Respondent-driven sampling on the Thailand-Cambodia border. I. Can malaria cases be contained in mobile migrant workers?

Abstract

BackgroundReliable information on mobility patterns of migrants is a crucial part of the strategy to contain the spread of artemisinin-resistant malaria parasites in South-East Asia, and may also be helpful to efforts to address other public health problems for migrants and members of host communities. In order to limit the spread of malarial drug resistance, the malaria prevention and control programme will need to devise strategies to reach cross-border and mobile migrant populations.MethodologyThe Respondent-driven sampling (RDS) method was used to survey migrant workers from Cambodia and Myanmar, both registered and undocumented, in three Thai provinces on the Thailand-Cambodia border in close proximity to areas with documented artemisinin-resistant malaria parasites. 1,719 participants (828 Cambodian and 891 Myanmar migrants) were recruited. Subpopulations of migrant workers were analysed using the Thailand Ministry of Health classification based on length of residence in Thailand of greater than six months (long-term, or M1) or less than six months (short-term, or M2). Key information collected on the structured questionnaire included patterns of mobility and migration, demographic characteristics, treatment-seeking behaviours, and knowledge, perceptions, and practices about malaria.ResultsWorkers from Cambodia came from provinces across Cambodia, and 22% of Cambodian M1 and 72% of Cambodian M2 migrants had been in Cambodia in the last three months. Less than 6% returned with a frequency of greater than once per month. Of migrants from Cambodia, 32% of M1 and 68% of M2 were planning to return, and named provinces across Cambodia as their likely next destinations. Most workers from Myanmar came from Mon state (86%), had never returned to Myanmar (85%), and only 4% stated plans to return.ConclusionInformation on migratory patterns of migrants from Myanmar and Cambodia along the malaria endemic Thailand-Cambodian border within the artemisinin resistance containment zone will help target health interventions, including treatment follow-up and surveillance.

Cross-Border Malaria: A Major Obstacle for Malaria Elimination

“…Economic migration is exacerbated when there are substantial differences in the economic development and job opportunities in neighbouring countries. For instance, economic stagnation in Myanmar and rapid economic development in Thailand have stimulated migration from Myanmar to Thailand (Carrara et al, 2013;Delacollette et al, 2009;Huguet and Punpuing, 2005;Khamsiriwatchara et al, 2011;Wangroongsarb et al, 2012), while temporary migration of seasonal workers from Cambodia to Thailand seems to be a key factor responsible for the malaria problem along the CambodianeThailand border (Hoyer et al, 2012;Kitvatanachai et al, 2003). It is estimated that 50e70% of all reported malaria cases in Argentina are linked to migration, in particular movement across the border from Bolivia; this migration is fuelled by economic growth on the Argentine side and is not well controlled due to a porous border between the two countries .…”

“…border crossings versus cross-border migrations) (Khamsiriwatchara et al, 2011). For example, migrations across the international borders of Yunnan Province, China, which shares >4000 km of border with Myanmar, Lao People's Democratic Republic (PDR) and Vietnam, take place unchecked (Hu et al, 1998;Clements et al, 2009).…”

“…For example, pilot trials of cross-border malaria control at the ThaieMyanmar and Chinesee Myanmar border areas suggest that organized control in these areas is feasible (Richards et al, 2009). Frequent population movements (every three months) across the Thai-Cambodia border and from the border area across Cambodia indicate the need for heightened surveillance for artemisinin resistance outside what has been designated as the containment zone (Khamsiriwatchara et al, 2011). Obviously, such cross-border activities demand coordination of governments between the neighbouring nations.…”

Using Respondent Driven Sampling to Identify Malaria Risks and Occupational Networks among Migrant Workers in Ranong, Thailand

“…In October 2009, an RDS study on migrant workers was carried out in Thailand along the Thai-Cambodia border and later a similar study was implemented in Cambodia to better understand internal migration patterns in two provinces on the border in the context of artemisinin resistance [10,11]. While there have been some studies along the northern stretch of the Thailand-Myanmar border [12–14], relatively little is known about migration along the southern portion of the border, which is believed to be a significant port of entry for many migrants from Myanmar.…”

Collecting data from migrants in Ghana: Lessons learned using respondent-driven sampling

“…Though four of the five most common countries for RDS studies are classified as LMIC, the use of RDS in migration research is often restricted to sampling hard-to-reach international migrant populations in high-income countries . There is a small but growing body of evidence that uses RDS to sample migrants in lower-middle income countries (e.g., Ukraine, Morocco, Kenya) and upper-middle income countries (e.g., South Africa, China, Thailand) (International Organization for Migration 2010; Khamsiriwatchara et al 2011;Tyldum and Johnston 2014;Okal 2016). In the limited evidence on the use of RDS for migrant populations outside of high-income countries, there is little detailed methodological reflection -either positive or negative -on the suitability of this technique for migrant populations in LMIC settings and the lessons learned.…”