Dhfr and dhps mutations in Plasmodium falciparum isolates in Mlandizi; Kibaha; Tanzania: association with clinical outcome

Sulfadoxine-pyrimethamine (SP); the current first line antimalarial drug in Tanzania; is compromised by evolution and spread of mutations in the parasite's dhfr and dhps genes. In the present study we established the baseline frequencies of Plasmodium falciparum dihydrofolate reductase (pfdhfr) and dihydropteroate synthase (pfdhps) mutant genotypes and their potential for predicting the in vivo efficacy of SP in Mlandizi; Tanzania. The efficacy of SP treatment was by following 116 children with uncomplicated falciparum malaria for 14 days after treatment. Infected blood samples were collected on filter paper at days 0; 3; 7 and 14. Parasite genomic DNA was extracted and point mutations at positions 51; 59; 108 and 164 of the dhfr gene and at 581; 540 and 437 of the dhps gene were analysed by nested Polymerase Chain Reaction/ Restriction Fragment Length Polymorphism. Out of 116 children enrolled; 98 (86) of eligible children demonstrated an adequate clinical response by day 14. There were 7.3early and 6.7late therapeutic failures. At day 0; only 8.0(4/50) the parasites showed no mutation at the dhfr locus; for dhps this was 73. Triple mutant dhfr alleles (Ile 51; Arg 59; Asn 108) occurred in 47; double mutant dhps (Gly 437; Glu 540) alleles in 7.9. No mutation was detected at codon 164 of the dhfr gene. The presence of triple dhfr mutant alleles was related to clinical failure; but did not show significant association (Fisher exact test; P=0.166; OR 2.15 0.77OR6.20). The higher rates of mutation on the dhfr do not spell a bright future for SP treatment in Tanzania. It is rational to think of an alternative first line antimalarial drug; while retaining SP for malaria intermittent treatment in pregnancy

Molecular monitoring of parasite resistance to artemisinin in Tanzania

Artemisinin-based combination therapies (ACTs) are recommended for use against uncomplicated malaria in areas of multi-drug resistant malaria; such as sub-Saharan Africa. However; their long-term usefulness in these high transmission areas remains unclear. It has been suggested that documentation of the S769N PfATPase6 mutations may indicate an emergence of artemisinin resistance of Plasmodium falciparum in the field. The present study assessed PfATPase6 mutations (S769N and A623E) in 615 asymptomatic P. falciparum infections in Tanzania but no mutant genotype was detected. This observation suggests that resistance to artemisinin has not yet been selected in Tanzania; supporting the Ministry of Healths decision to adopt artemether+lumefantrine as first-line malaria treatment. The findings recommend further studies to assess PfATPase6 mutations in sentinel sites and verify their usefulness in monitoring emergency of ACT resistance