the United Nations (FAO) and the World Organisation for Animal Health (OIE). The World Bank produced a first account of economic aspects of One Health (World-Bank, 2010, 2012), which can include health consequences of structural aspects such as political change (Roth et al., 2003) or globalized agriculture (Wallace et al., 2015). In the USA, a One Health commission coordinates and assembles many of the activities (‘www.onehealthcommission.org’ (accessed 27 March 2020)).The European Cooperation in Science and Technology (COST) funded the creation of a Network for Evaluation of One Health (NEOH), which developed an evaluation framework (Rüegg et al., 2017) and coined the term ‘One Health-ness’. One Health-ness is expressed as a mixed method index of quantitative and qualitative operational and infrastructural aspects of One Health. NEOH includes environmental, ecosystem and structural elements of health, and connects to the Sustainable Development Goals (SDGs) of the United Nations (Rüegg et al., 2017, 2018; Hitziger et al., 2018).
One Health has thus gained broad recognition as an integrated approach to health when compared with mainstream reductionist approaches in the health sciences. Yet, by expanding the integration of health towards broad social-ecological issues like antimicrobial resistance or deforestation, complex interactions can become ‘wicked’ and hardly tractable.
Rüegg and co-workers state: ‘There is a need to provide evidence on the added value of these integrated and transdisciplinary approaches to governments, researchers, funding bodies and stakeholders’ (Rüegg et al., 2018). We thus recall the foundational principles of One Health:
1. One Health is about cooperation between different academic disciplines underlying human and veterinary medicine in the first place, but without any barrier to natural and social sciences and the humanities. One Health also engages with non-academic actors in the co-production of knowledge (Berger-González et al., Chapter 6, this volume).
2. Cooperating partners will seek a benefit of working together sooner or later. To fully understand the range of potential benefits of a closer cooperation implies a deeper and comprehensive recognition and understanding of how humans and animals and their environment are interrelated at all scales. This is a necessary requirement of One Health but still not sufficient.
A sufficient requirement for One Health is demonstrating the benefits and added values resulting from the crosstalk and closer cooperation between human and animal health and all related disciplines and stakeholders.
We thus define One Health as any added value in terms of health of humans and animals, financial savings, social resilience and environmental sustainability achievable by the cooperation of human and veterinary medicine and other disciplines when compared to the two medicines and other disciplines working separately.
The equal focus on the health of people and animals is one of the characteristics that has differentiated the organization, strategy and practice of One Health from several other related fields, such as veterinary public health, resilience, ecohealth, and most recently, planetary health (Horton et al., 2014; Pongsiri et al., 2019). The latter two consider ecological resilience and sustainability more prominently (see more discussion on this below; also Bunch and Waltner-Toews, Chapter 4, this volume; Lerner and Zinsstag, Chapter 5, this volume).
Based on these characteristics, the challenge is to show how, through highly iterative processes and actions, both directly and indirectly, physicians serve animal health and veterinarians serve public health. We need methods that are capable of quantitatively and qualitatively measuring interactions at the interface of human and animal health. Such methods have been developed for survey design (Schelling and Hattendorf, Chapter 8, this volume), integrated surveillance and response (Aenishaenslin et al., Chapter 9, this volume), economics (Häsler et al., Chapter 10, this volume), animal-to-human transmission of infectious diseases (Chitnis et al., Chapter 12, this volume) and integrated health services (Danielsen and Schelling, Chapter 14, this volume). The postulate of an added value of such a closer cooperation is summarized in Zinsstag et al. (Chapter 31, this volume).
Cultural Differences in Human–Animal Relations and their Implications
Dealing with human and animal health as One Health inevitably sheds light on the human–animal relationship and bond. Domestication of wild animals was one of the fundamental cultural achievements of humans, and the use of animals for hunting and as livestock was critical for human development and culture. One Health, even in a more restricted definition as offered here, faces challenging questions regarding cultural differences in view of animals and how they are valued. Thus One Health should reflect on the normative aspects (values) of the human–animal relationship with emphasis on improving animal protection and welfare (see also Wettlaufer et al., Chapter 11, this volume; Hediger and Beetz, Chapter 26, this volume; and Fries and Tschanz Cooke, Chapter 27, this volume). Secondly, even if ecological resilience or health is not the primary outcome of concern, One Health implies an interface of humans and animals with the environment, which can be highly complex, requiring systemic approaches to the physical and social environment. They relate human and environmental systems and are also called social-ecological systems (SES). SES relate to theory of complexity (Ostrom, 2007). Thirdly, One Health empirical experience involves not only human and animal health professionals but also reaches out to many other academic domains, as well as to non-academic actors like public and private institutions, authorities, civil societies, communities and households. It engages with the public in a transdisciplinary way, considering all forms of academic and non-academic knowledge for practical problem solving at the animal–human interface. The strongest leverage of One Health is observed when it is applied to practical societal problem solving (Berger-González et al., Chapter 6, this volume).
Normative aspects of the human–animal relationship
Similarly to the human–human relationship, the human–animal relationship is governed by norms and values determined by culture and religion. Animals are regarded as intimate companions with a high emotional value or simply as prey with a financial value for their meat. Humans are also valued as prey by animals under certain circumstances. This is certainly one of the reasons for deep-seated fears against wildlife, which have led to the extinction or threat of extinction of predators in large parts of the world (White et al.,
