Exploring the Potential Transmission Risk of Schistosomiasis Japonica in the Lower Reaches of the Yangtze River, China

Vector snails are important in the life cycle of schisosomiasis, the need to understand the ecologic factors that could enhance snails’ survival and trigger schistosomiasis transmission necessitated this study. Therefore, the potential risk of schistosomiasis transmission was explored in Zhangjiagang region, a non-endemic area in lower reaches of Yangtze River, eastern of China. The key indictors, including snail survival rate, spawn rate, hatching rate and gland development, were investigated through the designed experiments, routine snail and infectious source surveillance. The results showed that there was no significant difference in surviving rate, spawn rate, hatching rate and gland development between groups of simulated environments in laboratory, similar finding in field experiments, which suggested that snails stand a high possibility to survive in these non-endemic areas once they spread into these areas from other places. And no snails and infectious source were found either in the previous routine monitoring in the past decades and the snail surveillance we conducted from 2007 to 2013. Therefore, there is little risk in the study areas in the lower reaches of the Yangtze River. However, the sporadic and imported cases are still seen in a few areas adjacent to the endemic or transmission interrupted areas as the important infectious source, thus become a risk of schistosomisis transmission or re-emergence in these areas where the snail exists. Hence, maintaining routine monitoring and surveillance can be one of the effective and efficient ways to prevent the re-emergence of Schistosomiasis.