RÉSUMÉ
Objective To develop a novel suspension concentrate of niclosamide (SCN) and evaluate its characteristics and molluscicidal effect against Oncomelania snails. Methods Niclosamide was milled by a sand granule mill and mixed with different amounts of wetting agent, dispersant agent, thickener, and water etc., to develop suspension concentrates, and its dispersion, suspensibility and stability were evaluated. According to the results of evaluation the best recipe and quality indexes for producing SCN were selected. The molluscicidal effects against Oncomelania snails were tested under lab condition and in field. Results The novel SCN contained 25% niclosamide (w/w), 1.5%-2.0% wetting agent (RS 3), 4% dispersant (FS 2), 0.10% thickener, a litte of other agent and water. The quality indexes which the SCN reached were as following: the content of niclosamide was more than 25%(w/w); the suspensibal rate was more than 90%; the pH was from 4 to 7; the size of more than 98% granules of niclosamide was smaller than 44?m; the thickener was smaller than 600 mpa.s. The SCN was very stable when it was stored in high or in low temperature. Under lab condition the LC 50 concentrations of SCN by the immersion method for 24, 48 and 72 hours were 0.0474 mg/L, 0.0412 mg/L and 0.0412 mg/L respectively while the LC 50 concentrations of 50% wettable powder of niclosamide (WPN) were 0.0947 mg/L, 0.0583 mg/L and 0.0442 mg/L. In the field death rates of the snails sprayed with 2.0 g/(L?m 2 ) of 25% SCN after 3, 7 and 15 days were 95.77%, 99.07%, 97.09% while the death rates of the snails sprayed with 2.0 g/(L?m 2 )of 50% WPN were 97.37%, 95.17% and 97.41%. Conclusion SCN had stable quality and high molluscicidal effect against Oncomelania snails, and it was suitable to be used in the field. The molluscicidal effect using 2.0 g/(L? m 2 ) of 25% SCN was similar with that using 2.0 g/(L?m 2) of 50% WPN.
RÉSUMÉ
Objective To establish rSAG1-IgM-ELISA with purified rSAG1 fusion protein for immunodiagnosis of toxoplasmosis. Methods The rSAG1 fusion protein was purified by Ni 2+ column. The ELISA plate was coated with different concentrations of rSAG1, reacted with pooled positive and negtive human sera. Goat anti-human IgM conjugated to horseradish peroxidase was used as the second antibody. The appropriate detecting condition of the rSAG1-IgM-ELISA assay was determined by orthogonal experiment. The reproducibility, sensitivity and specificity of the assay were assessed. Thirty-five IgM-positive and 57 IgM-negative human sera detected by the imported IgM-ELISA kit were detected with the rSAG1-IgM-ELISA. Results The purity of rSAG1 was above 90%. The appropriate detecting condition was that the coated rSAG1 was 2 5 ?g/ml, the human serum was in 1∶100 dilution, and the second antibody was in 1∶4000 dilution. The coefficient of variation (CV) value of IgM-positive and IgM-negative pooled sera were 13 8% and 7 7% respectively. The inhibition rate of the assay was 62 0% The positive correspondence rate and negative correspondence rate were 82 9% (29/35) and 91 2% (52/57) respectively,the total correspondence rate was 88 0%, compared with the imported IgM-ELISA kit. Conclusions The rSAG1-IgM-ELISA has high sensitivity and specificity, and good correspondence rate with the imported IgM-ELISA kit. It indicates that rSAG1-IgM-ELISA has potential value for early diagnosis of toxoplasmosis.
RÉSUMÉ
Objective To understand the variation in response of Oncomelania hupensis to niclosamide. Methods Snails were collected from 37 sampling areas distributed in 10 provinces (municipalities) using random environmental sampling methods in accordance with the different types and categories of snail habitats. In laboratory the snails were immersed in solutions of niclosamide for 24 and 48 hours at 25℃. Results 1.0 mg/L niclosamide showed 100% killing effect on snails in 24 hours. The LC 50 concentrations for snails immersed for 24 hours ranged from 0.0320 to 0.1689 mg/L with a mean value of 0.0920 mg/L. 0.5 mg/L niclosamide showed 100% killing effect on snails in 48 hours. The LC 50 values for snails immersed for 48 hours ranged between 0.0299 and 0.1114 mg/L with a mean of 0.0627 mg/L. There is a significant difference in snail sensitivity to niclosamide between sampling areas. Conclusion The sensitivity to niclosamide varied in snails from different sampling fields, but the chemical in a concentration of 1.0 mg/L showed 100% effect of killing snails, which is consistent to the manual of schistosomiasis control.