Cited by 121Malaria Research and ControlBird parasitology and diseasesHemoglobinopathies and Related Disorders

The persistence and oscillations of submicroscopic Plasmodium falciparum and Plasmodium vivax infections over time in Vietnam: An open cohort study

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Nguyen, Thuy-Nhien, von Seidlein, Lorenz, Nguyen, Tuong-Vy, Truong, Phuc-Nhi, Hung, Son Do, Pham, Huong-Thu, Nguyen, Tam-Uyen, Le, Thanh Dong +7 more·2018·The Lancet Infectious Diseases

Abstract

BACKGROUND: A substantial proportion of Plasmodium species infections are asymptomatic with densities too low to be detectable with standard diagnostic techniques. The importance of such asymptomatic plasmodium infections in malaria transmission is probably related to their duration and density. To explore the duration of asymptomatic plasmodium infections and changes in parasite densities over time, a cohort of participants who were infected with Plasmodium parasites was observed over a 2-year follow-up period. METHODS: In this open cohort study, inhabitants of four villages in Vietnam were invited to participate in baseline and subsequent 3-monthly surveys up to 24 months, which included the collection of venous blood samples. Samples were batch-screened using ultra-sensitive (u)PCR (lower limit of detection of 22 parasites per mL). Participants found to be infected by uPCR during any of these surveys were invited to join a prospective cohort and provide monthly blood samples. We estimated the persistence of Plasmodium falciparum and Plasmodium vivax infections and changes in parasite densities over a study period of 24 months. FINDINGS: Between Dec 1, 2013, and Jan 8, 2016, 356 villagers participated in between one and 22 surveys. These study participants underwent 4248 uPCR evaluations (11·9 tests per participant). 1874 (32%) of 4248 uPCR tests indicated a plasmodium infection; 679 (36%) of 1874 tests were P falciparum monoinfections, 507 (27%) were P vivax monoinfections, 463 (25%) were co-infections with P falciparum and P vivax, and 225 (12%) were indeterminate species of Plasmodium. The median duration of P falciparum infection was 2 months (IQR 1-3); after accounting for censoring, participants had a 20% chance of having parasitaemia for 4 months or longer. The median duration of P vivax infection was 6 months (3-9), and participants had a 59% chance of having parasitaemia for 4 months or longer. The parasite densities of persistent infections oscillated; following ultralow-density infections, high-density infections developed frequently. INTERPRETATION: Persistent largely asymptomatic P vivax and P falciparum infections are common in this area of low seasonal malaria transmission. Infections with low-density parasitaemias can develop into much higher density infections at a later time, which are likely to sustain malaria endemicity. FUNDING: The Wellcome Trust, Bill & Melinda Gates Foundation.

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  • Submicroscopic cases are not detected or treated, resulting in severe outcomes for the mother and child (anemia and severe malaria) while also perpetuating parasite transmission and disease endemicity.

    “submicroscopic cases are not detected or treated, resulting in severe outcomes for the mother and child (anemia and severe malaria) while also perpetuating parasite transmission and disease endemicity [20,23,24,25,26]”

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Authors
Nguyen, T.-N., von Seidlein, L., Nguyen, T.-V., Truong, P.-N., Hung, S. D., Pham, H.-T., Nguyen, T.-U., Le, T. D., Dao, V. H., Mukaka, M., Day, N. P., White, N. J., Dondorp, A. M., Thwaites, G. E., & Hien, T. T.
Affiliations
  • Oxford University Clinical Research Unit (VN)
  • Viện Sốt rét - Ký sinh trùng - Côn trùng Thành phố Hồ Chí Minh (VN)
  • Mahidol University (TH)
  • Churchill Hospital (GB)
Venue
The Lancet Infectious Diseases
Publisher
Elsevier BV
Published
2018-05
Volume
18
Issue
5
Pages
565-572
ISSN
1473-3099 (ISSN-L)
OpenAlex
W2785008802
Cited by
121
References
29
Citations by year
2026: 5 · 2025: 9 · 2024: 7 · 2023: 10 · 2022: 17 · 2021: 24 · 2020: 15 · 2019: 23 · 2018: 11
FWCI
17.40
Type
journal article
Language
en
Update notices
erratum (2018-05-01)
Open access
Locations
  • The Lancet Infectious Diseases (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, other-oa)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Greater South Information System
Funders
  • Wellcome Trust
  • Bill & Melinda Gates Foundation
Topics
  • Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Malaria Research and Control
  • Life Sciences › Immunology and Microbiology › Parasitology › Bird parasitology and diseases
  • Health Sciences › Medicine › Genetics › Hemoglobinopathies and Related Disorders
Keywords
Plasmodium falciparum, Plasmodium vivax, asymptomatic malaria, malaria co-infection, parasite density, malaria transmission, rural villages, Plasmodium malariae, Plasmodium reichenowi
MeSH terms
Adult, Female, Humans, Male, Middle Aged, Plasmodium falciparum, Plasmodium vivax, Vietnam, Cohort Studies, Malaria, Falciparum, Malaria, Vivax, Parasitemia

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