Post epidemic giardiasis and gastrointestinal symptoms among preschool children in Bergen, Norway. A cross-sectional study.

BACKGROUND: A surprisingly low number of children became ill with giardiasis during the large waterborne outbreak of Giardia lamblia in Bergen, Norway during autumn 2004. The aim of the present study was to evaluate the prevalence of giardiasis among exposed children one year after an outbreak and compare faecal carriage of Giardia and abdominal symptoms among exposed versus unexposed children one year after the epidemic. METHODS: Children between 1 and 6 years old were recruited from the local health care centres in Bergen municipality in the period between June 2005 and January 2006. One faecal sample per child was collected and examined for presence of Giardia with a rapid immunoassay antigen test, and parents were asked to answer a questionnaire. A total of 513 children participated, 378 in the group exposed to contaminated water, and 135 in the in the group not exposed. RESULTS: In the exposed group eleven children had been treated for giardiasis during the epidemic and none in the unexposed group. Giardia positive faecal tests were found in six children, all in the exposed group, but the difference between the groups did not reach statistical significance. All six Giardia positive children were asymptomatic. No differences were found between the groups regarding demographic data, nausea, vomiting, different odour from stools and eructation. However, the reported scores of abdominal symptoms (diarrhoea, bloating and stomach ache) during the last year were higher in the exposed group than in the unexposed group. CONCLUSIONS: A low prevalence of asymptomatic Giardia infection (1.7%) was found among exposed children around one year after the epidemic (1.2% overall prevalence in the study). In the present setting, pre-school children were therefore unlikely to be an important reservoir for continued transmission in the general population.

Evaluation of image quality and lesion perception by human readers on 3D CT colonography: comparison of standard and low radiation dose.

AIMS: We compared the prevalence of noise-related artefacts and lesion perception on three-dimensional (3D) CT colonography (CTC) at standard and low radiation doses. METHODS: Forty-eight patients underwent CTC (64 x 0.625 mm collimation; tube rotation time 0.5 s; automatic tube current modulation: standard dose 40-160 mA, low dose 10-50 mA). Low- and standard-dose acquisitions were performed in the supine position, one after the other. The presence of artefacts (cobblestone and snow artefacts, irregularly delineated folds) and the presence of polyps were evaluated by five radiologists on 3D images at standard dose, the original low dose and a modified low dose, i.e. after manipulation of opacity on 3D. RESULTS: The mean effective dose was 3.9 +/- 1.3 mSv at standard dose and 1.03 +/- 0.4 mSv at low dose. The number of images showing cobblestone artefacts and irregularly delineated folds at original and modified low doses was significantly higher than at standard dose (P < 0.0001). Most of the artefacts on modified low-dose images were mild. No significant difference in sensitivity between the dose levels was found for polyps > or =6 mm. CONCLUSIONS: Reduction of the effective dose to 1 mSv significantly affects image quality on 3D CTC, but the perception of > or =6 mm lesions is not significantly impaired.