A 5-year longitudinal study of schistosomiasis transmission in Shian village, the Anning River Valley, Sichuan Province, the Peoples' Republic of China

Baseline results showed a human S. japonicum prevalence of 42.0% (95% CI: 36.6-47.5). At follow-up, results showed that the incidence of S. japonicum infection in the selected human cohort in Shian decreased by three quarters from 46% in 2003 to 11.3% in 2006. A significant (P < 0.01) downward trend was also evident in the yearly adjusted (for water contact) odds ratios. Over the four years of follow-up, the incidence of S. japonicum infection in bovines declined from 11.8% in the first year to zero in the final year of follow-up.The substantial decrease in human (75%) and bovine (100%) incidence observed in Shian village can probably be attributed to the annual human and bovine PZQ treatment of positives; as seen in drug (PZQ) intervention studies in other parts of PRC. If an increase in schistosome transmission had occurred as a result of the TGD, it would be of negligible size compared to the treatment induced decline seen here. It appears therefore that the construction of the TGD had virtually no impact on schistosomiasis transmission in Shian village over the period of study. Furthermore, contrary to previous reports from Sichuan downplaying the role of animals in human schistosome transmission, bovines may indeed play a role.In the People's Republic of China (PRC), zoonotic schistosomiasis, caused by Schistosoma japonicum, is a chronic debilitating disease with 50 million people at risk of infection[1]. Endemic foci are located in the lake and marshland regions of Southern China (Jiangxi, Hunan, Jiangsu, Anhui and Hubei provinces), where the majority of transmission occurs, and in the hilly and mountainous regions of Sichuan and Yunnan[1]. Based on ecological, environmental, population genetic and molecular factors, Davis et al. [2] categorised schistosomiasis transmission in the PRC into four discrete ecosystems or transmission modes. These are represented by Poyang Lake (mode I), Dongting Lake (mode II), the Yangtze River isles of Anhui (mode II), the canal