title: Increasing prevalence of wildtypes in the dihydrofolate reductase gene of Plasmodium falciparum in an area with high levels of sulfadoxine/pyrimethamine resistance after introduction of treated bed nets.
abstract: In Magoda and Mpapayu villages in Tanzania, we have previously found comparable high prevalence of Plasmodium falciparum resistance to sulfadoxine/pyrimethamine (S/P) in vivo and of mutations in the dihydrofolate reductase (dhfr) and dihydropteroate synthetase (dhps) genes of P. falciparum responsible for resistance to S/P. In December 1998, Magoda received insecticide-treated nets (ITNs), whereas ITNs were introduced in Mpapayu in March 2001. We have studied the effect of ITNs on P. falciparum resistance genes by monitoring the prevalence of dhfr and dhps genotypes in children less than five years old living in the villages from 1998 to 2000. In 2000, after two years of bed net use, the prevalence of wild types in codon 51, 59, and 108 of dhfr increased significantly in Magoda compared with previous years. Furthermore, the prevalence of dhfr wild types was significantly higher in Magoda than in Mpapayu in 2000. The impact of ITNs on the transmission intensity seems not only to affect the overall malaria morbidity, but may even facilitate restoration of susceptibility to antimalarial drugs.
authors: Centre for Medical Parasitology, Institute of Medical Microbiology and Immunology, University of Copenhagen, Denmark. malif@biobase.dk
authors: Michael
authors: M
authors: Alifrangis
authors: Martha M
authors: MM
authors: Lemnge
authors: Anita M
authors: AM
authors: Rønn
authors: Method D
authors: MD
authors: Segeja
authors: Stephen M
authors: SM
authors: Magesa
authors: Insaf F
authors: IF
authors: Khalil
authors: Ib C
authors: IC
authors: Bygbjerg
mesh_terms: D000818:Animals; D000962:Antimalarials / Q000494:pharmacology*; D001512:Bedding and Linens; D002675:Child, Preschool; D009033:Culicidae; D017931:DNA Primers; D016054:DNA, Protozoan / Q000032:analysis; D004094:Dihydropteroate Synthase / Q000235:genetics; D004338:Drug Combinations; D004351:Drug Resistance; D005260:Female; D005493:Folic Acid Antagonists / Q000494:pharmacology*; D005838:Genotype; D006801:Humans; D007223:Infant; D007306:Insecticides / Q000008:administration & dosage; D016778:Malaria, Falciparum / Q000453:epidemiology* / Q000469:parasitology / Q000517:prevention & control; D008297:Male; D009032:Mosquito Control / Q000379:methods; D009154:Mutation; D010944:Plants; D010963:Plasmodium falciparum / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D016133:Polymerase Chain Reaction; D015995:Prevalence; D011739:Pyrimethamine / Q000494:pharmacology*; D013413:Sulfadoxine / Q000494:pharmacology*; D013636:Tanzania / Q000453:epidemiology; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics
chemical_list: D000962:Antimalarials; D017931:DNA Primers; D016054:DNA, Protozoan; D004338:Drug Combinations; D005493:Folic Acid Antagonists; D007306:Insecticides; C001205:fanasil, pyrimethamine drug combination; D013413:Sulfadoxine; D013762:Tetrahydrofolate Dehydrogenase; D004094:Dihydropteroate Synthase; D011739:Pyrimethamine