Implication of Prion Disease Across Geographic Populations: A Case Study Examining Wild North American Deer
Daniel Hardy, Warren Conway, Emily Wright, Emma McDonald, Matthew Buchholz, Emma Roberts, Robert Bradley
Spongiform encephalopathies are caused by the misfolding of a common prion protein (PrPC) into an infectious conformation (PrPSc).  Various prion amino acid polymorphisms are associated with three categories of spongiform encephalopathy: 1) familial, where disease alleles are inherited, 2) sporadic, in which mutations arise spontaneously, and 3) transmissible, where the prion disease is infectious among mammalian organisms.  Chronic wasting disease (CWD) is the only transmissible prion disease documented in free-ranging and captive animals, specifically Cervids (deer species).  Our hypothesis is that geographically-based genetic variation, arising in part from historical inter-species hybrid formation and  intentional translocations and movements, affects susceptibility to CWD.  The aims of this research are to establish a PrP allele database, determine if PrP allele distribution is consistent with mitochondrial haplotype (cytochrome b) distribution and inferred hybridization history, and predict whether deer species in different geographic regions will vary in susceptibility to CWD.  While transmission to humans has not been documented, the Centers for Disease Control and Prevention recommends testing any deer harvested in areas reported with CWD before consumption.  Several known codon variants affect susceptibility to prion misfolding, some that spontaneously result in disease and others that can confer resistance (Odocoileus virginianus, white-tailed deer: Q95H, G96S, A116G; O. hemionus, mule deer: S225F).  This is the first exploratory study to examine the PRNP exon 3 in North American deer species.  To date, we have found the amino acid substitutions Q95H and G96S (confers reduced susceptibility to CWD) in populations of white-tailed located in New York, South Carolina, and Texas.  Further, populations of mule deer in California and Alaska do not differ from other mule deer where CWD has been detected, indicating that mule deer populations in western states potentially have the same susceptibility to CWD.
Mule Deer Migrations and Highway Underpasses in Northern California
Molly Caldwell, Mario Klip
Roadways may pose barriers to long‐distance migrators such as some mule deer (Odocoileus hemionus). Highway underpasses mitigate wildlife‐vehicle collisions and can be an important management tool for protecting migration corridors; however, deterioration of crossing structures or incomplete highway fencing can contribute to roadkills. In northern California, 3 underpasses were built on United States Route 395 (Route 395) in Hallelujah Junction Wildlife Area (HJWA) in the 1970s for a migratory mule deer herd that had been negatively affected by highway traffic. To determine whether these underpasses were still reducing mule deer mortalities >40 years after construction, we investigated deer use of the underpasses from 2006–2019 using cameras, global positioning system (GPS) collars, and roadkill records. We used occupancy models, approximations of GPS‐collared mule deer movement paths, and roadkill locations to estimate the highway crossing patterns of deer. From camera data, there was higher use of the underpasses by deer during migration (spring [Mar–Jun], fall [Oct–Dec]) than in summer (Jul–Sep), when only resident deer were present. Eleven of 21 GPS‐collared migrating mule deer crossed Route 395. We estimated 30% of the crossings (by 7 of the 11 deer) occurred south of the underpasses where deer could easily access the highway because of short (1‐m high) and deteriorating highway fencing. Roadkill data confirmed that deer‐vehicle collisions were occurring south of the underpasses and at the underpasses. This was likely due to deteriorating infrastructure at the underpasses that allowed wildlife access to the highway. Overall, our study indicated that although underpasses can provide safe passage for migratory deer decades (>40 years) after their construction, deteriorating infrastructure such as fencing and gates can lead to wildlife mortalities on highways near underpasses. 
Temporal Variation of White-Tailed Deer Detection and Implications for Population Parameter Estimates – SRIP
Steven Gurney, Sonja Christensen, David Williams, Dwayne Etter, Melissa Nichols, Sarah Mayhew
White-tailed deer (Odocoileus virginianus) are an important game species, and the accurate estimate of population parameters is essential for the evaluation of management actions. This need is especially relevant in areas where population-management actions are aimed to mediate the spread of chronic wasting disease (CWD) in free-ranging deer. Camera trapping has become an increasingly common method for monitoring white-tailed deer populations, but many analytical methods fail to account for temporal variation in detectability, which can differ across age classes and between sexes. We plan to evaluate the effect of an antler point regulation change in an area with CWD on a deer population over three consecutive years. To optimize our precision, we must account for variation in detection over the sampling period. Our goal for this study is to evaluate temporal variation of white-tailed deer detection and implications for population parameter estimates. During 2019, we deployed 144 camera traps across a designated 5-county CWD Core Area (Kent, Newaygo, Ionia, Montcalm, and Mecosta; 9,332 km2) in the south-central Lower Peninsula of Michigan. Camera trapping will continue through 2022 and is restricted to 8 townships within the 5 counties, encompassing an area of approximately 749 km2. Between the months of July and September in 2019, we collected 797,407 photographs and characterized photos of deer based on total number of individuals, age, and sex. We are evaluating how detection for age and sex cohorts varies across time of day and sampling period, and how this may affect population estimation using site-structured models. Further, we are assessing how sample size and frequency of photos at sites affect our estimates and if subsampling produces sufficient precision and improved efficiency. Our findings will inform recommendations for addressing temporal detection variability on population parameter estimates using site-structured models and improve camera trap methods for wildlife more generally.
