Data collection methods and statistical consideration
All accessible aggregates of migrant workers in Kawthaung and Bokepyin townships, totaling 192 aggregates, were invited and agreed to participate in the study and included in the initial migrant mapping. From each aggregate, 20% of respondents were randomly selected for a structured interview. A targeted sample size was 408 respondents in total, with an assumption that 10% of the populations seek EDPT or used ITNs/LLINs within a specified time period, and a marginal error of 5% and 95% confidence level. One adult respondent from each family of participating migrants was consecutively interviewed, until the required sample size was reached. The mapping took about 40 days to cover 192 aggregates, the structured household interview 2–3 aggregates per day and 4–10 households were interviewed per aggregate in randomly selected 39 aggregates.
A mapping team was trained in the study aggregate mapping by the Myanmar Information Management Unit (MIMU) in the geospatial technology. The location of each mobile/migrant aggregate was treated as a spatial unit being marked by GARMIN e-Trex Geographical Positioning System (GPS) devices [13] and illustrated in Geographic Information System (GIS) based satellite maps from MIMU, applying ‘Migrant Mapping Tool’ (a recording form including geo-coordinates of each aggregate; see Additional files 1 and 2) introduced by International Organization of Migration (IOM) in Myanmar. Three to four key informants per aggregate joined the study interview. The interview questionnaires focused on economic activities, estimated population structure, and access to malaria care providers and on the assessment of specific strategies. A total of 408 structured-interviews, including 12 in-depth interviews (IDI), were conducted by using the structured-interview questionnaire that covered household and individual information (see Additional files 1 and 2). The guideline for the IDI was developed by Department of Medical Research (Lower Myanmar).