Pyae Linn Aung

Background Zoonotic malaria caused by Plasmodium knowlesi poses a growing threat to malaria elimination. In Thailand, Ranong Province reports the highest incidence nationally, yet the role of long-tailed macaques ( Macaca fascicularis ) as reservoir hosts across heterogeneous landscapes remains poorly characterized. Methods We describe a prospective, multidisciplinary study on Ko Chang using a spatial grid-cell framework, with dominant land-use type assigned per cell. We will produce a fine-scale land-use classification by combining satellite data with ground-truth observations, distinguishing easily confused land-use types, such as plantations and forest, and addressing the misclassification common in conventional datasets. Audio recording devices and camera traps will be deployed across the landscape and over time to measure macaque and, human presence across land-use classes. Household questionnaires will characterise human exposure. Existing P. knowlesi case records (2013–2024) and entomological data (2011–2022) will be integrated within a unified spatial framework to estimate land-use-specific exposure. Satellite imagery will be classified into land-use types using supervised learning model. Macaque detections will be summarised as a relative abundance index and modelled in an occupancy framework to estimate the probability of site use. Human distribution and movement will be derived from interviews, camera-trap and acoustic detections. Macaque and human abundance, with secondary entomological data, will be assigned to land-use classes as inputs to a population-attributable risk (PAR) model. These land-use-explicit abundance estimates will then be combined with zoonotic malaria prevalence from the literature as inputs to a transmission-dynamics model. Expected outcome is a fine-scale land-use map of Ko Chang; land-use-explicit estimates of macaque and human site use and relative abundance; land-use-specific estimates of population-attributable risk and transmission parameters. Conclusion This study will generate fine-scale, ground-validated landscape and reservoir-host–vector data, improving understanding of how macaque movement, human exposure, and land-use change drive spillover risk, and informing targeted interventions.

EXCLI Journal - Experimental and Clinical Sciences, International Online Journal for Advances in Sciences

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.

Background: Plasmodium knowlesi poses an emerging challenge for malaria control in Southeast Asia due to its zoonotic nature, diagnostic complexity and lack of species-specific control strategies. These factors complicate both prevention and case management efforts. Understanding both community awareness and healthcare provider perspectives is critical for informing targeted responses. This study aimed to assess awareness of P. knowlesi malaria among at-risk community members in southern Thailand and to explore contextual challenges through qualitative insights from healthcare providers, including provincial officers, district-based malaria control staff, and village health volunteers. Methods: An explanatory sequential mixed-methods design was employed between April and May 2025. A cross-sectional survey of 300 adults residing in three P. knowlesi -endemic districts was conducted using a structured questionnaire that included eight items assessing overall awareness. Descriptive statistics, violin plots, and multivariable generalized linear modeling were used to identify factors associated with awareness scores. Subsequently, semi-structured interviews were conducted with 28 healthcare providers across various administrative levels. Qualitative data were thematically analyzed. Results: Overall awareness of P. knowlesi malaria was moderate (mean score: 10.7/23; SD ± 2.9; range: 3.0–20.0). Female individuals, living farther from health facilities, receiving malaria-related health education, and having higher attitude scores were significantly associated with increased awareness ( p < 0.05). Healthcare providers reported a decline in P. knowlesi incidence, alongside persistent transmission risks in forested areas. Health education efforts were largely reactive, delivered following case detection, but often included information about monkey-to-human transmission. Conclusions: Awareness of P. knowlesi malaria remains suboptimal among high-risk populations, particularly among men, those who had received limited health education, and individuals with poor attitudes toward malaria. Integrated, proactive, and male-focused health promotion strategies are essential to enhance community knowledge and support disease control efforts.

Background: Asymptomatic, low-density Plasmodium vivax infections pose a significant challenge to malaria elimination because of their subclinical presentation and potential for ongoing transmission. However, the natural history of such untreated infections, including the extent to which they resolve spontaneously, remains poorly understood and has not been systematically studied for P. vivax. Methods: We conducted a longitudinal cohort study from 2018 to 2023 in northwestern Thailand, incorporating 14 rounds of mass blood surveys (MBS) covering approximately 5000 individuals. Blood samples were screened for P. vivax using both microscopy and polymerase chain reaction (PCR). Participants with PCR-positive, submicroscopic parasitemia were followed in subsequent surveys to assess infection dynamics. Turnbull survival analysis estimated time to spontaneous clearance, and Cox proportional hazards models identified demographic factors associated with clearance. Results: Among 210 P. vivax infections detected by microscopy and/or PCR, 154 were detected only by PCR. After excluding individuals lost to follow-up or with coinfections, 101 participants were analyzed. Most infections (72, 69.9%) cleared spontaneously within 3 subsequent MBS. Turnbull survival analysis revealed that the probability of persistent infections declined to 25.0% (95% CI: 4.0–100.0) by day 47 and 7.0% (95% CI: 1.0–38.0) by day 232. Clearance was not significantly associated with age, sex, nationality, occupation, or education. Conclusions: A considerable proportion of submicroscopic P. vivax infections resolved spontaneously without treatment, providing the first field-based evidence of this phenomenon. These findings suggest a role for naturally acquired immunity and highlight implications for surveillance and targeted intervention strategies in malaria elimination contexts.

