0. 05), Conclusion There was the same molluscicidal effect while the active content of SCN was a guarter of active content of WPN by immersion and spraying in the field. SCN is a novel form of niclosamide with high molluscicidal effect and of convenience to use in the field.

Objective To explore susceptibility of praziquantel(PQT) against Schistosoma japonicum in the repeated chemotherapy areas in Dongting Lake region of China. Methods Sixty mice were divided into two groups, and infected respectively by cercariae released from the infected snails which were collected from new and old endemic areas. After 5 weeks, the mice in each group were divided into control groups and treatment groups (PQT group). The mice in each PQT group were treated with a single oral dose of praziquantel (600 mg/kg). Three weeks post treatment, mice were dissected, and the number of adults, the stool eggs per gram (EPG), the liver EPG and the hatching rates were observed. Results The worm reduction rates of the PQT groups of new and old epidemic areas were 98.24% and 98.71% respectively, and the stool egg reduction rates 99.94% and 99.64%, the liver egg reduction rates 75.85% and 73.10%,and there were no significant differences between the new and old endemic areas. The stool hatching test was positive in the control groups, and negative in the PQT groups. Conclusion Susceptibility of praziquantel against Schistosoma japonicum does not decrease in repeated chemotherapy areas in Dongting Lake region.

Objective To evaluate the molluscicidal effect of BYW emulsion on Oncomelania snails. Methods The immersion and spraying methods were used in this study both in lab and field trials. Results The mortality of snails was 86.7% when the snails were immersed in 10.0 mg/L BYW emulsion solutions for 72 hours at room temperature 20 ℃, and LC_ 50 was 2.28 mg/L . However, the mortality of snails increased to 96.7%-100.0% when the snails were immersed in 1.25-10.00 mg/L BYW emulsion solutions for 48 hours at 25 ℃. In the field, 93.3%-100.0% snails died after being immersed in 0.5-2.0 mg/L BYW emulsion solutions for 4 days. In the spraying test, 5, 7, 15 days after spraying with 2.0 g/m~2 BYW emulsion, the mortalities of snails were 67.5%, 68.1% and 92.5% respectively. Conclusion BYW emulsion has a good molluscicidal effect but low toxicity to other animals.