Text: Dr. Timo Falkenberg
The novel coronavirus Sars-CoV-2, which is the pathogen causing the current wave of COVID-19 infections, has taken the world by surprise, with devastating consequences for national health systems and the global economy. Health experts have been warning of the pandemic risk posed by zoonotic diseases for years, stressing the urgency of developing integrated monitoring systems at the interface between humans and animals. Combining data collected by monitoring people, livestock and wildlife in an integrated system can help us better identify outbreaks of diseases and respond more quickly.
Zoonotic diseases are nothing new
Zoonotic diseases are transmitted from animals to humans or vice versa. Usually, these diseases emerge in wildlife populations and involve livestock as an intermediate host before being transmitted to the human population. The US Center for Disease Control (CDC) has estimated that 60 percent of all human infectious diseases are of zoonotic origin.
This includes diseases that have been around for quite a while, such as rabies, influenza and tuberculosis, but also more recently emerged diseases like Ebola, SARS and Zika. According to the CDC, 75 percent of newly emerging infectious diseases are of zoonotic nature. Health experts are therefore not investigating if zoonotic diseases could break out, but rather when and where the next outbreak will take place and how we can put effective early warning systems in place as well as quick response strategies.
Animals and humans are competing for habitat
The major reason for increased outbreaks of zoonotic diseases is an ever closer contact between humans and animals. Human population growth and the global economic development are causing a rising demand in food, especially in animal proteins, which in turn leads to more intensive farming. Other reasons are the expansion of human settlements and agricultural areas as well as the extraction of resources. In all these scenarios, humans are entering the natural habitat of wild animals, increasing contact between wildlife, livestock and humans. With their natural ecosystems and habitats destroyed, wild animals looking for food are forced to live in closer proximity to human settlements. Some animals are so well adapted to urban life that they become part of the urban cosmos, causing a constant risk of exchanging pathogens with the human population.
Animal markets in Asia, hunting and trade in Africa
Markets - especially “wet markets” frequently found in Asia - are major hot spots for the transmission of zoonotic diseases. On these crowded markets held in confined spaces, a large number of people comes into close contact with a large number of different animals (dead and alive), leading to close exposure between wildlife, livestock, merchants, traders and customers. This extreme proximity is the root cause of the exchange of pathogens and enables the potential outbreak of new zoonotic diseases. Elizabeth Maruma Mrema, acting executive secretary of the UN Biodiversity Convention, has called on the global community to help prevent future outbreaks of zoonotic diseases by banning wet markets. In light of the COVID-19 pandemic, such a ban seems legitimate. We must, however, make sure to consider all the consequences before taking such action. Banning wet markets could undermine the livelihoods of the many people working there. Furthermore, these markets would probably not simply disappear but be integrated into the black market, which would rather increase the risk of zoonotic diseases. Introducing strict regulations and monitoring mechanisms could therefore be a more effective measure to minimize the zoonotic risk posed by these markets.
Another aspect that enables the zoonotic transmission of pathogens is bushmeat trade, which is especially popular in African countries. One reason for this is that bushmeat hunters are exposed to wildlife diseases and can potentially carry pathogens into their communities. Another reason is that butchering, handling, transport and consumption of bushmeat facilitates the exchange of pathogens and the possible spread of zoonotic pathogens within the population at large, especially when suitable provisions and monitoring mechanisms are not in place or not enforced. Besides these prominent examples of zoonotic spillover hot spots, several cases have been reported all over the world in which the proximity between human populations and livestock and wildlife has facilitated the exchange of pathogens and therefore the emergence of zoonotic diseases. This is why it was only a matter of time until a new zoonotic pathogen would surface and be transmitted from person to person.
Cooperation beyond borders and disciplines is needed
We are living in a globalized world in which people, live animals, animal products and goods are moved and traded freely across borders and continents. Ultimately, the location in which a new disease breaks out is irrelevant as pathogens can spread quickly, proceeding to threaten the entire global population. For this reason, all countries in the world must cooperate and develop common integrated monitoring and preventive strategies for zoonotic diseases. As the relationships at the interface between humans, animals and nature that enable the threat posed by zoonotic diseases are very complex, expert knowledge across disciplines and cooperation between all sectors are required to be able to develop effective and sustainable interventions. The interdependent relationships between economic development, food production, livelihoods, integrity of ecosystems and health require a thorough and holistic approach and therefore systemic, integrated health strategies.
Developing an international “One Health” approach
In recognition of this requirement after the outbreak of influenza A/H5N1 (bird flu) in 2006 and influenza A/H1N1 (swine flu) in 2009, the World Health Organization (WHO), the World Organisation for Animal Health (OIE) as well as the Food and Agriculture Organization of the United Nations (FAO) concluded the “Tripartite Collaboration Agreement”. This joint agreement aims at preventing and managing zoonotic diseases and their economic, social and health impacts. At the same time, the “One Health” concept, which defines human, animal and environmental health as closely interconnected and interdependent, resurfaced in academia. While recognition of the “One Health” concept is growing all over the world, its implementation continues to be impeded by cross-sectorial conflicts, lack of funds and power imbalances.
The “One Health” concept
The term “One Health” stems from the field of veterinary medicine and is widely agreed to go back to Calvin Schwabe, who coined the term “One Medicine” in 1964. With his concept, Schwabe focused on the common ground between human and veterinary medicine and called for cooperation between the two medical disciplines. At the 2004 “One World, One Health” conference, the Wildlife Conservation Society drafted the twelve Manhattan Principles that underline the correlations between humans, animals and the environment and stress the importance of integrated approaches to understanding the complex dynamic of diseases and to developing preventive strategies. Today, “One Health” is commonly defined as “the common effort of several disciplines cooperating on local, national and global level to achieve optimal health outcomes for humans, animals and the environment.” Even though the “One Health” concept has been integrating an increasing range of topics, zoonotic diseases remain the key issue. Understanding the dynamic of zoonotic diseases, implementing integrated monitoring systems and developing preventive strategies are among the most important goals of “One Health”.
First lessons learned from COVID-19
The current COVID-19 outbreak has shown the importance of identifying the outbreak of zoonotic diseases early and developing global early warning systems, as this is the only way to prevent a zoonotic disease from becoming a pandemic. The “One Health” approach offers an integrated, cross-disciplinary perspective on the dynamics of zoonotic diseases and allows us to identify critical indicators and develop preventive strategies. “One Health” must therefore be more quickly accepted and implemented on local, national and global level to better prepare the world for identifying and fighting the next zoonotic diseases.
For more information on the One Health project, of which the University of Bonn is a partner, please refer to https://www.zef.de/onehealth.html.
The author
Dr. Timo Falkenberg is researcher at the Center of Development Research (ZEF) at the University of Bonn. Contact: Phone: +49 228 73-4634, e-mail: falkenberg@uni-bonn.de
Signs of life - keeping up the conversation
In “Signs of life - keeping up the conversation!” the University of Bonn is publishing articles written by members of the University, sharing personal impressions of the fight against the coronavirus as well the impact it has on our lives. The format is aimed at keeping the communication going and strengthening our University community in these difficult times. Articles written by members of the University are published, in no particular order, on this website, depicting different perspectives, initiating discussions and exchanging tips and food for thought on the current challenge. If you wish to contribute, please contact University Communications at kommunikation@uni-bonn.de.