Inferring Infection Risk of West Nile Virus from Wildlife: Connecting Habitat Selection and Seroprevalence in Free-Ranging White-Tailed Deer – SRIP
Avery Tilley, Sonja Christensen, Jonathan Trudeau
West Nile virus (WNV) is a mosquito-transmitted pathogen of humans, livestock, and wildlife that has extended rapidly across the United States since its initial 1999 introduction in New York City. WNV is maintained primarily in an enzootic cycle between ornithophilic mosquitoes and avian amplifying hosts, with mammals, including humans, serving as dead-end hosts. A mammalian host of particular interest is the white-tailed deer (WTD), given their role in the maintenance and distribution of WNV as identified through serosurveillance. The WTD serves as the primary mammalian blood meal for Culex species associated with WNV transmission, and WTD have a widespread distribution across varying habitats promoting a variety of interactions between WTD and mosquito vectors. For these reasons, it is critical to better understand the spatial ecology of WTD and how their use of habitat at a landscape level may be important for mitigating or monitoring WNV. This study seeks to evaluate WTD habitat use with respect to Culex habitat and whether WTD could serve as sentinel species for WNV monitoring due to advantages such as opportunistic serum collection from hunter-harvested deer. This study utilized WTD serum obtained from live, radio collared deer and tested for antibodies to WNV using a virus neutralization assay. Serum results were compared to habitat use of deer and that of known Culex habitat. Our findings suggest the distribution of deer may inform when and where WNV may present a risk on the landscape.
Quantifying Factors Affecting Chronic Wasting Disease Transmission Among Deer – SRIP
Samantha Courtney, Dwayne Etter, Sonja Christensen, David Williams
Chronic wasting disease (CWD) is projected to have long-term population impacts on white-tailed deer (Odocoileus virginianus) and negatively affect state economies. While the pathways for CWD transmission have been well characterized in previous studies, we do not fully understand factors that affect transmission and how those factors may interact. To better understand these factors, we asked: how do factors such as deer group size and contact, bioaccumulation of feces, and deer attractants affect the transmissibility of CWD? To answer this question, we sought to address several objectives 1) Quantify group size, composition, and physical contact rates among deer; 2) Estimate bioaccumulation of deer feces in congregation areas; and 3) Identify how attractants impact physical contact rates and bioaccumulation of feces. Our study is in an agricultural region of southern Michigan. We are observing deer during the post-breeding period (Jan-April), when they tend to congregate into larger groups, potentially increasing the interactions among related and unrelated deer, populations are stable, and deer are most easily observed. We are conducting road-based surveys and direct observations to characterize group size and composition, and selected deer behaviors in areas where deer naturally congregate. Using camera trapping, we are recording group composition and behaviors at baited sites and food plots. This design will allow us to compare deer behaviors that potentially increase transmission of CWD among the three congregation areas (e.g., natural forage, bait, and food plots). At food plots and bait sites, we will estimate bioaccumulation of deer fecal material because of its potential role in indirect transmission of CWD. We will report preliminary results from the 2021 field season. Our goal in quantifying these CWD transmissibility factors is to update existing risk models to help inform disease management.
