INTRODUCTION: Schistosomiasis is a global public health problem related to poverty. Factors such as lack of sanitation and family income contribute to the transmission and maintenance of the disease in poor regions. In this study, we evaluated socioeconomic parameters associated with Schistosoma mansoni infection in an endemic rural area of the state of Bahia, Brazil submitted to mass drug administration (MDA) of praziquantel over one year after treatment. METHODOLOGY: This cohort included all habitants of three villages in the rural area of Conde-Bahia-Brazil. All participants provided stool samples for Kato-Katz (KK). After baseline (D0) evaluation praziquantel (PZQ) was administered for all participants and they were then followed up and re-evaluated at 30 (D30), 180 (D180) and 360 (D360) days after treatment. RESULTS: A total of 340 individuals were included in D0, of which 55.6% (n=189) were positive for S. mansoni in the Kato-Katz. Most of the infected individuals (73.5%) showed a low parasite burden (1-99 epg). Considering the high KK positivity observed in baseline, participants underwent mass drug administration (MDA) with praziquantel (PZQ). Thirty days after PZQ treatment KK positivity reduced from 55.6% to 3.0%. At D180 and D360 the positivity of KK increased to 5.5% and 16.5%, respectively. Regarding socioeconomic conditions, 24.8% of included families do not have bathrooms at home, and 13.8% send their waste to the river or its surroundings. Considering the families that have bathrooms at home, 84.1% use a septic tank as a sanitary sewage system. Regarding family income, 84.6% of included individuals received less than one minimum wage. A questionnaire to assess the contact with local water bodies was applied and showed that 93.5% of included participants related contact with water in D0. Six months after treatment 66.7% related contact with water and one year after treatment the frequency of individuals who related contact with local water bodies was 77.1%. CONCLUSION: In this study, we describe a region with high prevalence of Schistosoma infection, with the predominance of low parasite burden. Mass drug administration of PZQ was able to significantly reduce the number of individuals positive for KK thirty days after treatment. However, since PZQ is not effective in preventing reinfections or against larval forms of Schistosoma, this number goes up again at six and twelve months after PZQ administration. The lack of basic sanitation and dependence of local water bodies for domestic and economic activities are the likely factors responsible for the maintenance of schistosomiasis in the region, even after the treatment of the population.