The health of people, animals, and the environment is intertwined. A health hazard for people may likely be a health hazard for animals. For example, smoking is not only harmful to people; it’s harmful to pets too. Medical advances in understanding and treating a disease in one species, such as heart disease in people, may be applied to other species. And a change in the environment can affect all living things, from people to animals to plants.
The One Health Initiative recognizes this inter-connectedness and advocates a comprehensive approach to health and environmental problems versus a piecemeal approach. By building bridges between physicians, veterinarians, environmental scientists, and public health professionals, the initiative aims to “promote, improve, and defend the health and well-being of all species.”1
“No one discipline or sector of society has enough knowledge and resources to prevent emergence or resurgence of diseases in today's globalized world. Through mutual collaborations, veterinarians and physicians can accomplish so much more to advance the health of humans and animals,” said Dr. Bernadette Dunham, former director of FDA’s Center for Veterinary Medicine. Dr. Dunham is currently a professor at the Milken Institute School of Public Health at George Washington University in Washington, D.C., where her focus is on One Health issues.
Zoonotic Diseases and Comparative Medicine
The link between human and animal health can be seen with bovine tuberculosis (TB) and brucellosis. Both are zoonotic diseases, meaning they can spread from animals to people. Bovine TB is a bacterial disease most commonly found in cattle and other animals such as bison, elk, and deer. Brucellosis is another bacterial disease seen in livestock such as cattle, goats, and sheep, wild animals such as bison and elk, and other animals. People can become infected with both bovine TB and brucellosis by consuming contaminated, unpasteurized (raw) milk or dairy products and through direct contact with infected live animals or carcasses.
In the U.S., it was once common for cattle to spread bovine TB and brucellosis to people. But efforts to eliminate both diseases in cattle and routine pasteurization of cow’s milk have led to a dramatic decline in the number of human cases. In the early 1900s, about 20 percent of TB cases in people were caused by bovine TB.2 Today, that number is less than 2 percent in the U.S.3 From 1930 to 1941, about 29,600 cases of brucellosis in people were reported in the U.S.4 But from 1993 to 2010, the number of reported human cases in the U.S. was less than 2,000.5
Initially, One Health efforts concentrated on preventing the spread of diseases from farm animals and wild animals to people. But more recently, One Health has begun to incorporate companion animals into its framework. In 2010, the World Small Animal Veterinary Association established a One Health committee that, at first, focused on monitoring and controlling diseases that can spread from dogs, cats, and other pets to people. But the committee has expanded its key goals to now include two other areas:
- The human-animal bond and the health benefits people receive from interacting with companion animals; and
- Comparative medicine for the benefit of both animal and human health. The field of comparative medicine looks at the similarities and differences between veterinary medicine and human medicine.
“One Health (formerly called One Medicine) is dedicated to improving the lives of all species—human and animal—through the integration of human medicine, veterinary medicine and environmental science.
One Health shall be achieved through:
- Joint educational efforts between human medical [schools], veterinary medical schools, and schools of public health and the environment;
- Joint communication efforts in journals, at conferences, and via allied health networks;
- Joint efforts in clinical care through the assessment, treatment and prevention of cross-species disease transmission;
- Joint cross-species disease surveillance and control efforts in public health;
- Joint efforts in better understanding of cross-species disease transmission through comparative medicine and environmental research;
- Joint efforts in the development and evaluation of new diagnostic methods, medicines and vaccines for the prevention and control of diseases across species and;
- Joint efforts to inform and educate political leaders and the public sector through accurate media publications."
Obesity and Diabetes as Examples of Comparative Medicine
Obesity—A Growing Problem Across Species
Obesity is a prime example of a medical condition that affects a variety of species, especially when the species share similar habits and environments. According to the Centers for Disease Control and Prevention, over 71 percent of Americans over the age of 20 are overweight or obese.6 And according to the Association for Pet Obesity Prevention, 56 percent of dogs and 60 percent of cats are overweight or obese.7 Obesity is also increasing in horses.
Obesity in both people and animals is complex and involves multiple factors, including genetic and environmental risk factors, diet, level of physical activity, stress level, and other lifestyle behaviors. But the basic cause is the same across species: there’s an energy imbalance where too many calories are consumed or too few calories are burned. More people and their pets are living a less physically active lifestyle but still eating an energy-rich diet.
Obesity goes a lot further than skin deep. It’s a major health hazard for all creatures, increasing the risk for several potentially serious health problems. Disorders linked to obesity in pets include:
- Orthopedic problems, such as osteoarthritis, torn or ruptured cruciate ligaments in the knees, and slipped disks in the back;
- Laminitis in horses, also called founder (a painful cause of lameness in which the delicate tissues that connect the small bone within a horse’s hoof to the inside of the hoof wall become inflamed and damaged);
- Breathing problems;
- Urinary and reproductive disorders;
- Some types of cancer;
- Type 2 diabetes in cats;
- Fatty liver disease in cats and horses;
- A decreased ability to handle heat;
- Increased risk of having anesthetic and surgical complications; and
- A shortened lifespan.
Overweight and obese pets lose out, both in terms of health-related quality of life and life expectancy. The list of obesity-related complications in people looks similar.
In 2013, the American Medical Association officially recognized obesity as a disease in people that requires medical attention. And although obesity is the most common nutritional disorder of dogs and cats in Western countries, the veterinary profession has been slow to formally call it a disease. That may change soon, however, as there’s a growing push to follow “our human counterparts’ move” and recognize pet obesity as a disease, said Dr. Ward, the founder of the Association for Pet Obesity Prevention.
