One Health is “the collaborative effort of multiple disciplines — working locally, nationally, and globally — to attain optimal health for people, animals, and the environment”.
One Health is a new phrase, but the concept extends back to ancient times. The recognition that environmental factors can impact human health can be traced as far back as to the Greek physician Hippocrates (c. 460 BCE – c. 370 BCE) in his text “On Airs, Waters, and Places”. He promoted the concept that public health depended on a clean environment.
The Italian physician Giovanni Maria Lancisi (1654–1720) was a pioneering epidemiologist, physician, and veterinarian, with a fascination in the role the physical environment played in the spread of disease in humans and animals. Lancisi may have been the first to advocate the use of mosquito nets for the prevention of malaria in humans but was also a pioneer in the control of rinderpest in cattle. The idea that human, animal and environmental healths are linked was further revived during the French Revolution by Louis-René Villerme (1782–1863) and Alexandre Parent-Duchâtelet (1790–1835) who developed the specialty of public hygiene.
In the late 19th century, German physician and pathologist Rudolf Virchow (1821–1902) coined the term “zoonosis”, and said, “…between animal and human medicine there are no dividing lines – nor should there be”. Canadian physician William Osler (1849–1919) traveled to Germany to study with Virchow. He returned to Canada and held joint faculty appointments at the McGill University Medical School and the Montreal Veterinary College. Osler was active as a clinical pathologist and internist at the Montreal General Hospital, but was also active in the promotion of veterinary health, and helped investigate a swine typhoid outbreak near Quebec City in 1878; he subsequently co-authored a monograph on parasites in Montreal’s pork supply with A. W. Clement, a veterinary student at Montreal Veterinary College.
In 1947, veterinarian James H. Steele furthered the concept in the U.S. by establishing the field of veterinary public health at the CDC. The phrase “One Medicine” was developed and promoted by Calvin W. Schwabe (1927–2006), a veterinary epidemiologist and parasitologist in his textbook “Veterinary Medicine and Human Health”.
In 1996, Gary M. Tabor, Alonso Aguirre, Mary Pearl, David Sherman, Mark Pokras, Eric Chivian, Paul Epstein and Gretchen Kauffman launched the Conservation Medicine: Ecological Health in Practice effort (Consortium for Conservation Medicine) with the Cummings School of Veterinary Medicine at Tufts University, Harvard Medical School’s Center for Health and the Global Environment and EcoHealth Alliance (formerly Wildlife Trust), with an institutional focus linking human, animal and ecological health.
“One Health” was mentioned in a story about Ebola hemorrhagic fever on April 7, 2003, when Rick Weiss of the Washington Post quoted William Karesh as saying, “Human or livestock or wildlife health can’t be discussed in isolation anymore. There is just one health. And the solutions require everyone working together on all the different levels.”
Emerging infectious diseases
Many emerging health issues are linked to increasing contact between humans and animals, intensification and integration of food production, and the expansion of international travel. As the number of new infectious diseases emerged in the 20th century, scientists began to recognize the challenges societies face regarding these threats that largely come from animals. Of the 1,415 microbes that are known to infect humans, 61 percent come from animals. For example, rodents transmit plague and typhus to humans, and domestic livestock is the original source of crowd diseases such as measles, mumps, and pertussis. One important exception is Mycobacteria tuberculosis. Genetic evidence suggests that Mycobacteria tuberculosis originated in human populations and spread to animals. Chimpanzees were a reservoir host for the human immunodeficiency virus. Global trade of wildlife exacerbates the problem of disease emergence.
The 1999 West Nile virus outbreak in New York City highlighted the links between human and animal health. In this outbreak, wild crows began dying about a month or so before people began getting sick. The simultaneous outbreaks were not recognized as caused by the same entity until Tracey McNamara, a veterinarian at the Bronx Zoo, tied them together when her exotic birds began getting sick. After it was recognized that the outbreaks were caused by West Nile virus, a new entity in the Western Hemisphere, the CDC established the National Center for Zoonotic, Vector-Borne, and Enteric Diseases, now the National Center for Emerging and Zoonotic Infectious Diseases.
Avian influenza (HPAI H5N1) epidemic that began in Hong Kong in 1997 showed the connection between animal and human health. The outbreak affected 18 people, killed 6, and provoked the culling of 1.5 million birds. The HPAI H5N1 virus resurfaced in isolated outbreaks between 1998 –2003, but a widespread outbreak occurred in mid-2003 in South Korea. Delays in international reporting and weak response measures contributed to the spread of the virus across Southeast Asia. In recognition of the global threat that avian influenza (HPAI H5N1) and other emerging zoonotic diseases posed, the Food and Agriculture Organization (FAO), World Health Organization (WHO), and World Organization for Animal Health (OIE) developed a strategic framework, a tripartite agreement, to work more closely together to address the animal-human-ecosystem interface.
Animals suffer from many of the same chronic diseases such as heart disease, cancer, diabetes, asthma, and arthritis as humans. Sometimes a disease entity is recognized in animals long before it is recognized in humans. For example, fear-induced heart failure was described in wildlife about thirty years before it was recognized in humans. Comparative medicine is the study of disease processes across species and is based on the study of naturally occurring diseases of animals that also afflict humans. The concept of comparative medicine is very old. The ancient Greeks understood that dissecting and studying animals could yield important clues to understanding human diseases. From Galen to William Harvey, comparative anatomical and physiological studies have been responsible for significant advances in medicine; Frederick Banting and Charles Best discovered insulin through such work.