Influence of Visual Perception on the Movement and Resource Selection of a Prey Species – SRIP
Blaise Newman, Karl Miller, Michael Cherry, Gino D’Angelo, Jordan Dyal
In heterogenous environments, an animal’s visual perception is dynamic and influences decision-making processes and behaviors. Visually available information is constrained by the physiological properties of an animal’s sensory system and the physical characteristics of its environment. For example, dappled forest light increases visual noise and complexity for animals and mobile prey may use these environments for concealment from visual, ambush predators. We aim to assess how the visual perception of white-tailed deer (Odocoileus virginianus) influences their patterns of movement and resource selection in visually dynamic environments. From 2018-2020 in Central Florida, we captured and fit 42 adult male white-tailed deer with GPS collars set to record locations every 6 hours. We adjusted collars of 14 bucks to record locations every 10 minutes during August-September 2019. We calculated dynamic light environments available to and used by collared deer during our study period using tree canopy cover, photoperiod, lunar phase, cloud cover, wind speed, and plant species composition. To evaluate patterns of movement and resource selection in these environments, we will use step selection functions for 6-hr locations and path selection functions for 10-min locations. We will simulate 10 available steps drawn at random from a distribution of step lengths and turning angles unique to each individual for every observed step or path. These analyses will allow us to account for individual variation and spatial covariates that vary in time. Findings from this study will expand our understanding of the visual ecology of prey species.
Comparison of Immobilization Efficacy of Nalbuphine-Medetomidine-Azaperone and Butorphanol-Azaperone-Medetomidine in Captive White-Tailed Deer – SRIP
Patrick Grunwald, Gino D’Angelo, Mark Ruder, Lisa Muller, David Osborn, Kaitlin Goode
Previous studies involving white-tailed deer (Odocoileus virginianus) use chemical agents to effectively immobilize animals and increase safety for deer and researchers during biological sampling. Current combinations of butorphanol-azaperone-medetomidine (BAM) are known to produce complete and long-lasting immobilization in white-tailed deer, but current research has not focused on post-immobilization physiological effects on deer. Nalbuphine-medetomidine-azaperone (NalMed-A) is an alternative to BAM, which has less stringent regulatory requirements for transport, storage, and use versus BAM. Currently, there are no published studies on the use of NalMed-A in white-tailed deer, but one study with Rocky Mountain elk (Cervus canadensis) showed promise for use in other cervids. To compare immobilization efficacy, quality, and residual effects of BAM and NalMed-A, our research will focus on potential physiological and behavioral changes produced by respective chemical immobilizations in captive white-tailed deer. We administered a dose of either 1.5 mL of BAM, 1.5 mL, or 2.0 mL of NalMed-A to deer in 3 treatment groups of 10 deer each. Before, during, and after immobilization treatments, we collected biological samples to measure glucocorticoid stress hormones and we conducted behavioral observations to determine treatment-related variation in stress levels and behavioral patterns. We measured respiration rate, pulse, rectal temperature, and hemoglobin oxygen saturation during immobilization to determine immediate physiological effects. We hypothesize there will be similar increases of stress hormone levels among treatments, but glucocorticoids will return to baseline metrics quickly. We hypothesize behavioral patterns will not differ pre- and post-treatment among treatment groups. We hypothesize that BAM and NalMed-A will produce similar induction times, quality of immobilizations, and recovery times on white-tailed deer. If these hypotheses hold true, BAM and NalMed-A can be regarded as equally effective chemical immobilization agents and use can be determined by factors such as cost and availability.
Modeling Hemorrhagic Disease in Deer Populations Relative to the Physiographic and Climate Covariates in the Great Plains Region of the United States – SRIP
Emma Kring, Gino D’Angelo, Mark Ruder, Michel Kohl, Liliana Salvador, Christopher Cleveland, David Stallknecht
Hemorrhagic disease (HD) of deer is caused by either epizootic hemorrhagic disease virus (EHDV) or bluetongue virus (BTV) from the Orbivirus genus in the Reoviridae family. HD is considered one of the most important diseases of white-tailed deer (Odocoileus virginianus) in North America, but the viruses may also affect other wild and domestic ruminants.  Both EHDV and BTV are transmitted by biting midges from the Culicoides genus. Recent observed changes in the historic spatial and temporal distribution of HD in the eastern United States have been reported and may be linked to changes in environmental conditions conducive to vector populations and virus transmission. However, patterns of HD remain poorly described across much of the Great Plains region in the United States. The objective of this study is to assess the relationship that climate covariates (e.g. temperature and precipitation) and landscape variables may have on the probability of reporting HD within the Great Plains. We will fit generalized linear mixed models (GLMMs) to annual HD survey data collected by the Southeastern Cooperative Wildlife Disease Study from the last four decades to simulate how different climate variables and ecoregions may affect reported HD at the county level. Overall, this model primarily will help explain the changing HD patterns in the Great Plains, but will also determine climate factors that may serve as predictors for increased disease risk. These predictors may assist risk communication and management strategies for state agencies, particularly in the Great Plains where adjustments to hunting regulations have been affected by severe HD occurrences.
