four localities, we modeled tick removal from four theoretical prey communities that span the range of habitat quality in the northeastern US. Results/Conclusions Model results estimated 2,500–4,500 ticks were removed by foraging snakes per site annually.This varied among sites because of spatial variation in rattlesnake diet composition. Rattlesnakes removed more ticks from more diverse prey communities than from less diverse prey communities which are typical of disturbed habitats. Because ticks are vectors for Lyme disease in the northeastern US, snake predators may play an important role in reducing tick burden and may reduce human exposure to Lyme disease. Levi et al. (2012) showed that reduced abundance of mammal predators increased numbers of ticks which in turn resulted in increased incidence of Lyme disease in humans. Our model results suggests apex predators like many species of vipers may play important roles in regulating incidence of Lyme disease through predation on small mammals. Timber rattlesnakes populations are declining under pressure from decreasing habitat and overharvest, especially in northern and upper midwestern populations where the incidence of Lyme disease is the highest. Our research highlights the importance of biodiversity for human health and identifies several research areas on the effectiveness of ecological education and conservation efforts for these important predators.

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... As generalist predators, they control populations of small mammals and therefore aid in controlling the spread of zoonotic diseases including viruses such as hantavirus and bacteria such as Lyme disease [12]. It was observed that Timber Rattlesnakes' small mammal consumption was responsible for the removal of 2500-4500 ticks per sampled site per year, which was proposed to reduce the incidence of Lyme disease in the areas where these snakes live [13]. Furthermore, healthy snake populations promote overall biodiversity, which is integral for maximizing ecosystem health and productivity [14]. ...
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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 ophi-diomycosis is unknown from this study, but the presence of numerous individuals with clinical disease warrants further investigation and possible conservation action.
... As generalist predators, they control populations of small mammals and therefore aid in controlling the spread of zoonotic diseases such as hantavirus and Lyme disease (Ostfeld and Holt, 2004). It was observed that Timber Rattlesnakes' small mammal consumption was responsible for the removal of 2500-4500 ticks per year, which would reduce the incidence of Lyme disease in the areas where these snakes live (Kabay, Caruso, and Lips, 2013). In addition, snakes are crucial to maintaining food chains in many ecosystems, as they serve as prey for higher level predators, including birds and other snakes. ...
Technical Report
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Report summarizes field and laboratory efforts to sample for snake fungal disease (Ophidiomycosis) at over 50 military installations throughout the United States and Puerto Rico.
... In Kentucky, C horridus is under no state protection, but is listed as a "species of greatest conservation need (SGCN)". C horridus plays an important predatory role in forest ecosystems, having the potential to control small mammal populations and perhaps subsequently influence disease dynamics (Clark 2002;Kabay et al. 2013). Although loss of mature forest habitat imperils C horridus populations generally, management is often focused on conservation of hibernacula, to which individuals display strong site fidelity (Brown 1993). ...
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Surface coal mining can permanently alter the rugged topography of Appalachia, which plays an important role in creating and maintaining the structure, composition, and diversity of this North American region's ecological communities. We used remote‐sensing datasets to characterize the past and future topographic impacts of surface coal mining on the mixed‐mesophytic forests of eastern Kentucky. To provide context, we examined the consequences of widespread topographic rearrangement for an imperiled ridgetop‐associated predator, the timber rattlesnake (Crotalus horridus). We found that surface mining disproportionately impacts ridgetop habitats, causing large reductions in suitable habitat for C horridus, and most likely other ridgetop‐dependent biota as well. Land permitted for surface mining is also concentrated in high topographic positions, and patterns of habitat loss are therefore likely to remain concentrated within these ecosystems. These permanent topographic shifts complicate restoration of pre‐existing microhabitats, create homogenized landscapes, threaten long‐term ecosystem health, and reduce the diversity of ecological communities.
... The perceived recent emergence of this fungal pathogen could be due to increased awareness of the disease, changing climatic variables, introduction of an exotic pathogen into a naive host population, or other uncharacterized factors. Nevertheless, snake species are of particular significance, as they are indicators of trophic dynamics and ecosystem health [68], and yield potential benefits to humans, such as the reduction of disease-carrying rodents [69]. ...
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Understanding how biological patterns translate into functional processes across different scales is a central question in ecology. Within a spatial context, extent is used to describe the overall geographic area of a study, whereas grain describes the overall unit of observation. This study aimed to characterize the snake skin microbiota (grain) and to determine host-microbial assemblage-pathogen effects across spatial extents within the Southern United States. The causative agent of snake fungal disease, Ophidiomyces ophiodiicola, is a fungal pathogen threatening snake populations. We hypothesized that the skin microbial assemblage of snakes differs from its surrounding environment, by host species, spatial scale, season, and in the presence of O. ophiodiicola. We collected snake skin swabs, soil samples, and water samples across six states in the Southern United States (macroscale extent), four Tennessee ecoregions (mesoscale extent), and at multiple sites within each Tennessee ecoregion (microscale extent). These samples were subjected to DNA extraction and quantitative PCR to determine the presence/absence of O. ophiodiicola. High-throughput sequencing was also utilized to characterize the microbial communities. We concluded that the snake skin microbial assemblage was partially distinct from environmental microbial communities. Snake host species was strongly predictive of the skin microbiota at macro-, meso-, and microscale spatial extents; however, the effect was variable across geographic space and season. Lastly, the presence of the fungal pathogen O. ophiodiicola is predictive of skin microbial assemblages across macro-and meso-spatial extents, and particular bacterial taxa associate with O. ophiodiicola pathogen load. Our results highlight the importance of scale regarding wildlife host-pathogen-microbial assemblage interactions.
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