Ebola, SARS, avian flu, MERS, Hanta, anthrax, plague. All of these illnesses are contenders for the top spot on any list of most terrifying diseases. But they have something else in common: they are all zoonotic, meaning they are transmitted to humans by other animal host or vector (disease carrier) species. If you think that we’ve been hearing a lot about zoonotic diseases (zoonoses) recently, you’re right. Zoonoses are on the rise; about 75% of newly emerging infectious diseases (that is, contagious diseases that are appearing for the first time) are zoonotic. Since 1980, more than 87 new zoonotic and/or vector-borne pathogens have been discovered, and in the last 15 years alone, there have been more than 15 deadly zoonotic or vector-borne disease outbreaks globally1.
Beyond the lives lost (whose value is incalculable), the cost of these outbreaks is staggering. The World Bank estimates that the price tag for the outbreaks of only 6 zoonotic diseases occurring from 1997 to 2009 was about US$80,000,000,0001. That’s 80 trillion dollars. Clearly, there is a lot of work to be done.
Canaries in the mine
Typically, we think of diseases in terms of the threat to human life. How likely are we to get the disease? How likely are we to die from it? But this sort of tunnel vision doesn’t work for zoonoses, because it ignores a huge part of the picture: the animals who harbor and are afflicted by the pathogen. In these cases, the health of animals, both domestic and wild, has a direct relationship with human health. The association is so intimate that- like modern day canaries- animal wellbeing can be used as sentinels for a suite of lethal pathogens3. One recent example: the sick and dying crows that signal the presence of West Nile virus.
The One Health movement is an attempt to embrace the reality of zoonoses. It’s the radically simple idea that human and animal health are interdependent. Adopted in response to global fear of an avian flu epidemic in the early 21st century, the One Health framework broadened the conversation to include not only humans, but also other susceptible animal species2,6. After contributing to the successful suppression of avian flu, One Health has continued to foster collaboration between medical, veterinary, and wildlife agencies, both nationally and internationally, to prevent disease outbreaks2.
That’s no small feat, and One Health collaborations can be massive and far-reaching. For example, the Integrated Control of Neglected Zoonoses in Africa (ICNZA) project, a One Health initiative, is a consortium of 21 European and African universities and research institutes that work on zoonotic disease clusters in 7 countries2. That is a huge accomplishment, and an important step toward addressing the true nature of diseases that do not respect borders or single out species.
The broad nature of One Health has made it malleable and encourages flexibility from stakeholders involved in public health initiatives. The framework has helped move research funding away from the traditional single disease approach, and there are groups advocating to expand the One Health concept to include environmental health and chronic (not infectious) diseases. But while the breadth of One Health may be its greatest strength, it is also a weakness2.
Two steps forward, one step back
The expansive nature of One Health makes the movement’s agenda difficult to articulate. This ambiguity may be why it has received little attention from the popular media2, and why there is little evidence that the concept has been widely adopted for addressing health issues4. It appears that although the One Health framework has proved useful, it remains predominately the province of the animal health community2 and has not been embraced by the human health sector.
Yet counterintuitively, the solution may not be to simplify. To date, few diseases have been the focus of One Health efforts; broadening its scope could bring in more partners and raise awareness of the movement’s goals5. It would be wonderful to see greater adoption of its methods; it is a critical acknowledgement of the complexity of zoonotic disease systems and offers important tools to combat them effectively. It is a powerful reminder that despite life’s diversity, there is only one health.
- Gebreyes, WA, J Dupouy-Camet, MJ Newport, CJB Oliveira, LS Schlesiger, YM Saif, S Kariuki, LJ Saif, W Saville, T Wittum, A Hoet, S Quessy, R Kazwala, B Tekola, T Shryock, M Bisesi, Patchanee, S Boonmar, & LJ King. 2014. The global One Health paradigm: challenges and opportunities for tackling infectious diseases at the human, animal, and environment interface in low-resource settings. PLOS Neglected Tropical Diseases, 8:e3257.
- Gibbs, EPJ. 2014. The evolution of One Health: a decade of progress and challenges for the future. Veterinary Record, 174:85-91.
- Hilborn, ED, & VR Beasley. 2015. One Health and cyanobacteria in freshwater systems: animal illnesses and deaths are sentinel events for human health risks. Toxins, 7:1374-1395.
- Hueston, W, J Appert, T Denny, L King, J Umber, & L Valeri. 2013. Assessing global adoption of One Health approaches. EcoHealth, 10:228-233.
- Jenkins, EJ, A Simon, N Bachand, and C Stephen. 2015. Wildlife parasites in a One Health world. Trends in Parasitology, 31:174-180.
- Ludwig, S, R Zell, M Schwemmle, & S Herold. 2014. Influenza, a One Health paradigm- novel therapeutic strategies to fight a zoonotic pathogen with pandemic potential. International Journal of Medical Microbiology, 304:894-901.
Image source: Creative Commons, https://en.wikipedia.org/wiki/Kevin_Richardson_(zookeeper)