The Relevance of Prior Parasitic Infection and The Risk of IBS And CFS

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Giardia lamblia (synonymous with Giardia intestinalis, Lamblia intestinalis and Giardia duodenalis) is a flagellated protozoan parasite that colonises and reproduces in the small intestine, causing giardiasis. The giardia parasite attaches to the epithelium by a ventral adhesive disc, and reproduces via binary fission. Giardiasis does not spread via the bloodstream, nor does it spread to other parts of the gastro-intestinal tract, but remains confined to the lumen of the small intestine.

A paper published in the esteemed journal GUT looked to see if there was a relationship between two commonly occurring conditions – IBS and CFS and giardia.[1]


Background Giardia lamblia is a common cause of gastroenteritis worldwide, but there is limited knowledge about the long-term complications.

Objective To estimate the relative risk of irritable bowel syndrome (IBS) and chronic fatigue 3 years after acute giardiasis.

Design Controlled historic cohort study with 3 years’ follow-up. Data collected by mailed questionnaire.

Setting Waterborne outbreak of giardiasis in the city of Bergen, Norway.

Participants 817 patients exposed to Giardia lamblia infection verified by detection of cysts in stool samples and 1128 matched controls.

Main outcome measures IBS and chronic fatigue.

Results The prevalence of IBS in the exposed group was 46.1%, compared with 14.0% in the control group, and the adjusted RR=3.4 (95% CI 2.9 to 3.8). Chronic fatigue was reported by 46.1% of the exposed group and 12.0% of the controls, the adjusted RR was 4.0 (95% CI 3.5 to 4.5). IBS and chronic fatigue were associated and the RR for the exposed group of having a combination of the two outcomes was 6.8 (95% CI 5.3 to 8.5). The RR was also increased for having just one of the two syndromes, 1.8 for IBS (95% CI 1.4 to 2.3) and 2.2 for chronic fatigue (95% CI 1.7 to 2.8).

Conclusions 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. 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.


As Nutritional Therapists or practitioners looking to support the recovery from infection or aid elimination of the infective agent, the role of probiotics is often explored. To determine effectiveness or proof of principle mice are sometimes used.

The probiotic Lgg Culturelle has been studies as an effective agent for the removal of giardia and whilst mice are not men this suggests there may be a role in the earlyinfective stage for a supportive supplementation with Lgg.[2],[3]


[1] Wensaas KA, Langeland N, Hanevik K, Mørch K, Eide GE, Rortveit G. Irritable bowel syndrome and chronic fatigue 3 years after acute giardiasis: historic cohort study. Gut. 2012 Feb;61(2):214-9. Epub 2011 Sep 12.  View Article

[2] Goyal N, Tiwari RP, Shukla G. Lactobacillus rhamnosus GG as an Effective Probiotic for Murine Giardiasis. Interdiscip Perspect Infect Dis. 2011;2011:795219. Epub 2011 Jun 2. View Abstract

[3] Shukla G, Devi P, Sehgal R. Effect of Lactobacillus casei as a probiotic on modulation of giardiasis. Dig Dis Sci. 2008 Oct;53(10):2671-9. Epub 2008 Feb 28. View Abstract

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