Doctors of the Animal Kingdom

by Kaitlyn Lew '20

Doctors aren’t just humans. Some animals don't need medical school to know how to heal themselves and others of their species.

 Behaviors of self-medication have been seen across various species– from caterpillar larvae to birds. Self-medication has been defined as the antiparasitic use of secondary plant chemicals or other non-nutritive substances [1]. Essentially, it is the ability to consume organic compounds to alleviate a disease or infection before or after it has been contracted [2]. These behaviors include the methods by which they use natural and man-made products to mitigate illnesses and symptoms. The study of self-medication in nonhumans is known as zoopharmacognosy [3].

Recently, it has been discovered that our close primate cousins, the orangutans, demonstrate similar abilities of treatment. Helen Morrogh-Bernard, behavioral ecologist of the Borneo Nature Foundation, has studied orangutans, also known as Pongo pygmaeus, for several decades.

To conduct their studies, Morrogh-Bernard and her colleagues trekked to the Sabangau Peat-swamp forest in Central Kalimantan province, Indonesia. Between 2003 to 2015, they observed over 20,000 hours of 10 orangutans chewing a special plant, called the Dracaena cantleyi. Combining the plant with their saliva, the orangutans would create a foamy lather with their saliva and rub it into their fur, and then massage the mixture over their arms and legs for about 45 minutes [4]. Interestingly, this plant is also used by the indigenous people in Central Kalimantan as a pain killer for the body. They typically use the plant as treatment for pain their arms after a stroke, muscular pain, and sore bones and swelling [5].

Scientists determined that this was the first instance of topical analgesic used in nonhuman animals [4]. At the Czech Academy of Sciences, Palacký University Olomouc, and the Medical University of Vienna, researchers conducted further studies on the plant’s chemical properties to investigate the plant’s medicinal qualities. In the lab, researchers combined the Dracaena cantleyi plant extract with human cells artificially cultivated from a dish and stimulated to produce cytokines, or an immune system response that causes inflammation, redness, and swelling [4]. Using sandwich ELISAs (enzyme-linked immunosorbent assay) to measure the levels of inflammatory cytokine interleukin-6 (IL-6), they discovered that the amount of inflammatory cells decreased when treated with the methanol extract of the Dracaena cantleyi [5]. These results confirm the medicinal effects of these plants.

The orangutans have used the medicinal properties of the plants to their advantage. Oftentimes, these pharmaceutical actions are innate behaviors rather than learned, such as in caterpillars and ants. However, scientists have determined that advanced animals can medicate themselves when they have cognitive abilities that allow them to observe, learn, and make conscious decisions [1]. The self-medication abilities of orangutans may have originated when one orangutan rubbed the plant on its skin to try to treat parasites and realized that it also had a pleasant pain-killing effect. Thus, the action may have been successful and imitated by other orangutans in the group. Additionally, medication is not only for the self but also applies to actively treating their kin and offspring.

The plants used for self-medication are not only imitated within the orangutan species, but also across other species in the same area. Even the indigenous populations observe sick animals to gather knowledge regarding the native plant life and which species are poisonous or beneficial. On a broader scale, studying how animals self-medicate may lead to the development of new drugs for humans. Many human treatments are plant-based, so imitating our primate cousins may unlock the keys to furthering modern medicine.
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Citations:

1. Roode, Jacobus C. de, et al. “Self-Medication in Animals.” Science, American Association for the Advancement of Science, 12 Apr. 2013, science.sciencemag.org/content/340/6129/150.
2. Abbott, Jessica. “Self‐Medication in Insects: Current Evidence and Future Perspectives.” Ecological Entomology, Wiley/Blackwell (10.1111), 12 May 2014, onlinelibrary.wiley.com/doi/abs/10.1111/een.12110.
3. Morrogh-Bernard, Helen Celia. “Fur-Rubbing as a Form of Self-Medication in Pongo Pygmaeus.” SpringerLink, Springer US, 18 June 2008, link.springer.com/article/10.1007/s10764-008-9266-5.
4. Main, Doug. “Orangutans Use Plant Extracts to Treat Pain.” Scientific American, 6 Apr. 2018, www.scientificamerican.com/article/orangutans-use-plant-extracts-to-treat-pain/.
5. Morrogh-Bernard, H. C., et al. “Self-Medication by Orang-Utans ( Pongo Pygmaeus ) Using Bioactive Properties of Dracaena Cantleyi.” Nature News, Nature Publishing Group, 30 Nov. 2017, www.nature.com/articles/s41598-017-16621-w.