Background: The recent resurgence of malaria in western Thailand has coincided with increased cross-border migration from Myanmar following political unrest. As short-term migrants from endemic areas may contribute to sustained local transmission, this study examined their malaria care-seeking behaviours and infection prevalence. Methods: A community-based cross-sectional study was conducted during March–April 2025 in six malaria-endemic villages of Tha Song Yang District, Tak Province, western Thailand. A structured questionnaire was administered, including a nine-item section on care-seeking behaviours. Malaria prevalence was determined by PCR testing of dried blood spot samples. Determinants of care-seeking scores were analysed using a generalized linear model, and infection risk was estimated using Firth logistic regression. Results: Among 300 participants (mean age: 34.5 ± 14.5 years; 47.3% male), over 60% recognised the need to seek care for fever or chills, yet only 35% reported doing so within 24 h of symptom onset. Although 98.0% preferred public health facilities, only 50.3% had ever visited one for suspected malaria. Higher care-seeking scores were associated with being a daily wage labourer (β = 0.66; 95% CI 0.01–1.31), infrequent return to Myanmar (β = 1.34; 95% CI 0.05–2.62), prior malaria experience (β = 1.08; 95% CI 0.59–1.58), and higher malaria knowledge (β = 0.34; 95% CI 0.24–0.44). Karen ethnicity was negatively associated with care-seeking (β = − 0.95; 95% CI − 1.74 to − 0.16). Six (2%) afebrile Plasmodium vivax infections were detected. Lower malaria knowledge (OR = 13.5; 95% CI 1.58–177.0) and care-seeking scores (OR = 5.86; 95% CI 1.15–57.7) were significantly associated with infection. Conclusions: Despite generally positive attitudes toward malaria, self-reported timely care-seeking among short-term Myanmar migrants remained limited. Socioeconomic status, migration patterns, ethnicity, and malaria knowledge significantly influenced care-seeking behaviours. The detection of asymptomatic P. vivax underscores the need for migrant-focused surveillance and targeted health education to support malaria elimination efforts.

Vector control has played a pivotal role in malaria control and elimination efforts, with insecticide-treated nets (ITNs) recognized as one of the most effective and widely accepted strategies. This study assessed ITN use and identified factors associated with non-use among individuals with access to ITNs in Myanmar. Data were drawn from the nationally representative 2015–2016 Myanmar Demographic and Health Survey. Access to ITNs was defined as having at least one ITN per two household members, and ITN use as having slept under an ITN the night before the survey. Descriptive statistics and multivariable logistic regression models were conducted using the “svyset” command in STATA to account for the two-stage stratified cluster sampling design. Among 6,140 individuals with access to ITNs, approximately one-third (31.6%, 95% CI 28.3%–35.0%) reported not using them. Factors associated with higher odds of ITN non-use were age 15–34 years (adjusted odds ratio [aOR]: 1.31; 95% CI 1.07–1.61) and ≥ 50 years (aOR: 1.33; 95% CI 1.07–1.67), rural residence (aOR: 1.82; 95% CI 1.10–3.01), and belonging to the fourth wealth quintile, representing higher socioeconomic status (aOR: 1.74; 95% CI 1.06–2.85). Despite having access to ITNs at that time, a substantial proportion of individuals in Myanmar did not use them. These historical findings highlight behavioural and contextual barriers that existed before recent health system disruptions due to political unrest and COVID-19. Although present-day challenges differ, understanding past determinants of ITN non-use remains valuable for designing behaviour change communication (BCC) strategies, especially in regions where ITN distribution remains feasible.

Background: Plasmodium vivax poses a major challenge for malaria elimination, primarily because of relapse. Primaquine mass drug administration (PQ-MDA) has played a decisive role in eliminating vivax malaria in many temperate countries, but its efficacy in tropical/subtropical areas remains underexplored. Methods: We conducted a cluster-randomized crossover trial to determine the effect of PQ-MDA on P. vivax transmission in northern Myanmar, a subtropical area in the Greater Mekong subregion with perennial malaria transmission. Participants from two groups of villages (groups 1 and 2) were administered 0.25 mg/kg/day PQ base for 14 days as directly observed therapy. During PQ-MDA administration, each group alternated as the control while the other received the intervention, with the groups switching after 9 months. Clinical malaria incidence and prevalence were monitored to determine the efficacy. Results: PQ was administered in 541 participants in group 1 and 667 in group 2 during August–September 2019 and June–July 2020, respectively. In both groups, clinical P. vivax incidence sharply declined to zero within a month of PQ-MDA and remained vivax-free for almost a year. During round 1 PQ-MDA, group 1 with MDA had a significant reduction in the prevalence of subclinical P. vivax compared to group 2 as the control, with a model-adjusted odds ratio (aOR) of 0.46 [95% confidence interval (CI): 0.25–0.83]. During round 2, group 2 exhibited an even lower aOR of 0.15 (95% CI: 0.03–0.65) for subclinical P. vivax infection. Conclusions: PQ-MDA was effective in reducing both clinical and subclinical P. vivax infections in a subtropical, low-endemicity setting. ClinicalTrialsRegistration: This study was registered with ClinicalTrials.gov (NCT06392152).