This is a part of the What is … Wednesdays feature, where we take scientific topics that might seem convoluted to some and make them more understandable.

The health of humans, animals, and plants are all related, though those three topics aren’t often discussed together. But with about 70% of all emerging and reemerging infectious diseases being zoonotic or vector-borne, an interdisciplinary field doing just that is becoming increasingly relevant. One Health aims to ensure optimal health of the environment, animals, and humans by addressing those groups collaboratively. 

The One Health approach encompasses ecology, veterinary medicine, and molecular biology, among other health-related subjects. This multisectorial field is important at all scales, from locally to internationally. Important topics in One Health include environmental contamination, zoonoses (diseases transferred between animals and humans), antimicrobial resistance, and food safety. 

one health diagram

Its importance

As the world’s population continues to grow, so does the impact humans have on the environment. Deforestation, changes in farming practices, and expanding human settlements all contribute to habitat loss and reductions in biodiversity, for example. Those same phenomena are also responsible for heightened interactions between humans and animals. Some bacteria and viruses can be spread between various human and animal hosts (a host is an organism in which a pathogen can survive). 

Thanks to modern technological innovations, humans are more connected than ever before – both physically and virtually. A person can travel across the globe in under a day, and with them they can carry germs from one place to another. 

All of these complex issues are of concern in One Health, which believes the best way to mitigate them is by drawing knowledge from experts in various fields. An outbreak of an emerging mosquito-borne parasitic infection could be mapped by an epidemiologist, but a parasitologist would have to weigh in on potential treatments based on the parasite’s metabolism, and a zoologist might gather data on the favorable conditions for the relevant mosquito species. Research chemists would create a medication for the disease, and public health officials would later arrange drug distribution campaigns. One Health considers all of these pieces of the puzzle as one. 

Established by veterinarian Dr. Roger Mahr in 2007, the One Health Initiative Task Force sought to cooperatively author a report on how to build a One Health following around the world. The following year, the One Health Commission was created to facilitate the global implementation of One Health principles and actions. The three goals of the One Health Commission are to connect One Health stakeholders, create strategic networks, and educate about One Health, all in an effort to cause a paradigm shift. 

Even in the absence of an active epidemic, One Health has a place in our daily lives. Safe handling of birds, reptiles, and rodents reduces the likelihood of contracting a zoonosis. People wear insect repellent outside to prevent mosquito and tick bites and in turn, the diseases they transmit. The virus that causes COVID-19 originated in a non-human animal host. 

infographic about all of the fields one health encompasses

Its application

Because of how transdisciplinary it is, One Health is relevant to many situations. A One Health approach has already been used in a number of outbreaks

In light of a number of zoonotic disease epidemics, Thailand’s Ministry of Health (in conjunction with the CDC’s Division of Global Health Protection) developed a smartphone application to report abnormal illnesses and deaths in animals and humans. This citizen science initiative allows health officials to work with farmers and volunteers, even those in rural areas, to anticipate infection outbreaks. Data collected by the app is stored into a database for easy analysis and reference. When necessary, the government can quickly deploy a rapid response team to prevent and control epidemics. 

Scores of children in Zamfara, a state in northern Nigeria, began experiencing gastrointestinal and neurological symptoms around May 2010. A few months prior, duck populations in the region had noticeably decreased. An investigation of the outbreak identified lead as the causative agent. Many residents of Zamfara mined gold for money, and when they came home from the mines, bringing lead dust along. Resulting harmful lead levels in the area led to the illnesses and deaths of hundreds of animals and children. It was and remains the most widespread lead poisoning epidemic known in history. 

The duck deaths from earlier in 2010 were an indicator of an impending hazard to humans; in this instance, the ducks were a sentinel species of unsafe lead levels. Lead is especially poisonous to children and animals. While it is difficult and expensive to eradicate lead from an environment, health officials could have begun mitigation efforts sooner had they recognized ducks as a sentinel species for the outbreak. Educational campaigns on the dangers of lead have aided in abating the prevalence of lead poisoning in Zamfara.

Hopefully you find some aspect of the broad field of One Health intriguing. Be sure to share something you learned with someone else! 

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