Future MDs learn 'One Health' approach to medicine When Travis Zack, MD, PhD, was accepted into Harvard Medical School, he didn't expect the curriculum to include shepherding a gaggle of geese into their cages. Yet here he was, clad in a safari coat at the Franklin Park Zoo, chasing the birds into the office next door. Through the One Health Clinical Elective offered each spring, Harvard medical students can spend a month working with different kinds of patients than they are accustomed to, like Sofina, the lemur with type 1 diabetes, or a camel named Cornelius with a fistula draining blood. Throughout the month, students perform annual checkups and vaccinations on zoo inhabitants, and they are always on call, ready to be beckoned to the animal hospital when a water buffalo breaks a metatarsal or an African antelope begins to show acute behavioral changes. "Too frequently we rely on a certain test or imaging to treat patients," said Richard Neal Mitchell, MD, PhD, a professor of pathology at Harvard who oversees the program. "At the zoo, it's a little more like the Wild West, where you don't have all your resources and you have to use more of your clinical wit to figure out what's going on," he said. "It informs the way students practice with people after that because they've developed the skills that will allow them to use a stethoscope, a pair of hands, and a mind connected to them to work through different diagnoses." Photo courtesy of Joseph Rosenthal, PhD Along with the physical skills developed in their clinical practice, working so closely with veterinarians can give students a heightened appreciation for animal medicine. Joseph Rosenthal, PhD, who took the elective last spring, said he learned to see each patient individually, considering factors he would have never considered in a human patient. He had to think creatively when working with Sofina, for example, because the lemur had only been trained to receive insulin once a day. If she was handled for longer periods of time, it would risk affecting the social dynamic of her pack -- the other lemurs might start to view Sofina as an outsider and turn on her. "Seeing the ingenuity of how zoo vets can approach the application of medicine to such wildly different species was truly staggering to witness," Rosenthal said. "In a single day, the veterinarians I worked with had to think about how to manage conscious and unconscious sedation in a turtle I can hold in my hand and a metric-ton zebra." One Health The elective is based on One Health initiatives, which aim to promote, improve, and defend the well-being of all species. These practices were frequently executed at the zoo as students studied infectious diseases and how habitat disturbances may result in a loss of biodiversity, which would have negative impacts on human health. Rosenthal at Zoo New England; photo courtesy of Joseph Rosenthal, PhD During his time in the elective, Zack worked on a project covering chytridiomycosis, a disease causing mass declines in amphibian populations. Zack had proposed using data from a new genomic sequencing technology to better characterize immunologic differences in amphibians in order to see which ones are susceptible and resistant to the disease, the type of thinking One Health aims to inspire. Students also spent time researching increased rates of Lyme disease and rodent populations in the East Coast, or how flooding may change the amount of snakes in a lake. They learned that increased rodent populations, caused by deforestation and urbanization, would multiply the amount of ticks and increase the amount of bacteria transmitted to humans. And how a change in snake populations could cause a surge of parasitic snails to invade residential areas. "Harvard has the Harvard School of public health but there is no set time to really talk about the state of the environment and how that plays into population and individual health, which is becoming more important due to things like climate change," said Zack, now an intern at the University of California San Francisco. "Who would've thought a small change in water level would change the ecosystem to a point where it would have human health consequences?" Natterson-Horowitz (bottom right) performing diagnostics on a gorilla at the Los Angeles Zoo; photo courtesy of Barbara Natterson-Horowitz, MD Eric Baitchman, DVM, vice president of animal health at Zoo New England (which includes Franklin Park Zoo and Stone Zoo), leads the One Health Clinical Elective and said the collaboration with Harvard is a perfect marriage. Most diseases and clinical signs presenting in the animal patients can be found in humans, and each case requires students to draw on what they have learned in the past 4 years. "What we want students to take away from this experience is that when they continue through their careers, they see beyond the single organ or patient they are treating to see all of their patients in the context of the ecosystem in which they live, and what they can do to promote the health of all," Baitchman said. "Experiencing similarities between animals and humans helps cement what they learn in medical school." Inception Baitchman had been considering a program like this for some time when a student emailed him to ask if he could be taken on as the zoo's first medical student. Baitchman enthusiastically allowed Gilad Evrony, MD, to spend a month at the zoo, where on his first day he took x-rays of a 150-pound African desert tortoise and began studying a meerkat with cardiomyopathy. Evrony had always been interested in the parallels drawn between human and animal medicine, but after reading Zoobiquity: The Astonishing Connection Between Human and Animal Health, by Barbara Natterson-Horowitz, MD, he realized he wasn't