Effects of Tick Salivary Antigen-Based Vaccine on Tick Feeding Parameters on White-Tailed Deer – SRIP
Alec Baker, Tammi Johnson, Pia Olafson, Albert Mulenga
White-tailed deer (Odocoileus virginianus) are a main host for blacklegged (Ixodes scapularis) and Lone Star ticks (Amblyomma americanum). The population increase of white-tailed deer in the twentieth century has correlated with the rise of various tick-borne pathogens that are known to be spread by blacklegged, Lone Star, and other species of ticks. White-tailed deer play a vital role in the reproductive success of these ticks since they are the main bloodmeal host for the adult life stages. Previous studies targeting white-tailed deer for tick control suggest that deer-targeted interventions have the potential to impact human disease. However, current methods of targeting white-tailed deer for tick control pose issues and are not sustainable options. Standard immunization protocols that require animals to be immunized more than once are not feasible when immunizing wildlife, the limitations being that capturing and identifying individuals for a follow up inoculation of the vaccine is difficult. Therefore, determining an effective immunization dosage of the tick salivary antigen-based vaccine that will only need to be administered to the host one-time has vital implications. Effective anti-tick immunization of white-tailed deer should be protective for the duration of the host’s life. A single dose salivary antigen-based vaccine that can reduce tick feeding success and reduce tick fecundity has important human-wildlife disease interface implications and could be used in future research and management targeting the livestock-wildlife disease interface involving tick vectors.
Landscape Predictors of Mule Deer Road Crossing Behavior in the American Southwest – SRIP
Kaitlyn Frank, Mark Ditmer, David Stoner, Neil Carter, William Currie
Road networks pose many well-documented threats to wildlife, from fragmenting habitats and restricting movement to causing mortality through vehicle collisions. For large, wide-ranging mammals like mule deer (Odocoileus hemionus), home range requirements and seasonal migrations often necessitate road crossings, posing threats to human safety, property, and deer survival. Research has shown wildlife road crossings and wildlife-vehicle collisions cluster in response to environmental factors. Although general relationships between crossings, collisions, and landscape features have been described, there is variation across locations and species in predictors of crossing frequency and collision risk. We aim to evaluate the extent to which various landscape, environmental, and human factors influence the location and timing of mule deer road crossings in and around Salt Lake City, UT. Specifically, we are interested in understanding how elevated artificial nightlight may influence deer road crossing locations. By integrating the latest NASA nightlight products with GPS collar data collected from 82 mule deer over a 7-year period, we used a resource-selection framework to assess factors influencing seasonal crossing intensities at a fine spatial scale (based on mean daily movement distances) and within individual seasonal home ranges. Additionally, we analyzed mule deer road mortality data collected within the study area during the same time period to assess the relationship between mortality risk and use of road segments. Preliminary results suggest independent spatial clustering of both mule deer road crossing and road mortality locations. Further analysis will assess the extent to which a variety of landscape factors influence deer selection of crossing points. Furthering our understanding of influential landscape factors in crossing point selection, especially how artificial nightlight may attract or repel human-tolerant species of wildlife from roadways, presents an opportunity to mitigate collision risk while improving population management strategies for an economically and ecologically important species in an expanding metropolitan area.
Impacts of Chronic Wasting Disease on Arkansas’s White-Tailed Deer Population – SRIP
Marcelo Jorge, Richard Chandler, Gino D’Angelo, Mark Ruder, Michael J. Chamberlain, Dana Jarosinski
Chronic wasting disease (CWD) is a fatal neurological disease of cervids that was first discovered in 1967 in Colorado and is a growing concern to natural resource managers across the United States and internationally. CWD was first detected in Arkansas in elk (Cervus canadensis) during 2015 and later in white-tailed deer (Odocoileus virginianus) during 2016.  Subsequent surveillance demonstrated a high CWD prevalence (>20%) in deer within a 10-county region, indicating that CWD was in the state for decades. Previous CWD research has provided valuable information on transmission, environmental persistence of prions, diagnostic methods, and surveillance approaches, among others. However, important knowledge gaps still exist that hinder management decisions. The objectives of our research include understanding the effects of CWD on deer survival, recruitment, and behavior in Arkansas. We are using an epidemiological case-control study design involving the capture of positive and presumed negative individuals. We will also recapture as many individuals as possible over the 5-yr study. We are using active and passive sampling techniques including GPS/radio telemetry, CWD testing, and trail camera grids to provide rigorous estimates of white-tailed deer demographic parameters and CWD infection rates.  Ultimately, we will develop a spatially-explicit population model that will forecast the effects of agency management actions on the spread of CWD and the consequences to the white-tailed deer herd.   

Location: Virtual Date: November 3, 2021 Time: 11:00 am - 12:00 pm