An Increase in Giardia duodenalis Infection among Children Receiving Periodic Anthelmintic Treatment in Bangladesh

During a deworming study in northern Bangladesh, the prevalence of Giardia duodenalis increased significantly among three groups of children receiving periodic treatment with mebendazole. This was first observed in the treatment group (Group A) of a 12-month study. Giardia increased from 5 to 31 per cent in Group A (n = 49 chi 2 = 10.42, P < 0.005), but did not increase significantly in the placebo group (Group B) (11 to 18 per cent; chi 2 = 0.4, P = NS). The prevalence of Giardia in the treatment and placebo groups was not significantly different at the beginning of the study (n = 89, chi 2 = 0.8, P = NS). During a 6-month follow-up study, children in Groups…