Spatial targeting of interventions against malaria

Malaria transmission is strongly associated with location. This association has two main features. First, the disease is focused around specific mosqu ito breeding sites and can normally be transmitted only within certain dist ances from them: in Africa these are typically between a few hundred metres and a kilometre and rarely exceed 2-3 kilometres. Second, there is a marke d clustering of persons with malaria parasites and clinical symptoms at par ticular sites, usually households. in localities of low endemicity the leve l of malaria risk or case incidence may vary widely between households beca use the specific characteristics of houses and their locations affect conta ct between humans and vectors. Where endemicity is high, differences in hum an/vector contact rates between different households may have less effect o n malaria case incidences. This is because superinfection and exposure-acqu ired immunity blur the proportional relationship between inoculation rates and case incidences, Accurate information on the distribution of malaria on the ground permits interventions to be targeted towards the foci of transm ission and the locations and households of high malaria risk within them. S uch targeting greatly increases the effectiveness of control measures. On t he other hand, the inadvertent exclusion of these locations causes potentia lly effective control measures to fail. The computerized mapping and manage ment of location data in geographical information systems should greatly as sist the targeting of interventions against malaria at the focal and househ old levels, leading to improved effectiveness and cost-effectiveness of con trol.