The Covid-19 crisis has confronted humanity and governance bodies with a new challenge, that of the global spread of an infectious and highly transmissible pathogen. This health crisis has shaken up our relationship with living beings, but also with health. While these questions resurface in times of crisis, reflections on the interface between humans, animals, and the environment are not new for thinkers and scientists such as Rudolf Virchow, Aldo Leopold, Rachel Carson, or Calvin Schwabe.
The scientific community has been warning for years that the practices and mentalities of globalization are leading to an increase in the frequency of pandemics and health problems in general. Anthropogenic pressures on biodiversity, such as deforestation, urbanization, intensive agriculture, or even the trafficking of wild species, are constantly increasing these risks. Indeed, the destruction of ecosystems multiplies the contacts between animal species and human beings, thus increasing the risk of transmission and emergence of new diseases: at least 60% of infectious human diseases have an animal origin.
In this respect, the FAO emphasizes that the increase in infectious diseases coincides with the accelerated destruction of tropical forests, reservoirs of a very rich biodiversity, and their fragmentation in recent years. It was deforestation and agricultural intensification that led to the appearance of the Nipah virus in Malaysia. Other pandemics that have marked this century, such as AH5N1, AH1N1, avian flu, or Ebola have shown that transmission models require an ecological approach and an in-depth knowledge of the animal/human bio-interface. While risk assessments focus on the transmission of pathogens from animals to humans, animal health is also largely affected by human-transmitted diseases, e.g. the spread of tuberculosis in gorillas and chimpanzees.
Moreover, biodiversity plays an essential role in environmental systems, both as a pivot of the ecosystem balance and as a regulator of climate dynamics. Therefore, environmental degradation and the depletion of natural resources directly affect all living organisms, of which humanity is an integral part. In fact, the WHO estimates that the impacts of environmental degradation on health are responsible for 23% of deaths and 25% of chronic diseases in the world. For example, eutrophication, i.e. the excess of nutrients in an ecosystem, responsible for the proliferation of green algae in the coastal areas of Brittany, is entirely correlated to anthropic origins, including the massive use of fertilizers, intensive livestock farming, wastewater discharge, and deforestation. It causes oxygen deprivation that destroys biodiversity and has already threatened the lives of animals and humans. These phenomena are amplified by the acceleration of climate change, including the increase in greenhouse gas concentration levels, the fragmentation of habitats and the disruption of biogeochemical cycles.
Humans and animals share the same environment, whose condition affects their health. Their multiple interactions within these three systems are at the origin of the complex health issues we are facing. This awareness led to the development of the One Health paradigm in the 2000s, with a vision of biological conservation following the SARS epidemic. In 2004, the Wildlife Conservation Society established the "Manhattan Principles," 12 recommendations aimed at establishing a more holistic approach to preventing epidemic and epizootic diseases and maintaining the integrity of ecosystems for the benefit of humans, animals, and biodiversity. In 2010, a tripartite agreement between the World Health Organization (WHO), the Food and Agriculture Organization of the United Nations (FAO), and the World Organization for Animal Health (OIE) was signed. The objective was to strengthen the prevention, detection and elimination of public health risks in a multisectoral vision. The investigation went even further when in 2008, the British zoologist Peter Daszak published a study of global trends in emerging infectious diseases in which it listed 335 emerging infectious diseases (EIDs) between 1940 and 2004, 60.3% of which would come from zoonoses, that is to say, from a transfer from animals to humans.
