Praziquantel Pretreatment Reduces Schistosoma japonicum Infection in Mice by Targeting Immature Worm Stages

Schistosomiasis remains a significant public health concern, with <i>Schistosoma japonicum</i> infection endemic in certain regions of Asia. Praziquantel (PZQ), primarily known as an effective therapeutic agent, has recently shown potential as a prophylactic measure against delayed <i>S. japonicum</i> infections. This study investigated the preventive efficacy of PZQ pretreatment at varying cercarial infection intensities and determined the parasite developmental stages targeted by the pretreatment in a mouse model. Results demonstrated that PZQ pretreatment significantly reduced both worm burdens and liver egg counts at low (10 and 20 cercariae) and high (100 cercariae) infection intensities, with reductions in worm burdens ranging from approximately 48% to 60% and liver egg counts by 47% to 73% compared to control groups (<i>p</i> < 0.05). Further analysis revealed that the mortality of parasites in PZQ-pretreated mice predominantly occurred during the juvenile schistosomula stages, particularly in worms younger than 15 days post-infection. These findings provide critical evidence supporting the application of PZQ pretreatment as a practical prophylactic measure to prevent <i>S. japonicum</i> infections, particularly in populations and animals frequently exposed to contaminated water in endemic areas.