Malaria elimination in Sub-Saharan Africa: essential tools and identifiable targets

虽然疟疾仍然影响着世界人口的很大一部分，但在过去几年中，疟疾的发病率已大幅下降，这也要归功于诸如用杀虫剂处理过的蚊帐等干预措施的扩大。在撒哈拉以南非洲国家，包括疟疾负担最重的冈比亚，也观察到这种减少。疟疾不再是一个主要的公共卫生问题，甚至可以被消灭，这种想法可以在20世纪50年代的上一次尝试之后再次被引入。放弃这一计划主要有两个原因：缺乏资金支持和使用单一战略，没有考虑到疟疾传播的极端可变性。现在人们认识到，支持任何消除努力所需的知识是有限的，在这方面的新尝试应该得到强有力的研究组成部分的支持。这项拟在冈比亚开展的研究项目旨在为撒哈拉以南非洲国家疟疾控制项目提供必要的知识和工具，以进一步消除疟疾。冈比亚是开展拟议的研究计划的理想场所，因为1。该国在减少疟疾负担方面极为成功，并致力于进一步减少疟疾负担；2. MRC实验室拥有所需的专业知识、先进的技术平台和必要的国际合作来实现该计划的目标。这两个因素的结合在西非是独一无二的，它为开展一项研究规划提供了一个黄金机会，该规划可以对撒哈拉以南非洲实施消除努力的方式产生深远影响。活动分为两个平行和互补的部分：一部分旨在了解疟疾传播的动态以及为什么在几公里内就会有很大差异的原因；另一部分的目标是改进能够识别疟疾感染者但其他方面健康的人（疟疾携带者）的诊断测试。对于前者，将对12个村庄的人口进行3个传播季节的集中随访，以了解谁是疟疾携带者以及感染如何在人群中传播。将收集关于病媒种群的信息，包括杀虫剂耐药性的存在，以及关于人类行为的信息，以部分解释研究村庄之间可能存在的差异。在研究结束时，我们将更好地了解疟疾寄生虫是如何传播的，以及尽管预防和治疗措施覆盖率很高，但保持每年传播的重要决定因素是什么。关于诊断测试，目前可在现场使用的测试无法检测出一部分有助于维持传播的感染者。我们将尝试两种方法，一种旨在开发易于使用的分子测试，可以检测大多数感染个体，另一种通过检测寄生虫或宿主的蛋白质来寻找感染的“标记”，这些蛋白质只能在感染个体中找到。后者可以提供必要的知识，以开发更灵敏的测试。这一研究项目的结果对任何一个愿意消灭疟疾的撒哈拉以南非洲国家都很重要。它们将通过国际和区域会议以及国际同行审查的出版物和通讯传播。此外，通过冈比亚国家疟疾控制规划，可以通过当地媒体以更广泛的公众可获得的形式传播结果。

Though still affecting an important proportion of the world population, malaria has declined substantially in the last few years, thanks also to the scale up of interventions such as bed nets treated with insecticide. Such decrease has been observed also in sub-Saharan African countries, including The Gambia, where the malaria burden is the highest. The idea that malaria can be reduced at the point where it would not be a major public health problem anymore or would even be eliminated has been re-introduced again after the previous attempt in the 1950s. This was abandoned mainly for two reasons: lack of financial support and use of a single strategy that did not take into account the extreme variability of malaria transmission. It is now recognised that the knowledge needed to support any elimination effort is limited and that a new attempt in this direction should be supported by a strong research component. This proposed research program to be carried out in The Gambia aims at providing sub-Saharan African National Malaria Control Programs with the necessary knowledge and tools to move farther, towards malaria elimination. The Gambia is the ideal place to carry out the proposed research program because 1. The country has been extremely successful in reducing the malaria burden and aims at reducing it further; 2. The MRC laboratories have the required expertise, the advanced technological platform and the necessary international collaborations to achieve the program's objectives. The combination of these two factors is unique in West Africa and offers a golden opportunity to carry out a research programme that can have a profound influence on the way elimination efforts will be implemented in sub-Saharan Africa. Activities are divided into two parallel and complementary sections: one section aims at understanding the dynamics of malaria transmission and the reasons why this can substantially differ within few kilometres; the other section will aim at improving diagnostic tests able to identify malaria infected but otherwise healthy people (malaria carriers). For the former, the populations of 12 villages will be intensively followed up for 3 transmission seasons to understand who the malaria carriers are and how the infection spreads across the populations. Information on the vector population, including the presence of insecticide resistance, and on the human behaviour will be collected to partly explain the likely differences between the study villages. At the end of the study we will have a better understanding on how the malaria parasites spread and what are the important determinants that maintain transmission from one year to the other, despite the high coverage of preventive and curative measures.Concerning diagnostic tests, the currently available tests that can be used in the field cannot detect a proportion of infected people that contributes in maintaining transmission. We will try two approaches, one aiming at developing easy-to-use molecular test that can detect most infected individuals, and the other looking at "markers" of infection by detecting parasite's or host's proteins that can be found only in infected individuals. The latter could provide the knowledge necessary to develop a more sensitive test. The results of this research program will be important for any sub-Saharan African country willing to go towards elimination of malaria. They will be disseminated through international and regional conferences, and by international peer-reviewed publications and communications. In addition, through the Gambian National Malaria Control Program, results may be disseminated through the local press in a form accessible to a wider public.