"All things are connected. Whatever befalls the earth befalls the children of the earth."—Chief Seattle

In 2020, the U.S. Congress designated January One Health Month to "promote awareness of organizations focused on public health, animal health, and environmental health […]." While the term "One Health" is relatively new, according to the Centers for Disease Control, the concept dates to the 1800s, when scientists noted the similarity in disease processes among animals and humans. Despite that recognition, human and animal medicine has been practiced separately in this country for more than 200 years.

According to Dr. Sue VandeWoude, director of the Colorado State University's One Health Institute, One Health is a wide-ranging concept focused on the intersection of animal, human, and environmental health.

One Health advocates like VandeWoude focus attention and resources on the critical interconnectedness of animals, humans, and the environment and the benefits of multidisciplinary collaboration. They believe the concept offers a promising pathway for research with the potential to improve our global well-being.

"A subset of this concept is that humans and animals get similar diseases," said VandeWoude.

"We can take advantage of the similarities in physiology, anatomy, exposure, and environmental influences on disease across species to promote, understand, and solve both human and animal health problems. A good example of this opportunity is cancer."

COMPANION ANIMALS AND CANCER

In the veterinary cancer community, it's often said that cancer doesn't care if you have two legs or four. Cancer in pets and people share remarkably similar characteristics, including appearance under a microscope, tumor growth and spread, and response to conventional treatment (chemotherapy, surgery, and radiation). These similarities provide an important opportunity to enhance the treatment of pets with cancer and speed up discovery for all cancer patients.

Comparative oncology is the study of naturally occurring cancers in more than one species. Colorado State University's Flint Animal Cancer Center has been a leader in the field for more than forty years. FACC's long-term partnership with scientists and medical doctors at the University of Colorado Cancer Center is a valuable illustration of the power of interdisciplinary collaboration.

Based on the strength of the CSU/CU partnership and the desire to expand the field of comparative oncology, in 2015, Dr. Rodney Page, director of the FACC, led an initiative to convene a first-of-its-kind workshop hosted by the Institute of Medicine's National Cancer Policy Forum (now the National Academy of Medicine's National Cancer Policy Forum). The meeting, The Role of Clinical Studies for Pets with Naturally Occurring Tumors in Translational Cancer Research, served as a springboard for collaborations between human and veterinary medicine and helped release millions of dollars in competitive funding from the National Cancer Institute.

Since the workshop, Page has continued to foster cross-disciplinary partnerships nationwide while setting a new focus on pets, people, cancer, and the environment – a One Health approach to studying cancer.

"Companion animals, in particular, offer beneficial insight into human cancer because they drink the same water, breathe the same air, often eat the same food, and even sleep in our beds," said Page. "As a result, they could potentially offer early warning signs of environmental exposures harmful to people."

Two years ago, Page and Dr. Wendy Shelton, a long-time policy consultant for the FACC, approached the National Academies of Science, Engineering, and Medicine with an idea for a second workshop to explore the role of companion animals as sentinels for environmental exposures in people. They connected with Linda Birnbaum, Ph.D., retired director of the National Institute of Environmental Health Sciences (NIEHS) and currently a Scholar in Residence at Duke University, who agreed to chair the workshop.

"In the spirit of One Health, the goal of the workshop was to promote improved interdisciplinary collaboration because we believe companion animals offer a promising and underutilized pathway for research with the potential to improve animal and human health," said Birnbaum.

PETS AS SENTINELS

The Role of Companion Animals as Sentinels for Predicting Environmental Exposure Effects on Aging and Cancer Susceptibility in Humans workshop featured the research of 30 leading scientists, including veterinarians, medical doctors, toxicologists, and epidemiologists. The public event was held in Washington D.C. with sponsorship support from the FACC and the University of Colorado Cancer Center, numerous other academic and non-profit organizations, as well as the NIEHS, National Cancer Institute, National Institute on Aging, and the Environmental Protection Agency. In addition to in-person guests, the workshop livestream received more than 2,900 views over three days.

