Giardia lamblia Infection Linked to IBS, Chronic Fatigue

Laurie Barclay, MD

September 13, 2011

September 13, 2011 — Giardia lamblia infection is linked to increased risks for irritable bowel syndrome (IBS) and chronic fatigue, according to the results of a historic cohort study reported online September 12 in Gut.

"Giardia lamblia is a common cause of gastroenteritis worldwide, but there is limited knowledge about the long-term complications," write Dr. Knut-Arne Wensaas, from the Department of Public Health and Primary Health Care at the University of Bergen in Bergen, Norway. "...IBS is a common short- and long-term complication after bacterial gastroenteritis."

The goal of the study was to assess the relative risk for IBS and chronic fatigue 3 years after acute infection with G lamblia, using follow-up data collected by mailed questionnaire. The investigators compared 817 patients with G lamblia infection during a waterborne outbreak of giardiasis in Bergen vs 1128 healthy control participants matched for age and sex. Detection of cysts in stool samples allowed confirmation of infection.

In the group with giardiasis, 46.1% went on to have IBS during 3-year follow-up vs 14.0% of the control group (adjusted relative risk [RR], 3.4; 95% confidence interval [CI], 2.9 - 3.8). The prevalence of chronic fatigue was 46.1% vs 12.0%, respectively (adjusted RR, 4.0; 95% CI, 3.5 - 4.5).

IBS was associated with chronic fatigue. In the group with giardiasis, the RR of having a combination of these 2 conditions was 6.8 (95% CI, 5.3 - 8.5), and the risk was also greater for having either IBS (RR, 1.8; 95% CI, 1.4 - 2.3) or chronic fatigue (RR, 2.2; 95% CI, 1.7 - 2.8).

Although the prevalence of IBS and chronic fatigue is generally higher in women, the study participants showed no evidence of a sex bias.

"Infection with Giardia lamblia in a non-endemic area was associated with a high prevalence of IBS and chronic fatigue 3 years after acute illness, and the risk was significantly higher than in the control group," the study authors write. "This shows that the potential consequences of giardiasis are more serious than previously known. Further studies are needed, especially in areas where giardiasis is endemic."

Limitations of this study include lack of data about previous IBS, chronic fatigue, and related health problems, and response rate of 65% in the exposed group and 31.5% among the control group.

"Gender is not a strong risk factor for irritable bowel syndrome after giardiasis," the study authors conclude. "It is important to consider Giardia lamblia as a cause of infectious gastroenteritis. Knowledge about long-term complications from giardiasis will aid counselling and treatment of particular patients."

An open grant from the Municipality of Bergen covered the cost for production and mailing of the questionnaire and for the services delivered by Statistics Norway. Dr. Wensaas was partly funded by the Norwegian Medical Association’s Funds for Research in General Practice. The other study authors have disclosed no relevant financial relationships.

Gut. Published online September 12, 2011.


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