New report highlights the impact of environmental changes on One Health
A new WHO/Europe report specifically examines the role of the environment, from a health perspective, focusing on animal-borne diseases (in which animals are a ‘vehicle’ for disease) , expanding to include certain non-communicable diseases, such as those caused by chemicals that can contaminate foods of animal origin and injuries caused by contact with animals, such as bites.
One Health is an integrative and interdisciplinary approach to designing and implementing actions and policies at the human-animal-environmental health interface. However, the role of the environment in this triad has often been overlooked. One Health has traditionally focused on communicable diseases, such as zoonoses and diseases caused by antimicrobial resistant pathogens and unsafe foods.
New report – “A health perspective on the role of the environment in One Health”, coordinated by the WHO European Center for Environment and Health, builds on global and regional action plans that WHO has developed with the other One Health partners: the World Organization for Animal Health (WOAH, formerly OIE), the Food and Agriculture Organization of the United Nations (FAO) and the United Nations Program United for the Environment (UNEP).
The report describes the role of the environment in One Health as threefold:
- The environment acts as a reservoir, where nutrients and living organisms are accumulated and transported. This includes pathogens such as bacterial species and antimicrobial resistance genes as well as organic and inorganic residues, chemicals and metals.
- The environment is the substrate for chemical and ecological processes that provide a myriad of ecosystem services to humans, including those that are essential for human health. In the context of disease, environmental processes transform chemicals into bioavailable (which can be absorbed by the body) and bioaccumulative (which accumulate over time, for example through contaminated food) forms. Evolutionary processes can create new pathogens that can infect humans or spread antimicrobial resistant microbes and genes.
- The environment is a mediator of health, inducing positive or negative effects on the health of animals and humans.
Changes in the environment
Anthropogenic environmental stressors, such as land use change, biodiversity decline, climate change and environmental pollution, cause or exacerbate animal-borne diseases.
- Land use change leads to fragmentation of ecosystems which improves human contact with natural areas and wildlife. Habitat degradation – for example through agriculture, urbanization and deforestation – leads to the proliferation of species adapted to humans and living in close contact with them. Increased environmental stress impairs wildlife immunity, causing pathogens to be excreted into the environment and infected other individuals and species, including humans.
- Declining biodiversity is strongly linked to increased prevalence and elevated risk of zoonotic disease and undermines the dilution effect that often reduces the spread of pathogens and infection rates in humans. Globally, land use change as well as hunting and wildlife trade are major causes of biodiversity loss that are also central drivers of the transmission of zoonotic pathogens to humans. .
- Climate change and rising temperatures lead to the spread of zoonotic hosts and vectors, increasing the human population exposed to vector-borne diseases. Rising temperatures further stimulate the rate of reproduction of pathogens and vectors. Foodborne infections also proliferate with rising temperatures.
- Pollution accumulates in the environment and further in the fatty tissues of animals, making food the main source of human exposure to pollutants, causing certain non-communicable diseases such as cancer. Accumulation of antibiotics in the environment for prolonged periods promotes gene exchange and mutations within organisms that create new resistant pathogens. Finally, wildlife contact with humans in rural and residential areas can lead to injuries, attacks, and bites.
- The report ends with some forward-looking suggestions. The WHO – both globally and within the WHO European Region – has several strategies and documents dealing with the protection of ecosystems, action against climate change and the dangerous effects of chemicals.
In this context, efforts to restore natural habitats, biodiversity and clean environments could be integrated into these strategies as urgent matters to protect human health. Monitoring of pathogens and antimicrobial resistance genes in the environment using environmental genomics methods could occur alongside increasing surveillance within wildlife. Finally, to foster cooperation across borders and disciplines, ecologists, environmental scientists, and evolutionary biologists should play a greater role at the One Health table.
Similarly, raising awareness and building capacity in industry, agriculture, urban planning, food safety and engineering could promote practices that better protect environmental health. , animals and humans.