Sustaining control of Schistosomiasis mansoni in western Côte d'Ivoire : results from a SCORE study, one year after initial praziquantel administration

The Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) has launched several large-scale trials to determine the best strategies for gaining and sustaining control of schistosomiasis and transitioning toward elimination. In Côte d'Ivoire, a 5-year cluster-randomized trial is being implemented in 75 schools to sustain the control of schistosomiasis mansoni. We report Schistosoma mansoni infection levels in children one year after the initial school-based treatment (SBT) with praziquantel and compare with baseline results to determine the effect of the intervention.; The baseline cross-sectional survey was conducted in late 2011/early 2012 and the first follow-up in May 2013. Three consecutive stool samples were collected from 9- to 12-year-old children in 75 schools at baseline and 50 schools at follow-up. Stool samples were subjected to duplicate Kato-Katz thick smears. Directly observed treatment (DOT) coverage of the SBT was assessed and the prevalence and intensity of S. mansoni infection compared between baseline and follow-up.; The S. mansoni prevalence in the 75 schools surveyed at baseline was 22.1% (95% confidence interval (CI): 19.5-24.4%). The DOT coverage was 84.2%. In the 50 schools surveyed at baseline and one year after treatment, the overall prevalence of S. mansoni infection decreased significantly from 19.7% (95% CI: 18.5-20.8%) to 12.8% (95% CI: 11.9-13.8%), while the arithmetic mean S. mansoni eggs per gram of stool (EPG) among infected children slightly increased from 92.2 EPG (95% CI: 79.2-105.3 EPG) to 109.3 EPG (95% CI: 82.7-135.9 EPG). In two of the 50 schools, the prevalence increased significantly, despite a DOT coverage of >75%.; One year after the initial SBT, the S. mansoni prevalence had decreased. Despite this positive trend, an increase was observed in some schools. Moreover, the infection intensity among S. mansoni-infected children was slightly higher at the 1-year follow-up compared to the baseline situation. Our results emphasize the heterogeneity of transmission dynamics and provide a benchmark for the future yearly follow-up surveys of this multi-year SCORE intervention study

Molecular characterization and distribution of Schistosoma cercariae collected from naturally infected bulinid snails in northern and central Côte d’Ivoire

Accurate identification of schistosome species infecting intermediate host snails is important for understanding parasite transmission, schistosomiasis control and elimination. Cercariae emerging from infected snails cannot be precisely identified morphologically to the species level. We used molecular tools to clarify the distribution of the Schistosoma haematobium group species infecting bulinid snails in a large part of Côte d’Ivoire and confirmed the presence of interspecific hybrid schistosomes. Methods Between June 2016 and March 2017, Bulinus snails were sampled in 164 human-water contact sites from 22 villages of the northern and central parts of Côte d’Ivoire. Multi-locus genetic analysis (mitochondrial cox1 and nuclear ITS) was performed on individual schistosome cercariae shed from snails, in the morning and in the afternoon, for species and hybrid identification. Results Overall, 1923 Bulinus truncatus, 255 Bulinus globosus and 1424 Bulinus forskalii were obtained. Among 2417 Bulinus screened, 25 specimens (18 B. truncatus and seven B. globosus) shed schistosomes, with up to 14% infection prevalence per site and time point. Globally, infection rates per time point ranged between 0.6 and 4%. Schistosoma bovis, S. haematobium and S. bovis × S. haematobium hybrids infected 0.5%, 0.2% and 0.4% of the snails screened, respectively. Schistosoma bovis and hybrids were more prevalent in B. truncatus, whereas S. haematobium and hybrid infections were more prevalent in B. globosus. Schistosoma bovis-infected Bulinus were predominantly found in northern sites, while S. haematobium and hybrid infected snails were mainly found in central parts of Côte d’Ivoire. Conclusions The data highlight the necessity of using molecular tools to identify and understand which schistosome species are transmitted by specific intermediate host snails. The study deepens our understanding of the epidemiology and transmission dynamics of S. haematobium and S. bovis in Côte d’Ivoire and provides the first conclusive evidence for the transmission of S. haematobium × S. bovis hybrids in this West African country. Trial registration ISRCTN, ISRCTN10926858. Registered 21 December 2016; retrospectively registered (see: http://www.isrctn.com/ISRCTN10926858)Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. The attached file is the published pdf

Sustaining control of schistosomiasis mansoni in moderate endemicity areas in western Côte d'Ivoire : a SCORE study protocol

