Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands.
Department for Health Evidence, Biostatistics Research Group, Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, The Netherlands.
PLoS Negl Trop Dis. 2022 Jun 28;16(6):e0010279. doi: 10.1371/journal.pntd.0010279. eCollection 2022 Jun.
Soil-transmitted helminths affect almost 2 billion people globally. Hookworm species contribute to most of the related morbidity. Hookworms mainly cause anaemia, due to blood loss at the site of the attachment of the adult worms to the human intestinal mucosa. The World Health Organization (WHO) aims to eliminate hookworm morbidity by 2030 through achieving a prevalence of moderate and heavy intensity (M&HI) infections below 2%. In this paper, we aim to assess the suitability of this threshold to reflect hookworm-attributable morbidity.
METHODOLOGY/PRINCIPAL FINDINGS: We developed a hierarchical statistical model to simulate individual haemoglobin concentrations in association with hookworm burdens, accounting for low haemoglobin values attributable to other causes. The model was fitted to individual-level data within a Bayesian framework. Then, we generated different endemicity settings corresponding to infection prevalence ranging from 10% to 90% (0% to 55% M&HI prevalence), using 1, 2 or 4 Kato-Katz slides. For each scenario, we estimated the prevalence of anaemia due to hookworm. Our results showed that on average, haemoglobin falls below the WHO threshold for anaemia when intensities are above 2000 eggs per gram of faeces. For the different simulated scenarios, the estimated prevalence of anaemia attributable to hookworm ranges from 0% to 30% (95%-PI: 24% - 36%) being mainly associated to the prevalence of M&HI infections. Simulations show that a 2% prevalence of M&HI infections in adults corresponds to a prevalence of hookworm-attributable anaemia lower than 1%.
CONCLUSIONS/SIGNIFICANCE: Our results support the use of the current WHO thresholds of 2% prevalence of M&HI as a proxy for hookworm morbidity. A single Kato-Katz slide may be sufficient to assess the achievement of the morbidity target. Further studies are needed to elucidate haemoglobin dynamics pre- and post- control, ideally using longitudinal data in adults and children.
土壤传播的蠕虫影响着全球近 20 亿人。钩虫物种导致了大部分相关的发病率。钩虫主要引起贫血，这是由于成虫附着在人体肠道黏膜上时发生的失血。世界卫生组织（WHO）旨在到 2030 年消除钩虫发病率，目标是将中度和重度感染（M&HI）的患病率降低到 2%以下。在本文中，我们旨在评估这一阈值是否适合反映钩虫引起的发病率。
方法/主要发现：我们开发了一个层次统计模型，以模拟个体血红蛋白浓度与钩虫负荷之间的关系，同时考虑到其他原因导致的低血红蛋白值。该模型在贝叶斯框架内对个体水平的数据进行拟合。然后，我们使用 1、2 或 4 张加藤厚涂片，生成不同的流行率设置，对应于从 10%到 90%（0%到 55%M&HI 流行率）的感染率。对于每种情况，我们估计了因钩虫引起的贫血患病率。我们的结果表明，平均而言，当强度高于 2000 个虫卵/克粪便时，血红蛋白会降至 WHO 贫血阈值以下。对于不同的模拟场景，归因于钩虫的贫血患病率估计在 0%到 30%（95%置信区间：24%至 36%）之间，主要与 M&HI 感染的流行率相关。模拟表明，成年人中 2%的 M&HI 感染流行率对应于低于 1%的钩虫相关性贫血患病率。
结论/意义：我们的结果支持使用当前的 WHO 2%M&HI 流行率阈值作为钩虫发病率的替代指标。一张加藤厚涂片可能足以评估发病率目标的实现情况。需要进一步的研究来阐明控制前后的血红蛋白动态，理想情况下使用成年人和儿童的纵向数据。
