title: Adaptive evolution and fixation of drug-resistant Plasmodium falciparum genotypes in pregnancy-associated malaria: 9-year results from the QuEERPAM study.
abstract: Sulfadoxine-pyrimethamine (SP) has been widely deployed in Africa for malaria control and molecular evidence of parasite drug-resistance is prevalent. However, the temporal effects on the selection of Plasmodium falciparum are not well understood. We conducted a retrospective serial cross-sectional study between 1997 and 2006 to investigate changes in drug-resistant malaria among pregnant women delivering at a single hospital in Blantyre, Malawi. P. falciparum parasites were genotyped for parasite clone multiplicity and drug-resistance mutations, and the strength of selection upon mutant genotypes was quantified. Five mutations in the dihydrofolate reductase and dihydropteroate synthase genes began at moderate frequencies and achieved fixation by 2005; the frequency of the highly-SP-resistant "quintuple mutant" haplotype increased from 19% to 100%. The selective advantage of alleles and haplotypes were quantified with selection coefficients: Selection was positive on all mutant alleles and haplotypes associated with SP resistance, and the relative fitness of the quintuple mutant haplotype was 0.139 (95% C.I. 0.067-0.211), indicating a substantial positive selective advantage. Mutations that confer higher levels of resistance to SP did not emerge. SP-resistant haplotypes were rapidly selected for and fixed in P. falciparum populations infecting pregnant women while SP was widely deployed in Malawi. These results underscore the pressing need for new preventive measures for pregnancy-associated malaria and provide a real-world model of the selection landscape malaria parasites.
authors: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC 27599, USA. taylo115@email.unc.edu
authors: Steve M
authors: SM
authors: Taylor
authors: Alejandro
authors: A
authors: Antonia
authors: Gaoqian
authors: G
authors: Feng
authors: Victor
authors: V
authors: Mwapasa
authors: Ebbie
authors: E
authors: Chaluluka
authors: Malcolm
authors: M
authors: Molyneux
authors: Feiko O
authors: FO
authors: ter Kuile
authors: Stephen J
authors: SJ
authors: Rogerson
authors: Steven R
authors: SR
authors: Meshnick
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics*; D000293:Adolescent; D000328:Adult; D003430:Cross-Sectional Studies; D004094:Dihydropteroate Synthase / Q000235:genetics; D004351:Drug Resistance / Q000235:genetics*; D019143:Evolution, Molecular; D005260:Female; D005787:Gene Frequency; D005838:Genotype; D006801:Humans; D016778:Malaria, Falciparum / Q000453:epidemiology / Q000469:parasitology*; D008295:Malawi / Q000453:epidemiology; D009154:Mutation; D010963:Plasmodium falciparum / Q000187:drug effects / Q000235:genetics*; D011247:Pregnancy; D015597:Pregnancy Complications, Parasitic / Q000453:epidemiology / Q000469:parasitology*; D012189:Retrospective Studies; D012641:Selection, Genetic; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics; D055815:Young Adult
chemical_list: D013762:Tetrahydrofolate Dehydrogenase; D004094:Dihydropteroate Synthase