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Volume 11 Supplement 1

Challenges in malaria research

  • Oral presentation
  • Open Access

Extended malaria parasite clearance time in African children following artemisinin-combination therapy enhances transmission to Anopheles mosquitoes

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Malaria Journal201211 (Suppl 1) :O20

  • Published:


  • Malaria
  • Artemisinin Resistance
  • Uncomplicated Falciparum Malaria
  • Gametocyte Carriage
  • Parasite Clearance Time


Artemisinin resistance was recently shown to have spread or emerged on the Thailand/Myanmar border. Evidence is accumulating that the parasite clearance time after artemisinin-based combination therapy (ACT) is increasing in settings in Asia and Africa. It is currently unknown if an extended parasite clearance time after ACTs has consequences for the individual patient or confers a higher malaria transmission potential.

Methods and findings

298 children in Mbita, Western Kenya, with uncomplicated falciparum malaria were randomized to artemether-lumefantrine(AL, n = 153)ordihydroartemisinin-piperaquine(DP, n = 145). Parasite carriage post-treatment was determined by microscopy and qPCR, gametocyte carriage by quantitative nucleic acid sequence based amplication. Infectiousness to mosquitoes was determined by mosquito membrane feeding assays. Both drugs were efficacious as judged by standard trial outcomes. Sub-patent residual parasitaemia on day 3 was detected by qPCR in 36.11% (95% CI 25.11 - 48.29) of children treated with AL, and in 30.16% (95% CI 19.23 - 43.02) of children treated with DP. After adjustment for age, treatment arm and enrolment parasite density, children with an extended parasite clearance time were significantly more likely to have microscopically detected recurrent parasitaemia during follow-up (Odds Ratio: 19.51, 95% CI 5.24 - 72.71, p < 0.001). Children with an extended parasite clearance time were also more likely to be infectious to mosquitoes (Odds Ratio 2.76; 95% CI 1.14 - 6.67, p = 0.02) and gave rise to a higher oocyst load in mosquitoes (Incidence Rate Ratio 2.80, 95% CI 1.49 - 5.24, p = 0.001).


Our findings indicate that an extended parasite clearance time after ACTs has consequences for the individual patient and for the population at large due to higher transmission potential. The high prevalence of residual sub-patent parasitaemia after treatment may be due to novel parasite genotypes with reduced drug sensitivity, inadequate population-level immunity, or the higher sensitivity of qPCR for detection of persisting parasites.

Authors’ Affiliations

Department of Infection & Immunity, London School of Hygiene and Tropical Medicine, London, UK
Human Health Division, International Centre for Insect physiology and Ecology, Mbita Point, Kenya
Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
Kenya Medical Research Institute, Nairobi, Kenya
Kilimanjaro Clinical Medical Research Institute, Kilimanjaro Christian Medical Centre, Moshi, Tanzania
Ifakara Health Institute, Bagamoyo, Tanzania
KIT Biomedical Research, Royal Tropical Institute, Amsterdam, The Netherlands


© Beshir et al; licensee BioMed Central Ltd. 2012

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


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