In opening remarks, Dr. Ned Sharpless, director of the National Cancer Institute, characterized the last decade and the decade to come as the golden age of cancer research.

"We've seen rapid progress, where we're not just treating but curing some cancers," said Sharpless. "Nonetheless, there are pockets of concern. I'm concerned and have been for some time about the impact of environmental carcinogens."

Scientific consensus shows that a significant portion of cancer diagnoses in people are attributed to non-genetic factors from carcinogens found in the air, water, household goods, and lifestyle choices like smoking and diet. 

Sharpless added, "We need new thinking, new approaches, new ideas to link environmental carcinogens to a given cancer, approaches that are efficient and cost-effective […] and I think companion animals are one approach."

Unfortunately, teasing out the impact of environmental exposures on health is complicated. Each day and throughout a lifetime, people are exposed to a mixture of pollutants. And it may be decades before the cumulative effects of those exposures result in a cancer diagnosis. That's where companion animals may play an important role.

"Given that our pets have much shorter lifespans, but they are living in the same environments with us, monitoring exposures and cancer outcomes in dogs and cats can provide a more rapid assessment of potential cancer risks associated with certain exposures," said Dr. James DeGregori, workshop presenter and deputy director of the University of Colorado Cancer Center.

Understanding which toxins and surface contaminants people and pets are exposed to is important, but to DeGregori's point, learning whether these exposures pose potential cancer risks requires time. A helpful method to observe outcomes is through a longitudinal study, which follows a group of participants over time, often many years.

The Golden Retriever Lifetime Study (GRLS) and the Dog Aging Project (DAP) provide proof of principle for longitudinal One Health research. Launched in 2012, the GRLS follows 3,000 golden retrievers from birth to death. The study seeks to identify nutritional, environmental, lifestyle, and genetic risk factors for cancer and other diseases in dogs. Similarly, the Dog Aging Project is following tens of thousands of companion dogs for ten years to understand how genes, lifestyles, and environment influence aging. In addition to helping canines, these large, prospective studies may speed up our understanding of diseases like cancer and aging in people.  

Likewise, longitudinal studies in people gather information to advance understanding of everything from disease to mental health to environmental exposures. Currently, the Human Health Exposure Analysis Resource seeks to understand the impact of the environment on human health over a lifetime. The National Cancer Institute also sponsors and supports a variety of long-term studies, including the Connect for Cancer Prevention Study.

As the workshop progressed, many wondered, what if longitudinal studies and other exposure research merged to follow people and their pets? What could we learn?

Workshop presenter Heather Stapleton, Ph.D., an environmental chemist from Duke University, shared her recent work with silicone tags worn by dogs and their owners, which showed a strong correlation between exposures to more than 150 airborne toxicants and surface contaminants. Her work offers one example of how we can simultaneously gather data from people and their pets.

Rena Jones, Ph.D., NCI cancer environmental epidemiologist, offered a look at the sophisticated geospatial tracking exposure models she uses in her work that could provide a translatable system for monitoring the same geographic exposures in pets.

The possibility of new multi-species study designs and the use of Geographic Information System technology to gather comparative exposure data offer promising new directions for research.

VandeWoude, who attended the workshop, shared her enthusiasm for the future.

"It's exciting to think about next steps and being intentional about combining pets and people into future studies, and developing non-traditional collaborations. There's been a lot of discussion about what the impact of One Health could be; the purpose of this [workshop] was to jump-start specific research priorities. The wide-ranging expertise coupled with the enthusiasm to learn what other researchers are doing illustrates that we're at a place in time when people are excited about interdisciplinary opportunities."

At the opening of the workshop, Sharpless called for new approaches as we enter the next decade of the "golden age" of cancer research. With the interdisciplinary collaborations required to develop solutions for different species, it's possible One Health encompasses exactly the out-of-the-box thinking we need. In that case, we may not only be encountering the golden age of cancer research but entering the dawn of the golden age of One Health, too.