Effects of the praziquantel-based control of schistosomiasis japonica in China

In 2000-2002, the effects of the praziquantel-based control of Schistosoma japonicum (in which each subject found infected in the October of each year is given a single dose of the drug) were examined at 20 or 21 surveillance sites across China. The pre- and post-treatment prevalences and intensities of infection were compared at each site and after pooling using a random-effects method. One year after treatment, in the communities that had the higher prevalences of infection (> 10%) before treatment, the mean prevalence of infection was found to have fallen by 20.15% [95% confidence interval (CI) = 6.95%-31.48%] and the geometric mean intensities of infection (measured as eggs/g faeces) in the currently infected individuals and the entire study cohort were found to have fallen, by 22.91% (CI= 14.69%-30.34%) and 33.93% (CI= 11.69%-50.68%), respectively (P<0.05 for each). In the communities that had lower prevalences of infection pre-treatment, however, no statistically significant reductions in the intensity of infection were observed, although the prevalences in the communities that had pre-treatment prevalences of 6%-10% did fall significantly post-treatment, by a mean of 24.50% (CI=5.35%-39.83%; P<0.05). These observations indicate that the current annual surveys for infection, in which those found infected are each given a single dose of praziquantel, should help keep the prevalence of human infection with S. japonicum low in China, although chemotherapy alone is unlikely to eradicate the parasite.