Maximising the impact of chemoprevention on the malaria burden in children in areas of seasonal transmission

点击翻译按钮获取中文摘要

Malaria is a parasitic disease transmitted by mosquitoes that kills approximately 850,000 people every year, mostly children under five years of age living in sub-Saharan Africa. Prevention of malaria is key to achieving Millennium Development Goals. The epidemiology or disease pattern of malaria varies widely across Africa, both in terms of intensity (the number of infections individuals are exposed to), and seasonality (how the pattern of risk varies over the course of the year).In areas of Africa where malaria is only a problem during a short rainy season, monthly courses of antimalarial drugs can prevent malaria in children very effectively. This approach, called seasonal malaria chemoprevention (SMC), may also be useful in places where malaria is transmitted for longer each year. However, the impact in such areas is not well understood.Another form of prevention that would be easier for African countries to put into practice would be to treat malaria patients with long-lasting artemisinin combination therapies (LACTs), which prevent further malaria infections for several weeks. Malaria does not affect all children equally: a fraction of children repeatedly experience malaria, while other children remain healthy. Repeated malaria leads to severe anaemia, an important cause of death in areas where malaria is endemic. LACTs would prevent some repeated malaria attacks, and may be a simple and effective way to target limited resources at the individuals who most need protection. This may be particularly beneficial in areas with seasonal malaria transmission because repeated malaria attacks are likely to occur close together in time. In such areas, LACTs could help ensure that a child's first attack each year is their last.Dr Matthew Cairns, an epidemiologist based at the London School of Hygiene & Tropical Medicine, will use a multi-disciplinary approach to investigate these issues.Studies of malaria conducted in West Africa will provide data on the epidemiology of malaria in different areas. Data will be analysed to quantify the fraction of the total malaria and anaemia burden that occurs soon after a previous malaria attack, and which might therefore be prevented by replacing standard antimalarials with LACTs. This analysis will also determine the situations in which malaria is most unevenly focused on a small sub-group of children, and identify characteristics associated with high risk. This could lead to changes in which antimalarials are recommended as policy in some parts of Africa. A mathematical model developed by Dr Cairns will be extended to determine the impact of LACTs and SMC in a range of areas, using a range of assumptions about the effectiveness of drugs and the use of treatment by different children. The model will also allow exploration of the impact of combining these two interventions, which might be very expensive to do in a clinical trial. If the predicted impact of SMC is sufficient, this could lead to expansion of the area where SMC is deployed. Data from a clinical trial in Ghana investigating these two forms of prevention (arranged outside the fellowship), will be analysed to determine the real-life impact of these interventions, and help improve the accuracy of the model predictions.Computer based simulations including rainfall and other climatic data will then be used to identify the geographical areas where SMC and LACTs are likely to be useful, and their potential impact on disease and on transmission of malaria. Maps will be produced showing results at sub-country level. Results of the research will help policy makers at the World Health Organisation and in malaria-endemic countries to make decisions on the recommended treatment for malaria, and to plan and prioritise where to deploy these two forms of malaria prevention. Both interventions could have an important impact on the health of African children within the next five years.