Bergen giardiasis outbreak – a study from primary care

Project Department: Uni Research Health (group: Research Unit for General Practice in Bergen) period: 01.01.07 - 31.12.10

Project results

During the outbreak of giardiasis in the autumn of 2004 most patients presented to their general practitioner and received treatment and follow up in primary care.

Several patients did not recover as expected following treatment: Of the 119 patients identified at two general practices 89 were treated with metronidazole. Fourteen (17%) were treated twice and 10 (11%) trice. In the end five patients with severe persisting symptoms were referred to the hospital.

Six months after the outbreak only three of the patients (2,5%) had the parasite detected in stool samples, but 37% reported persisting gastrointestinal symptoms. After one year this proportion was down to 19%.

The results from this project inspired the setting up of larger epidemiologic studies 2, 3, 6 and 10 years after the outbreak

About the project

This project was part of Knut-Arne Wensaas’ PhD thesis from 2011: «Giardiasis in Bergen. Outbreak and clinical consequences».

The parasite Giardia lamblia is the cause of acute and chronic gastroenteritis with varying clinical presentation. Patients consulted their GP at different stages of the infection, and the main consequences of the outbreak were handled in primary care. The outbreak in Bergen, unlike other outbreaks of giardiasis in Europe and North America, prompted several research projects investigating the acute clinical consequences and complications for the patients.

In this project 134 patients presenting at one of two general practices with giardiasis based on a clinical case definition were identified. As many patients had fallen sick several weeks before the outbreak was detected inclusion based on a positive stool sample or specific diagnosis would exclude many cases. 119 of the patients consented to participate in the study.