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Are We Too Clean?

Biodiversity Within the Human Body

Co Authors:

Amanda J. Chunco
Department of Environmental Studies
Elon University

Jennifer K. Uno
Department of Biology
Elon University


This case study focuses on the relationship between the microbiome (the suite of species that live in or on the human body) and autoimmune and allergic diseases. At the center of the case is Amelia, a young woman living with Crohn's disease. As the case unfolds, students learn about the hygiene hypothesis that modern, "cleaner" living conditions may be linked to the rise of autoimmune disorders throughout the developed world. After students learn the basics of the hygiene hypothesis, they are asked to design an experiment to test it. They are then introduced to some of the modern experimental treatments for autoimmune disorders, including fecal transplants and worm therapy. These treatments aim to restore a more diverse microbiome to the human body. The case ends by relating the human body to an ecosystem, and asks students to think about how ecological principles are being used to treat human diseases. The case was written for a sophomore level biodiversity class and a sophomore level physiology class, but could easily be used in introductory biology or similar courses.

  • Define the hygiene hypothesis.
  • Interpret trends from different data sources.
  • Design an appropriate experiment to test a specific hypothesis.
  • List some consequences of changing the biodiversity in our bodies and homes for human health.
  • Relate ecological ideas to human health.
  • Use information to evaluate treatment options for Crohn's disease.
  • Discuss possible contributors for the onset of Crohn's and other autoimmune diseases.
Keywords: microbiome; allergy; autoimmune; parasites; hygiene hypothesis; ecology; microbiota; Crohn’s disease; fecal transplant; helminth therapy;
Topical Area: N/A
Educational Level: Undergraduate lower division, Undergraduate upper division
Formats: PDF
Type/Method: Interrupted
Language: English
Subject Headings: Biology (General)   Ecology   Environmental Science   Physiology  
Date Posted: 9/26/2016
Date Modified: N/A
Copyright: Copyright held by the National Center for Case Study Teaching in Science, University at Buffalo, State University of New York. Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work.

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