Ross Amanda, Maire Nicolas, Molineaux Louis, Smith Thomas
Swiss Tropical Institute, Basel, Switzerland.
Am J Trop Med Hyg. 2006 Aug;75(2 Suppl):63-73. doi: 10.4269/ajtmh.2006.75.63.
The intensity of Plasmodium falciparum transmission has multifarious and sometimes counter-intuitive effects on age-specific rates of severe morbidity and mortality in endemic areas. This has led to conflicting speculations about the likely impact of malaria control interventions. We propose a quantitative framework to reconcile the various apparently contradictory observations relating morbidity and mortality rates to malaria transmission. Our model considers two sub-categories of severe malaria episodes. These comprise episodes with extremely high parasite densities in hosts with little previous exposure, and acute malaria episodes accompanied by co-morbidity or other risk factors enhancing susceptibility. In addition to direct malaria mortality from severe malaria episodes, the model also considers the enhanced risk of indirect mortality following acute episodes accompanied by co-morbidity after the parasites have been cleared. We fit this model to summaries of field data from endemic areas of Africa, and show that it can account for the observed age- and exposure-specific patterns of pediatric severe malaria and malaria-associated mortality in children. This model will allow us to make predictions of the long-term impact of potential malaria interventions. Predictions for children will be more reliable than those for older people because there is a paucity of epidemiologic studies of adults and adolescents.
恶性疟原虫传播强度对疟疾流行地区特定年龄组的严重发病和死亡率有着多方面且有时违反直觉的影响。这引发了关于疟疾控制干预措施可能产生的影响的相互矛盾的猜测。我们提出了一个定量框架，以协调将发病率和死亡率与疟疾传播相关联的各种明显相互矛盾的观察结果。我们的模型考虑了严重疟疾发作的两个子类别。其中包括既往接触较少的宿主中寄生虫密度极高的发作，以及伴有合并症或其他增加易感性的危险因素的急性疟疾发作。除了严重疟疾发作导致的直接疟疾死亡外，该模型还考虑了寄生虫清除后伴有合并症的急性发作后间接死亡风险的增加。我们将此模型与非洲流行地区的现场数据总结进行拟合，结果表明它可以解释观察到的儿童严重疟疾和疟疾相关死亡率的年龄和接触特定模式。该模型将使我们能够预测潜在疟疾干预措施的长期影响。对儿童的预测将比老年人的预测更可靠，因为针对成年人和青少年的流行病学研究较少。
