The SARS-CoV-2 pandemic highlighted the interconnectedness of human, animal, and environmental health, emphasizing the need for a One Health approach. The spillover of SARS-CoV-2 into wildlife, particularly white-tailed deer, has raised significant public health concerns due to documented animal-to-human transmission and the potential for novel variant emergence. Detections of SARS-CoV-2 in deer across the US, beginning in 2020, revealed the presence of multiple strains closely related to those circulating in human populations, indicating repeated human-to-deer transmission and the ability of deer to sustain the virus within their populations. This poses a complex challenge due to the diverse settings where humans and deer interact, and the involvement of multiple agencies with potentially conflicting objectives and jurisdictions. This research directly addresses the need for a comprehensive strategy by evaluating the relative effectiveness of single-sector versus multi-sector approaches to mitigating SARS-CoV-2 transmission in deer populations.

Previous research has documented SARS-CoV-2 infections in various animal species, including farmed mink and white-tailed deer. Studies have shown close relationships between viral strains in deer and those circulating in nearby human populations, suggesting repeated human-to-deer transmission. The emergence of novel variants in deer populations further underscores the risk of sustained transmission and potential zoonotic spillback. Existing literature also highlights the challenges of managing zoonotic diseases through a One Health approach, particularly when considering the complex governance structures and potentially conflicting objectives of different managing agencies. This study builds upon this existing body of knowledge by quantitatively assessing the relative effectiveness of various management strategies.

The study employed a multisectoral approach, convening a One Health guidance committee comprised of representatives from wildlife management (WM), agricultural management (AM), and public health (PH) agencies. The committee defined fundamental objectives, identified causal chains of SARS-CoV-2 transmission (both direct and indirect, though the study focused on direct transmission due to evidence of viral replication in the upper respiratory tract), and specified management alternatives. A dynamic compartmental model was developed to simulate SARS-CoV-2 transmission in wild deer (rural and suburban settings) and captive deer (low- and high-density facilities). The model considered human-to-deer and deer-to-deer transmission, incorporating parameters estimated from empirical data and expert elicitation. The model evaluated the efficacy of various single-sector and One Health alternatives in reducing SARS-CoV-2 prevalence, per capita cumulative infections, and the probability of virus persistence. Two scenarios were explored, representing differing combinations of wild and captive deer settings and human-deer interaction levels.

The analysis revealed significant differences in the effectiveness of single-sector versus One Health approaches. Single-sector interventions, such as deer vaccination (AM), public education on PPE use (PH), or density reduction (WM), showed some reduction in transmission but had limited impact compared to the multi-sector strategy. The probability of human-to-deer transmission was higher in captive settings, especially high-density facilities. Deer-to-deer transmission was also more likely to be sustained in captive herds. The One Health alternative, involving collaborative actions across all three sectors, proved drastically more effective than any single-sector approach in eliminating SARS-CoV-2 transmission in captive deer and substantially reducing transmission in wild deer. Specific findings regarding the efficacy of individual interventions include the high effectiveness of vaccination in captive deer and the effectiveness of density reduction in wild deer. However, the integrated multi-sectoral approach significantly outperformed any individual intervention. This is quantified through measures such as median prevalence of SARS-CoV-2, per capita cumulative infections, and the probability of persistence across multiple simulation runs. The results are presented in boxplots illustrating the distribution of these metrics across simulations for different scenarios and interventions.

The findings strongly support the necessity of a One Health approach for effectively mitigating SARS-CoV-2 transmission in deer populations. The superior performance of the collaborative, multi-sector strategy highlights the limitations of single-agency actions in addressing complex, interconnected systems. The success of vaccination in captive settings points to the potential of this intervention, pending the development of a deer-specific vaccine. Density reduction also proved effective in wild deer, aligning with previous studies on disease transmission and density. However, practical challenges exist in implementing a fully coordinated One Health strategy due to jurisdictional boundaries and potentially conflicting priorities across different agencies. The study provides crucial insights into the trade-offs between different intervention strategies, informing policy decisions and resource allocation.

This study provides compelling evidence for the effectiveness of One Health collaborations in mitigating SARS-CoV-2 transmission in deer. The superior performance of the multi-sector approach compared to single-sector interventions highlights the interconnected nature of human, animal, and environmental health and the need for coordinated efforts. Future research should focus on addressing the practical challenges of implementing One Health strategies and on developing and evaluating broader-spectrum vaccines for use in deer populations. Further investigation into the ecological and epidemiological factors influencing SARS-CoV-2 transmission in deer is also warranted.

The study's model made certain simplifying assumptions, such as a closed population and uniform distribution of deer, which may affect the generalizability of results to specific real-world contexts. While the model included four different deer-human interaction settings, further refinement could incorporate more detailed spatial dynamics and heterogeneity in human-deer contact rates. The study also focused primarily on direct transmission; exploring the role of indirect transmission pathways could provide a more comprehensive understanding of the disease dynamics. Finally, the study did not fully evaluate all eight identified objectives, focusing on three primary disease-related metrics. A more comprehensive analysis encompassing all objectives would provide a more nuanced picture of the trade-offs involved in different management strategies.