Sensitivity of Oncomelania hupensis to niclosamide: a nation-wide survey in China.

Jianrong Dai,Youzi Li,Wei Wang,Yuntian Xing,Guoli Qu,Yousheng Liang

doi:10.3390/ijerph110303086

Abstract

Schistosomiasis japonica, transmitted by the intermediate host snail Oncomelania hupensis of the causative agent Schistosoma japonicum, remains a major public-health concern in China, and control of this snail is one of the major approaches used in attempts to interrupt the transmission of this neglected tropical disease. Niclosamide is currently the only commercial molluscicide available for the control of O. hupensis snails in China. The purpose of this study was to evaluate the current sensitivity of O. hupensis to niclosamide in China. O. hupensis snails derived from 17 sampling sites from eight schistosomiasis-endemic provinces of China were used for the molluscicidal tests. Active adult snails (10 for each drug concentration), were immersed in solutions of 1, 0.5, 0.25, 0.125, 0.063, 0.032, 0.016 and 0.008 mg/L of 50% wettable powder of niclosamide ethanolamine salt (WPN) for 24 and 48 h at 25°C, and then the snail mortality was estimated and LC50 values were calculated. All field-derived O. hupensis snails were dead following immersion in 0.5 and 1 mg/L WPN for 24 h, whereas no death was observed after immersion in 0.008 mg/L WPN for 24 h. Immersion in 0.5, 0.25, 0.125, 0.063, 0.032 and 0.016 mg/L WPN for 24 h resulted in 80%–100%, 63.33%–100%, 0%–85%, 0%–50%, 0%–15%, and 0%–5% snail mortalities, respectively. The 24 h WPN LC50 values for the O. hupensis snails derived from the 17 sampling sites in China ranged from 0.0743 to 0.2285 mg/L, and no significant difference was detected by the Kolmogorov-Smirnov test (p = 0.2). The results indicate that there is no regional variation in the current susceptibility to niclosamide in O. hupensis populations in China. It is suggested that the current sensitivity of niclosamide against O. hupensis remains high and has not changed after more than two decades of repeated, extensive application for snail control in the main endemic areas of China.

Highlights

Schistosomiasis, a snail-transmitted parasitic disease, is a major neglected tropical disease affecting more than 207 million people in the tropical and subtropical regions around the world [1]. great success has been achieved in its control in China, schistosomiasis japonica is still one of the four communicable diseases that have been given high priority by the central government [2,3,4].It is estimated that over 0.7 million people are infected with the parasite in China, and the snail hostOncomelania hupensis is detected in habitats with an area of 3.73 billion m2 [5,6,7]
All field-derived O. hupensis snails were dead following immersion in 1 mg/L wettable powder of niclosamide ethanolamine salt (WPN) for 24 h, whereas no death was observed after immersion in 0.008 mg/L WPN for 24 h
The 24 h WPN LC50 values for the O. hupensis snails derived from the 17 sampling sites in

Summary

Introduction

Schistosomiasis, a snail-transmitted parasitic disease, is a major neglected tropical disease affecting more than 207 million people in the tropical and subtropical regions around the world [1]. great success has been achieved in its control in China, schistosomiasis japonica is still one of the four communicable diseases that have been given high priority by the central government [2,3,4].It is estimated that over 0.7 million people are infected with the parasite in China, and the snail hostOncomelania hupensis is detected in habitats with an area of 3.73 billion m2 [5,6,7]. Schistosomiasis, a snail-transmitted parasitic disease, is a major neglected tropical disease affecting more than 207 million people in the tropical and subtropical regions around the world [1]. It is estimated that over 0.7 million people are infected with the parasite in China, and the snail host. It has been proved that the transmission of S. japonicum is governed by the geographical distribution of its snail host; control of the O. hupensis snails, as a major part of the National Schistosomiasis. In China, many approaches have been used for the control of O. hupensis; snail control with chemicals remains the most widely used method to kill the snail intermediate host till [11,12,13].

Objectives

Methods

Results

Discussion

Conclusion