Change in Plasmodium falciparum genotype during successive malaria episodes in Gabonese children.

Extensive polymorphism in the malaria parasite Plasmodium falciparum is one of the major obstacles to controlling the disease. With the aim of analysing the dynamics of P. falciparum inoculations, we investigated the parasite genotypes of successive malaria episodes. Polymerase chain reaction was performed on blood samples collected longitudinally from 31 children in Lambaréné, Gabon. The polymorphic regions of the merozoite surface antigens 1 and 2 were used as genetic markers. The data show that children in this area are exposed to many different P. falciparum strains. In a few cases, the same parasite genotypic pattern was observed in samples from two consecutive clinical attacks indicating probable recrudescences after therapy. In six cases the first successive infections with a particular merozoite surface antigen (MSA)-2 strain (3D7) were followed by infections with the other MSA-2 genotype (FC27). In all other cases the genetic characteristics of the parasite were different from one infection to the next, indicating that reinfection was caused by a new parasite strain.