Temporal Dynamics of Subclinical Malaria in Different Transmission Zones of Myanmar

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  • 1 Duke Global Health Institute, Duke University, Durham, North Carolina;
  • | 2 Department of Medical Research, Ministry of Health and Sports, Yangon, Myanmar;
  • | 3 National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, Shanghai, China;
  • | 4 Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, Zhejiang, China;
  • | 5 Defense Services Medical Research Center, Nay Pyi Taw, Myanmar;
  • | 6 PPD, Morrisville, North Carolina;
  • | 7 National Malaria Control Program, Myanmar Ministry of Health and Sports, Nay Pyi Taw, Myanmar;
  • | 8 University of Maryland School of Medicine, Baltimore, Maryland

Countries in the Greater Mekong Subregion have committed to eliminate Plasmodium falciparum malaria by 2025. Subclinical malaria infections that can be detected by highly sensitive polymerase chain reaction (PCR) testing in asymptomatic individuals represent a potential impediment to this goal, although the extent to which these low-density infections contribute to transmission is unclear. To understand the temporal dynamics of subclinical malaria in this setting, a cohort of 2,705 participants from three epidemiologically distinct regions of Myanmar was screened for subclinical P. falciparum and P. vivax infection using ultrasensitive PCR (usPCR). Standard rapid diagnostic tests (RDTs) for P. falciparum were also performed. Individuals who tested positive for malaria by usPCR were followed for up to 12 weeks. Regression analysis was performed to estimate whether the baseline prevalence of infection and the count of repeated positive tests were associated with demographic, behavioral, and clinical factors. At enrollment, the prevalence of subclinical malaria infection measured by usPCR was 7.7% (1.5% P. falciparum monoinfection, 0.3% mixed P. falciparum and P. vivax, and 6.0% P. vivax monoinfection), while P. falciparum prevalence measured by RDT was just 0.2%. Prevalence varied by geography and was higher among older people and in those with outdoor exposure and travel. No difference was observed in either the prevalence or count of subclinical infection by time of year, indicating that even in low-endemicity areas, a reservoir of subclinical infection persists year-round. If low-density infections are shown to represent a significant source of transmission, identification of high-risk groups and locations may aid elimination efforts.

Author Notes

Address correspondence to Christopher V. Plowe, Center for Vaccine Development and Global Health, University of Maryland School of Medicine, 685 W. Baltimore St., Baltimore, MD 21201. E-mail: plowe.chris@gmail.com

Financial support: The study was funded by an International Center for Excellence in Malaria Research grant from the National Institute of Allergy and Infectious Diseases (5U19AI129386). Grants from the Bill & Melinda Gates Foundation (OPP1109551 and OPP1171753) supported the establishment of the study laboratories in Myanmar, and a grant from the NIH Fogarty International Center (D43TW010917) supported training of some of the authors and study staff. Start-up funds from Duke University supported the reference laboratory in North Carolina.

Authors’ addresses: Joseph R. Egger, Alyssa Platt, Thynn K. Thane, Manfred Meng, Joyce Hogue, Christine F. Markwalter, Thura Htay, Zaw W. Thein, Aye K. Paing, Zin M. Tun, Swai M. Oo, and Poe P. Aung, Duke Global Health Institute, Duke University, Durham, NC, E-mails: joseph.egger@duke.edu, alyssa.platt@duke.edu, thynn.thane@duke.edu, manfred.meng@duke.edu, joyce.hogue@duke.edu, christine.markwalter@duke.edu, thurahtay1988@gmail.com, zwthein.1987@gmail.com, ayekyawtpaing.tgi@gmail.com, zinmintun36732@gmail.com, dr.mon.2011@gmail.com, and poepaung@gmail.com. Kay T. Han, Department of Medical Research, Ministry of Health and Sports, Yangon, Myanmar, E-mail: drkaythwehan@yahoo.com. Huang Fang, Xiao X. Wang, and Tu Hong, National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, Shanghai, China, E-mails: huangfang@nipd.chinacdc.cn, xxwang@cdc.zj.cn, and tuhong@nipd.chinacdc.cn. Xiao Nong Zhou, National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, Shanghai, China, and Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, Zhejiang, China, E-mail: zhouxn1@chinacdc.cn. Tin M. Hlaing and Myo Thant, Defense Services Medical Research Center, Nay Pyi Taw, Myanmar, E-mails: hlaingtm@gmail.com and kgthant@gmail.com. Zay Y. Han, Duke Global Health Institute, Duke University, Durham, NC, and Department of Medical Research, Ministry of Health and Sports, Yangon, Myanmar, E-mail: zayyar.han@duke.edu. Ryan Simmons, Duke Global Health Institute, Duke University, Durham, NC, and PPD, Morrisville, NC, E-mail: Ryan.Simmons@ppd.com. Aung Thi, National Malaria Control Program, Myanmar Ministry of Health and Sports, Nay Pyi Taw, Myanmar, E-mail: aungthi08@gmail.com. Myaing M. Nyunt and Christopher V. Plowe, University of Maryland School of Medicine, Baltimore, MD, E-mails: myaingnyunt@gmail.com and plowe.chris@gmail.com.

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