Improving control of African schistosomiasis: towards effective use of rapid diagnostic tests within an appropriate disease surveillance model.

Contemporary control of schistosomiasis is typically reliant upon large-scale administration of praziquantel (PZQ) to school age children. Whilst PZQ treatment of each child is inexpensive, the direct and indirect costs of preventive chemotherapy for the whole school population are more substantive and, at the national level where many schools are targeted, maximising cost effectiveness and the health impact are essential requirements for ensuring longer-term sustainability (i.e. >5 years). To this end, the WHO has issued a set of treatment guidelines, inclusive of re-treatment schedules, such that, where possible, treatment decisions by school are based upon local disease prevalence as determined by parasitological and/or questionnaire methods. As each diagnostic method has known shortcomings, presumptive treatment of at-risk schools may initially be preferred, especially if the existing infrastructure for disease surveillance is poor. It is against this background of school-based preventive chemotherapy that a rapid diagnostic test (RDT) for schistosomiasis is most urgently needed, not only to improve initial disease surveillance but also to focus drug delivery better through time. In this paper, the development, evaluation and application of selected diagnostic tests are reviewed to identify barriers that impede progress, foremost of which is that a new disease surveillance and evaluation model is required where the in-country price of each RDT ideally needs to be less than US$1 to be cost effective both in the short- and long-term perspective.