the only one spending his free time researching diagrams of whale hearts after a cardiology lecture or finding out exactly how bears hibernate without regularly urinating. He reached out to Natterson-Horowitz to let her know about his work at the Franklin Park Zoo, thinking she would be interested to know about his own species-spanning approach to medicine. She was absolutely delighted -- it was precisely her motivation to inspire similar educational, collaborative offshoots between physicians and veterinarians. In fact, she used the deposit from her book to host her first annual "Zoobiquity" conference in Los Angeles in 2011. By chance, the 2015 conference was held in Boston and Evrony attended, along with other veterinarians and physicians from across the country. The group spent a day doing guided rounds at the zoo and comparing glioblastoma in an alpaca and a school principal, for example, or separation anxiety in a shih tzu and a second-grade boy. The One Health principles shared at the conference resonated with Evrony; back at the zoo, he applied them to the case of the meerkat with cardiomyopathy. Evrony left to pursue his residency and could no longer continue the project, but it has since expanded into a collaboration between Zoo New England and scientists at the Broad Institute of MIT and Harvard, investigating the heritability of the disease. Compared with rodent populations, meerkats serve as a better model in understanding the disease in humans, Baitchman said. Since the cause of cardiomyopathy is unknown in more than half of childhood cases, finding a species that is susceptible to the disease and can be studied in this manner is an opportunity to work toward a cure, Evrony said. "The human animal, I came to appreciate, is but a single point among a cloud of points revealing otherwise invisible physiologic trends and questioning principles often taken for granted," Evrony wrote in JAMA about his experience. "This perspective also seemed an inexhaustible source of research ideas with potential to affect both human and animal health." Natterson-Horowitz examining a lion at the Los Angeles Zoo; photo courtesy of Barbara Natterson-Horowitz, MD In the laboratory, Natterson-Horowitz said clinical trials can be combined to share information in ways that benefit both animals and humans, something already being done by researchers like Cheryl London, DVM, PhD, whose results studying lymphoma in dogs may be able to advance treatment in humans in the future. More broadly, collaboration can also explain how things like climate change, the presence of endocrine-disrupting chemicals, and antibiotic residue are affecting the planet's inhabitants similarly, and differently. "Every single problem in human medicine, whether it's a cardiologic, psychological, or infectious disease, can be understood more broadly and in a deeper way by bringing in the comparative perspective and an evolutionary lens," Natterson-Horowitz said. "I think people are beginning to see these opportunities, whether it's in comparative genomics, clinical trials, environmental threats, or finding evolutionary origins of disease." Expanding Reach The One Health concept is becoming more widely disseminated and accepted. At the 86th General Session of the World Organisation for Animal Health (OIE) in May, the OIE, the Food and Agriculture Organization of the United Nations, and the World Health Organization joined forces in support of the One Health approach. Citing a surge in population, trade, and agricultural expansion as environmental threats, they urged improved collaboration between health experts dealing with humans, animals, and ecosystems to find solutions to emerging diseases. But on the ground level, One Health isn't on most physicians' radars just yet. In a 2017 study assessing healthcare relationships between veterinary and human medical professionals, the One Health concept was reportedly not sufficiently "alive" in the minds of most healthcare professionals, with only a quarter of respondents saying they had read a professional journal related to the other sector. However, the study also showed that if the two areas of study shared a "common goal," their work could lead to further collaboration and knowledge-sharing. Since the One Health Clinical Elective program started in 2015, all of the students who have taken the elective have gone on to pursue their residencies. But the lessons they have learned will continue to persist in their medical practice, research, and personal lives. "We're living in a human world, isolated from other life forms, sharing this planet," said Wataru Ebina, MD, PhD, who went through the One Health Clinical Elective and is now in his residency at New York University. "By learning about how other life forms are also battling similar diseases, I felt more connected to the rest of the world." Mitchell is currently working with Baitchman to form a similar program for the Medical Engineering/Medical Physics Graduate students interested in writing their thesis on cases at the zoo, and by next summer, residents at Brigham and Women's Hospital will begin attending a similar, shorter rotation as a part of their circuit. Within the past few years, several students have reached out to Baitchman from across the country, curious about his process and wanting to start similar partnerships between their own universities and local zoos. Although such programs are in their beginning stages, the ideas that drive them are not new. To quote Rudolf Virchow, the 19th century pathologist, "Between animal and human medicine, there is no dividing line -- nor should there be. The object is different but the experience obtained constitutes the basis of all medicine." 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