Determinants of treatment response to sulfadoxine-pyrimethamine and subsequent transmission potential in falciparum malaria.
Drug resistance is contributing to increasing mortality from malaria worldwide. For assessment of the role of resistance-conferring parasite mutations on treatment responses to sulfadoxine-pyrimethamine (SP) and transmission potential, 120 subjects with uncomplicated falciparum malaria from Buenaventura, Colombia, were treated with SP and followed for 21 days in the period February 1999 to May 2000. Exposures of interest were mutations in Plasmodium falciparum dihydrofolate reductase (DHFR) and dihydropteroate synthase that confer resistance to pyrimethamine and sulfadoxine, respectively. Although SP was highly efficacious (96.7%), the presence together of DHFR mutations at codons 108 and 51 was associated with longer parasite clearance time (relative hazard = 0.24, p = 0.019) more so than the 108 mutation alone (relative hazard = 0.45, p = 0.188). This association remained after controlling for potential confounders. Infections with these mutations were also associated with the presence of gametocytes, the sexual form of the parasite responsible for transmission, 14 and 21 days after treatment (p = 0.016 and p = 0.048, respectively). Higher gametocytemia is probably due to DHFR mutations prolonging parasite survival under drug pressure, resulting in longer parasite clearance time and allowing asexual parasites to differentiate into gametocytes. These results suggest that even when SP efficacy is high, DHFR mutations that are insufficient to cause therapeutic failure may nevertheless increase malaria transmission and promote the spread of drug resistance.
Secretaría Departamental de Salud del Valle, Cali, Colombia.
Fabián
F
Méndez
Alvaro
A
Muñoz
Gabriel
G
Carrasquilla
Diana
D
Jurado
Myriam
M
Arévalo-Herrera
Joseph F
JF
Cortese
Christopher V
CV
Plowe
D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D000962:Antimalarials / Q000494:pharmacology* / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D004094:Dihydropteroate Synthase / Q000235:genetics; D004338:Drug Combinations; D004351:Drug Resistance / Q000235:genetics*; D005260:Female; D006801:Humans; D007223:Infant; D016778:Malaria, Falciparum / Q000188:drug therapy / Q000635:transmission*; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000235:genetics; D018512:Parasitemia / Q000188:drug therapy / Q000635:transmission; D010963:Plasmodium falciparum / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D011739:Pyrimethamine / Q000494:pharmacology* / Q000627:therapeutic use; D013413:Sulfadoxine / Q000494:pharmacology* / Q000627:therapeutic use; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics; D016896:Treatment Outcome
D000962:Antimalarials; D004338:Drug Combinations; C001205:fanasil, pyrimethamine drug combination; D013413:Sulfadoxine; D013762:Tetrahydrofolate Dehydrogenase; D004094:Dihydropteroate Synthase; D011739:Pyrimethamine