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  • In addition to the effect

    2019-05-14

    In addition to the effect of vector control against malaria and HAT on lymphatic filariasis endemicity over several years, recent improvements in NTD mapping strategies and diagnosis of have greatly affected the outcomes of surveys undertaken to establish the burden of NTDs in Africa. More accurate mapping efforts, revealing lower than previously thought numbers of individuals requiring interventions, should give renewed impetus to efforts to meet the 2020 target for elimination of lymphatic filariasis.
    Nathan C Lo and colleagues (October, 2015) conclude that community-wide treatment programmes can be a highly cost-effective way to control morbidity of schistosomiasis and soil-transmitted helminthiasis, even in communities with low disease burden. This work is a timely contribution to an important issue; however, methodological shortcomings affect the conclusions.
    We are delighted by the interest in our study of the cost-effectiveness of expanded community-wide treatment against schistosomiasis and soil-transmitted helminthiasis. In response to the critique by Hugo Turner and colleagues, we offer the following points for consideration. First, the use of binary disability weights for schistosomiasis is conservative, standard practice, and used by the Global Burden of Diseases study, among others. Although we agree that better data is needed to inform disability as a function of schistosomiasis burden, we employed these conventional disability weights because such data are limited and we recognised disability even at low disease burden. Importantly, the use of a binary disability weight is in fact conservative with respect to cost-effectiveness, since no treatment benefit is given unless an infection is cured. Indeed, recalculation with intensity-stratified disability weights reveals that community-wide treatment is even more cost effective (; methods are further detailed in the ). Second, concern is raised over our use of a constant relation between parasitic worm burden and egg production from one helminth CMX001 cost to another. We tested alternative species-specific values for this poorly measured parameter and found that our results are highly robust ().
    As other researchers have done, Amy Pickering and colleagues (November, 2015) focused on short-recall diarrhoea incidence as the main outcome in their randomised trial of the effects of a community-led sanitation intervention in Mali. As Pickering and colleagues noted, Selection indicator has well known flaws associated not only with seasonality, but also with potential reporting bias and other measurement errors. These flaws raise the possibility of crucial type II errors that justify a serious reappraisal of the long-standing practice of using this indicator as the primary means to evaluate sanitation interventions. With good reasons, then, Pickering and colleagues chose child anthropometric indicators, particularly growth outcomes, as secondary outcomes. Before this study, however, the existing experimental literature neglected the important issue of the timing of growth faltering, which almost entirely takes place in utero and in the first 24 months of life. Since exposure to improved sanitation was quite short in all of these evaluations (lasting 6–24 months) and all these studies focused on children aged 0–59 months, the relevant statistical tests mixed together younger children for whom sanitation plausibly benefits linear growth with older children for whom sanitation plausibly offers little or no benefits. Consistent with this so-called exposure bias, Pickering and colleagues reported no effect of sanitation interventions on linear growth for the children aged from 24 months to less than 60 months (2–5 years) at enrolment, but showed an effect for those aged younger than 24 months (<2 years) at enrolment, and the largest effect for children aged younger than 12 months (<1 year) at enrolment. Moreover, since findings published in 2015 from the SHINE project showed that environmental enteropathy (also termed environmental enteric dysfunction) starts in utero through maternal infection, full exposure to improved sanitation facilities ought to, theoretically, include children whose mothers had sanitation for the full duration of their pregnancy, if not before. Collectively these findings suggest that future sanitation intervention trials should consider focusing on child growth as the primary indicator of interest; record when toilet facilities were first put in to use (to measure duration of exposure); and focus on assessing the nutritional effects on younger children (0–2 years), including exposure in utero.