 Subjects will be randomly allocated to either Group A single 40 mgkg oral dose or Group B single 60 mgkg oral dose, as described in sections 6.4.3 and 6.4.4. Praziquantel tablets will be provided by TDR. During four hours after treatment the subjects will be observed for safety assessment, and one day and 21 days after treatment they will be interviewed about the following symptoms related to praziquantel side-effects: abdominal pain, diarrhea, vomiting, nausea, drowsiness, general malaise, edema, skin rash, urticaria, myalgia, heartburn, fever, dizziness and headache Guisse et al, 1997, Am. J. Trop. Med. Hyg., 56: 511-514, 1997. The follow-up visits to assess efficacy and morbidity will be at 21 days, six months and 12 months after treatment, when the subjects will be surveyed by the Kato-Katz method two stool samples within five-day interval, two slides each. Weight and height will be measured at 6 and 12 months follow-up. Ultrasound will be repeated at 6 and 12 months follow-up visits for the participants who presented periportal fibrosis or liverspleen enlargement in the baseline D0 exam. 