How should we consider health in a world where demographic, ecological and social dynamics are increasing pressure at the human-animal-nature interface? The “One Health” approach invites us to renew our vision of health. This starts with the recognition that the well-being of human populations is completely interdependent with that of the living beings and ecosystems around us.
Health, a global well-being shared by humans, animals and ecosystems
Health, experienced by each one of us and shared by all, is a priority for people around the world. This sector tends to remain very anthropocentric, reduced to the distresses and diseases of humans. It is however urgent today that we renew our vision of health in view of the demographic, ecological and social dynamics that drive the world. This comes first by recalling the multidimensional and positive aspect of health, which the World Health Organization defined back in 1946 as “a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity”. At the turn of the 21st century, a second realization adds itself to this idea, that of the interdependence between this human well-being and the health of animals and ecosystems. Several conceptual health approaches are developed, in particular the “One Health” approach discussed here. This concept has emerged over the past ten years in the works of three international organizations – WHO, the World Organisation for Animal Health (OIE) and the United Nations Food and Agriculture Organisation (FAO) – as well as in the strategies of several States (France, Vietnam, European Union…). The “One Health” approach recalls that human health cannot be considered alone and that it is intrinsically linked to animal and ecosystem health.
This idea is not fundamentally new and refers to ancient conceptions of health which have been forgotten and little applied. The association of health with an overall well-being shared by humans, animals and ecosystems is particularly forceful in a changing world where thought and expertise tend to operate in silos.
Figure 1: Diagram of the “One Health” interfaces
Reference: Based on Destoumieux Garzon D. et al., Frontiers in Veterinary Science, 2018
Increased pressure between humans, animals and the environment
A renewed “One Health” vision is today not only relevant but necessary due to a set of anthropogenic factors. The pressure at the interface between humans, animals and their environment is increasing and detrimental to health. Demographic pressure, growing urbanization and the rise in migrations and movements are all elements of globalization that break down barriers and increase contacts between humans, animals and natural areas. In addition to this, pollution and certain production methods contribute to biodiversity loss. Climate change and natural disasters are changing the face of the planet and modifying the human-nature interfaces. All of these elements have an impact on ecosystems at various levels and, along with them, the overall well-being of the planet. They lead to risks of (re)emergence of diseases and dissemination of pathogens, including drug-resistant strains of microorganisms.
It is in this context that a growing international awareness expressed itself through the “One Health” approach. One of the underlying facts it often recalls is that two-thirds of human infectious diseases come from animals (“zoonoses”), a rate which even reaches 75% in the case of emerging infectious diseases. Several cross-border epidemics, such as avian flu or more recently the Ebola virus disease, have illustrated this fluid transmission of diseases between the animal kingdom and human populations, often facilitated by aggravating environmental contexts. Increasing antimicrobial resistance, which can spread between animals, food, environmental vectors and humans, has also raised awareness in “One Health”. The poor animal conditions and welfare caused by certain farming methods within unhealthy environments lead to an excessive use of antibiotics which, through food, can harm human health and well-being too. However, this integrative approach goes beyond zoonoses and antimicrobial resistance by putting health in perspective with other major environmental and climate issues.
Figure 2: The “One Health” iceberg: emerged and emerging topics
Image credit: Jeremy Wanner
From biodiversity conservation…
The “One Health” approach draws awareness on the links between biodiversity, which signals a healthy ecosystem, and human and animal health. These links are tangible in the field of nutrition, where biodiversity plays a key role in providing for the varied and sustainable agricultural productivity behind nutrient-rich diets. Biodiversity is also a valuable resource for medical research and traditional medicine. Its erosion can have an impact on the reservoirs of infectious agents and thereby on the spread of diseases. A link often neglected between biodiversity and human health is at the level of microorganisms, the most abundant form of biodiversity on Earth. The importance of the human microflora for the immune system, its role in non-communicable diseases and its links with the biodiversity of ecosystems on a larger scale are all areas of the biodiversity-health nexus that need to be further explored. The same applies to the links between urban biodiversity and physiological and mental health, which are sometimes described as the spiritual co-benefits of biodiversity.
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…to climate change adaptation
The “One Health” approach also draws attention to the health impacts of climate change. By neglecting this dimension of the planetary climate challenge and the development of more resilient health systems, no adaptation strategy can truly be effective. Many impacts of global warming on human and animal health are already being felt and anticipated. Extreme heat leads to an increase in cardiovascular or respiratory diseases, and natural disasters and rainfall fluctuations foster water-borne diseases. Climate change also has the capacity of modifying the geographical scope of certain species, including mosquitos, which carry vector-borne diseases like malaria or chikungunya.
The challenges and opportunities of the “One Health” approach for development
Over the past ten years, the “One Health” approach has benefited from enhanced attention and support. It is mainly characterized by the creation in 2010 of a tripartite “One Health” alliance between three international organizations, WHO, OIE and FAO. Development actors are showing increasing interest in “One Health”, especially the World Bank.
The implementation of the approach is however still in its early stages. It generally limits itself to the management of zoonoses by strengthening the coordination between human and animal health surveillance and response systems. This is, for instance, the objective of the World Bank “REDISSE” program in West Africa, or the regional epidemiological investigation and surveillance network “SEGA” supported by AFD in the Indian Ocean. A few pilot programs related to the environmental and climate concerns of the approach are however emerging, including a new project by the French Facility for Global Environment (FFEM). Located in the north of Kibale National Park in Uganda, it aims to develop agroecology and protect biodiversity while monitoring the exposure impact of chemical pollutants from agricultural practices on human and animal health.
Much remains to be done to address the dual challenge taken up by the “One Health” approach: to renew our vision of health and translate this paradigm shift in concrete actions. Development actors have a major role to play in ensuring it benefits the most fragile parts of the world. To do so, strong intersectoral dialogue is needed to increase interdisciplinary collaboration in the field of health. AFD and its partners have the opportunity to lead and participate in these captivating discussions, more than ever necessary to build a world in common.
The opinions expressed on this website are those of the authors and do not necessarily reflect the official position of their institutions or of AFD.