A strain of actinomyces (named as 218 powder) was seperated from snail-inhabitated soil and was identified as streptomyces diatatochromogenes. The corrected mortality rate of snails exposed to 0. 1 % concentration of the shaking fermentation liquid was 96% -100%, and that of the snails exposed to 10 mg/L of 218 powder as industrial product for 48 h in the laboratory was 98.0%. The hatching rate of snail eggs exposed to 100 mg/L of the bacterial powder for 48 h was 9. 0%. The corrected mortality of snails exposed to 75 mg/L of bacterial powder for 48 h in the field was 96. 9%, and this biological molluscicide did not damage plants but had some slow acting toxicity to fish.

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.

0.05), and the all had significant differences in 2 to 4 months post-infection compared with the normal controls (P