Change of niclosamide concentration in soil through heaping and the effect of Oncomelania control / 复旦学报（医学版）

ABSTRACT

Objective To analyze the concentration, distribution and decreasing trend of niclosamide in soil through soil heaping mixed with niclosamide and the effect of Oncomelania control, and to explore the appropriate dosage for the 'heaping' method. Methods The soil samples were collected from six groups in Tezi township, Puge county, Sichuan Province, and the dosages were 16, 8, 4, 2, 1 and 0 g/m~2, respectively. After ultrasonic extraction, centrifugence and concentration, the samples were finally determined by high-performance liquid chromatography (HPLC). The mortality rate of snails was observed after 3 days and 7 days. Results The standard error and range of niclosamide in soil were large. There was no significant difference in concentration of niclosamide between the surface layer and deep layer of soil (P>0.05). After 5 months, niclosamide still could be determined in groups of 4 g/m~2. The mortality rate of snails decreased as the concentration of niclosamide decreased (P<0.05). After 5 months, in the group of 4 g/m~2 dosage, the 3 and 7 days mortality rate of snails were 5.33% and 9.33% in the surface layer, higher than the control group (P<0.05). Conclusions The heaping method is an efficacious measure of controlling snails and its recommended dosage is 4 g/m~2.