BackgroundMalaria control in sub-Saharan Africa relies upon prompt case management with artemisinin-based combination therapy (ACT). Ring-stage parasites, measured by sbp1 quantitative reverse-transcriptase PCR (qRT-PCR), were previously reported to persist after ACT treatment and hypothesized to reflect temporary arrest of the growth of ring-stage parasites (dormancy) following exposure to artemisinins. Here, the persistence of ring-stage parasitemia following ACT and non-ACT treatment was examined. MethodsSamples were used from naturally infected Malian gametocyte carriers who received dihydroartemisinin-piperaquine (DP) or sulfadoxine-pyrimethamine (SP-AQ) with or without gametocytocidal drugs. Gametocytes and ring-stage parasites were quantified by qRT-PCR during 42 days of follow-up. ResultsAt baseline, 89% (64/73) of participants had measurable ring-stage parasites. Following treatment, the proportion of ring-stage parasite-positive individuals and ring-stage parasite densities declined for all four treatment groups. Participants who received DP had 81% lower post-treatment ring-stage parasite density compared to participants who received SP-AQ (pday 14=0.011 and pday 28=0.068). No association of ring-stage persistence with gametocyte carriage was observed. Conclusions Our findings of lower ring-stage persistence after ACT treatment without an effect of gametocytocidal partner drugs affirms the use of sbp1 as ring-stage marker. Lower persistence of ring-stage parasites after ACT treatment suggests the marker may not reflect dormant parasites whilst it was predictive of re-appearance of parasitemia.
