Plasmodium falciparum parasites in French Guiana: limited genetic diversity and high selfing rate

The genetic characteristics of Plasmodium falciparum isolates collected in French Guiana, where malaria transmission is low and occurs in isolated foci, were studied. Blood samples were collected from 142 patients with symptomatic malaria and typed using a polymerase chain reaction-based strategy for merozoite surface protein-(MSP-1) block 2, the MSP-2 central domain, and glutamate-rich protein (GLURP) repeat domain polymorphism. This showed that the parasite population circulating in French Guiana presented a limited number of allelic forms (4, 2, and 3 for MSP-1 block 2, MSP-1, and GLURP, respectively) and a small number of mixed infections, contrasting with the large genetic diversity of parasite populations and infection complexity reported for Africa, Asia, and other parts of South America. Two groups of isolates displaying identical 3 loci allele combinations were further studied for the Pf332 antigen, histidine-rich protein-1, thrombospondin-related anonymous protein, and Pf60 multigene family polymorphism. Within each group, most isolates were identical for all markers tested. This suggests a high rate of self-fertilization of P. falciparum parasites in French Guiana, resulting in homogenization of the population. The implications of these findings for malaria control in areas of low endemicity are discussed.