Surveillance for schistosomiasis japonica in China from 2000 to 2003.

According to the protocol of the national surveillance project, longitudinal observation of the endemic situation of schistosomiasis japonica in China has been carried out at 20 sentinel surveillance sites, commencing in 2000. After four years of surveillance, the infection rate of Schistosoma japonicum gradually decreased in seven sentinel sites. In 10 sites, infection rates remained relatively stable over time, while there was a marked increase in one site. No clear trend became apparent in the remaining two sites. Significant reductions of densities of living intermediate host snails and infected snails were noted in only two sites. In turn, the endemic situation was not well controlled in most of the other sentinel sites. The infection cattle rate fluctuated yearly in the majority of the sites and maintained a high level. During the four years of surveillance, acute cases of schistosomiasis japonica among humans were found in each of the yearly cross-sectional surveys, and the number of patients with advanced schistosomiasis did not change significantly. The surveillance results obtained thus far indicate that current control strategies continue to reduce morbidity due to schistosomiasis. However, concerted control efforts must continue for a long time and the surveillance of intermediate host snail and animal reservoirs (e.g. cattle) should be strengthened.