Control of clonorchiasis by repeated treatments with praziquantel.

The present study aimed to evaluate control efficacy of clonorchiasis by two schemes of repeated treatment with praziquantel at two endemic villages in China. Residents of one village at Guangxi Autonomous Region were treated and examined 6-monthly and of another at Liaoning Province 12-monthly. In residents that took 25 mg/kg x 3 (total 75 mg/kg) of praziquantel every 6 months for one year the egg positive rate showed a significant drop from 69.0% to 17.1%. In contrast, a group of same praziquantel medication once showed a slight marginal decrease in the egg rate from 18.9% to 12.2% after one year. Of 39 subjects examined 3 times, 56.4% were cured, 7.7% persistently positive, one (2.6%) reinfected after cure or newly infected, but 25.6% were persistently negative. The present finding suggests that 6-monthly medication with 75 mg/kg of praziquantel should effectively lower the prevalence but incomplete for control of clonorchiasis in heavy endemic areas.