[Integration and demonstration of key techniques in the surveillance and forecast of schistosomiasis in Jiangsu Province II Molluscicidal effect of 5% niclosamide ethanolamine granules in large-scale settings].

OBJECTIVE: To evaluate the field molluscicidal effect of 5% niclosamide ethanolamine granules, so as to provide a novel Oncomelania hupensis snail control approach for emergency treatment of high-risk settings. METHODS: Snail control tests with spraying of 5% niclosamide ethanolamine granules were conducted in two settings of 2 counties, and the dose-, time- and setting-specific field molluscicidal effects were tested. RESULTS: In the small-scale setting, spraying of 5% niclosamide ethanolamine granules at doses of 30, 40 and 50 g/m2 resulted in 54.55%, 68.41% and 73.45% 1-day snail mortality, 57.27%, 68.59% and 80.28% 3-day snail mortality, and 63.49%, 77.58% and 85.55% 7-day snail mortality, respectively, and no significant differences were detected in 1- and 3-day snail mortality caused by spraying of 5% niclosamide ethanolamine granules at doses of 30 and 40 g/m2 (all P > 0.05), while significant difference was found in the 7-day snail mortality (χ2 = 4.549, P < 0.05). In addition, spraying of 5% niclosamide ethanolamine granules at doses of 40 and 50 g/m2 resulted in comparable 1-, 3- and 7-day snail mortality (all P > 0.05). In the large-scale setting, spraying of 5% niclosamide ethanolamine granules at a dose of 40 g/m2 resulted in 85.29% and 87.70% 3-day snail mortality, 83.89% and 91.02% 7-day snail mortality, and 83.41% and 91.84% 15-day snail mortality in the environment-cleaning group and non-cleaning group, respectively. The overall snail mortality was 90.02% in the environment-cleaning group 3 to 15 days after spraying, which was significantly higher than that (84.28%) in the non-cleaning group (χ2 = 9.950, P < 0.05). After 15 days of spraying with 5% niclosamide ethanolamine granules at a dose of 40 g/m2, the densities of living snails reduced from 19.90 and 19.83 snails/0.1 m2 to 0.60 and 2.60 snails/0.1 m2 in the environment-cleaning group and non-cleaning group, with 96.98% and 86.89% reductions, respectively. CONCLUSION: The appropriate dose of 5% niclosamide ethanolamine granules is 40 g/m2 for snail control in the field, and environment cleaning of vegetation with a height of more than 50 cm may improve the molluscicidal efficacy.