Background: Giardia lamblia is endemic in many tropical and subtropical areas of the world, and in Europe and North America a common cause of waterborne outbreaks of gastroenteritis. In 2004, approximately 5000 people were sick with giardiasis during an outbreak in Bergen, Norway.
Objective: To investigate the presence of gastrointestinal complaints and persistent infection in a 1-year period after acute giardiasis.
Methods: From a population (N = 7100) assigned to two general practice clinics, a cohort of 134 patients with clinically defined giardiasis was identified. Of these, 118 gave consent to take part in this study. The patients were asked to submit stool samples 6 months after the acute infection and to return questionnaires delivered by mail 6 and 12 months after the outbreak. Main outcome measures were proportion of patients with persistent infection and/or gastrointestinal symptoms.
Results: Stool samples were submitted by 69.5% (82/118) of the patients after 6 months, and three were positive for G. lamblia. After 6 months, 37.3% (44/118) of the patients reported gastrointestinal symptoms related to their Giardia infection. This proportion went down to 19.2% (19/99) after 12 months. The reported water intake prior to the outbreak was significantly higher in patients with persistent symptoms, but there was no association with gender and neuroticism as has been shown in other studies of functional gastrointestinal disorders.
Conclusion: Persistent gastrointestinal symptoms are a common complication after giardiasis in a population most likely previously unexposed to G. lamblia. The results show the need for further investigation of the mechanism involved.