Early detection is critical to managing CWD effectively and the average number of national samples needed for adequate testing annually is increasing. We surveyed state wildlife agencies to determine their budget dedicated to CWD surveillance, monitoring and testing, the number of samples tested, average wait time for results, and if sampling goals were met in 2019 and 2024. We also asked where CWD samples are collected from and if replacement tags are offered to hunters who harvest a CWD positive deer. Since 2019, agencies have allocated an additional $13 million nationally for CWD; a 128% increase. Contributing to this additional cost is a 38% increase in sampling efforts from 2019 to 2023, with 43 states testing nearly 250,000 samples. Despite the increasing cost and manpower required for testing, average wait time for results decreased from 36 to 29 days since 2019, with at least four states offering results in one week. Increased surveillance has forced agencies to diversify how samples are collected and agencies reported nearly ten different sources, with clinically suspect deer the most popular (96%). Forty-two states rely heavily on hunter harvested deer with 18 states offering replacement tags to hunters who take a CWD positive animal. Fortunately, 26 states met their sampling goals in 2023, with at least eight more reaching their goals in individual CWD surveillance zones or counties. Our results shed light on the drain that CWD has on wildlife agency resources and the intensive and opportunistic sampling that is crucial to manage the disease.
Efforts to standardize terminology are valuable across scientific disciplines for improving clarity, enabling consistent evaluation of research findings, reducing confusion, and improving the accuracy of scientific communication. Chronic wasting disease (CWD) has become a marked and expanding threat to cervid health and North American conservation. The Surveillance Optimization Project for CWD (SOP4CWD) was implemented to provide quantitative modeling and data warehousing tools to partnering wildlife agencies to improve surveillance efficiency in free-ranging populations. This interdisciplinary collaboration recognized a need for a standardized glossary of CWD-related epidemiology, disease management, and mathematical modeling terminology to effectively unite monitoring and control efforts across scientific disciplines and managerial jurisdictions. Using an expert elicitation approach, we compiled a comprehensive list of terms relevant to CWD and standardized definitions agreed upon simultaneously by persons with disease, statistical, and deer ecology expertise. We augmented the glossary with terms commonly found in the academic literature surrounding CWD. The final glossary will facilitate consistency in communication and promote coordination of CWD surveillance, research, management, and mitigation across vast jurisdictional boundaries.
Scavengers can impact the geographic spread of pathogens through complex interactions that can either decrease or increase the risk of transmission. Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy fatal to cervids and has been detected throughout much of the United States and internationally. Chronic wasting disease prions have long environmental persistence, and some scavengers have been shown to pass infectious CWD prions through their digestive tracts. We designed a study in a CWD-endemic area of northwestern Arkansas to determine which scavengers routinely feed on white-tailed deer carcasses and may be involved in movement of CWD prions. Using videos from game cameras, we recorded species that visited white-tailed deer carcasses and calculated abundance, presence duration, and feeding rate. American crows had the greatest number of individuals per video (5.33, 95% CI: 3.88 – 7.32), followed by turkey vultures (3.03, 2.21 – 4.16), and black vultures (2.94, 2.14 – 4.04). Black vultures had the longest bout duration in minutes (10.46, 8.01 – 13.67), followed by bald eagles (9.00, 6.88 – 11.77) and turkey vultures (8.45, 6.47 – 11.04). Bald eagles (50%, 38 – 62%), black vultures (49%, 40 – 58%), and American black bears (45%, 33-56%) spent the greatest proportion of time feeding. Species rank varied across metrics but the average of the three behavioral measurements indicated that black vultures, bald eagles, and turkey vultures had the greatest potential to ingest and potentially move CWD prions. Our research highlights the need to experimentally evaluate more avian scavengers for the potential to shed infectious prions.
