Sustainability in the context of One Health: definitions, concepts and a framework for analysis

Abstract Introduction: This thesis addresses the conceptual and operational ambiguity surrounding sustainability in One Health and global health security. Despite widespread rhetorical endorsement and a growing policy emphasis, sustainability remains under-defined and inconsistently applied across the human, animal, and environmental health sectors. The central aim of this research was to develop and empirically validate a cross-sectoral conceptual framework and definition of sustainability for application in One Health initiatives. The specific objectives were to synthesise existing definitions across disciplines develop an integrated framework; explore expert understandings of sustainability; and assess how existing global health security tools, namely the WHO Joint External Evaluation (JEE) and the WOAH Performance of Veterinary Services (PVS) tool, reflect sustainability concepts and are perceived by policymakers. Methods: A multi-method design was employed, grounded in interpretivist and social constructionist epistemologies. First, an umbrella systematic review was conducted to identify sustainability definitions and frameworks across disciplines. The resulting synthesis informed the development of an integrated definition and meta conceptual framework. This was followed by a document analysis of the JEE and PVS tools and two rounds of semi-structured qualitative interviews with an international group of One Health and health security experts. Results: Based on the research findings, the proposed definition conceptualises sustainability as: “A quality-assured system, strategy, service, programme, project, intervention or initiative, which is equitably and justly delivered while being socially, economically and environmentally viable, that continues to be implemented while effective and adapts as needed over a defined period of time, to produce a state of optimised health benefits across humans, animals and ecosystems without compromising the ability of future generations to meet their health and well-being needs.” The corresponding framework incorporates both process dimensions (e.g., governance, financing, institutional capacity, adaptability, systemic integration) and outcome dimensions (e.g., ecological resilience, sustained health improvements, equity). Interview and document analysis findings independently affirmed the framework dimensions’ relevance across sectors and scales and highlighted the limited and fragmented integration of sustainability in global health security tools. They also illuminated that the meaning and determinants of sustainability not only vary across sectors, but are also deeply shaped by epistemic tradition, disciplinary background, power relations, and socioeconomic and political context. Discussion and Conclusion: The deterioration of multilateral development financing, increased geopolitical polarisation and weakening of public trust in institutions all challenge the sustainability of health systems and their capacity to address complex, cross-sectoral threats. The research offers a theoretically grounded and practically applicable framework for embedding sustainability into One Health programme design, evaluation, and governance. It also highlights the inadequacy of current health security assessments in addressing long-term resilience and multisectoral integration. This thesis contributes to bridging conceptual gaps and advancing a shared understanding of sustainability in global health at a time of funding contractions and mounting ecological and institutional fragility.