Genetic diversity of Plasmodium falciparum and its relationship to parasite density in an area with different malaria endemicities in West Uganda.

Field populations of Plasmodium falciparum can be effectively genotyped by PCR-amplification of selected fragments of the Merozoite Surface Proteins 1 and 2 (MSP1 and MSP2). Genetic diversity of P. falciparum populations in areas with different transmission levels (holo- vs. mesoendemic) was investigated in Kabarole District, West Uganda. 225 samples positive for P. falciparum were analysed by amplification of polymorphic regions and classified according to prevalence of allelic families. A large number of alleles was detected for each locus: 22 for MSP1 block 2 and 24 for MSP2 and, 175 (78%) of MSP1 alleles and 143 (64%) of MSP2 showed multiple infections within a range of 2-8 clones. Significant differences between holoendemic and mesoendemic areas in regards of population structure and number of multiclonal infections of P. falciparum were not apparent. However, a significant correlation between parasite density, selected MSP2 loci and differences between parasite density in monoclonal vs. multiclonal infections occurred. Multiplicity of infection was age-dependent.