Molecular surveillance of drug-resistance associated mutations of Plasmodium falciparum in south-west Tanzania

Background In Tanzania, drug-resistant malaria parasites are an increasing public health concern. Because of widespread chloroquine (CQ) resistance Tanzania changed its first line treatment recommendations for uncomplicated malaria from CQ to sulfadoxine-pyrimethamine (SP) in 2001. Loss of SP sensitivity is progressing rapidly. SP resistance is associated with mutations in the dihydrofolate reductase ( pfdhfr ) and dihydropteroate synthase ( pfdhps ) genes. Methods In samples from 86 patients with uncomplicated Plasmodium falciparum malaria from Mbeya and Matema, Mbeya region, south-western Tanzania, the occurrence of mutations was investigated in the pfcrt and pfmdr1 genes which are associated with CQ resistance and in pfdhfr and pfdhps , conferring SP resistance, as well in cytb which is linked to resistance to atovaquone. Results Pfcrt T76 occurs in 50% and pfmdr1 Y86 in 51.7%. Pfdhfr triple mutations coexisting with pfdhps double mutations were detected in 64.3% of the P. falciparum isolates. This quintuple mutation is seen as a possible predictive molecular marker for SP treatment failure. Mutations of the cytb gene were not detected. Conclusion These findings of a high prevalence of mutations conferring SP resistance correspond to data of in vivo SP efficacy studies in other regions of Tanzania and underline the recommendation of changing first-line treatment to artemisinin-based combination therapy.