The convergence of people, animals, and our environment has created a new dynamic—one in which the health of each group is inextricably interconnected. The challenges associated with this dynamic are demanding, profound, and unprecedented. While the demand for animal-based protein is expected to increase by 50% by 2020, animal populations are under heightened pressure to survive, and further loss of biodiversity is highly probable.2
Compounding that is the fact that, of the 1,461 diseases now recognized in humans, approximately 60% are due to multi-host pathogens characterized by their movement across species lines.3 And, over the last three decades, approximately 75% of new emerging human infectious diseases are defined as zoonotic.4 Our increasing interdependence with animals and their products may well be the single most critical risk factor to our own health and well-being with regard to infectious diseases.
At the same time, pollution and contamination of our environment has greatly reduced the health and sustainability of our environment. Such degradation of the environment will continue to create favorable settings for the expansion of existing infectious diseases, as well as an increasing number of acute and chronic non-infectious disease events detrimental to both human and animal health. In addition, non-infectious threats include toxins and chemical contaminants, such as endocrine-disrupting chemicals in the environment (Our Stolen Future, Theo Colborn, 1996).8
Other examples include the melamine contamination of pet foods, fire-retardant carpet chemicals causing adverse effects in pet cats, and marine toxins in manatees. While we have experienced remarkable medical advances, there is a growing concern that the world's youngest generation could be the first in history to experience a reduction in life expectancy and health in general, compared to prior generations. This is already being seen in SubSahara Africa and, most recently, in females in various parts of the US.
Although new opportunities have emerged to promote health in the rapidly changing human, animal, and environment domains, our ability to protect, improve, and advance health cannot be based on strategies and mindsets in the past. Rather, we need to adopt an integrated, holistic approach that reflects both our profound interdependence and the realization that we are part of a larger ecological system—exquisitely and elaborately connected.
We suggest that the strategy to better understanding and addressing the contemporary health issues created by the convergence of human, animal, and environmental domains is the concept of One Health. The term One Health has been defined by the Task Force as the collaborative efforts of multiple disciplines working locally, nationally, and globally, to attain optimal health for people, animals, and our environment. Achieving the end point of One Health is truly one of the critical challenges facing humankind today.
Central to the concept of One Health is the control of infectious diseases which have helped shape the course of human history. There is every indication that infectious diseases will continue to have a significant impact on our health, and the emergence and re-emergence of pathogens will threaten the health and well being of people and animals throughout the 21st century.
In addition, according to Jared Diamond, in his book, "Guns, Germs and Steel,"9 microbes causing diseases such as measles, smallpox, influenza, and tuberculosis likely evolved from animal diseases as a result of the advent of agriculture and the domestication of animals approximately 8-10,000 years ago. Today, microbes pose an increasing threat.
In their article entitled "Microbial Threats to Health, Emergence, Detection, and Response"10 (NAS, 2003), authors from the Institute of Medicine suggest that a group of factors have simultaneously converged to create a "perfect microbial storm." The most important of these factors include:
Most of these factors are man-made, and have produced a remarkable new milieu referred to as "the global mixing bowl," in which microbes have much greater opportunities to create new niches, cross species boundaries, travel worldwide very quickly and establish new beachheads in the populations of people and animals. They are also invading our environment, where they are being uniquely maintained in nature outside of living hosts. The convergence of these domains is creating threats to the health of all three.
Numerous examples point to the critical need to address these threats, including:
The words of Dr. Gro Harlem Brundtland, former director of the World Health Organization (WHO), were indeed prophetic. In her speech12 at the United Nations Global Leadership Awards on April 19, 2001, she stated that in a modern world, bacteria and viruses travel almost as fast as money. With globalization, a single microbial sea washes over all humankind and there are no health sanctions.12 In actuality, that sea washes not over just all humankind, but also across all animal and environmental domains.
Beyond infectious diseases, it is important to note that "noncommunicable" conditions and risks are crossing species and adversely affecting both animal and human health. Examples include obesity and exposure to secondhand tobacco smoke among pets, pet-owners, and their children.
There is nothing on the horizon to suggest that any of these factors are abating. In fact, these factors are likely to accelerate in intensity and complexity, and will surely create consequences and implications of unprecedented scope and scale and global economic devastation much greater than any previous time in history. By adopting the tenets of One Health, we can devise integrated strategies to control that sea and prevent these threats from crossing domains.