Segregation analysis detects a major gene controlling blood infection levels in human malaria.

The profound influence that the genetic makeup of the host has on resistance to malaria infection has been established in numerous animal studies. This genetic heterogeneity is one of the main causes of the difficulties in developing an effective malaria vaccine. Segregation analysis is the first step in identifying the nature of genetic factors involved in the expression of human complex diseases, as infectious diseases. To assess the role of host genes in human malaria, we performed segregation analysis of blood parasite densities in 42 Cameroonian families by using both the unified mixed model and the class D regressive model of analysis. The results provide clear evidence for the presence of a recessive major gene controlling the degree of infection in human malaria. Parameter estimates show a frequency of .44-.48 for the deleterious allele, indicating that about 21% of the population is predisposed to high levels of infection.