Resistance to niclosamide in Oncomelania hupensis, the intermediate host of Schistosoma japonicum: should we be worried?

Abstract

As the currently only available molluscicide, niclosamide has been widely used for snail control for over 2 decades in China. There is therefore a concern about the emergence of niclosamide-resistant snail populations following repeated, extensive use of the chemical. The purpose of this study was to investigate the likelihood of niclosamide resistance in Oncomelania hupensis in China. Active adult O. hupensis snails derived from 20 counties of 10 schistosomiasis-endemic provinces of China, of 10 snails in 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-1 of a 50% wettable powder of niclosamide ethanolamine salt (WPN) for 24 and 48 h at 25 °C, and the median lethal concentration (LC50) was estimated. Then, the 24- and 48-h WPN LC50 values were compared with those determined in the same sampling sites in 2002. The results indicated that the 24- and 48-h WPN LC50 values for O. hupensis were not significantly different from those determined in 2002 (P = 0.202 and 0.796, respectively). It is concluded that the current sensitivity of O. hupensis to niclosamide has not changed after more than 2 decades of repeated, extensive application in the main endemic foci of China, and there is no evidence of resistance to niclosamide detected in O. hupensis.

Approaches being used in the national schistosomiasis elimination programme in China: a review

“…Currently, niclosamide remains the most widely used chemical molluscicide for snail control in the endemic field of schistosomiasis worldwide [63, 64], and a real-time determination of the active niclosamide concentration is of great importance to achieve the molluscicidal efficacy and reduce the environmental toxicity [65, 66]. A niclosamide detector was developed for the rapid determination of the niclosamide concentration in the endemic field (Fig.…”

De Novo Transcriptome Analysis of Oncomelania hupensis after Molluscicide Treatment by Next-Generation Sequencing: Implications for Biology and Future Snail Interventions

“…As schistosomiasis is a neglected tropical disease mainly governed by the geographical distribution of O . hupensis , snail control, as a major component of the schistosomiasis control program, is still key in attempts to interrupt the transmission of the disease [ 11 , 12 ] and may be an important component of an integrated strategy for the elimination of schistosomiasis [ 7 , 13 , 14 ].…”

“…Because niclosamideis currently the only chemical available for snail control, the possibility of the emergence of resistance to this compound in the intermediate host snails has received considerable attention. Although resistance has not been demonstrated [ 12 , 28 ], the response of O . hupensis snails to niclosamide has exhibited regional variation in China [ 12 , 28 ] which make the resistance development possible.…”

In vitro assessment of Schistosoma mansoni cercaricidal activities of Solanum nigrum and Callistemon citrinius leaves extracts and cercarial genetic changes by RAPD-PCR

“…Molluscicidal plants are inexpensive, safe and appropriate for local snail control [6,7] . Consequently, more efforts focused on detecting safe molluscicides of plant origin [8], especially if they have miracidicidal and cercaricidal activities [9] .…”