Evaluating the efficacy of different praziquantel treatment regimens using egg and circulating anodic antigen (CAA) detection methods in a Schistosoma mansoni endemic area in northeastern Brazil

This study evaluated the efficacy of different treatment regimens with PZQ against Schistosoma mansoni infection. Residents of the Patioba and Colônia Miranda villages (Sergipe, Brazil) with a confirmed diagnosis of S. mansoni infection were randomized into one of the study groups and treated with a standard dose of PZQ (Group 1); with two doses spaced 24 hours apart (Group 2); or with two doses spaced 30 days apart (Group 3). Efficacy was assessed 30 days after the final treatment, based on the detection of eggs in feces using the Kato-Katz (KK) method and on the detection of CAA in urine using the Up-Converting Particle Lateral Flow (UCP-LF) assay. A total of 88 participants, who tested positive for infection by KK and UCP-LF CAA at baseline, were included in the statistical analysis. Cure rates (CRs) reached 100 % in all three study groups, according to KK. The UCP-LF CAA revealed that not all participants were cured, with the highest cure rate observed in Group 2 (69.6 %%), followed by Group 3 (57.7 %) and Group 1 (43.8 %). An Intensity Reduction Rate (IRR) of 100 % and >97 % was observed in all groups, based on KK and UCP-LF CAA, respectively. Reduction in S. mansoni burden was observed over time, with the IRR in all groups exceeding the efficacy threshold established by the WHO (>90 %). Cure rates varied according to the diagnostic method used, being overestimated when based on egg quantification, highlighting the importance of using more sensitive tools for the detection of active infections and monitoring the efficacy of PZQ.