HIGHER RESISTANCE TO PLASMODIUM-FALCIPARUM INFECTION IN PATIENTS WITHHOMOZYGOUS SICKLE-CELL DISEASE IN WESTERN KENYA

Sickle haemoglobin (HbS) is considered to be protective against malari a. Malaria is fatal in homozygous sickle cell (HbSS) disease. In a cro ss-sectional survey by alkaline Hb-electrophoresis of 766 residents of Western Kenya near Lake Victoria, 20 were found to have HbSS disease, 120 sickle cell trait (HbAS) and 626 the normal genotype (HbAA). Bloo d slides for malarial parasites (MPs) were performed in 728 cases, i.e . 592 HbAAs, 116 HbASs and all 10 HbSSs. Malaria parasites were found in 261 (35.8%) HbAAs, 42 (58%) HbASs and 4 (0.5%) HbSSs. Malaria preva lences per genotypic group were 44.1% (261 out of 592) in HbAAs, 36.2% (42 out of 116) in HbASs, and 20% (4 out of 20) in HbSSs. The relativ e risk of malarial infection was 0.33 in the HbSSs compared to both Hb AAs and HbASs. It seems that the protection conferred by HbS against m alaria is more marked in HbSS disease than in HbAS and is HbS-content related, and that the balanced polymorphism in the HbS-malaria relatio nship is maintained by higher mortality risk of HbAAs due to malaria a nd high mortality risk of HbSSs caused by complications of HbSS.