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Malaria Journal

, 16:56

First Online: 31 January 2017Received: 27 November 2016Accepted: 19 January 2017DOI: 10.1186-s12936-017-1703-5

Cite this article as: Tripura, R., Peto, T.J., Veugen, C.C. et al. Malar J 2017 16: 56. doi:10.1186-s12936-017-1703-5


BackgroundCambodia has seen a marked reduction in the incidence of Plasmodium falciparum over the past decade without a corresponding decline in Plasmodium vivax incidence. It is unknown to what extent local transmission is sustained by a chain of clinical and sub-clinical infections or by continued re-introduction via migration. Using an ultrasensitive molecular technique, 20 villages in western Cambodia were surveyed to detect the low season prevalence of P. falciparum and P. vivax and local treatment records were reviewed.

MethodsDuring March to May 2015 cross-sectional surveys were conducted in 20 villages in Battambang, western Cambodia. Demographic and epidemiological data and venous blood samples were collected from 50 randomly selected adult volunteers in each village. Blood was tested for Plasmodium infections by rapid diagnostic test RDT, microscopy and high volume 0.5 ml packed red blood cell quantitative polymerase chain reaction uPCR. Positive samples were analysed by nested PCR to determine the Plasmodium species. Malaria case records were collected from the Provincial Health Department and village malaria workers to determine incidence and migration status.

ResultsAmong the 1000 participants, 91 9.1% were positive for any Plasmodium infection by uPCR, seven 0.7% by microscopy, and two 0.2% by RDT. uPCR P. vivax prevalence was 6.6%, P. falciparum 0.7%, and undetermined Plasmodium species 1.8%. Being male adjusted OR 2.0; 95% CI 1.2-3.4; being a young adult <30 years aOR 2.1; 95% CI 1.3–3.4; recent forest travel aOR 2.8; 95% CI 1.6–4.8; and, a history of malaria aOR 5.2; 95% CI 2.5–10.7 were independent risk factors for parasitaemia. Of the clinical malaria cases diagnosed by village malaria workers, 43.9% 297-634 and 38.4% 201-523 were among migrants in 2013 and in 2014, respectively. Plasmodium vivax prevalence determined by uPCR significantly correlated with vivax malaria incidences in both 2014 and 2015 p = 0.001 and 0.002, respectively, whereas no relationship was observed in falciparum malaria p = 0.36 and p = 0.59, respectively.

DiscussionThere was heterogeneity in the malaria parasite reservoir between villages, and Plasmodium prevalence correlated with subsequent malaria incidence. The association was attributable chiefly to P. vivax infections, which were nine-fold more prevalent than P. falciparum infections. In the absence of a radical cure with 8-aminoquinolines, P. vivax transmission will continue even as P. falciparum prevalence declines. Migration was associated with over a third of incident cases of clinical malaria.

Trial registration NCT01872702. Registered 4 June 2013

KeywordsMalaria Plasmodium Falciparum Plasmodium vivax Asymptomatic Sub-clinical Sub-microscopic uPCR Cambodia AbbreviationsACTartemisinin-based combination therapy

DHA-PQPdihydroartemisinin–piperaquine phosphate

EDTAethylenediaminetetraacetic acid

ITNsinsecticide-treated bed nets

MDAmass drug administration

nested PCRnested polymerase chain reaction

uPCRultrasensitive polymerase chain reaction

VMWsvillage malaria workers

Rupam Tripura and Thomas J. Peto contributed equally to this work

Electronic supplementary materialThe online version of this article doi:10.1186-s12936-017-1703-5 contains supplementary material, which is available to authorized users.

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Autor: Rupam Tripura - Thomas J. Peto - Christianne C. Veugen - Chea Nguon - Chan Davoeung - Nicola James - Mehul Dhorda - Richa


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