ENVIRONMENTAL AND ENTOMOLOGICAL RISK-FACTORS FOR THE DEVELOPMENT OF CLINICAL MALARIA AMONG CHILDREN ON THE KENYAN COAST

Several malariometric studies have examined the impact on human-vector contact of house construction, demographics, bed net and insect repel lent use. However, few studies have documented the significance of the se proximate determinants on the risks of clinical disease. We underto ok a matched case-control study of the risks of both mild clinical mal aria and severe life-threatening malaria according to a range of putat ive factors which would influence the frequency of child-vector encoun ters in Kilifi district on the Kenyan coast. Among 394 severe disease cases, 380 age-matched mild disease cases, and their respective locati on and age-matched community controls, we were unable to demonstrate a ny statistically significant effect upon disease outcome of house cons truction, presence of domestic animals, or bed net use. Higher populat ion density within a 250 m radius of the homes conferred significant p rotection from the risks of developing severe malaria compared to comm unity controls. The risks of developing severe malaria compared to the community controls and the transition from mild to severe disease wer e statistically significantly lower in those who reported use of mosqu ito coils, local repellents or aerosol insecticides. We concluded that it is likely that the impact of household features on disease outcome is dependent upon both the density of infecting mosquitoes and acquir ed immunity within a given locality.