A three year follow-up of chemotherapy with oxamniquine in a Brazilian community with endemic schistosomiasis mansoni.

Oral oxamniquine was tested as a control strategy for endemic schistosomiasis in a rural area of Bahia, Brazil. Adults were treated with a single dose (12.5 to 15 mg per kg) and children (less than 12 years old) with a total of 20 mg per kg in two doses. The 191 (infected) persons treated represented 69% of the infected population in the study area. Follow-up stool examinations (Kato-Katz method) at one, 3, 6, 13, 25 and 33 months showed the cure rate declining from 80% at three months to 46% at 33 months. Over one half of those not cured showed a decrease in egg counts throughout the follow-up which, after 33 months, remained 66% below the pre-treatment levels. Stool examinations conducted on all study area residents during three years before chemotherapy showed the prevalence and intensity of Schistosoma mansoni infection to be high and stable. 33 months after the chemotherapy the prevalence was 41% and for infected individuals the geometric mean egg count was 121 epg, a decline of respectively 35% and 40% from pre-treatment levels for each index. Chemotherapy of infected persons with oxamniquine protected the community as a whole from high worm burdens for almost three years, although at this point the prevalence began to rise towards pretreatment levels.