Reducing malaria transmission in forest-going mobile and migrant populations in Lao PDR and Cambodia: protocol for stepped-wedge cluster-randomised controlled trial | BMC Infectious Diseases

This study has three components – a randomized controlled open-wedge trial to evaluate the effectiveness of the personal protection package in reducing the prevalence of plasmodium sp. Infection in MMPs entering the forest and individuals in their residential villages; a mixed-methods study to examine the acceptability of a personal protection package, the feasibility of implementing a personal protection package as a vector control intervention, and MMPs’ knowledge, attitude, and practice related to malaria prevention; and cost analysis to determine the cost-effectiveness of implementing a personal protection package. The main text of this paper focuses on the study with other study components and data collection tools described in Supplementary File 1.


The intervention in the experiment is a personal protection package to be used by the forestry MMPs for prevention plasmodium sp. Infection. The package was developed in consultation with relevant implementing partners: National Malaria Programs: Cambodia National Center for Parasitology, Entomology and Malaria Control and Laos Center of Malariology, Parasitology and Entomology; and NGOs: Health Poverty Action (HPA), PEDA and CHIAs in Cambodia and Laos.

The intervention package includes three items – a WHO pre-qualified long-life insecticidal hammock net (LLIHN) (high-density polyester monofilament yarn mixed with 2% (w/w) permethrin), two bottles of insect repellent (1-piperidinecarboxylic acid 2-(2-hydroxyethyl)-1- methylpropyl ester, also known as icaridin) and a health communication brochure tailored to MMP. In addition to the booklet, behavior change communication will also be provided in the form of group health communication sessions and health communication posters placed at or near the MMP’s workplaces. The intervention package is distributed through the Malaria Volunteers run by the implementing partners.


The primary outcome of this study is the prevalence of plasmodium sp. Infection diagnosed by rapid diagnostic test (RDT). Secondary findings from this study include symptomatic malarial infection diagnosed by RDT, plasmodium sp. infection determined by polymerase chain reaction (PCR), plasmodium sp. Infections with drug resistance mutations, prevalence and levels of antibodies against plasmodium sp. and mosquito saliva antigens (Table 1).

Table 1 Outcome measurements of the study

result collection plan

Data required to determine the primary endpoint of the study, plasmodium sp. Infection diagnosed by RDT and secondary outcome 2A (Table 1) are recorded by malaria volunteers in their routine malaria case registry, a standardized form developed and used by implementation partners. When a person presents to a malaria volunteer for an RDT for malaria, they are asked to put an additional two drops of blood on a piece of filter paper. Immediately before receiving the RDT test from the malaria volunteer, bloodstains are collected on filter paper from all approved individuals.

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Whenever possible, used RDT cassettes and dried bloodstains will be saved and stored to extract DNA and antibodies to determine secondary results 2B, 2C, 2D, 2E, 2F and 2G using PCR and ELISA methods as previously described [16, 19,20,21].

Study environment and population

Villages and workplaces in malaria-endemic areas in Cambodia (Preah Vihear, Stung Treng and Ratanakiri provinces) and Laos (Attapeu, Cahmpasack, Khammouane, Saravanh and Savannakhet provinces) are included in this experiment (Fig. 1). The participants will be forest-walking MMPs [11] These include traditional slash-and-burn and paddy farming communities, seasonal farm workers, informal sector forest workers, transient or mobile camp residents associated with commercial projects (road/pipeline construction, large-scale logging, etc.), and formal and informal frontier workers.

Fig. 1
illustration 1

Map of study areas (map generated with the tmap package in R version 3.6.1 using basemaps from the GADM database of global administrative areas version 2.8. URL:

Eligibility Criteria

Provinces included in the trial were selected based on the presence of a malaria volunteer network in the province, the capacity of implementing partners for field implementation, high malaria burden, and high MMP activity.

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Implementing Partner-managed villages/workplaces in the selected provinces will be screened by Implementing Partner investigators and staff against the following exclusion criteria. A village/site is excluded from the study if it: (1) has no malaria cases or an annual parasite incidence of less than 1 in any of the last three years (2018-2020), (2) has no MMPs, (3) does not have a malaria volunteer actively working in the village/workplace, (4) has a government health facility for malaria services, or (5) has another malaria volunteer program run by organizations other than the implementing partners.

After the village/site is selected, the MMPs are included in the study for receiving the intervention (ie personal protection package) with the following criteria: (1) they currently live in the selected villages/worksites and (2) there are of the following types of workers – traditional slash-and-burn and paddy farming communities who visit their forest farms (usually ethnic minorities), seasonal agricultural workers, informal sector forest workers (hunters, small-scale gemstone/gold miners, people who collect forest products (precious timber, lumber, rattan /bamboo), temporary or mobile camp residents involved in commercial projects (road/pipeline construction, large-scale logging, deep-sea port projects, etc.) border migrants.

Study design and sample

The study design for the study component of this study is an open-wedge, cluster-randomized controlled trial, randomized at village/workplace level, conducted over a 12-month period after a one-month baseline period (Fig. 2). . The study will be conducted between March 2022 and February 2023. The Personal Protection Package for MMPs will be implemented sequentially in at least 488 villages served by approximately 488 Village Malaria Workers (~428 in PDR Laos and ~60 in Cambodia). Villages from each country are randomized into 11 blocks, with the blocks transitioning from control (no personal protection package) to intervention (with personal protection package) states in random order at monthly intervals (10 blocks of 44 villages for the first 10 steps and a block of 48 villages , which were converted in the last step). All eligible MMPs in the participating villages will receive the intervention during the study, but the month in which they transition from a control to intervention state will be randomized.

Fig. 2
figure 2

Timetable for the phased implementation of the personal protection package in the selected villages

study power

It is estimated that approximately 11 RDTs will be performed per month at each study site (village/site), giving an approximate total of 64,416 RDT tests over 12 months. Given this sample size, the study will be able to demonstrate a minimal relative reduction of 34% in the probability (OR=0.66) of RDT-detectable malaria infection attributable to the intervention (assuming within-village correlation).[ICC]= 0.42 [16]; 5% significance; 90% performance and 1% RDT malaria prevalence). Performance estimation was based on estimating an intervention effect using experimental data from a stepwedge cluster randomized design assuming generalized linear mixed modeling (GLMM) analysis.

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data analysis

Data entry is managed in a REDCap database developed by the Burnet Institute. Both descriptive and primary outcome study analyzes will be performed for the graded wedge cluster randomized study. To assess the effectiveness of personal protection package distribution, the difference in malaria infection prevalence across the intervention and control periods is estimated using GLMM (logit link function and binomial distribution) crossed with time-dependent fixed factors for intervention status and time Implemented random village and time effects to account for the inherent dependencies of the data given the step wedge design. We will also examine any village-specific heterogeneity in effect by specifying a random effect for the intervention and the extent to which the intervention’s effectiveness is time-dependent. Model terms for countries (main and interaction effects) are added to GLMM and used to assess the extent of country-specific heterogeneity of the intervention effect. Analysis of secondary outcomes also includes multilevel modeling (ie linear mixed modeling (LMM) and GLMM). The statistical analysis is performed with Stata version 17.

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