Abstract:
BACKGROUND : The ability of Plasmodium falciparum parasites to develop resistance to widely used anti-malarials
threatens malaria control and elimination efforts. Regular drug efficacy monitoring is essential for ensuring effective
treatment policies. In low transmission settings where therapeutic efficacy studies are often not feasible, routine
surveillance for molecular markers associated with anti-malarial resistance provides an alternative for the early detection
of emerging resistance. Such a longitudinal survey of changes in the prevalence of selected molecular markers
of resistance was conducted in the malaria-endemic regions of Mpumalanga Province, South Africa, where malaria
elimination at a district-level is being pursued.
METHODS : Molecular analyses to determine the prevalence of alleles associated with resistance to lumefantrine
(mdr86N, crt76K and mdr1 copy number variation) and sulfadoxine–pyrimethamine (dhfr triple, dhps double, SP
quintuple) were conducted between 2001 and 2018, while artemisinin resistance markers (kelch13 mutations) were
assessed only in 2018.
RESULTS : Parasite DNA was successfully amplified from 1667/2393 (70%) of malaria-positive rapid diagnostic tests
routinely collected at primary health care facilities. No artemisinin resistance-associated kelch13 mutations nor amplification
of the mdr1 gene copy number associated with lumefantrine resistance were observed. However, prevalence
of both the mdr86N and crt76K alleles increased markedly over the study period, with all isolates collected in 2018
carrying these markers. SP quintuple mutation prevalence increased steadily from 14% in 2001 to 96% in 2018. Mixed
alleles at any of the codons assessed were rare by 2018.
CONCLUSION : No kelch13 mutations confirmed or suspected to be associated with artemisinin resistance were
identified in 2018. Although parasites carrying the mdr86N and crt76K alleles associated with reduced lumefantrine
susceptibility were strongly selected for over the study period, nearing fixation by 2018, the marker for lumefantrine
resistance, namely increased mdr1 copy number, was not observed in this study. The increase in mdr86N and crt76K
