Single low dose primaquine to reduce gametocyte carriage and Plasmodium falciparum transmission after artemether-lumefantrine in children with asymptomatic infection: a randomised, double-blind, placebo-controlled trial

Abstract

BackgroundA single low dose (0.25 mg/kg) of primaquine is recommended as a gametocytocide in combination with artemisinin-based combination therapies for Plasmodium falciparum but its effect on post-treatment gametocyte circulation and infectiousness to mosquitoes has not been quantified.MethodsIn this randomised, double-blind, placebo-controlled trial, 360 asymptomatic parasitaemic children aged 2-15 years were enrolled and assigned to receive: artemether-lumefantrine (AL) and a dose of placebo; AL and a 0.25 mg/kg primaquine dose; or AL and a 0.40 mg/kg primaquine dose. On days 0, 2, 3, 7, 10 and 14, gametocytes were detected and quantified by microscopy, Pfs25 mRNA quantitative nucleic acid sequence based amplification (QT-NASBA), and quantitative reverse-transcriptase PCR (qRT-PCR). For a subset of participants, pre- and post-treatment infectiousness was assessed by mosquito feeding assays on days -1, 3, 7, 10 and 14.ResultsBoth primaquine arms had lower gametocyte prevalences after day 3 compared to the placebo arm, regardless of gametocyte detection method. The mean (95 % confidence interval) number of days to gametocyte clearance in children with patent gametocytes on day 0 (N = 150) was 19.7 (14.6 – 24.8), 7.7 (6.3 – 9.1) and 8.2 (6.7 – 9.6) for the AL-placebo, the 0.25 mg/kg primaquine dose and the 0.40 mg/kg primaquine dose arms, respectively. While 38.0 % (30/79) of selected gametocytaemic individuals were infectious before treatment, only 1/251 participant, from the AL-placebo group, infected mosquitoes after treatment.ConclusionsWe observed similar gametocyte clearance rates after 0.25 and 0.40 mg/kg primaquine doses. Infectivity to mosquitoes after AL was very low and absent in primaquine arms.ClinicalTrials.gov RegistrationNCT01935882Electronic supplementary materialThe online version of this article (doi:10.1186/s12916-016-0581-y) contains supplementary material, which is available to authorized users.

Comparison of molecular quantification of Plasmodium falciparum gametocytes by Pfs25 qRT-PCR and QT-NASBA in relation to mosquito infectivity

“…Blood samples from patent gametocyte carriers were collected during clinical trials in Mali and Burkina Faso [20, 21]. In the study undertaken in Mali, male participants with at least 32 gametocytes per μL of blood based on gametocyte enumeration against 500 white blood cells (WBC), assuming 8000 WBCs/µL, were recruited.…”

“…The study in Burkina Faso was approved by the London School of Hygiene and Tropical Medicine ethics committee, and the Comité d’Ethique pour la Recherche en Santé (Ministère de la Santé du Burkina Faso) and was registered with ClinicalTrials.gov, Number NCT01935882 [21]. …”

Microorganism-mediated behaviour of malaria mosquitoes

“…Treatment of malaria in all endemic countries in the world is mainly by artemisinin-lumefantrine, which kills all stages of malaria parasites (WHO, 2015b;Gonçalves et al, 2016).…”

“…The 18S qPCR was run in duplicate and the average value of the two runs was used in the analyses. Mature gametocytes were detected by NASBA on the Pfs25 mRNA gene , with a slight modification in the potassium chloride concentration used: 60 instead of 80 mM as described in Gonçalves et al (2016), using the NucliSens Basic Kit for amplification, in a total reaction volume of 10 µL per reaction.…”

“…Infected children had acquired the infection naturally. Attractiveness of all children was tested again three weeks after antimalarial treatment with artemisininlumefantrine, which rapidly clears asexual parasites and also has a pronounced effect on posttreatment gametocyte prevalence and density (Gonçalves et al, 2016;WWARN, 2016).…”