Anti-folate drug resistance in Africa: meta-analysis of reported dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) mutant genotype frequencies in African Plasmodium falciparum parasite populations.
BACKGROUND
Mutations in the dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) genes of Plasmodium falciparum are associated with resistance to anti-folate drugs, most notably sulphadoxine-pyrimethamine (SP). Molecular studies document the prevalence of these mutations in parasite populations across the African continent. However, there is no systematic review examining the collective epidemiological significance of these studies. This meta-analysis attempts to: 1) summarize genotype frequency data that are critical for molecular surveillance of anti-folate resistance and 2) identify the specific challenges facing the development of future molecular databases.


METHODS
This review consists of 220 studies published prior to 2009 that report the frequency of select dhfr and dhps mutations in 31 African countries. Maps were created to summarize the location and prevalence of the highly resistant dhfr triple mutant (N51I, C59R, S108N) genotype and dhps double mutant (A437G and K540E) genotype in Africa. A hierarchical mixed effects logistic regression was used to examine the influence of various factors on reported mutant genotype frequency. These factors include: year and location of study, age and clinical status of sampled population, and reporting conventions for mixed genotype data.


RESULTS
A database consisting of dhfr and dhps mutant genotype frequencies from all African studies that met selection criteria was created for this analysis. The map illustrates particularly high prevalence of both the dhfr triple and dhps double mutant genotypes along the Kenya-Tanzania border and Malawi. The regression model shows a statistically significant increase in the prevalence of both the dhfr triple and dhps double mutant genotypes in Africa.


CONCLUSIONS
Increasing prevalence of the dhfr triple mutant and dhps double mutant genotypes in Africa are consistent with the loss of efficacy of SP for treatment of clinical malaria in most parts of this continent. Continued assessment of the effectiveness of SP for the treatment of clinical malaria and intermittent preventive treatment in pregnancy is needed. The creation of a centralized resistance data network, such as the one proposed by the WorldWide Antimalarial Resistance Network (WWARN), will become a valuable resource for planning timely actions to combat drug resistant malaria.
Sridaran
Sankar
S
Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, 1600 Clifton road NE, Mail Stop D-67 Atlanta, GA, 30333, USA. vxu0@cdc.gov.
McClintock
Shannon K
SK
Syphard
Luke M
LM
Herman
Karen M
KM
Barnwell
John W
JW
Udhayakumar
Venkatachalam
V
D000349:Africa; D019943:Amino Acid Substitution; D000962:Antimalarials / Q000494:pharmacology*; D016054:DNA, Protozoan / Q000235:genetics; D004094:Dihydropteroate Synthase / Q000037:antagonists & inhibitors / Q000235:genetics*; D004338:Drug Combinations; D004351:Drug Resistance; D005787:Gene Frequency; D005838:Genotype; D006801:Humans; D050505:Mutant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D020125:Mutation, Missense; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D015800:Protozoan Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D011739:Pyrimethamine / Q000494:pharmacology; D013413:Sulfadoxine / Q000494:pharmacology; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics*
D000962:Antimalarials; D016054:DNA, Protozoan; D004338:Drug Combinations; D050505:Mutant Proteins; D015800:Protozoan Proteins; C001205:fanasil, pyrimethamine drug combination; D013413:Sulfadoxine; D013762:Tetrahydrofolate Dehydrogenase; D004094:Dihydropteroate Synthase; D011739:Pyrimethamine
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