The One Health Initiative is the effort to increase communication and collaboration between disciplines such as human medicine, veterinary medicine, public health, environmental health, and other related fields 1. The hope is that by promoting collaboration, shared knowledge could improve the health of all species.
There are innumerable reasons why sharing knowledge between scientific disciplines is vital. Comparative medicine relies on the shared characteristics between the anatomy and physiology of humans and other animals, as well as similarities in disease pathogenesis. This knowledge is then used to establish animal models for biomedical research, which can help in the development of drugs, vaccines, medical devices, and increase understanding of infectious diseases and cancer. Identifying animal models that accurately reflect human disease is key, and requires input from those with knowledge of the physiology and pathology in both humans and potential animal models.
The large and increasing prevalence of zoonotic diseases is another reason why cooperation between human and veterinary medicine is of utmost importance. Of all the diseases which affect humans, ~60% are caused by pathogens which also infect non-human animals 2. Zoonotic diseases have become more problematic in recent decades, as ~75% of the infectious diseases that have emerged in the human population in the last 30 years have been zoonotic 2. Goals of the One Health initiative include improving surveillance, prevention, control, diagnosis, and treatment of zoonotic disease through joint efforts from various health disciplines, especially veterinary and human medicine.
The events surrounding the emergence of West Nile virus (WNV) in the United States in 1999 provide some of the best evidence that human and animal medicine have remained too distinct. WNV first entered the US in New York City during the summer of 1999. Crows, now known to be one of most highly susceptible North American WNV hosts, began dying in large quantities in June, but the New York state wildlife pathologist misdiagnosed 400 crow samples 3. Birds at the Bronx Zoo began dying on August 10th; by September 23, the zoo had lost a total of 27 birds 4. It was the zoo’s pathologist, Dr. Tracy McNamara, who started putting the puzzle pieces together when she realized that the encephalitis she was seeing in her birds may have something to do with the human disease outbreak that the city announced on Labor Day, which was misattributed to St. Louis encephalitis (SLE). She knew that her animals could not be dying from SLE, as it is generally asymptomatic in birds 3. Dr. McNamara appealed to both the USDA and the CDC to test her samples, and was met with resistance. One of the main problems she faced was jurisdictional, as neither government department wanted to claim responsibility for the health of wild and exotic species 5. People also did not want to believe that there was a link between the avian deaths and the human disease. Dr. McNamara finally got the Army to test her samples, and it was discovered that it was West Nile virus that was the causative agent. By that point it was September. In 1999, 62 individuals were infected with West Nile virus, 7 of whom died, statistics which may have been lower had there been more rapid identification of WNV 6.
Developing an effective surveillance program for West Nile virus activity took time, and retrospective analysis from avian samples collected during 2000 has revealed that WNV was evident in samples at least 2 weeks before the first human case 7. However, WNV birds were collected 3 months before the first human infection, so if laboratory testing had been conducted more swiftly there might have again been more advanced warning, and prevention of human disease 8. Today, WNV surveillance data is collected for human infections, sentinel chicken flocks, mosquitoes, veterinary cases, and dead birds (which rely on public reporting) 6. In 2012, there was a large WNV outbreak, resulting in increased avian and human deaths. The data has not yet been finalized, but the confirmed 5,387 human infections and 243 human deaths represent the most severe seasonal WNV epidemic since 2003 6.
Given the prevalence of zoonotic diseases, it would be impossible to have healthy people without also ensuring the health of other animals. That’s one of the reasons I get upset when I hear professors at JHSPH say things along the lines of “since this is a school of public health, obviously we’re going to focus more on human health.” We understand that multihost pathogens cannot be generally eliminated if you only focus on control in a single host, so I believe that public health is doing human health a disservice if it narrows its focus and ignores other species.
One Health is by no means a new concept, but one that has taken on increased importance given the globalization of our world, the growing prevalence of zoonotic infectious diseases, and the use of animal models in biomedical testing. Facing emerging medical problems as a collective force is perhaps the best way for all health professionals to ensure the well-being of all animal species, including humans.
1. One Health initiative. http://www.onehealthinitiative.com/.
2. King LJ, Anderson LR, Blackmore CG, et al. Executive summary of the AVMA One Health initiative task force report. J Am Vet Med Assoc. 2008;233(2):259-261.
3. Keynote by Dr. Tracey McNamara — 2012 Zoobiquity conference. http://www.youtube.com/watch?v=cBk9X4iwhmE. Updated 2012.
4. Steele KE, Linn MJ, Schoepp RJ, et al. Pathology of fatal West Nile virus infections in native and exotic birds during the 1999 outbreak in New York City, New York. Vet Pathol. 2000;37(3):208-224.
5. Microbeworld Video. One Health and the lessons learned from the 1999 West Nile virus outbreak (MWV46). http://www.microbeworld.org/podcasts/microbeworld-video/898-one-health-and-the-lessons-learned-from-the-1999-west-nile-virus-outbreak-mwv46-. Updated 2011.
6. CDC. West Nile virus. http://www.cdc.gov/ncidod/dvbid/westnile/index.htm. Updated 20122013.
7. Mostashari F, Kulldorff M, Hartman JJ, Miller JR, Kulasekera V. Dead bird clusters as an early warning system for West Nile virus activity. Emerg Infect Dis. 2003;9(6):641-646.
8. Eidson M. “Neon needles” in a haystack – the advantages of passive surveillance for West Nile virus. West Nile Virus: Detection, Surveillance, and Control. 2001;951:38-53.