By Valérie Balvert and Candela Iglesias Chiesa
Over 60% of all emerging infectious diseases are zoonoses, which are diseases that have jumped from animals to humans. This means that human-animal interactions have a critical influence on human health.
However One Health is not only about zoonotic diseases… It also concerns issues such as food and water safety, antimicrobial resistance, environmental contamination, neglected tropical diseases, and more!
Another important factor in the One Health framework is the environment we share. Think about climate-induced disasters (e.g. droughts, wildfires, floods), deforestation, air pollution, etc. All of these environmental factors have an impact on both human and animal health. The intersections of these three sectors: animal, human and environmental is what the “One health approach” considers.
The COVID-19 pandemic with its potential animal origin, and the impacts of climate change have highlighted the importance of One Health approaches to common health threats. In this blog post, we look into the meaning of this term, its origin, what One Health approaches look like in practice, and challenges.
What is One Health?
The CDC defines One Health as “a collaborative, multisectoral, and transdisciplinary approach — working at the local, regional, national, and global levels — with the goal of achieving optimal health outcomes recognizing the interconnection between people, animals, plants, and their shared environment” (CDC, 2022).
In other words, One Health recognizes the interconnection between human health, animal health, and environmental health. It aims to bring sectors working in human health (e.g the MInistry of Health, Epidemiological Surveillance), to work together with those concerned with plants and animals (e.g. Veterinary, Agronomy) and those focused on environmental issues (e.g. Environmental ministries or departments), and to involve various disciplines from all three sectors such as; veterinarians, public health professionals, doctors, epidemiologists, wildlife experts, ecologists, etc. No easy task by all means!
Origins of the One Health concept
Although the term is fairly new, the knowledge and holistic view of health that is reflected in current One Health approaches goes back a very long time. Time for a little history lesson!
As described by Riley et al. (2021), the concept of One Health aligns with indigenous knowledge from thousands of years ago. The holistic traditional view which links human, animal, and environmental health, also defines wellness as a balance between physical, mental, emotional, and spiritual health.
In Europe, scientists started to recognize the link between human and animal health in the 1800’s. Dr. Virchow, a German pathologist, introduced the term “zoonosis” to describe diseases that are passed between animals and humans. This idea was then conceptualized into “One Medicine” by Calvin Schwabe, also called the father of veterinary epidemiology, in the 1980s. Schwabe urged collaboration between professionals in human and animal health to jointly tackle common public health threats.
It is as a result of multiple zoonotic outbreaks in the early 2000’s (SARS, avian flu, West Nile virus) that the concept evolved to the term “One Health”. In 2006, for instance, the One Health Initiative was established. This U.S. initiative was founded by a team consisting of physicians and veterinarians. Its goal is the promotion of collaboration across sectors and between disciplines, from local to global levels, in order to mitigate risks arising from the interactions between humans, animals, and the environment.
How exactly can humans, animals, and the environment all affect each other?
There are many different ways in which all three influence each other, here are a few examples.
Exhibit A: Vector Borne diseases. Think about vector borne diseases; malaria, zika, dengue, etc. Vectors such as mosquitos, ticks, and fleas can carry pathogens and transmit these diseases to humans, or other animals, through bites. Environmental factors play an important role in the occurrence of such interactions. For instance, proximity to still water, warmer temperatures, and humidity create a perfect climate for mosquitoes to survive and breed.
Climate change impacts the spread of vector borne diseases in a variety of ways. Warmer temperatures and increased rainfalls (which increase areas of standing water) result in more suitable areas for the survival and breeding of mosquitoes that transmit certain diseases, like dengue. As the areas inhabited by the mosquitoes expand beyond the traditional tropical and subtropical ones, so will the populations at risk of catching the disease. Moreover, the length of warm seasons also extends the duration of disease transmission seasons.
Exhibit B: Bees in danger and our agricultural output. The fauna has an important role in the ecosystem. Bees, for example, do not only provide us with honey, they are also key pollinators responsible for many of our flowers, plants, and important for our agricultural production. Due to human action leading to ecosystem destruction and global warming, bees are now endangered. This could have an impact on our agricultural output.
Exhibit C. Antimicrobial resistance (AMR). Misuse of antimicrobials (e.g. antibiotics) that are consumed by people or used in industrial animal farming practices, can cause resistant bacteria to develop (read more on antimicrobial resistance here). These resistant bacteria can spread to the general population through soil and water or consumption of contaminated food products.
What does the One Health approach look like in practice?
In One Health approaches, the cooperation, collaboration, and communication across the three sectors (human, animal, environmental health) and between disciplines is highly promoted.
Let’s look at one recent example:
COVID-19 infections in otters from the Georgia Aquarium (U.S.)
COVID-19 provided us with some practical examples of how One Health can look like, through the close monitoring of animals infected by SARS-CoV-2 (the virus causing COVID-19).
