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Childhood Helminth Exposure Is Protective Against Inflammatory Bowel Disease: A Case Control Study in South Africa

Chu, Kathryn M. MD*; Watermeyer, Gillian MBChB; Shelly, Lauren MD; Janssen, Julia BA§; May, Thaddaeus D. MD; Brink, Kerrigan BSN; Benefeld, Gameda BSN; Li, Xuhang PhD**

doi: 10.1097/MIB.0b013e31827f27f4
Original Clinical Articles

Background: Inflammatory bowel disease (IBD) is more common in countries with improved hygiene, suggesting that environmental exposures may be associated with its development. The primary objective of this study was to examine the association between self-reported childhood helminth infection and the development of IBD in South Africa.

Methods: Unmatched case–control study. Logistic regression was used to model associations with IBD.

Results: There were 88 patients with Crohn’s disease (CD), 63 with ulcerative colitis (UC), and 219 control subjects. Of the 151, 93 (61.6%) IBD subjects (35 of 63 [55.6%] had UC and 58 of 88 [65.9%] had CD) reported childhood helminth exposure compared with 200 of 219 (91.3%) non-IBD subjects (P < 0.001). Helminth infection (adjusted odds ratio [AOR] = 0.2; 95% confidence interval [CI], 0.1–0.4), shared housing (AOR = 0.1; 95% CI, 0.04–0.4), and raw beef consumption (AOR = 0.2; 95% CI, 0.1–0.6) were protective, whereas urban dwelling (AOR = 4.2; 95% CI, 2.0–8.8) and parental tertiary education (AOR = 18.2; 95% CI, 3.2–103.7) were associated with CD. Helminth infection (AOR = 0.2; 95% CI, 0.1–0.6), mixed race (AOR = 0.1; 95% CI, 0.03–0.5), smoking (AOR = 0.2; 95% CI, 0.07–0.5), shared housing (AOR = 0.1; 95% CI, 0.01–0.4), and raw beef consumption (AOR = 0.1; 95% CI 0.04–0.5) were protective against UC, whereas parental tertiary education (AOR = 12.7; 95% CI, 1.0–157.4) was associated with UC.

Conclusion: This study demonstrates a protective association of childhood helminth infection against the development of IBD and supports the “hygiene hypothesis” that improved living conditions may increase the incidence of IBD. Our epidemiologic conclusions provide support that helminths may have immunomodulatory effects which provides protection against the development of IBD later in life.

Article first published online 1 February 2013

*Department of Surgery, School of Medicine, Johns Hopkins Medical University, Baltimore, Maryland

Gastrointestinal Unit, Groote Schuur Hospital, University of Cape Town, Cape Town, South Africa

Department of General Medicine and Pediatrics, University of Illinois, College School of Medicine, Chicago, Illinois

§Division of General Internal Medicine, General Medicine Clinic, San Francisco General Hospital, University of California San Francisco, San Francisco, California

Department of Pediatric Gastroenterology and Nutrition, Baylor College of Medicine, Houston, Texas

Division of Human Genetics, University of Cape Town, Cape Town, South Africa

**GI Division, Department of Medicine, Johns Hopkins Medical University School of Medicine, Baltimore, Maryland.

Reprints: Kathryn M. Chu, MD, PO Box 535, Hluvukani, South Africa 1363 (e-mail:

Supported by grants from the Johns Hopkins Center for Global Health and the University of Cape Town, South Africa.

Received June 19, 2012

Accepted June 20, 2012

© Crohn's & Colitis Foundation of America, Inc.
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