Epidemiology of Giardia lamblia infection in children: cross-sectional and longitudinal studies in urban and rural communities in Zimbabwe.

Stool specimens from 3,038 children in rural and urban areas near Harare were examined for Giardia lamblia cysts. Preliminary studies, using specimens collected on three consecutive days from 157 known cyst passers, showed that over 89% of infections could be diagnosed on single stool specimens by examination of Gomori-stained smears. The overall prevalence of giardial infection was 19.4% with significantly more urban children (21.1%) passing cysts than rural children (16.7%). In urban areas the highest prevalence was in young (5-6 year) children, while in rural areas, the highest prevalence was in older (9-10 year) children. Of 132 children treated with Entamizole a metronidazole-diloxanide combination, 127 (96.2%) had ceased excreting cysts by the fifth treatment day. Follow-up examination of these children showed a high rate of reinfection, with 29.6% excreting cysts during the year following treatment. During the same period 13.3% of previously uninfected children had started passing cysts, while over half of infected, but untreated, children had undergone apparent "self-cure." Younger children were more likely to be reinfected than older children, and continued excreting cysts for a longer period of time.