Sociodemographic and behavioral determinants of Plasmodium vivax-specific antibody responses among short-term Myanmar migrants in Thailand.

BACKGROUND

Migrant populations from malaria-endemic countries pose challenges to elimination efforts in low-transmission settings. This study assessed Plasmodium vivax-specific antibody responses and associated sociodemographic and behavioral determinants among short-term Myanmar migrants in Thailand.

METHODS

A cross-sectional survey was conducted in March-April 2025 among 300 short-term Myanmar migrants in six malaria high-burden villages of Tha Song Yang District, Tak Province. Sociodemographic and behavioral data were collected via structured questionnaires. Finger-prick dried blood spots were collected to quantify IgG responses to eight P. vivax antigens using a multiplexed Luminex assay. Predicted recent exposure was defined using a previously developed and validated random forest classification algorithm, applying a 95% specificity threshold. Logistic regression models were used to identify factors associated with predicted recent exposure, while linear regression models examined associations with a composite antibody score representing overall seroreactivity across multiple antigens.

RESULTS

Among 294 PCR-negative participants, 104 (35.4%) were predicted as recently exposed. In multivariable logistic models, higher odds of predicted recent exposure were observed for age 30-39 years (aOR = 3.11, 95% CI 1.15-8.80), secondary education or above (aOR = 3.28, 95% CI 1.09-10.3), and Karen ethnicity (aOR = 3.68, 95% CI 1.42-10.0). Protective factors included seasonal (aOR = 0.28, 95% CI 0.08-0.95) and temporary work (aOR = 0.26, 95% CI 0.08-0.84), and income > 5,000 THB (aOR = 0.17, 95% CI 0.06-0.45). Exposure was also higher among those living > 15 min from a health facility (aOR = 2.07, 95% CI 1.00-4.43) and with negative malaria attitudes (aOR = 2.02, 95% CI 1.04-4.03). Higher composite antibody levels were observed among males (β = 1.17, 95% CI 0.07-2.28, p = 0.038), older participants (β = 0.12/year, 95% CI 0.08-0.17, p < 0.001), and agricultural workers (β = 2.58, 95% CI 0.01-5.14, p = 0.049). In contrast, higher income (β = - 3.83 per 10,000 THB, 95% CI - 6.28 to - 1.37, p = 0.002), longer stay (β =  - 0.02/day, 95% CI - 0.04 to - 0.00, p = 0.025), and weekly returns to Myanmar (β = - 2.44, 95% CI - 4.14 to - 0.74, p = 0.005) were associated with lower antibody levels.

CONCLUSIONS

Among PCR-negative short-term migrants, one-third showed evidence of predicted recent P. vivax exposure. Antibody levels varied by demographic, occupational, and mobility-related factors, supporting the use of sero-surveillance to inform border elimination strategies.