Molluscicidal efficacies of different formulations of niclosamide: result of meta-analysis of Chinese literature

Abstract

The control efforts on Oncomelania hupensis, the intermediate snail host of Schistosoma japonicum, cannot be easily excluded from the integrated approach of schistosomiasis control in China. Application of chemical compounds, molluscicides, in snail habitats is a common method for snail control in addition to environmental modification. We conducted a systematic review and meta-analysis to assess the molluscicidal effects of the currently recommended 50% niclosamide ethanolamine salt wettable powder and a new 4% niclosamide ethanolamine salt powder developed by Chinese researchers. Literature was searched from three Chinese databases, i.e. Chinese Biomedical Database, VIP Database and Wanfang Database, on field mollusciciding trials of niclosamide in China (from January 1, 1990 to April 1, 2010). Molluscicidal effects on reduction of snail population of the 50% or 4% niclosamide formulations in field trial were evaluated 3 days, 7 days or 15 days post-application. Out of 90 publications, 20 papers were eventually selected for analysis. Publication bias and heterogeneity tests indicated that no publication bias existed but heterogeneity between studies was present. Meta-analysis in a random effect model showed that the snail mortality of 3, 7 and 15 days after spraying the 50% niclosamide ethanolamine salt wettable powder were 77% [95%CI: 0.68-0.86], 83% [95%CI: 0.77-0.89], and 88% [95%CI: 0.82-0.92], respectively. For the 4% niclosamide ethanolamine salt powder, the snail mortality after 3, 7 and 15 days were 81% [95%CI: 0.65-0.93], 90% [95%CI: 0.83-0.95] and 94% [95%CI: 0.91-0.97], respectively. Both are good enough to be used as molluscicides integrated with a schistosomiasis control programme. The 4% niclosamide ethanolamine salt powder can be applied in the field without water supply as the surrogate of the current widely used 50% niclosamide ethanolamine salt wettable powder. However, to consolidate the schistosomiasis control achievement gained, it is necessary to continuously perform mollusciciding more than twice annually in the field.

Figure 1

The flow diagram of paper review process.

Figure 2

Linear regression test of funnel plot asymmetry for the 50% molluscicides niclosamide ethanolamine salt wettable powder 3 days (A), 7 days (B) and 15 days (C) post spraying, and for the 4% niclosamide ethanolamine salt powder 3 days (D), 7 days (E) and 15 days (F) post dusting, respectively. (A: t = 0.5716, df = 21, p-value = 0.5737; B: t = 1.05, df = 20, p-value = 0.30; C: t = -1.66, df = 16, p-value = 0.12; D: t = -0.27, df = 5, p-value = 0.80; E: t = -2.25, df = 8, p-value = 0.06; F: t = -0.62, df = 8, p-value = 0.56)

Figure 3

Molluscicidal effects (individual and pooled results) of the 50% niclosamide ethanolamine salt wettable powder 3 days after spraying.

Figure 4

Molluscicidal effects (individual and pooled results) of the 50% niclosamide ethanolamine salt wettable powder 7 days after spraying.

Figure 5

Molluscicidal effects (individual and pooled results) of the 50% niclosamide ethanolamine salt wettable powder 15 days after spraying.

Figure 6

Molluscicidal effects (individual and pooled results) of the 4% niclosamide ethanolamine salt powder 3 days after dusting.

Figure 7

Molluscicidal effects (individual and pooled results) of the 4% niclosamide ethanolamine salt powder 7 days after dusting.

Figure 8

Molluscicidal effects (individual and pooled results) of the 4% niclosamide ethanolamine salt powder 15 days after dusting.