A new look at the protection of hemoglobin AS and AC genotypes against plasmodium falciparum infection: a census tract approach.

A total of 4,097 randomly selected children under 5 years in Accra, Ghana were investigated for Hb type, malarial parasite species, and parasite density. Even though malarial infection rates in this metropolitan population were lower as compared to holoendemic areas, the differential survival of Hb S carriers was confirmed. In addition, similar but less pronounced survival effects were seen in Hb C heterozygotes. Hb S carriers had the highest infection rates. More females than males were infected. Individuals with a moderate parasite count (less than 50,000/ml) were seen more commonly amoung AS and AC individuals as compared to AA controls. It is postulated that heterozygotes have a better immunological defense against the deleterious effects of P. falciparum infection because persistent parasitemia stimulates antibody production.