Procedures
vivax, fever, malaria, vomiting, malaria infection
MALARIA, MALARIA, DRUG ALLERGIES
Before initiation of the study, a series of community sensitisation and engagement activities were conducted in villages. Information focused on the concepts of chemoprophylaxis, malaria transmission, and exposure to mosquitos in forests. Engagement activities included meetings conducted by a dedicated community engagement team led by staff fluent in Khmer and local languages, supported by the district health department, administrative authorities, village malaria workers, and village leaders. Details of community engagement and acceptability have been published separately.At baseline, basic demographic and epidemiological data were collected. A physical examination and a symptom questionnaire were completed by qualified study staff. All prescribed medications used within the previous 7 days and a history of any drug allergies were recorded. An RDT for the detection of malaria was performed for participants with fever or a history of fever in the previous 24 h. Volunteers who tested positive were excluded and received standard antimalarial treatment from the village malaria worker.Together with the National Center for Parasitology, Entomology and Malaria Control (Phnom Penh, Cambodia), artemether–lumefantrine was chosen as the study intervention, to be compared with a multivitamin (with no antimalarial effect) in the control group of the trial. Artemether–lumefantrine was obtained as Coartem from Novartis Saglik, Istanbul, Turkey (batch: KP663; manufacture date: August, 2019; expiry date: July, 2021). Each tablet contained 20 mg of artemether and 120 mg of lumefantrine. The multivitamin used in the trial was NANPROVIT-TAB, composed of vitamin A (retinol; 2500 IU), vitamin D3 (200 IU), vitamin B1 hydrochloride (thiamine; 5 mg), vitamin B2 (2 mg), vitamin B6 hydrochloride (pyridoxine; 2 mg), nicotinamide (4 mg), vitamin C (30 mg), and calcium pantothenate (1 mg), and was manufactured by Chea Chamnan Laboratoire, Phnom Penh, Cambodia (lot number: 200847). Participants received either two doses of artemether–lumefantrine (four tablets per dose) or two doses of multivitamin (one tablet per dose) per day for 3 days initially, followed by the same daily dosing once a week while travelling in the forest and for a further 4 weeks after leaving the forest. The first dose of study drugs was administered as directly observed therapy (DOT) by trained study staff. For this first dose, the full dose or a half dose of the study drug was repeated in case of vomiting within 30 min or 60 min, respectively. Participants were informed that the multivitamin had no antimalarial effect, and all were encouraged to continue to use other measures to protect themselves against malaria throughout. Subsequent doses were administered as so-called smart DOT, whereby intake was observed by a dedicated volunteer within the group of forest goers.Participants were followed up between days 28 and 35 (1 month), between days 56 and 63 (2 months), and between days 84 and 91 (3 months)—ie, after each of three consecutive periods of 28 days plus a 7-day window. During follow-up, data were collected on duration of stay and locations visited in the forest, purpose of forest visits, accompanying forest goers, and potential risk factors for malaria infection. Brief physical examinations were performed, including aural temperature, and a symptom questionnaire was completed during each follow-up visit by qualified staff members. Participants were asked to report any diagnostic tests or treatment for malaria since the last follow-up visit. In case participants declared at the time of the follow-up visit no intention to return to the forest in the coming 4-week period, no further follow-up visits were scheduled, but 4 weeks of terminal chemoprophylaxis following their last day in the forest were completed. For those who declared an intention to return to the forest, they continued in the study for another period of 28 days up to a maximum of three periods.Passive surveillance of clinical malaria continued throughout the study period, and records from local treatment providers were collected routinely. For participants who had an episode of RDT-confirmed clinical malaria at any time after enrolment up to the last follow-up visit, dried blood spots (three spots, 200 μL for each spot) for parasite DNA were collected on Whatman filter paper (Cytivia, Marlborough, MA, USA) by the village malaria worker. Laboratory procedures were the same as for baseline blood spot samples described below. Participants with malaria were treated by the village malaria worker in accordance with Cambodian malaria treatment guidelines (artesunate–mefloquine for both vivax and falciparum malaria).Dried blood spots (three 200 μL spots) were collected on Whatman filter paper from finger pricks for parasite PCR from all participants at baseline, immediately before drug administration, and at each follow-up visit. Samples were stored in a plastic ziplock bag with silica gel and were sent to the Molecular Tropical Medicine Laboratory at Mahidol Oxford Tropical Medicine Research Unit, Bangkok, Thailand. Parasite DNA was extracted using the QIAmp DNA Mini Kit (Qiagen, Hilden, Germany) following the manufacturer's instructions. For For assessment of study drug adherence in 43 randomly selected study participants who received artemether–lumefantrine, a 1 mL venous blood sample was collected in pre-chilled heparin tubes at the 4th, 8th, and 12th week follow-up visits for assessment of plasma lumefantrine concentrations. Allowing for anticipated loss to follow-up, this method would provide 100 samples for analysis. This testing was feasible only in villages in which pre-chilled heparin tubes could be used during follow-up. Randomisation was done by computer using the list of enrolled individuals in these villages. Samples were transported back on ice to the local laboratory for centrifugation at 2000 g for 7 min, after which 0·5 mL plasma was obtained and stored in liquid nitrogen. Plasma samples were sent on dry ice to the Pharmacology Laboratory at Mahidol Oxford Tropical Medicine Research Unit, Bangkok, Thailand, for measurement of lumefantrine concentrations using published methods.