Chronic Wasting Disease (CWD) poses a significant challenge to wildlife disease management, driven by the highly infectious nature of prions, the potential for both direct and indirect transmission routes, and the prolonged progression of the disease in infected cervids. These features greatly complicate surveillance and control efforts in both free-ranging and captive cervid populations. Recent advances in Real-Time Quaking-Induced Conversion (RT-QuIC) assays and related technologies are contributing to a paradigm shift in CWD surveillance. Due to its remarkable sensitivity and specificity, RT-QuIC offers the detection of prions in a variety of environmental and biological samples that were previously untestable. Simultaneously, agent-based epidemiological modeling informed by CWD biology and cervid demographics (e.g., OvCWD) offers a valuable framework for designing and optimizing novel RT-QuIC-based surveillance strategies. We present three innovative RT-QuIC testing applications that enhance CWD surveillance: (1) detection of CWD prions in cervid saliva on non-porous surfaces, (2) monitoring prions in environmental matrices such as soil and water near herd congregation sites, and (3) testing of skeletal remains years after deposition. Surveillance data derived from both wild and captive white-tailed deer populations across these three areas are summarized. We show how these three approaches can be used strategically with agent-based epidemiological models to guide efforts to prevent disease spread, identify and remediate environmental prion reservoirs, and ultimately improve the sustainability of cervid populations. Our findings underscore the potential of integrating RT-QuIC surveillance with epidemiological modeling to transform CWD management through proactive, data-driven strategies.
Chronic wasting disease (CWD) is a fatal prion disease affecting members of the Cervidae family and is present in both wild and captive cervid populations across the United States. CWD continues to spread among captive facilities, with new positive facilities being detected each year. CWD can quickly become established in these facilities due to the close and prolonged contact among deer and repeated exposure to infected individuals or contaminated environments. Early detection is crucial for managing CWD; however, identifying a rare event like CWD introduction in a large population presents significant challenges. Furthermore, the number of samples required to achieve a high level of confidence in detecting CWD increases for low prevalence scenarios, making it particularly difficult to detect a single infected deer in a captive facility. Thus, CWD often remains undetected in the early phase of the outbreak, mainly because of the logistical constraints on wildlife agencies' ability to match the sample size targets. To address these challenges, we developed an agent-based modeling approach that enhances the estimation of CWD detection probability in captive deer facilities. Specifically, we define CWD detection probability as the confidence in identifying the single infected deer within a population, based on a given number of samples tested over the course of a year. Our modeling approach integrates CWD testing records from captive deer facilities, along with herd size, composition, and individual deer transfer histories, to quantify the likelihood of undetected CWD within a facility. These annual detection probability estimates provide a measure of confidence in identifying a single CWD-infected deer within a population, based on the number of deer that tested negative throughout the year. This approach improves the effectiveness of CWD surveillance by enabling the prioritization of surveillance efforts across captive facilities, using the model-derived quantitative metric of detection probability. By refining this estimation process, we provide improved surveillance approach and inform better CWD management strategies in captive cervid populations.
Chronic wasting disease (CWD) is a fatal prion disease of cervids, considered to be one of the greatest threats to white-tailed deer populations. Effective management for CWD hinges on understanding how abundance, survival and recruitment are affected by the disease. Using 3 years of data from GPS collars, radio telemetry, trail cameras, and CWD testing of both live and deceased deer, we investigated the effects of CWD on population demographics for a white-tailed deer population in Arkansas’ CWD management zone. We analyzed our data using an integrated hierarchical model in a Bayesian framework to estimate survival, recruitment, movement and disease transmission across 3 study sites with different levels of CWD prevalence. Sample CWD prevalence from both ante- and postmortem sample testing was >20%. Deer that tested positive for CWD had lower annual survival and reproductive rates than presumed negative deer. Populations with the highest prevalence of CWD had lower densities and higher female to male sex ratios. Our results provide insights into the dynamics of CWD in the Southeastern United States and suggest CWD is working in concert with environmental factors to alter age structure and reduce population abundance.