The musculoskeletal system is particularly well-suited to comparative medicine studies since acute and chronic disorders of bones and joints have the same counterparts in humans and animals. Information gained from one species can be directly translated to another, thereby advancing the diagnosis and treatment of musculoskeletal disorders. Since the early 1930s, comparative orthopedic research has incorporated the One Health concept. Otto Stader, a small animal veterinarian, used a comparative medicine approach and developed the first form of external skeletal fixation, the Stader splint, as a way to stabilize fractures in dogs. During World War II, Navy surgeons improved the treatment of fractures in sailors by incorporating Stader’s advances. During the 1940s and 50’s, Jacques Jenny, a veterinary surgeon, performed one of the first intra-medullary pinning procedures in animals and significantly advanced fracture repair strategies in horses and humans. In 1966, Sten-Erik Olsson and John L. Marshall, both of whom had medical and veterinary medical degrees, founded the first laboratory dedicated to comparative orthopedic research at the Hospital for Special Surgery in New York. In the 21st century, comparative orthopedic laboratories are located throughout the world and use both a comparative and translational research approach in an effort to improve diagnostic capabilities, enhance preventive and therapeutic strategies, and advance the understanding of disease mechanisms. Comparative research has led to advances in fracture fixation, total joint replacement, and cartilage repair—both in veterinary and human medicine.
Urbanization, globalization, climate shift and terrorism have brought the need for a more diverse public health workforce to the forefront of public planning. Changes in land use, creation, and operation of large terrestrial and marine food production units and microbial and chemical pollution of land and water sources have created new threats to the health of both animals and humans. For example, deforestation for agriculture can lead to the emergence of zoonotic diseases. One Health is a unifying concept to bring together human health care practitioners, veterinarians, and public and environmental health professionals. By strengthening epidemiologic and laboratory investigations that assess the role of environmental influences, this partnership can help to develop and apply sustainable and effective community health interventions.
In 2004, the Wildlife Conservation Society (WCS) convened a group of conservation and health experts at Rockefeller University in New York and developed the phrase “One World – One Health” in order to promote the recognition of the impact of land use and wildlife health on human health. William B. Karesh, one of the leaders of the WCS effort, wrote articles in Foreign Affairs about the health links between humans, animals, and the environment.
The One Health Commission (OHC), a 501(c)3 non-profit organization based in the U.S., was created out of the joint efforts of leaders from multiple disciplines. Briefly, in 2007 Roger Mahr, then president of the American Veterinary Medical Association (AVMA), invited Ronald Davis, then President of the American Medical Association (AMA), to open conversations to bring the animal and human medical communities together. The two organizations each followed with supportive resolutions: in June 2007, the AMA unanimously adopted a “One Health” resolution, and a similar resolution was passed by AVMA in July 2008. A One Health Initiative Task Force (OHITF), made up of prominent health profession leaders and liaisons from the AVMA, AMA and the American Public Health Association (APHA), worked together from 2007-2008 to prepare an Executive Summary giving twelve recommendations for advancing and realizing the One Health concept. One of those recommendations was the creation of a One Health Commission. Initially led by Roger Mahr as CEO, the OHC was based first in Kansas then was headquartered for three years (2011-2013) at Iowa State University until Mahr’s retirement in 2013. In late 2013 the OHC Board appointed Cheryl Stroud to become Executive Director and the Commission was moved from Iowa to the Research Triangle Park region of North Carolina.
“One Health Initiative” is a multidisciplinary collaborative approach to solving global and environmental health challenges. The One Health Initiative Autonomous pro bono team started the One Health Initiative website in 2008 which has since been serving as a global repository for all news and information pertaining to One Health. Organizations supporting this movement include the American Medical Association, American Veterinary Medical Association, the UC Davis One Health Institute, the American Society of Tropical Medicine and Hygiene, The American Association of Public Health Physicians, the Centers for Disease Control and Prevention (CDC), the United States Department of Agriculture (USDA), the National Oceanic and Atmospheric Administration (NOAA) and the U.S. National Environmental Health Association (NEHA. Additionally, more than 850 prominent scientists, physicians, and veterinarians worldwide have endorsed the initiative.
Since 2008, the European Union “has promoted the OH approach, and it has already been integrated into certain EU strategy documents.” In the United States, the CDC has a One Health website with One Health resources.
The 1st International One Health Congress met in February 2011 in Melbourne, Australia. In 2013, the 2nd International One Health Congress met in Bangkok, Thailand. The 1st One Health Conference in Africa was held in July 2011 in Johannesburg, South Africa.
The World Bank is investigating how to demonstrate the cost effectiveness of a One Health approach to global health. In June 2012, the World Bank published the economic benefits of One Health.
The importance of One Health is promoted by scientists in many countries and supported by prominent organizations including the World Health Organization, Food, and Agriculture Organization, World Organization for Animal Health, The International Federation for Animal Health, Global Alliance for Rabies Control, New Zealand Centre for Conservation Medicine (NZCCM), Hubert in Asia the One Health Global Network, the University of California One Health Center, Academic Hospital Utrecht and Utrecht Life Sciences and the Infection Ecology and Epidemiology Network, Uppsala, Sweden.