As the COVID-19 pandemic continues, it has become painfully evident how vulnerable economic systems can be to widespread and persistent diseases.
在低收入和中等收入国家，特别是在撒哈拉以南非洲地区，农业扮演着基本的发展角色，因为它构成了该国经济体的主要组成部分，占总劳动力的一半以上。尽管主要以生存农业和低生产率为特征，但农业仍然是缓解贫困的最强大工具，促进家庭收入的多元化和增长，并允许获得改进的生产技术。
Simultaneously, however, agricultural development facilitated by the construction of large-scale irrigation schemes foster the propagation of schistosomiasis, a water-based debilitating parasitic disease that affects an estimated 250 million people, more than 85% of whom live in sub-Saharan Africa. The parasite species that cause the two main forms of schistosomiasis in Africa are曼氏菌（引起肠道血吸虫病）和血吸虫haematobium(causing urogenital schistosomiasis).
该疾病的特征是一个复杂的生命周期，涉及两个繁殖阶段，第一种是在特定的淡水蜗牛物种中无性恋，后者充当中间宿主，然后在人类宿主中有性繁殖。在未经治疗的人类中，先进的血吸虫病形式导致肾衰竭，膀胱癌，肝纤维化以及艾滋病毒传播的风险增加。最高的寄生虫负担通常由学龄儿童承担，这种疾病与贫血，发育迟缓和认知缺陷有关，导致学校表现不佳和辍学率更高。包括灌溉管和水库在内的主要水基础设施的开发和管理通过扩展适合中间宿主蜗牛的栖息地来改变疾病分布的动力。由于这些长期影响，血吸虫病被认为会对受感染的个人，家庭和受影响的社区施加巨大的健康，社会和财务负担。
因此，血吸虫病动态，水资源发展和经济发展是密切相互联系的。但是，它们的并发效果和关节动态尚待充分探索。在我们的论文中，我们通过研究血吸虫病对农业生产的负担来填补这一空白。我们表明，这种负担很大：我们估计，消除布基纳法索的血吸虫病将使平均农作物产量增加7％左右，而高感染簇的平均农作物产量升至32％。对于一个内陆的撒哈拉以南国家，例如布基纳法索（Brkina Faso），那里有80％的人口在农业部门工作，这种影响尤其引人注目。
与疾病的衰弱性质一致，我们确定疾病的经济负担不会直接影响生产所需的劳动或物理投入量（例如种子和机械），而是降低了其有效性。换句话说，慢性血吸虫病导致农民成为能力较低to farm efficiently: this generates a spiral of deleterious effects that can have potentially dramatic consequences, particularly in countries such as Burkina Faso where agriculture is mostly of the subsistence type.
更糟糕的是，这种负担在贫困和减贫措施（例如水资源开发）上的矛盾加强。我们发现，贫困家庭的负担不成比例（高强度群集32％），并且靠近大型水坝的村庄经历了由于血吸虫病而导致的农业产量损失要高得多（约20％）。
地理因素在其中发挥了关键作用,因为这增加我n yield loss due to schistosomiasis is contained within a radius of 20-30km from the dams, and villages located at a further distance from the dams suffer a reduced burden. The consequences from the standpoint of inequality are substantial: these large water infrastructures are in majority built for hydroelectrical purposes and geared towards urban electrification. This means that those who live in the areas adjacent to the dams suffer the most deleterious consequences in terms of disease burden, whilst reaping only a small part of their benefits. Fortunately, our results are not entirely bleak. Smaller-scale water infrastructures, which are equally fundamental measures of poverty control, especially in the poorest parts of the sub-Saharan region, do not seem to amplify the economic burden of schistosomiasis, and hence should be incentivized and strengthened.
We obtain our results by exploiting recent developments in disease mapping. We obtain high-resolution schistosomiasis prevalence maps via Bayesian geostatistical methods, which have been used in a variety of public health contexts but have not yet been paired with survey data on households and agricultural production. Because of the complexity of the dynamics of schistosomiasis and its interlinkages with such a large set of socioeconomic and environmental factors, we implement a novel mix of methods. We use the spatial density of the snail intermediate host of the血吸虫通过机器学习和空间技术来建立因果关系并完善分析的寄生虫。
Our study illustrates the potential benefits of combining epidemiological and economic methods in the analysis of the human cost of endemic diseases. Our approach is “data-hungry”, especially in the study of the impact of endemic diseases at a household level, which can represent a hurdle for wider application. Yet, recent methodological and technological advances increasingly allow researchers to access a wealth of information which was until recently unthinkable. Conditional on this, our approach can be applied to any other country in which schistosomiasis is endemic and indeed, to the economic impact of many other diseases.
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