Increased multiplicity of Plasmodium falciparum infections and skewed distribution of individual MSP1 and MSP2 alleles during pregnancy in Ndiop, a Senegalese village with seasonal, mesoendemic malaria

Pregnancy is associated with a greater susceptibility to Plasmodium falciparum infections, which may result in serious complications affecting both the mother and the fetus. To compare allelic diversity and multiplicity of infection in the same women during and outside pregnancy, we conducted a retrospective analysis of the monthly fingerprick blood samples collected during a longitudinal survey conducted in Ndiop, a Senegalese village with mesoendemic malaria. Merozoite surface protein-1 (msp1) block 2 and merozoite surface protein-2 (msp2) genotypes were determined for 308 blood samples collected from 20 women. Pregnancy was associated with a significantly higher prevalence of P. falciparum infection, higher parasite densities, and a higher multiplicity of infection. The highest multiplicity of infection was observed in the youngest pregnant women. Because of co-linearity, it was not possible to dissociate the impact of age from that of parity on multiplicity of infection. Some individual msp1 and msp2 alleles showed a highly skewed pregnancy-associated distribution. These results indicate that pregnancy is associated with increased permissiveness to a large number of clones, as well as with infection by specific genotypes.