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Meta-Analysis
. 2015 Dec 28;9(12):e0004290.
doi: 10.1371/journal.pntd.0004290. eCollection 2015 Dec.

Systematic Review and Meta-analysis of the Impact of Chemical-Based Mollusciciding for Control of Schistosoma mansoni and S. haematobium Transmission

Affiliations
Meta-Analysis

Systematic Review and Meta-analysis of the Impact of Chemical-Based Mollusciciding for Control of Schistosoma mansoni and S. haematobium Transmission

Charles H King et al. PLoS Negl Trop Dis. .

Abstract

Background: Programs for schistosomiasis control are advancing worldwide, with many benefits noted in terms of disease reduction. Yet risk of reinfection and recurrent disease remain, even in areas with high treatment coverage. In the search for means to better prevent new Schistosoma infections, attention has returned to an older strategy for transmission control, i.e., chemical mollusciciding, to suppress intermediate host snail species responsible for S. mansoni and S. haematobium transmission. The objective of this systematic review and meta-analysis was to summarize prior experience in molluscicide-based control of Bulinus and Biomphalaria spp. snails, and estimate its impact on local human Schistosoma infection.

Methodology/principal findings: The review was registered at inception with PROSPERO (CRD42013006869). Studies were identified by online database searches and hand searches of private archives. Eligible studies included published or unpublished mollusciciding field trials performed before January 2014 involving host snails for S. mansoni or S. haematobium, with a primary focus on the use of niclosamide. Among 63 included papers, there was large variability in terms of molluscicide dosing, and treatment intervals varied from 3-52 weeks depending on location, water source, and type of application. Among 35 studies reporting on prevalence, random effects meta-analysis indicated that, on average, odds of infection were reduced 77% (OR 0.23, CI95% 0.17, 0.31) during the course of mollusciciding, with increased impact if combined with drug therapy, and progressively greater impact over time. In 17 studies reporting local incidence, risk of new infection was reduced 64% (RR 0.36 CI95% 0.25, 0.5), but additional drug treatment did not appear to influence incidence effects.

Conclusion/significance: While there are hurdles to implementing molluscicide control, its impact on local transmission is typically strong, albeit incomplete. Based on past experience, regular focal mollusciciding is likely to contribute significantly to the move toward elimination of schistosomiasis in high risk areas.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Flow chart for study selection.
The flow diagram indicates the numbers of titles and studies reviewed in preparation of the current systematic review and meta-analysis of chemical mollusciciding effects on Biomphalaria and Bulinus spp. in Schistosoma-endemic areas.
Fig 2
Fig 2. Working molluscicide treatment intervals reported by snail control programs, by region.
Horizontal bars, grouped according to world region, indicate the operative between-treatment intervals (in days) used for mollusciciding in 47 different schistosomiasis control programs in Asia (green), Africa (blue), South America (red), and Caribbean locations (orange).
Fig 3
Fig 3. Change in local human prevalence of Schistosoma infection during mollusciciding control projects.
Individual lines represent the shift from pre-control prevalence (left side) to prevalence after implementation of chemical mollusciciding (right side) by schistosomiasis control programs. Black lines indicate programs that used niclosamide mollusciciding alone, green lines indicate programs that combined mollusciciding with anti-schistosomal drug treatments as part of control, and the dashed blue lines indicate studies where non-niclosamide molluscicides were utilized.
Fig 4
Fig 4. Odds ratios for Schistosoma infection, as measured by human prevalence, after implementation of mollusciciding programs.
Black circles indicate odds ratios estimated by random effects meta-analysis for Schistosoma infection prevalence after mollusciciding, as compared to pretreatment levels. Whisker bars indicate the 95% confidence interval for the OR estimates. Asterisks (*) indicate that the graphing of the upper confidence limit was truncated for that category (numeric details are provided in Supporting Information file S1 Table). Results are shown for all studies reporting human prevalence data before and after control (top line, N = 35), and for study subgroup categories classified according to parasite species, geographic region, which age groups were included, the types of water bodies treated, and whether the program included snail control (SC) only, or mollusciciding combined with some form of drug treatment intervention.
Fig 5
Fig 5. Meta-regression of Schistosoma infection prevalence log-odds ratio according to the duration of mollusciciding control.
Red squares indicate the point estimates for individual studies, graphed as the log odds ratio of infection after mollusciciding (y axis) against the reported duration of snail control (x axis). The dark line indicates the best-fit regression line for the combined studies, anchored at zero effect at time 0. The thin lines indicate the 95% confidence band for the regression.
Fig 6
Fig 6. Risk ratios for interval Schistosoma infection incidence after implementation of mollusciciding programs.
Black circles indicate risk ratios (RR) estimated by random effects meta-analysis for Schistosoma infection incidence after mollusciciding, as compared to pretreatment levels. Whisker bars indicate the 95% confidence interval for the RR estimates. Numeric details are provided in Supporting Information file S3 Table. Results are shown for all studies reporting human incidence data after implementation of control (top line, N = 17), and for study subgroup categories classified according to parasite species, geographic region, which age groups were included, the types of water bodies treated, and whether the program included snail control (SC) only, or mollusciciding combined with some form of drug treatment intervention, including targeted mass drug administration (MDA).
Fig 7
Fig 7. Change in local human incidence of Schistosoma infection during mollusciciding control projects.
Individual lines represent the shift from pre-control incidence (left side) to incidence measured after implementation of chemical mollusciciding (right side) by schistosomiasis control programs. Black lines indicate programs that used niclosamide mollusciciding alone, green lines indicate programs that combined mollusciciding with anti-schistosomal drug treatments as part of control.
Fig 8
Fig 8. Meta-regression of Schistosoma infection incidence log-risk ratio according to the duration of mollusciciding control.
Green circles indicate the point estimates for individual studies, graphed as the log risk ratio of infection after mollusciciding (y axis) against the reported duration of snail control (x axis). The dark line indicates the best-fit linear regression line for the combined studies, anchored at zero effect at time 0. The thin lines indicate the 95% confidence band for the regression.

References

    1. King CH, Dangerfield-Cha M. The unacknowledged impact of chronic schistosomiasis. Chronic Illness. 2008;4:65–79. 10.1177/1742395307084407 - DOI - PubMed
    1. King CH, Dickman K, Tisch DJ. Reassessment of the cost of chronic helmintic infection: a meta-analysis of disability-related outcomes in endemic schistosomiasis. Lancet. 2005;365:1561–1569. - PubMed
    1. WHO. Preventive chemotherapy in human helminthiasis: coordinated use of anthelminthic drugs in control interventions: a manual for health professionals and programme managers. Geneva: World Health Organization; 2006.
    1. Bustinduy AL, Sousa-Figueiredo JC, Adriko M, Betson M, Fenwick A, Kabatereine N, et al. Fecal occult blood and fecal calprotectin as point-of-care markers of intestinal morbidity in Ugandan children with Schistosoma mansoni infection. PLoS Negl Trop Dis. 2013;7(11):e2542 10.1371/journal.pntd.0002542 - DOI - PMC - PubMed
    1. Stothard JR, Sousa-Figueiredo JC, Betson M, Bustinduy A, Reinhard-Rupp J. Schistosomiasis in African infants and preschool children: let them now be treated! Trends Parasitol. 2013;29(4):197–205. 10.1016/j.pt.201302001 - DOI - PMC - PubMed

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