In Atlanta, USA, for instance, COVID-19 broke out among otters in an aquarium. Mid-March 2021, several of the otters were showing signs of respiratory illness which led the aquarium’s veterinary team to ask the State Veterinarian’s office and the local Department of Public Health for permission to test the otters for a potential COVID-19 infection. The results turned out to be positive.
From that moment, CDC’s One Health Office and Georgia Aquarium closely worked together on an epidemiological investigation aiming to understand more about COVID infections in highly susceptible animals (e.g. otters, minks, ferrets) and the potential risk of mutations and spillovers* to other animals and humans. This required good communication, coordination, and collaboration between experts of the veterinarian and public health fields, from local, state, and federal levels.
You can read more stories about One Health in Action here.
With strong public health efforts and collaboration between all involved disciplines, epidemics can be avoided. This is what Resolve to Save Lives (RTSL) wants to depict in their annual report on “Epidemic That Didn’t Happen”, which also features some excellent examples of One Health approaches.
*A spillover refers to a pathogen (e.g. a virus) which has jumped from their usual reservoir/host (e.g. animal) to another one (e.g. human).
Challenges with One Health approaches
The biggest challenge with the One Health approach is one about communication, collaboration and the organization of our systems.
Institutional silos. In most countries, and even at a global level, historically, human, animal/agriculture and environmental sectors have developed in siloes. Think about it, your country most likely has a Ministry of Health, a Ministry of Agriculture and Animal Farming (or similar), and a Ministry or department focused on the Environment. They have separate budgets, separate administrations and are staffed by professionals from separate disciplines that don’t “speak the same language”.
Rarely (even though it is happening more and more often) are there high level governance structures or forums that allow these sectors to come together, share budgets and collaborate effectively.
Trans-disciplinary collaboration. On top of the siloed nature of our institutions, there is the “small” challenge of interdisciplinary collaboration. As mentioned above, One Health involves a large number of disciplines within each of the three sectors. But these disciplines don’t train together, don’t work together, and don’t even use the same jargon. When was the last time that, as a public health specialist, you talked to a farmer or a veterinary student for professional reasons?
As discussed by Diane Peters (2022) in her piece “Making the case for One Health”, despite more and more classes covering the topic of One Health, it is rare to actually see medicine and veterinary students (much less ecology or environmental studies) having such classes together. Furthermore, differences in terminologies (veterinary vs. medical jargon) makes communication between the students already difficult. Peters also discusses the difficulties of involving other disciplines, such as social scientists, as veterinarians often take the lead in One Health projects.
Training students early on how to work together with people from other fields would already strengthen their transdisciplinary skills and ability to work together in the future. A great example of such collaboration programs is the Cambodian Applied Veterinary Epidemiology Training (CAVET) program.
The CAVET program was established in 2012 to address the challenges of zoonotic diseases in Cambodia such as the avian influenza in poultry and rabies in dogs, which both present a high threat to both animal but also human health. It is run by experts from human, animal, and environmental sectors. Participants of this program, which is composed of classroom instructions as well as field-based practice and research projects, include veterinarians, veterinary students, wildlife officers, human and animal lab technicians, and physicians. This program aims to address gaps in coordination, collaboration, and communications across these disciplines that affect zoonotic disease prevention and control.
Financial resources. Unequal financial resources across disciplines (e.g. the human health sector being better funded than the animal health sector) also present a challenge, and can create friction and competition. Furthermore, as mentioned by the WHO, “One of the biggest barriers across the countries is the lack of centralized One Health general funding, with budgets for One Health relevant activities still mostly distributed through specific ministries. Limited financing between disease events restricts continuing action and development, with each new response often having to start from scratch”.
I hope this post clarified the One Health approach for you and gave you some insights as to why it exists and how it can look like in practice. If you have some good examples of One Health practices, do share in the comments!
One Health Basics | One Health | CDC
The Threats of Climate Change to Endangered Bee Species | Earth.Org
One Medicine, One Health, One World – PMC (nih.gov)
One Health in Indigenous Communities: A Critical Review of the Evidence – PMC (nih.gov)
CDC’s One Health Office and Georgia Aquarium Work Together to Investigate Otters with SARS-CoV-2
Epidemics That Didn’t Happen – Prevent Epidemics
One Health in G20 countries (who.int)
Links to online course related to One Health
Are you curious about One Health and not sure if you want to study a whole degree in this area? Here are a few links to free online courses on the topic. Feel free to share your thoughts or recommend other available courses!
- Top One Health Courses – Learn One Health Online (coursera.org)
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1 thought on “The One Health Approach: What is it and why is it so important?”
One of the good example of one health collaboration is for the veterinarian and environmental health practitioners should work hand in hand to ensure whole some and healthy meat in the abattoir, this will help in the prevention of zoonotic diseases in our communities.