perspective, the current practice of transporting livestock on foot, say from Ireland to France for slaughter, is not acceptable. Similarly, in developing countries, small ruminants and poultry are transported hundreds of kilometres under congested conditions, often without water, and sometimes severely beaten. Slaughtering practices should aim to reduce stress during animal handling. As part of economic growth, meat consumption has grown massively in the last decades. Livestock plays an important role especially in the livelihoods of hundreds of millions of small-scale farmers. However, ruminant livestock production contributes to the emission of greenhouse gases, and reduction of ruminant meat consumption is part of the overall strategy to avert climate change (Gordon et al., Chapter 25, this volume).
Fig. 2.2. Camels and donkeys in Ethiopia (A) and a woman milking a horse in Kyrgyzstan (B). Photos courtesy of J. Zinsstag.
Animals are also, one might say mostly, used in agriculture in developing countries for ploughing, transport and traction of carriages. While cattle and camels used for ploughing or transport are usually well treated, there is undeniably huge suffering in horses and donkeys used for transport. Donkeys are among the worst-treated animals worldwide and urgently need better treatment and husbandry. There is increasing research on livestock, companion animals and wildlife in developing countries. However, there is almost a complete lack of legislation on animal testing. Care should be taken that animal testing is not exported from industrialized countries to evade stringent regulations. We should not forget the welfare standards for pets, which may similarly undergo huge suffering. For example, dogs and cats are often abandoned at the beginning of the summer holidays, so that owners do not have to care for them.
From a One Health perspective, the notion of burden of disease should be extended to animals to reflect the toll of life and suffering of humans and animals, for example in road traffic, which causes hundreds of thousands of wildlife deaths. Road safety should then be expressed as causing this number of human and this number of animal casualties. Modern highway planning effectively protects animal life by utilizing fencing, bridges and tunnels for safe animal movement. While animal lives can be counted, estimating animal suffering and disability, similarly to human burden measures like the disability adjusted life year (DALY), is hardly possible because of the variation of norms and values across cultures and production systems. For example, how would expected years of life for male calves or fattening pigs be adequately assessed? There is an ongoing and controversial debate, but still not enough research undertaken, in development of a combined metric of human and animal disease burden. The recent introduction of the zDALY, an adjusted indicator to estimate the burden of zoonotic diseases, is controversial because it puts a monetary value on human life depending on local purchasing power (Torgerson et al., 2018; Häsler et al., Chapter 10, this volume). Improving animal welfare remains a permanent challenge to any effort and ethical aspiration of One Health (Wettlaufer et al., Chapter 11, this volume).
One Health as embedded in landscapes
One Health as presented here is not an isolated idea. There are earlier more limited and also broader concepts. We should mention Evgeny Pavlovsky’s (1884–1965) concept of disease nidality. He considered pathogens from an ecological perspective having their own ecological niche. This might be a specific space in an ecosystem or an animal or organ to which they are most adapted. For example, marmots in Mongolia carry Yersinia pestis, the agent of plague, without symptoms. Occasionally, marmot hunters become ill with plague after handling marmot carcasses.
Calvin Schwabe met Evgeny Pavlovsky in Leningrad in 1965 and wrote in his memoirs:
The only noteworthy work-related event in Leningrad was my meeting with Eugene Pavlovsky, the dean of the Soviet descriptive epidemiologists, formal developer of medical ecological notions like ‘landscape epidemiology’ and ‘natural foci of infections’. … He had read Veterinary Medicine and Human Health [(Schwabe, 1984) reference added] already and said he was pleased to see an American author write on the ‘Ecological Study of Disease’, which was my title of the 1st edition chapter introducing epidemiology.
(C. Schwabe, unpublished)3
More recent examples of landscape–disease interactions include the ways in which emerging diseases, such as those associated with West Nile virus and Borrelia burgdorferi, are related to urban landscape design (Waltner-Toews and Waltner-Toews, 2017).
One of the most prominent interactions of human and animal health is veterinary public health (VPH), which is defined as the contribution of veterinary medicine to public health. VPH is well established in international organizations, governmental administrations and academia. VPH was originally conceived by the Centers for Disease Control in Atlanta by James H. Steele. Schwabe refers to it as ‘the innovative Veterinary Public Health Unit founded by Jim Steele, … helping to demonstrate the value of an organised and systematic capability for disease intelligence’ (C. Schwabe, unpublished)4.
Compared to One Health, VPH mainly serves public health. Conceptually, it does not consider a mutual benefit from public health for animal health.
A much broader concept is an ‘ecosystem approach to health’ or ‘ecohealth’. Ecohealth considers inextricable linkages between ecosystems, society and health (Rapport et al., 1999). It seeks in-depth understanding of ecological processes and their relation to human and animal health. For example, using an ecohealth approach it was demonstrated that mercury poisoning of fish and impending health risks for humans in the Amazon were not due to upstream gold mining but due to soil erosion following deforestation (Forget and Lebel, 2001). Ecohealth has become an internationally scholarly movement organized by Ecohealth International.5 Ecohealth is a systemic approach, tackling complex problems as embedded in non-linear systems dynamics quantitatively and qualitatively. It involves transdisciplinary approaches, connecting academic and non-academic knowledge in a mutual learning process. It includes all stakeholders from communities to authorities as actors in the research process, pays particular attention to gender and social equity and thrives to put knowledge into action through policy change, interventions and improvement of practices (Charron, 2012). Hence, One Health is embedded in and an integral part of the ecohealth concept (Zinsstag, 2012).
Knowledge and information in veterinary and medical sciences are growing continuously, with the consequence that we know more and more about progressively narrower subjects. The ongoing and accelerated fragmentation of veterinary and medical science is not conducive to complex problem solving, and we face an increasing risk for misinterpretation, for example, in comparative diagnosis and pathology (Cardiff et al., 2008; Zinsstag et al., 2009). Mainstream reductionist research seeks to explain phenomena at an increasingly smaller scale. On the other hand, major current challenges, like development of antimicrobial resistance in a complex environment, call for rethinking modern theory of health of
