Evaluation of Praziquantel Dosage for Treatment of Schistosomiasis in Highly Endemic Areas of Northeastern Brazil

This is a double blind, randomized, PZQ 40mg/Kg- controlled clinical trial. Subjects 10-19 years old living in communities of the Northeast of Brazil will be identified and invited to participate in this study.

Well trained field health agents will first make a sketch map of the village (depicting the location of houses, main water courses, snail habitats and water-contact sites) and apply a household questionnaire to obtain personal data from residents to identify the individuals in the 10-19 years age range, as well as to record sanitary standards of the houses and water-contact reported behaviour as described by Pieri et al. (1998, Mem. Inst. Oswaldo Cruz, 93, Suppl 1: 259-264).

Meetings with the Caricé Community Association will be held in order to explain to the inhabitants the purpose, the objectives of the study, and how the study will be conducted.

Thereafter, all residents between 10 and 19 yrs of age will be interviewed at their homes regarding the fulfilment of the inclusion/exclusion criteria. Those who fulfil the criteria and agree to participate in the screening phase of the trial (signed Screening Informed Consent) will be given stool vials and asked to provide stool samples (two samples within 5-day intervals) that will be collected at their homes in the following days, stored in heat-proof containers and taken to the premises of the Service of Reference for Schistosomiasis Diagnosis of the CPqAM to be promptly prepared for examination by the Kato-Katz method (Katz et al, 1972, Rev. Inst. Med. Trop. Sao Paulo, 14: 397-400) aiming to identify positive cases and estimate individual egg load. Females on childbearing age will also be asked to provide a urine sample for pregnancy test. Pregnant women will only be treated with Praziquantel after weaning, as currently recommended by Funasa, and will be excluded from the trial. The 2 stool samples provided by each individual will be analysed for S. mansoni infection. Two slides will be prepared from each stool sample, and the mean value of the 4 slides (as measured by number of eggs/g of stool) will be calculated. Only those harbouring at least 100 epg who are able and willing to follow-up will be invited to participate in the study. At this stage, individuals with positive diagnosis for S. mansoni and that for any reason were excluded from the study will receive standard treatment for schistosomiasis.

In the enrolment visit the subjects eligible for the study, will be examined by the physician and interviewed to assess inclusion/exclusion criteria. Those who fulfill all criteria will be invited to participate in the trial and will go through the Informed Consent Form procedure (see details in section 6.14). For those who accept to participate and provide a written Informed Consent: weight and height will be measured, a 5ml venous blood sample will be collected and an abdominal ultra-sound exam will be performed. After all these procedures, the patient will be assigned to the treatment.