Objective To understand the eco-hydraulics characteristics of Biomphalaria straminea,the intermediate host of Schistosoma mansoni. Methods The drainage method and settlement tube method were applied to measure B. straminea's den-sity and hydrostatic settling velocity respectively. Results The density of B. straminea was 1.04-1.16 g/cm3,and the average value was 1.08 g/cm3. The hydrostatic settling velocity was 2.32-12.92 cm/s. Conclusions The eco-hydraulics characteristics of B. straminea is different from Oncomelania hupensis,and more attention should be paid to the hydraulic measures for the con-trol of B. straminea.

The spread of schistosomiasis seriously threaten the health of people and hinder the economic and social develop-ment in China. The water conservancy combined with schistosomiasis prevention and control effectively controlled the spread of schistosomiasis by controlling the spread of Oncomelania hupensis,the only intermediate host of Schistosoma japonicum. This pa-per reviews the evolution of the strategy of schistosomiasis prevention and control in China and points out the historical role of wa-ter conservancy combined with schistosomiasis prevention and control. Furthermore,this article analyzes the problems and chal-lenges of water conservancy combined with schistosomiasis prevention and control in the new period. In response to the challeng-es,the new strategy of water conservancy combined with schistosomiasis prevention and control is put forward,including:devel-oping the research of the new strategy of water conservancy combined with schistosomiasis prevention and control,enhancing the research of water conservancy technology combined with schistosomiasis prevention and control,improving the efficiency and ap-plicability of water conservancy projects combined with schistosomiasis prevention and control,strengthening the guidance of wa-ter conservancy technology combined with schistosomiasis prevention and control,and perfecting the evaluation system.

Objective To explore the relationship between the distribution characteristics and the habitat factors of the invasive B. straminea in South China. Methods From October 2016 to August 2017, the breeding condition and habitat factors of B. straminea were investigated in the rivers of Shenzhen and its adjacent areas in the dry season, normal season and wet reason. The generalized additive model (GAM) was used to study the main habitat factors affecting the distribution density of B. straminea. Results The distribution characteristics of B. straminea showed obvious aggregation and unevenness in space. In terms of time, the density of snails was the highest in the dry season, followed by the normal water season and the least in the wet season. The GAM model analysis showed that the main habitat factors affecting the distribution density of B. straminea were water depth, water temperature, flow velocity, dissolved oxygen, and total phosphorus. When the flow velocity and water temperature were 0.25 m / s and 26 °C, respectively, the largest distribution density of snails might appear. The distribution density of B. straminea was positively correlated with dissolved oxygen and total phosphorus. Conclusion B. straminea is suitable to live in the water environment with poor water quality. In the future, the monitoring should be strengthened to provide reference for the prevention and control of the spread of the snails.

Objective To study the dynamic diffusion characteristics of Biomphalaria straminea in Shenzhen, Dongguan and Huizhou of Southern China. Methods B. straminea was monitored at 25 investigation points along 10 river channels in Shenzhen, Dongguan and Huizhou by salvaging method. The diffusion characteristics of snails along with water in the Guihua New Village section of the Guanlan River and the Dawei Village section of the Longgang River were analyzed by GPS location drift test. In addition, the influence of flooding on the diffusion of B. straminea in the Kuichong River both before and after Typhoon ^"Shanzhu^" was analyzed by monitoring the hydrology and distribution of snails. Results In March and October from 2016 to 2018, a total of 1 176 kg of floating objects were salvaged in rivers in Shenzhen, Dongguan and Huizhou. Scattered B. straminea were found on water hyacinths. Drift test of floats with GPS showed that the average drift speed of GPS floating objects was close to the river surface velocity. Affected by river current and wind direction, the GPS floats quickly drifted to the river bank and stopped in the stagnant area due to the blockade of water plants, stone and the bending of the shoreline. The drift distance of each time was between 136 - 715m. The test results of salvaged floating objects found that the loss rates of B. straminea were 46.70% - 60.00% and 22.10% - 30.80%, in the Guihua New Village section of the Guanlan River and the Dawei Village section of the Longgang River, respectively, which were significantly affected by the floating weight, river velocity and drifting distance. The analysis of the hydrology and distribution of B. straminea in the Kuichong River both before and after Typhoon ^"Shanzhu^" showed that the density of B. straminea in the river was significantly reduced by the flood. Conclusion B. straminea is mainly transported as suspended matter in water body, and flooding was an important factor in its long-distance diffusion.