Abstract
BackgroundPreventive chemotherapy with praziquantel is the cornerstone of schistosomiasis control. However, in some social-ecological settings, the prevalence and/or intensity of Schistosoma infection does not lower meaningfully despite multiple rounds of preventive chemotherapy, a phenomenon termed persistent hotspot (PHS). We assessed the characteristics of PHS in a Schistosoma mansoni-endemic area of Côte d’Ivoire.MethodsIn October 2016, a cross-sectional survey was conducted in 14 schools in the western part of Côte d’Ivoire, one year after multiple rounds of preventive chemotherapy. In each school, 50 children aged 9–12 years provided two stool samples and one urine sample. Stool samples were subjected to triplicate Kato-Katz thick smears for S. mansoni diagnosis. Urine samples were examined by a filtration method for S. haematobium eggs. PHS was defined as failure to achieve a reduction in the prevalence of S. mansoni infection of at least 35% and/or a reduction of infection intensity of at least 50%. Six schools underwent more detailed investigations, including a questionnaire survey for demographic characteristics and a malacological survey.ResultsIn the six schools subjected to detailed investigations, the overall prevalence of S. mansoni and S. haematobium was 9.5% and 2.6%, respectively. Four schools were classified as PHS. The S. mansoni prevalence in the four PHS was 10.9% compared to 6.6% in the remaining two schools. The S. mansoni infection intensity, expressed as arithmetic mean eggs per gram of stool (EPG) among infected children, was 123.8 EPG in PHS and 18.7 EPG in the other two schools. Children bathing in open freshwater bodies were at higher odds of S. mansoni infection (odds ratio: 4.5, 95% confidence interval: 1.6–12.6). A total of 76 human-water contact sites (53 in PHS and 23 in the other schools) were examined and 688 snails were collected, including potential intermediate host snails of Schistosoma (Biomphalaria pfeifferi, Bulinus forskalii, Bu. globosus and Bu. truncatus).ConclusionChildren in PHS schools bathed more frequently in open freshwater bodies, and hence, they are more exposed to Schistosoma transmission. Our findings call for an integrated control approach, complementing preventive chemotherapy with other interventions, particularly in PHS settings.
Highlights
Preventive chemotherapy with praziquantel is the cornerstone of schistosomiasis control
None of the children were concurrently infected with both S. mansoni and S. haematobium
No statistically significant differences were observed between persistent hotspot (PHS) and low-prevalence schools with regard to the proportion of children with parents using water from safe water sources. These results indicate that the difference in schistosomiasis mansoni endemicity between PHS and low-prevalence schools was not explained by sources of water collection for drinking and cooking
Summary
Preventive chemotherapy with praziquantel is the cornerstone of schistosomiasis control. In 2016, 52.8 million school-aged children requiring preventive chemotherapy received praziquantel, a coverage of 54% [4]. In order to strengthen the current evidence-base for decisions about preventive chemotherapy for gaining and sustaining control of schistosomiasis, the Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) implemented a series of large-scale, multi-year trials in sub-Saharan Africa [5, 6]. In Côte d’Ivoire, a SCORE study pertaining to sustaining control of schistosomiasis mansoni was carried out in 75 schools in the western part of the country. Schools were included when the prevalence of Schistosoma mansoni was between 10% and 24%, as determined by duplicate Kato-Katz thick smears among 50 children aged 13–14 years [7]. Similar results have been reported elsewhere in sub-Saharan Africa [9,10,11,12]
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