Publication: Microgeography and molecular epidemiology of malaria at the Thailand-Myanmar border in the malaria pre-elimination phase
Issued Date
2015
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eng
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Mahidol University
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BioMed Central
Bibliographic Citation
Malaria Journal. Vol.14, (2015), 198
Suggested Citation
Parker, Daniel M., Matthews, Stephen A., Guiyun Yan, Guofa Zhou, Lee, Ming-Chieh, Jeeraphat Sirichaisinthop, Kirakorn Kiattibutr, Qi Fan, Peipei Li, Jetsumon Sattabongkot, Liwang Cui Microgeography and molecular epidemiology of malaria at the Thailand-Myanmar border in the malaria pre-elimination phase. Malaria Journal. Vol.14, (2015), 198. doi:10.1186/s12936-015-0712-5 Retrieved from: https://repository.li.mahidol.ac.th/handle/20.500.14594/3093
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Title
Microgeography and molecular epidemiology of malaria at the Thailand-Myanmar border in the malaria pre-elimination phase
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Abstract
Background: Endemic malaria in Thailand continues to only exist along international borders. This pattern is
frequently attributed to importation of malaria from surrounding nations. A microgeographical approach was used
to investigate malaria cases in a study village along the Thailand–Myanmar border.
Methods: Three mass blood surveys were conducted during the study period (July and December 2011, and May
2012) and were matched to a cohort-based demographic surveillance system. Blood slides and filter papers were
taken from each participant. Slides were cross-verified by an expert microscopist and filter papers were analysed
using nested PCR. Cases were then mapped to households and analysed using spatial statistics. A risk factor analysis
was done using mixed effects logistic regression.
Results: In total, 55 Plasmodium vivax and 20 Plasmodium falciparum cases (out of 547 participants) were detected
through PCR, compared to six and two (respectively) cases detected by field microscopy. The single largest risk
factor for infection was citizenship. Many study participants were ethnic Karen people with no citizenship in either
Thailand or Myanmar. This subpopulation had over eight times the odds of malaria infection when compared to
Thai citizens. Cases also appeared to cluster near a major drainage system and year–round water source within the
study village.
Conclusion: This research indicates that many cases of malaria remain undiagnosed in the region. The spatial and
demographic clustering of cases in a sub-group of the population indicates either transmission within the Thai
village or shared exposure to malaria vectors outside of the village. While it is possible that malaria is imported to
Thailand from Myanmar, the existence of undetected infections, coupled with an ecological setting that is conducive
to malaria transmission, means that indigenous transmission could also occur on the Thai side of the border. Improved,
timely, and active case detection is warranted.