Quantifying the dual threat of Plasmodium vivax and Anopheles stephensi in a P. falciparum endemic pre-elimination setting in sub-Saharan Africa

量化撒哈拉以南非洲恶性疟原虫地方性预消灭环境中间日疟原虫和斯氏按蚊的双重威胁

• 批准号: 10726003
• 负责人: Wendy PrudhommeOMeara
• 金额: $ 22.83万
• 依托单位: DUKE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-08-01 至 2025-07-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10726003
• 关键词: Acceleration; Address; Africa; Africa South of the Sahara; African; Aftercare; Anopheles Genus; Antigens; Antimalarials; Area; Blood typing procedure; Case Management; Case Study; Classification; Clinical; Collaborations; Country; County; Coupled; Culicidae; Detection; Diagnostic; Documentation; Ecology; Erythrocytes; Ethiopia; Exclusion; Foundations; Future; Genetic; Goals; Health; Health care facility; Home; Horns; Household; Human; Individual; Infection; Invaded; Kenya; Larva; Learning; Liver; Malaria; Measures; Modeling; Molecular; Morbidity - disease rate; Parasites; Patients; Phase; Plasmodium falciparum; Plasmodium vivax; Population; Prevalence; Relapse; Reporting; Reproducibility; Rest; Risk Factors; Testing; Time; Universities; Work; blood group; disorder control; emerging pathogen; evidence base; fighting; high risk; infection rate; infectious disease model; mortality; multidisciplinary; neglect; patient screening; programs; transmission process; treatment strategy; vector

Project Summary/Abstract: 30 lines Although Plasmodium vivax causes more than 7 million malaria cases each year, it has typically been excluded from malaria control programming in sub-Saharan Africa (SSA) due to the absence of reported cases and the assumption that the predominantly Duffy-negative population is invulnerable to P. vivax infection. However, there is growing evidence that P. vivax is indeed present in SSA and that Duffy-negative individuals can be infected, albeit at lower rates than their Duffy-positive counterparts. In addition, the recent documentation of Anopheles stephensi, a highly competent vector for both P. vivax and P. falciparum, in the Horn of Africa raises the possibility that P. vivax transmission may be enhanced by this emerging vector as it spreads southward into SSA. As Kenya approaches pre-elimination phase in its fight against malaria, it is facing the dual threat of the invasive An. stephensi vector and an unknown burden of the largely neglected P. vivax species. While models have shed some light on the potential spread of An. stephensi into SSA, these predictions and their potential impact on P. vivax transmission remain to be confirmed or quantified. Here, we focus on Turkana, a semi-arid region of northern Kenya where we recently documented low levels of year-round P. vivax for the first time. Turkana county borders Ethiopia, where P. vivax is endemic and An. stephensi presence has recently been confirmed. Across the border in Kenya, there is little to no information available on P. vivax prevalence, clinical burden, or its relationship with Duffy blood groups. Furthermore, An. stephensi surveillance has not been mounted in Turkana, despite the fact that it is predicted to have the highest risk of An. stephensi invasion. First, we propose to measure the clinical burden of P. vivax and its relationship with Duffy blood groups through passive case detection. By working with select health facilities across the county to screen and test patients seeking malaria treatment, we can measure the prevalence of P. vivax in suspected malaria cases and compare the rate of infections in different Duffy blood groups. Second, by conducting follow-ups with treated patients, we will quantify the rate at which P. vivax infections relapse due to dormant hypnozoite presence following the clearance of P. falciparum parasites, a phenomenon that has been well documented in many areas where P. falciparum and P. vivax are co-endemic. This will allow us to estimate the underlying silent reservoir of liver-stage P. vivax infection. Third, we will identify vectors likely involved in P. vivax transmission by collecting and classifying the species of mosquitoes and/or larvae from the homes of P. vivax cases, with particular emphasis on detecting An. stephensi. Evidence from this study will provide the foundation for understanding the conditions in which P. vivax could potentially spread from Turkana across Kenya and would have broad application, informing malaria surveillance and control strategies in Kenya and other areas across SSA where P. vivax and An. stephensi may have an increasing impact.

项目摘要/摘要：30 行 尽管间日疟原虫每年导致超过 700 万例疟疾病例，但它通常是 由于没有报告病例，被排除在撒哈拉以南非洲 (SSA) 的疟疾控制规划之外 以及主要达菲阴性人群对间日疟原虫感染免疫的假设。 然而，越来越多的证据表明 SSA 中确实存在间日疟原虫，并且达菲阴性个体 可能会被感染，尽管其感染率低于达菲阳性的同类。此外，最近 斯蒂芬按蚊（Anopheles stephensi）的文献，它是间日疟原虫和恶性疟原虫的高度有效的载体，在 非洲之角提出了这种新兴媒介可能增强间日疟原虫传播的可能性，因为它 向南蔓延至SSA。随着肯尼亚抗击疟疾的斗争接近预消除阶段， 面临着入侵An的双重威胁。斯蒂芬西向量和很大程度上的未知负担 被忽视的间日疟原虫物种。虽然模型已经揭示了 An 的潜在传播。斯蒂芬西进入 SSA，这些预测及其对间日疟原虫传播的潜在影响仍有待证实或 量化。在这里，我们重点关注图尔卡纳，这是我们最近记录的肯尼亚北部的一个半干旱地区 间日疟原虫全年处于低水平。图尔卡纳县与埃塞俄比亚接壤，间日疟原虫在那里流行 和安。斯蒂芬西的存在最近得到证实。在肯尼亚边境，几乎没有任何东西 有关间日疟原虫患病率、临床负担或其与达菲血型关系的可用信息。 此外，安.尽管有预测，但图尔卡纳尚未安装斯蒂芬西监视 An 的风险最高。史蒂芬西入侵。首先，我们建议测量间日疟原虫的临床负担 通过被动病例检测及其与达菲血型的关系。通过与精选健康合作 在全县范围内对寻求疟疾治疗的患者进行筛查和检测的设施，我们可以测量 疑似疟疾病例中间日疟原虫的流行情况及不同达菲血中感染率的比较 组。其次，通过对接受治疗的患者进行随访，我们将量化间日疟原虫的发生率 恶性疟原虫清除后，由于休眠子的存在而导致感染复发， 这种现象在恶性疟原虫和间日疟原虫同时流行的许多地区都有详细记录。 这将使我们能够估计肝脏阶段间日疟原虫感染的潜在潜伏库。第三，我们将 通过收集和分类蚊子种类来识别可能参与间日疟原虫传播的媒介 和/或来自间日疟原虫病例家中的幼虫，特别注重检测间日疟原虫。斯蒂芬西。证据 这项研究将为了解间日疟原虫可能存在的条件奠定基础 从图尔卡纳传播到整个肯尼亚，并将具有广泛的应用，为疟疾监测和预防提供信息 肯尼亚和撒哈拉以南非洲其他地区的控制策略，其中间日疟原虫和按蚊。斯蒂芬西可能有一个 影响力不断增加。