Submicroscopic gametocytes and the transmission of antifolate-resistant Plasmodium falciparum in Western Kenya.
BACKGROUND
Single nucleotide polymorphisms (SNPs) in the dhfr and dhps genes are associated with sulphadoxine-pyrimethamine (SP) treatment failure and gametocyte carriage. This may result in enhanced transmission of mutant malaria parasites, as previously shown for chloroquine resistant parasites. In the present study, we determine the association between parasite mutations, submicroscopic P. falciparum gametocytemia and malaria transmission to mosquitoes.


RESULTS
Samples from children treated with SP alone or in combination with artesunate (AS) or amodiaquine were genotyped for SNPs in the dhfr and dhps genes. Gametocytemia was determined by microscopy and Pfs25 RNA-based quantitative nucleic acid sequence-based amplification (Pfs25 QT-NASBA). Transmission was determined by membrane-feeding assays. We observed no wild type infections, 66.5% (127/191) of the infections expressed mutations at all three dhfr codons prior to treatment. The presence of all three mutations was not related to higher Pfs25 QT-NASBA gametocyte prevalence or density during follow-up, compared to double mutant infections. The proportion of infected mosquitoes or oocyst burden was also not related to the number of mutations. Addition of AS to SP reduced gametocytemia and malaria transmission during follow-up.


CONCLUSIONS
In our study population where all infections had at least a double mutation in the dhfr gene, additional mutations were not related to increased submicroscopic gametocytemia or enhanced malaria transmission. The absence of wild-type infections is likely to have reduced our power to detect differences. Our data further support the use of ACT to reduce the transmission of drug-resistant malaria parasites.
Oesterholt
Mayke J A M
MJ
Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Alifrangis
Michael
M
Sutherland
Colin J
CJ
Omar
Sabah A
SA
Sawa
Patrick
P
Howitt
Christina
C
Gouagna
Louis C
LC
Sauerwein
Robert W
RW
Bousema
Teun
T
D000818:Animals; D037621:Artemisinins / Q000494:pharmacology; D000077332:Artesunate; D002353:Carrier State / Q000469:parasitology; D002675:Child, Preschool; D004338:Drug Combinations; D004351:Drug Resistance / Q000187:drug effects*; D005493:Folic Acid Antagonists / Q000494:pharmacology*; D005838:Genotype; D005854:Germ Cells / Q000166:cytology* / Q000187:drug effects*; D006801:Humans; D007223:Infant; D007630:Kenya; D016778:Malaria, Falciparum / Q000469:parasitology / Q000628:therapy / Q000635:transmission*; D009154:Mutation / Q000235:genetics; D018512:Parasitemia / Q000469:parasitology; D010963:Plasmodium falciparum / Q000166:cytology* / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D011739:Pyrimethamine / Q000494:pharmacology; D013413:Sulfadoxine / Q000494:pharmacology; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics
D037621:Artemisinins; D004338:Drug Combinations; D005493:Folic Acid Antagonists; C001205:fanasil, pyrimethamine drug combination; D000077332:Artesunate; D013413:Sulfadoxine; D013762:Tetrahydrofolate Dehydrogenase; D011739:Pyrimethamine