Significant parallels exist between people and animals regarding the causes of obesity, its associated complications, and how to prevent and manage obesity in patients. Preventing obesity—through a balanced diet and regular exercise—should be a priority in both human and veterinary medicine.
Managing obesity in both people and pets involves a healthy diet, calorie restriction, and regular exercise. Sometimes, weight loss drugs are prescribed. FDA has approved several weight loss drugs for people, and one drug, Slentrol (dirlotapide), is FDA-approved to manage obesity in dogs.
The biggest hurdle for both pets and people isn’t the initial weight loss; the real challenge is maintaining the lower body weight by sustained long-term lifestyle changes. For owners who are also overweight or obese, the human-animal bond can motivate them to stick to a healthy lifestyle. There is great value in people and pets exercising together. For example, people who have a dog are more likely to get exercise from walking, which in turn may help prevent a number of obesity-related disorders in both the owner and the dog. The benefits are clearly mutual!
Helping pet owners develop a healthy lifestyle for themselves and their four-legged companions is at the heart of a One Health approach to obesity.
Diabetes in Cats and People
Diabetes is a metabolic disorder that results in high blood glucose (blood sugar) levels. In type 2 diabetes—the most common form of diabetes in people—the body doesn’t use insulin properly. Normally produced by beta cells inside the pancreas, insulin helps the body use or store the glucose (sugar) from food for energy. In people and animals with diabetes, the glucose builds up in the blood instead of going into cells. An immediate effect is that the cells are starved for energy. And over time, the high blood glucose levels may cause skin and eye complications, nerve damage, and other problems.8
Diabetes is also common in cats, and feline diabetes closely resembles type 2 diabetes in people in many ways. For example, in both species, the disease is typically seen in middle-age patients, is associated with obesity, and is on the rise. As suggested in the article, Feline Models of Type 2 Diabetes Mellitus, "the incidence of diabetes in cats is increasing for the same reasons it is increasing in humans—an increase in obesity and a decrease in physical activity.”9 Both people and cats are eating more, but exercising less.
Because feline diabetes shares many of the same features, risk factors, and complications as type 2 diabetes in people, cats are a good animal model for studying the human disease. Studies in cats may lead to better ways to prevent and treat diabetes in both felines and humans.10
A human-centric approach to studying health problems, such as obesity and diabetes, doesn’t do much good for animals. And insights gained from understanding diseases in animals may benefit people (and vice versa). A two-way approach to One Health tackles problems from an animal perspective as well as a human perspective for the benefit of all, and in the end, that’s really what One Health is all about.
For more information on One Health and the One Health Commission go to:
1One Health Initiative website. Mission statement. Available at: https://onehealthinitiative.com/mission-statement/. Accessed Nov 1, 2016.
2 Animal and Plant Health Inspection Service website. What is One Health? Available at: https://www.aphis.usda.gov/animal_health/one_health/downloads/one_health_info_sheet.pdf.
3 Centers for Disease Control and Prevention website. Mycobacterium bovis (bovine tuberculosis) in humans. Available at: www.cdc.gov/tb/publications/factsheets/general/mbovis.htm. Accessed Oct 28, 2016.
4 Animal and Plant Health Inspection Service website. What is One Health? Available at: https://www.aphis.usda.gov/animal_health/one_health/downloads/one_health_info_sheet.pdf. Accessed Oct 28, 2016.
5 Centers for Disease Control and Prevention website. Brucellosis surveillance. Available at: www.cdc.gov/brucellosis/resources/surveillance.html. Accessed Oct 28, 2016.
6 Centers for Disease Control and Prevention website. Obesity and overweight. Available at: www.cdc.gov/nchs/fastats/obesity-overweight.htm. Accessed Oct 5, 2018.
7 Association for Pet Obesity Prevention website. 2018 Pet Obesity Survey Results. Available at: https://petobesityprevention.org/2018. Accessed January 14, 2021.
8 American Diabetes Association website. Type 2 Diabetes: Life Doesn’t End with Type 2 Diabetes. Available at: www.diabetes.org/diabetes-basics/type-2/facts-about-type-2.html. Accessed Nov 1, 2016.
9 Henson MS, O’Brien TD. Feline models of type 2 diabetes mellitus. ILAR J 2006;47:234-242.
10 Osto M, Zini E, Reusch CE, et al. Diabetes from humans to cats. Gen Comp Endocrinol 2013;182:48-53.
References for a One Health Approach to Obesity
- Burns K. Taking on obesity as a disease—statement, sessions, and toolkit address the excess weight so common now in cats, dogs, and horses. JAVMA News 2018. Available at: https://www.avma.org/News/JAVMANews/Pages/181001a.aspx. Accessed Mar 8, 2019.
- Day MJ. One Health approach to preventing obesity in people and their pets. J Comp Path 2017;156:293-295.
- Johnson PJ, Wiedmeyer CE, Messer NT, et al. Medical implications of obesity in horses—lessons for human obesity. J Diabetes Sci Technol 2009;3:163-174.
- Salt C, Morris PJ, Wilson D, et al. Association between life span and body condition in neutered client-owned dogs. J Vet Intern Med 2019;33:89-99.
- Sandøe P, Palmer C, Corr S, et al. Canine and feline obesity: a One Health perspective. Vet Rec 2014;175:610-616.
- Zoran DL. Obesity in dogs and cats: a metabolic and endocrine disorder. Vet Clin Small Anim 2010;40:221-239.