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

项目概要/摘要：30行 虽然间日疟原虫每年造成700多万例疟疾病例，但它通常是一种常见的疟疾。 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 以及假设主要为Duffy阴性的群体对间日疟原虫感染是无害的。 然而，越来越多的证据表明，间日疟原虫确实存在于SSA中， 也可能被感染，尽管感染率低于达菲阳性的同类。加之近期 斯氏按蚊是间日疟原虫和恶性疟原虫的高度有效媒介， 非洲之角提出了间日疟原虫传播可能被这种新兴媒介增强的可能性，因为它 向南扩散到SSA。随着肯尼亚在防治疟疾方面接近消灭前阶段， 正面临入侵的安的双重威胁。斯蒂芬西矢量和一个未知的负担， 被忽视的间日疟原虫物种。虽然模型已经揭示了安的潜在传播。斯蒂芬西into 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， 量化。在这里，我们把重点放在图尔卡纳，肯尼亚北方的一个半干旱地区，我们最近记录了 全年间日疟原虫首次处于低水平。图尔卡纳县与埃塞俄比亚接壤，间日疟原虫在埃塞俄比亚流行 和一个.史蒂芬西的存在最近得到了证实。在肯尼亚边境， 关于间日疟原虫患病率、临床负担或其与Duffy血型关系的可用信息。 此外，安。斯蒂芬西监测尚未安装在图尔卡纳，尽管事实上，它是预测， 安的风险最高。斯蒂芬西入侵首先，我们建议测量间日疟原虫的临床负担 通过被动病例检测，探讨其与Duffy血型的关系。通过与Select Health合作 在全国各地的设施，以筛选和测试寻求疟疾治疗的病人，我们可以衡量 疑似疟疾病例间日疟原虫感染率及不同Duffy血感染率比较 组其次，通过对治疗患者进行随访，我们将量化间日疟原虫感染的比率， 恶性疟原虫清除后，由于休眠的催眠虫的存在，感染复发， 这一现象在恶性疟原虫和间日疟原虫共同流行的许多地区已有充分的记录。 这将使我们能够估计潜在的沉默水库肝脏阶段间日疟原虫感染。三是 通过收集和分类蚊子种类，确定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，特别强调检测An.史蒂芬西证据 这项研究将为了解间日疟原虫可能在哪些条件下 从图尔卡纳传播到肯尼亚各地，将有广泛的应用，为疟疾监测提供信息， 控制策略在肯尼亚和其他地区在整个撒哈拉以南非洲地区，其中P. vivax和安。斯蒂芬西可能有一个 影响越来越大。

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.