In a review paper to appear in the November issue of the journal Philosophical Transactions of the Royal Society B, Hart examines parallels between such disease-avoiding strategies in animals and humans. He also explores the possibility that humans needed to develop a more complex system for disease prevention when they started eating meat. Eating meat may have reduced their intake of health-promoting plant compounds, leading to more frequent illnesses. he said.
One example of how animals instinctively make use of herbal medicine as a disease-preventing strategy is when dogs eat grass. (Benjamin Hart/UC Davis courtesy photo)
“The existence of disease-causing viruses, bacteria and parasites represents a profound force that shapes behavior in both humans and animals,” said Hart, a distinguished professor emeritus in the UC Davis School of Veterinary Medicine.
“We often forget this because the animals that are closest to us live in clean environments, are vaccinated against diseases and receive medical care when they are sick,” he said. “But it was much different for their ancestors, which evolved and thrived in natural environments that were teeming with pathogens and parasites.”
Hart’s study deals with the historical theme of comparative medicine, the branch of biomedical research that focuses on the similarities and differences in disease processes in all higher animals. With its schools of veterinary medicine and medicine as well as its primate center, Mouse Biology Program and Center for Comparative Medicine, UC Davis plays a leading role in exploring these processes and fostering an appreciation for the interconnections among humans, animals and ecosystems, a concept known as One Health.
In his new paper, Hart describes five disease-preventing behaviors observed in animals, including:
• avoidance or removal of disease-causing pathogens or parasites using techniques like grooming of skin parasites, licking wounds or swatting biting flies;
• quarantine through preventing territorial intrusion by members of the same species and cannibalization of sick newborns that could infect littermates;
• use of herbal medicine by consuming plants that purge intestinal parasites, or nesting with plants such as bay leaves that kill fleas;
• boosting the immune system through exposing young animals to other members of the same species; and
• helping sick or injured group mates.
None of the animal species included in the review made use of more than one or two of the strategies to prevent or cope with disease.
Hart said that the strategies are reflected in the “four pillars” of human medicine — quarantine, medication, immunization, and nursing and caring.
Funding for this study was provided by the National Institutes of Health, the National Science Foundation, and the UC Davis Center for Companion Animal Health.
About UC Davis
For more than 100 years, UC Davis has engaged in teaching, research and public service that matter to California and transform the world. Located close to the state capital, UC Davis has more than 32,000 students, more than 2,500 faculty and more than 21,000 staff, an annual research budget that exceeds $684 million, a comprehensive health system and 13 specialized research centers. The university offers interdisciplinary graduate study and more than 100 undergraduate majors in four colleges — Agricultural and Environmental Sciences, Biological Sciences, Engineering, and Letters and Science. It also houses six professional schools — Education, Law, Management, Medicine, Veterinary Medicine and the Betty Irene Moore School of Nursing.