Helicobacter pylori infection among children in Sweden

Since Helicobacter pylori was first identified in 1983 convincing data has linked the infection to the development of gastritis and peptic ulcer disease and H. pylori has further been implicated in gastric carcinogenesis. Evidence suggests that H. pylori is one of the most common bacterial infections world-wide, and Aldhood seems to be the critical time for acquisition although the exact routes of transmission remain elusive. The aims of the present studies were to identify the age of acquisition of H. pylon infection among children in Sweden and to identify risk factors for the infection. We further wanted to elucidate the possible role of H. pylori infection on gastrointestinal (GI) symptoms in children at school age. The non-invasive diagnostic methods for H. pylori infection used in the studies were validated. A seroepidepidemiological follow-up of 294 Swedish-born children (having Swedishborn parents) from 6 months to 11 years revealed the highest incidence rate of 13 new infections per 100 child-years for the period between 18 and 24 months. This resulted in a prevalence of 10% in the 2-year-olds. Transient infections were found to be common, resulting in an overall decline of the prevalence to 3 % in the 11-year-olds. A cross-sectional community-based study of 695 10-12-year-old children (response rate 81%) confirmed the low seroprevalence among children with parents born in Scandinavia. Major differences in H. pylon prevalence were seen among Swedish children of different ethnic origin indicating that exposure opportunity within the family is a strong determinant for childhood H. pylori infection. Low socio-economic status and large family size were independent risk factors for infection among children with appreciable exposure opportunity at home. Also the time spent by the child in the country of origin seemed to matter for the risk of contracting the infection early in life. Close contacts between children outside the family, such as those at day-care centres and in school classes with a high H. pylori prevalence, did not increase the risk of H. pylori infection, pointing at intrafamilial transmission as the major route of transmission in the present setting. Also, intrafamilial transmission of H. pylori infection seemed to be dominated by mother-to-child transmission. Use of antibiotics during childhood did not decrease the prevalence of H. pylori infection. H. pylori infection was not found to be associated with an increased risk of recurrent abdominal pain (RAP) or GI symptom among school children. However, the possibly more virulent Type 1 strain (CagA+ and VacA+) infections were strongly and inversely associated with abdominal pain and reflux symptoms, while Type 2 infected children seemed to be at increased risk for having reflux symptoms, RAP and weekly abdominal pain. Serology by ELISA and Immunoblot, as well as 13C-UBT, were demonstrated to be useful diagnostic methods for H. pylori infection in children provided that adjusted cut-offs are used. The presence of specific H. pylori immunoreactive bands (as measured by Immunoblot) seemed to vary according to geographic origin also for children living in the same country