Global Assessment of Schistosomiasis Control Over the Past Century Shows Targeting the Snail Intermediate Host Works Best

BackgroundDespite control efforts, human schistosomiasis remains prevalent throughout Africa, Asia, and South America. The global schistosomiasis burden has changed little since the new anthelmintic drug, praziquantel, promised widespread control.MethodologyWe evaluated large-scale schistosomiasis control attempts over the past century and across the globe by identifying factors that predict control program success: snail control (e.g., molluscicides or biological control), mass drug administrations (MDA) with praziquantel, or a combined strategy using both. For data, we compiled historical information on control tactics and their quantitative outcomes for all 83 countries and territories in which: (i) schistosomiasis was allegedly endemic during the 20th century, and (ii) schistosomiasis remains endemic, or (iii) schistosomiasis has been "eliminated," or is "no longer endemic," or transmission has been interrupted.Principal FindingsWidespread snail control reduced prevalence by 92 ± 5% (N = 19) vs. 37 ± 7% (N = 29) for programs using little or no snail control. In addition, ecological, economic, and political factors contributed to schistosomiasis elimination. For instance, snail control was most common and widespread in wealthier countries and when control began earlier in the 20th century.Conclusions/SignificanceSnail control has been the most effective way to reduce schistosomiasis prevalence. Despite evidence that snail control leads to long-term disease reduction and elimination, most current schistosomiasis control efforts emphasize MDA using praziquantel over snail control. Combining drug-based control programs with affordable snail control seems the best strategy for eliminating schistosomiasis.背景：尽管已采取防控措施，人体血吸虫病（schistosomiasis）仍在非洲、亚洲及南美广泛流行。自抗蠕虫药（anthelmintic drug）吡喹酮（praziquantel）有望实现广泛防控以来，全球血吸虫病疾病负担并未出现明显改观。 方法：本研究针对过去一个世纪全球范围内的大型血吸虫病防控实践展开评估，通过识别可预测防控项目成功的关键因素开展研究：包括钉螺防控（如使用杀螺剂或生物防控手段）、采用吡喹酮的大规模药物给药（mass drug administrations, MDA），或二者结合的联合防控策略。本研究共纳入83个国家和地区的历史防控措施及其量化效果数据，这些地区需满足以下任一条件：(i) 20世纪期间被报道存在血吸虫病地方性流行；(ii) 当前血吸虫病仍为地方性流行；或(iii) 血吸虫病已被"消除"、"不再流行"，或传播已被阻断。 主要研究结果：全面实施钉螺防控可使血吸虫病感染率降低92%±5%（样本量N=19），而仅采用少量或未实施钉螺防控的项目仅能降低37%±7%（样本量N=29）。此外，生态、经济与政治因素均对血吸虫病的消除具有影响。例如，钉螺防控在较为富裕的国家以及20世纪早期即启动防控工作的地区更为普遍且实施范围更广。 结论与意义：钉螺防控是降低血吸虫病感染率的最有效手段。尽管已有证据表明钉螺防控可实现疾病的长期降低与消除，但当前多数血吸虫病防控工作仍优先采用吡喹酮大规模药物给药而非钉螺防控。将药物防控方案与经济可行的钉螺防控措施相结合，似乎是消除血吸虫病的最佳策略。