History is marked by an evolution of the relationship between humans, animals and the environment in terms of health, thus shaping perceptions and research in the approach to disease, epidemics, and their management. These questions took a new turn during the 20th century, reflecting the debates around the issue of public health. Faced with the evidence of interactions within the human-animal-environment interface in the course of pandemics, the concept of health has become progressively more inclusive. At the same time, a systemic approach has been adopted, aiming to cross disciplines, knowledge and expertise to provide multi-sectoral responses to food risks, zoonotic risks, and threats to public health. Thus, One Health insists on the recognition of animal and environmental health as dependent on human activities and impacting human health. It is the health of all. To promote this transdisciplinary cooperation, the European Joint Programme (EJP) "One Health" supervised by the Anses (Agence Nationale Sécurité Sanitaire Alimentaire Nationale) has been established and the One Planet Summit has enabled the Prezode initiative, a research program to prevent the risks of zoonotic emergences and pandemics.
Following this example, the Prefecture of Mayotte, the ARS Indian Ocean, and the Directorate of Food, Agriculture and Forestry of Mayotte (DAAF) have worked for a collaborative management of the Rift Valley Fever pandemic in 2018-2019. RVF has been on the WHO's list of emerging priority diseases since 2015. This zoonotic viral disease, which occurred in late November 2018 in Mayotte, primarily affects livestock by causing abortions and mortality in young animals. Humans can be infected through contact with fluids from infected animals or through mosquito bites, in the form of an influenza-like syndrome. As of May 2019, 121 animal outbreaks and 132 human cases have been identified. Coordinated work conducted by teams of researchers since 2008 had enabled the implementation of surveillance systems on the island, one focused on animals, developed jointly with the veterinary services of Mayotte and CIRAD, the other on humans. This study has enabled us to deepen our knowledge of the transmission of the virus, allowing for a more systemic management of the crisis. In response, orders banning the marketing of non-heat-treated milk and the export of live animals, raw meat and milk produced by ruminant farms in Mayotte have been in force since February 2019. In addition, a series of recommendations for farmers, feeding, and protection from mosquito bites have been widely shared. This case illustrates the importance of implementing a One Health approach to comprehensively address public, animal and environmental health at local, national and global scales.
In April 2020, in the midst of the Covid-19 pandemic, experts from the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) called for putting nature conservation at the heart of governance to manage the crisis from a long-term perspective for humans and nature in a One Health approach. Scientists say that future pandemics are likely to be more frequent, to spread more rapidly and to have much more devastating economic, environmental and human impacts if we do not take care of the impacts of our measures over time.
While this One Health concept has been recognized for several years, its implementation remains incomplete. Disciplinary boundaries persist, environmental priority is not integrated into political agendas, and environmental destruction persists. It is becoming fundamental to consolidate the bases of a health ecology, centered on the interdependence between socio-cultural practices, human and animal health and ecosystems, and to integrate them into the political decision-making process. As Jean-François Guégan, Director of Research at INRAE and former member of the High Council for Public Health (HCSP), stated in an interview with Le Monde: "we will not solve the problem without treating the cause, i.e. the disturbances that our globalized world exerts on natural environments and biological diversity.”
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[1] J. Zinsstag, E. Schelling, D. Waltner-Toews, M. A. Whittaker, M. Tanner, coord. 2020. One Health, une seule sante Théorie et pratiquedes approches intégrées de la santé Quae. ISBN : 978-1-78064-341-0 [2] https://www.who.int/fr/ [3] Raphaëlle Métras, W. John Edmunds, Chouanibou Youssouffi, Laure Dommergues, Guillaume Fournié, Anton Camacho, Sebastian Funk, Eric Cardinale, Gilles Le Godais, Soihibou Combo, Laurent Filleul, Hassani Youssouf, and Marion Subiros. 2020. Estimation of Rift Valley fever virus spillover to humans during the Mayotte 2018–2019 epidemic. PNAS [4] Professors Josef Settele, Sandra Díaz and Eduardo Brondizi and Dr. Peter Daszak. 2020.COVID-19 Stimulus Measures Must Save Lives, Protect Livelihoods, and Safeguard Nature to Reduce the Risk of Future Pandemics. IPBES [5] Claire Legros. 2020. « Si nous ne changeons pas nos modes de vie, nous subirons des monstres autrement plus violents que ce coronavirus ». Le Monde