Impact of praziquantel treatment and early reinfection patterns in a mixed Schistosoma mansoni and Schistosoma haematobium infection focus in the Democratic Republic of Congo

Objective To evaluate the impact of single versus mixed Schistosoma infections on the efficacy of PZQ treatment as well as on the dynamics of reinfection after treatment. Methods We followed 388 randomly selected residents of a village co‑endemic for Schistosoma haematobium and S. mansoni , screening them for Schistosoma infection every three weeks across a nine‑week period. Kato-Katz stool examination was used to detect eggs of S. mansoni and urine filtration to detect eggs of S. haematobium . At every visit, those who were positive for schistosomiasis were treated with 40mg/kg praziquantel. Treatment outcomes (cure rate (CR), egg reduction rate (ERR), cumulative cure rate (CCR) and cumulative egg reduction rate (CERR)) and reinfection rates were compared between age groups, sex and pre-treatment co-infection status using McNemar and Wilcoxon tests. Results Baseline infection prevalence was similar for S. mansoni (60.8%) and S. haematobium (60.3%), with 36.6% of mixed S. haematobium - S. mansoni infection. Infection intensity was higher in mixed compared to single infection (200.7 versus 70 epg for S. mansoni , p < 0.001; 29 versus 9.6 ep10mL for S. haematobium , p < 0.001). After one praziquantel treatment, CR of 62.7% and 94.6%, with ERR of 97.5% and 96.5%, were found for S. haematobium and S. mansoni , respectively. After 3 rounds of praziquantel treatment, CCR of 75% and 93.7%, with CERR of 95.6% and 97.5%, were recorded for S. haematobium and S. mansoni , respectively. In addition, treatment efficacy was significantly higher in single than in mixed infections (CR = 76.7% versus 58%, p = 0.01; ERR = 90.2% versus 96.5%, p < 0.001; CCR = 76.7% versus 58%, p = 0.01; CERR = 90.2% versus 96.5%, p < 0.001), and in older than in younger (<16 years) age groups. No significant associations were found between (co-)infection status and reinfection rate. Conclusion Our results show that pre-treatment co-infection status can affect schistosomiasis treatment outcomes for S. haematobium but does not affect the post-treatment reinfection. These results could help in tailoring control activities in co-endemic areas.