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[Evaluation on molluscicidal effect of suspension concentrate of metaldehyde and niclosamide]
Zi-Ping Bao1, Chun-Li Cao, Jian-Rong Dai
1National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, WHO Collaborating Center for Malaria, Schistosomiasis and Filariasis, Shanghai 200025, China.
Objective:
To evaluate the molluscicidal effect of suspension concentrate of 26% metaldehyde and niclosamide (MNSC) in laboratory and field.
Methods:
The experiment of MNSC against Oncomelania snails were performed by immersion and spray methods with different time in laboratory and field, and the wettable powder of 50% niclosamide ethanolamine salt (WPN) and fresh water were set as the controls.
Results:
In laboratory, by immersion method (immersion for 24 h), LC50 of MNSC was 0.058 3 mg/L, which was lower than 0.094 7 mg/L of WPN. For the concentrations of 2.0 mg/L and 1.0 mg/L of MNSC by immersion method (immersion for 24, 48 h and 72 h, respectively), the death rates of snails were all 100%. In laboratory, by the spray method, the snail death rates were higher than 97% on the 3rd and 7th day when the dosage of MNSC was higher than 1.0 g/m2. In the field, by the immersion method, the snail death rates of MNSC (2 g/m3) for 24, 48 h and 72 h were 97.78% -100% in Hubei Province and 97.50% - 100% in Anhui Province, respectively, the rates of WPN were 98.89% - 100% and 97.56% - 100%, respectively, and the snail death rates of MNSC and WPN were both 100% in Jiangsu Province. In the field, by the spray method, the snail death rates of MNSC for 1, 3 d and 7 d were 83.12% - 94.64% in Jiangsu Province, 67.81% - 86.67% in Hubei Province and 72.80% - 100% in Anhui Province, respectively. The snail death rates of WPN for 1, 3 d and 7 d were 78.40% - 86.11%, 77.27% - 87.50% and 83.81% - 98.51%, respectively. In Hunan Province, the snail death rates of MNSC and WPN after spraying for 7 d were 94.94% and 94.20%, respectively, after spraying for 15 d, the rates were 86.67% and 89.38%, respectively.
Conclusions:
The molluscicidal effect of MNSC is as the same as WPN by immersion and spray methods in laboratory and field. MNSC has the characteristics of good water solubility, quick dispersing and easy using. In addition, the efficiency component of MNSC is half of WPN. So MNSC is a novel form of molluscicide which is worthy of promotion in field.
Insights
The new molluscicide, suspension concentrate of 26% metaldehyde and niclosamide (MNSC), shows effectiveness comparable to existing treatments. MNSC offers advantages like easy application and half the active ingredient concentration, making it a promising alternative for snail control.
Area of Science:
- Environmental Science
- Pest Management
- Toxicology
Context:
- Schistosomiasis control relies on effective molluscicides to target snail intermediate hosts.
- Existing molluscicides like wettable powder of 50% niclosamide ethanolamine salt (WPN) have limitations.
- Developing novel, efficient, and user-friendly molluscicides is crucial for public health initiatives.
Purpose:
- To evaluate the molluscicidal efficacy of a new suspension concentrate formulation containing 26% metaldehyde and niclosamide (MNSC).
- To compare the effectiveness of MNSC against Oncomelania snails with a standard formulation (WPN) under laboratory and field conditions.
- To assess the performance of MNSC using both immersion and spray application methods.
Summary:
- Laboratory studies demonstrated MNSC's potent molluscicidal activity, with LC50 values lower than WPN and achieving 100% mortality at specific concentrations via immersion.
- Both immersion and spray methods in field trials across multiple provinces showed MNSC achieving high snail mortality rates (97-100% and 83-94%, respectively), comparable to WPN.
- MNSC exhibited excellent water solubility, rapid dispersion, and ease of use, with a significantly lower active ingredient concentration compared to WPN.
Impact:
- MNSC demonstrates comparable molluscicidal efficacy to WPN, suggesting it is a viable alternative for snail intermediate host control.
- The formulation's improved physical properties (solubility, dispersibility, ease of use) enhance practical application in public health programs.
- MNSC's reduced active ingredient requirement offers potential environmental and economic benefits, supporting its promotion for widespread field use.
