Age-group associations of schistosomiasis prevalence from trial data, Côte d'Ivoire, Kenya and the United Republic of Tanzania

Objective To determine if the prevalence of schistosomiasis in children aged 9­12 years is associated with the prevalence in 5­8-year-olds and adults after preventive chemotherapy in schools or the community. Methods We combined data from four community-randomized, preventive chemotherapy trials in treatment-naïve populations in Côte d'Ivoire, Kenya and the United Republic of Tanzania during 2010­2016 according to the number of praziquantel treatments and the delivery method. Schistosoma mansoni infection was sought on two slides prepared from each participant's first stool using the Kato­Katz technique. We assessed associations between S. mansoni prevalence in 9­12-year-olds and 5­8-year-olds and adults in the community before and after treatment using Bayesian regression models. Findings Stool samples from 47 985 5­8-year-olds, 81 077 9­12-year-olds and 20 492 adults were analysed. We found associations between the prevalence in 9­12-year-olds and that in 5­8-year-olds and adults after preventive treatment, even when only school-age children were treated. When the prevalence in 9­12-year-olds was under 10%, the prevalence in 5­8-year-olds was consistently under 10%. When the prevalence in 9­12-year-olds was under 50%, the prevalence in adults after two or four rounds of preventive chemotherapy was 10%­15% lower than before chemotherapy. Post-chemotherapy age-group associations were consistent with pre-chemotherapy associations in this analysis and previous studies. Conclusion The prevalence of S. mansoni infection in 9­12-year-olds was associated with the prevalence in other age groups and could be used to guide community treatment decisions.

Circulating Anodic Antigen (CAA): A Highly Sensitive Diagnostic Biomarker to Detect Active Schistosoma Infections-Improvement and Use during SCORE.

The Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) was funded in 2008 to conduct research that would support country schistosomiasis control programs. As schistosomiasis prevalence decreases in many places and elimination is increasingly within reach, a sensitive and specific test to detect infection with Schistosoma mansoni and Schistosoma haematobium has become a pressing need. After obtaining broad input, SCORE supported Leiden University Medical Center (LUMC) to modify the serum-based antigen assay for use with urine, simplify the assay, and improve its sensitivity. The urine assay eventually contributed to several of the larger SCORE studies. For example, in Zanzibar, we demonstrated that urine filtration, the standard parasite egg detection diagnostic test for S. haematobium, greatly underestimated prevalence in low-prevalence settings. In Burundi and Rwanda, the circulating anodic antigen (CAA) assay provided critical information about the limitations of the stool-based Kato-Katz parasite egg-detection assay for S. mansoni in low-prevalence settings. Other SCORE-supported CAA work demonstrated that frozen, banked urine specimens yielded similar results to fresh ones; pooling of specimens may be a useful, cost-effective approach for surveillance in some settings; and the assay can be performed in local laboratories equipped with adequate centrifuge capacity. These improvements in the assay continue to be of use to researchers around the world. However, additional work will be needed if widespread dissemination of the CAA assay is to occur, for example, by building capacity in places besides LUMC and commercialization of the assay. Here, we review the evolution of the CAA assay format during the SCORE period with emphasis on urine-based applications.