High prevalence of dihydrofolate reductase gene mutations in Plasmodium falciparumparasites among pregnant women in Nigeria after reported use of sulfadoxine-pyrimethamine

AbstractThis study assesses the prevalence of asymptomatic Plasmodium falciparumparasitemia positivity and P. falciparum dihydrofolate reductase(pfdhfr) mutations in parasite isolates among pregnant women in Southwest Nigeria. Plasmodium falciparumparasitemia was confirmed by microscopy and nested PCR in 200 pregnant women attending antenatal care. The prevalence of pfdhfrpolymorphisms was determined by direct sequencing of the gene fragments containing the C50R, N51I, C59R, S108N, and I164L mutations. Information on the use of antimalarial drugs and methods applied to prevent malaria were obtained by a questionnaire. The prevalence of asymptomatic P. falciparuminfection was 30% (60/200). The frequency of the pfdhfrtriple-mutant alleles (N51I, C59R, and S108N) was 63% (38/60); none of the isolates carried the I164L mutation. Among the investigated pregnant women, 40% used un-prescribed antimalarials such as dihydroartemisinin (18%), chloroquine (14%) or pyrimethamine (9%), while only 20.5% used sulfadoxine-pyrimethamine for prevention and 39.5% did not use any drug. The prevalence of P. falciparumparasitemia (37%) was higher among pregnant women who had not taken any antimalarial drugs. A significant difference in the prevalence of the pfdhfrtriple-mutant alleles was observed among women who took SP (90%) compared to those who did not take any drug (82%) and women who took dihydroartemisinin (67%) p = 0.007). Poor adherence to the World Health Organisation (WHO) strategies for malaria prevention among pregnant women was observed in addition to high prevalence of pfdhfrmutations. These findings underline the need to improve control of malaria among pregnant women in the study area.