An economic framework for One Health investment: A critical tool for decision makers.

One Health operationalization needs political and financial support and decision makers need to have an economic rationale for their actions. Therefore, both advocates and decision makers need economic methodologies to highlight the value of One Health. The objective of this paper is to propose a conceptual framework grounded in six economic principles that can serve as building blocks for an investment case for One Health. Some of these principles relate to the implementation of interventions, showing how One Health approaches can be more efficient. These include inefficiencies in resource allocation, economies of scope, scale and joint production and distributional considerations. The other principles, public goods and externalities and incentive compatibility focus on outcomes, helping to identify how an investment in one sector creates a benefit in another. The economic principles were also used in two conceptual case studies (Leptospirosis and anti-microbial resistance) to provide illustrative examples. The case studies demonstrate how investment in One Health not only helps to address health risks such as Leptospirosis but can provide significant synergistic benefits such as improving agricultural production and livelihoods. They also highlight a critical point that while One Health is generally associated with collaboration between sectors, many of its benefits arise not from working together, but from each sector being adequately equipped to fulfill its core functions. Effective animal and environmental health services are essential foundations for One Health operationalization. Investing in the capacity of these sectors is therefore not just beneficial-it is the critical driver of One Health value.