Schistosomiasis is a parasitic disease that occurs in the tropics and subtropics. The mainstay of control is preventive chemotherapy with praziquantel. In Africa, an estimated 230 million people require preventive chemotherapy. In western Côte d'Ivoire, infections with Schistosoma mansoni are widespread. To provide an evidence-base for programme decisions about preventive chemotherapy to sustain control of schistosomiasis, a 5-year multi-country study with different treatment arms has been designed by the Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) and is currently being implemented in various African settings, including Côte d'Ivoire.; We report the study protocol, including ethics statement and insight from a large-scale eligibility survey carried out in four provinces in western Côte d'Ivoire. The study protocol has been approved by the ethics committees of Basel and Côte d'Ivoire. A total of 12,110 children, aged 13-14 years, from 264 villages were screened for S. mansoni using duplicate Kato-Katz thick smears from single stool samples. Among the schools with a S. mansoni prevalence of 10-24%, 75 schools were selected and randomly assigned to one of three treatment arms. In each school, three stool samples are being collected from 100 children aged 9-12 years annually and one stool sample from 100 first-year students at baseline and in the final year and subjected to duplicate Kato-Katz thick smears. Cost and coverage data for the different intervention arms, along with environmental, political and other characteristics that might impact on the infection prevalence and intensity will be recorded in each study year, using a pretested village inventory form.; The study will document changes in S. mansoni infection prevalence and intensity according to different treatment schemes. Moreover, factors that determine the effectiveness of preventive chemotherapy will be identified. These factors will help to develop reasonable measures of force of transmission that can be used to make decisions about the most cost-effective means of lowering prevalence, intensity and transmission in a given setting. The gathered information and results will inform how to effectively sustain control of schistosomiasis at a low level in different social-ecological contexts.; ISRCTN99401114 (date assigned: 12 November 2014)

Study participation of schoolchildren at the baseline survey and one-year follow-up survey.

<p>The flowcharts show the study participation of 9- to 12-year-old schoolchildren at the baseline survey (A), which was conducted from December 2011 to February 2012, and the first follow-up survey (B), which was carried out one-year post-treatment in May 2013, in western Côte d’Ivoire.</p

Dynamics of the <i>S</i>. <i>mansoni</i> infection intensity in schools of treatment arms A and B.

<p>The graphs show the change of the <i>S</i>. <i>mansoni</i> infection intensity expressed as change in arithmetic mean eggs per gram of feces (AM EPG) from the baseline survey, which was conducted from December 2011 to February 2012, to the first follow-up survey, which was carried out one-year post-treatment in May 2013, in 9- to 12-year-old schoolchildren from 25 schools per treatment arm in western Côte d’Ivoire. Arm A: schools receive praziquantel treatment annually for four years, Arm B: schools receive praziquantel treatment the first two years of the study, followed by two years of “drug holiday”. Red star: <i>S</i>. <i>mansoni</i> infection intensity decreased significantly.</p

Correlation between coverage rate and the changes in the <i>S</i>. <i>mansoni</i> infection intensity.

<p>Scatter plot illustrating the correlation between the coverage rates achieved in a directly observed school-based treatment round implemented in 50 schools in western Côte d’Ivoire in June 2012, and the % changes in the <i>S</i>. <i>mansoni</i> arithmetic mean infection intensity observed between the baseline survey, which was conducted from December 2011 to February 2012, and the first follow-up survey, which was carried out one-year post-treatment in May 2013, in 9- to 12-year-old schoolchildren.</p

Dynamics of the <i>S</i>. <i>mansoni</i> prevalence in schools of treatment arms A and B.

<p>The graphs show the change of the <i>S</i>. <i>mansoni</i> prevalence from the baseline survey, which was conducted from December 2011 to February 2012, to the first follow-up survey, which was carried out one-year post-treatment in May 2013, in 9- to 12-year-old schoolchildren from 25 schools per treatment arm in western Côte d’Ivoire. Arm A: schools receive praziquantel treatment annually for four years, Arm B: schools receive praziquantel treatment the first two years of the study, followed by two years of “drug holiday”. Red star: <i>S</i>. <i>mansoni</i> prevalence increased significantly.</p

<i>S</i>. <i>mansoni</i> prevalence and infection intensity (AM EPG) at the baseline and follow-up survey.

<p>The maps show the spatial distribution of the changes in the <i>S</i>. <i>mansoni</i> prevalence and in the infection intensity expressed as arithmetic mean eggs per gram of feces (AM EPG) between the baseline survey (A), which was conducted from December 2011 to February 2012, and the first follow-up survey (B), which was carried out one-year post-treatment in May 2013, in western Côte d’Ivoire. Arm A: schools receive praziquantel treatment annually for four years, Arm B: schools receive praziquantel treatment the first two years of the study, followed by two years of “drug holiday”.</p