Human Malaria: Segregation Analysis of Blood Infection Levels in a Suburban Area and a Rural Area in Burkina Faso

Centre Muraz, O.C.C.G.E., Bobo-Dioulasso, Burkina FasoThe genetic control of blood infection levels in human malaria remains unclear.Case control studies have not demonstrated a strong association between candi-date genes and blood parasite densities as opposed to surveys that have focusedon severe malaria. As an alternative approach, we used segregation analyses todetermine the genetic control of blood parasitemia. We surveyed 509 residents(53 pedigrees) in a rural area and 389 residents (41 pedigrees) in an urban areaduring 18 months. Each family was visited 20 times and 28 times in the urbanarea and in the rural area; the mean number of parasitemia measurements persubject was 12.1 in the town and 14.9 in the village. The intensity of transmis-sion of Plasmodium falciparum was 8-fold higher in the rural area than in theurban area. Using the class D regressive model for both populations, we foundthat blood parasite densities were correlated between sibs. We obtained strongevidence for a major effect, but we found that the transmission of this majoreffect was not compatible with a simple Mendelian model, suggesting a morecomplex mode of inheritance. Moreover, there was a strong interaction betweenmajor effect and age, suggesting that the influence of the putative major genemay be more prominent in children than in adults. Further nonparametric link-age studies, such as sib pair analysis, that focus on children would help us betterunderstand the genetic control of blood infection levels. Genet. Epidemiol. 15:435–450, 1998.