ABSTRACT
Background: Functional gastrointestinal disorders and fatigue may follow acute infections. This study aimed to estimate the persistence, prevalence and risk of irritable bowel syndrome and chronic fatigue six years after Giardia infection.

Methods: Controlled prospective study of a cohort of 1252 individuals who had laboratory confirmed Giardia infection during a waterborne outbreak in 2004. In total, 748 cohort cases (exposed) and 878 matched controls responded to a postal questionnaire six years later (in 2010). Responses were compared to data fromthe same cohort three years before (in 2007).

Results: The prevalences of irritable bowel syndrome (39.4%) by Rome III criteria and chronic fatigue (30.8%) in the exposed group six years after giardiasis were significantly elevated compared to controls with adjusted RRs of 3.4 (95% CI: 2.9 to 3.9) and 2.9 (95% CI: 2.3 to 3.4) respectively. In the exposed group the prevalence of irritable bowel syndrome decreased by 6.7% (RR: 0.85; 95% CI: 0.77 to 0.93), while the prevalence of chronic fatigue decreased by 15.3%from three to six years after Giardia infection (RR:
0.69; 95% CI: 0.62 to 0.77). Giardia exposure was a significant risk factor for persistence of both conditions and increasing age was a risk factor for persisting chronic fatigue.

Conclusions: Giardia infection in a non-endemic setting is associated with an increased risk for irritable bowel syndrome and chronic fatigue six years later. The prevalences of both conditions decrease over time indicating that this intestinal protozoan parasite may elicit very long term, but slowly self-limiting, complications.

Irritable bowel syndrome and chronic fatigue six years after Giardia infection: a controlled prospective cohort study by K Hanevik et al in Clin Infect Dis.  2014 Aug 12. pii: ciu629 [Epub ahead of print]