Evaluating the variation in the projected benefit of community-wide mass treatment for schistosomiasis: Implications for future economic evaluations

Abstract

BackgroundThe majority of schistosomiasis control programmes focus on targeting school-aged children. Expanding the use of community-wide mass treatment to reach more adults is under consideration. However, it should be noted that this would require a further increase in programmatic resources, international aid, and commitment for the provision of praziquantel. Consequently, it is important to understand (i) where a change of strategy would have the greatest benefit, and (ii) how generalisable the conclusions of field trials and analytical studies based on mathematical models investigating the impact of community-wide mass treatment, are to a broad range of settings.MethodsIn this paper, we employ a previously described deterministic fully age-structured schistosomiasis transmission model and evaluate the benefit of community-wide mass treatment both in terms of controlling morbidity and eliminating transmission for Schistosoma mansoni, across a wide range of epidemiological settings and programmatic scenarios. This included variation in the baseline relative worm pre-control burden in adults, the overall level of transmission in defined settings, choice of effectiveness metric (basing morbidity calculations on prevalence or intensity), the level of school enrolment and treatment compliance.ResultsCommunity-wide mass treatment was found to be more effective for controlling the transmission of schistosome parasites than using a school-based programme only targeting school-aged children. However, in the context of morbidity control, the potential benefit of switching to community-wide mass treatment was highly variable across the different scenarios analysed. In contrast, for areas where the goal is to eliminate transmission, the projected benefit of community-wide mass treatment was more consistent.ConclusionWhether community-wide mass treatment is appropriate will depend on the local epidemiological setting (i.e. the relative pre-control burden in adults and transmission intensity), and whether the goal is morbidity control or eliminating transmission. This has important implications regarding the generalisability of cost-effectiveness analyses of schistosomiasis interventions. Our results indicate that areas with poor school-enrolment/coverage could benefit more from community-wide treatment of praziquantel and should potentially be prioritised for any change in strategy. This work highlights the importance of not over-generalising conclusions and policy in this area, but of basing decisions on high quality epidemiological data and quantitative analyses of the impact of interventions in a range of settings.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-017-2141-5) contains supplementary material, which is available to authorized users.

A cost analysis of options for schistosomiasis control MDA programs targeting children aged five years and below in uMkhanyakude District of KwaZulu-Natal Province, South Africa

“…Our ndings indicate that economies of scale will exist when the MDA program is implemented at sub-district level (population: 15 000). In practice, the economies of scale will only exist up to a speci c threshold beyond which diseconomies of scale will cause the average of cost of treating a child in the MDA program will increase [16,36].…”

“…Community-wide treatment has been found to be the most cost-effective strategy to control schistosomiasis [16]. To align schistosomiasis control chemotherapy with the WHO strategy for global schistosomiasis control, the inclusion of children aged ve years and below is paramount [17,18].…”

Vaccination or mass drug administration against schistosomiasis: a hypothetical cost-effectiveness modelling comparison

“…Due to the limited understanding of the causal link between schistosomiasis morbidity and burden, caution should be employed when interpreting modelling results regarding the amount of schistosomiasis morbidity averted by different interventions [37]. In principle, the disability-adjusted life year (DALY) averted would be an ideal metric to use, but further research is needed in this area to make this possible [37].…”

“…In principle, the disability-adjusted life year (DALY) averted would be an ideal metric to use, but further research is needed in this area to make this possible [37]. …”

“…To measure the benefit of applying an intervention, we counted the total number of days that each individual has a heavy-intensity infection (HII), as measured by the Kato–Katz test [30] and recorded the total heavy-intensity infection years averted relative to the baseline of no intervention over a 30 year time horizon. Heavy-intensity infections have been chosen as this accounts for the majority of negative health and societal effects (although we acknowledge significant schistosomiasis-related conditions such as anemia occur even for light-infections, and present alternative results where health benefits are measured in infection years averted in Additional file 1: Figures S2, S3) [37]. …”