Molecular epidemiology of residual Plasmodium vivax transmission in a paediatric cohort in Solomon Islands

Quah, Yi Wan, Waltmann, Andreea, Karl, Stephan, White, Michael T., Vahi, Ventis, Darcy, Andrew, Pitakaka, Freda, Whittaker, Maxine, Tisch, Daniel J., Barry, Alyssa, Barnadas, Celine, Kazura, James, and Mueller, Ivo (2019) Molecular epidemiology of residual Plasmodium vivax transmission in a paediatric cohort in Solomon Islands. Malaria Journal, 18. 106.

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Background: Following the scale-up of intervention efforts, malaria burden has decreased dramatically in Solomon Islands (SI). Submicroscopic and asymptomatic Plasmodium vivax infections are now the major challenge for malaria elimination in this country. Since children have higher risk of contracting malaria, this study investigated the dynamics of Plasmodium spp. infections among children including the associated risk factors of residual P. vivax burden.

Methods: An observational cohort study was conducted among 860 children aged 0.5–12 years in Ngella (Central Islands Province, SI). Children were monitored by active and passive surveillances for Plasmodium spp. infections and illness. Parasites were detected by quantitative real-time PCR (qPCR) and genotyped. Comprehensive statistical analyses of P. vivax infection prevalence, molecular force of blood stage infection (molFOB) and infection density were conducted.

Results: Plasmodium vivax infections were common (overall prevalence: 11.9%), whereas Plasmodium falciparum infections were rare (0.3%) but persistent. Although children acquire an average of 1.1 genetically distinct P. vivax blood-stage infections per year, there was significant geographic heterogeneity in the risks of P. vivax infections across Ngella (prevalence: 1.2–47.4%, p < 0.01; molFOB: 0.05–4.6/year, p < 0.01). Malaria incidence was low (IR: 0.05 episodes/year-at-risk). Age and measures of high exposure were the key risk factors for P. vivax infections and disease. Malaria incidence and infection density decreased with age, indicating significant acquisition of immunity. G6PD deficient children (10.8%) that did not receive primaquine treatment had a significantly higher prevalence (aOR: 1.77, p = 0.01) and increased risk of acquiring new bloodstage infections (molFOB aIRR: 1.51, p = 0.03), underscoring the importance of anti-relapse treatment.

Conclusion: Residual malaria transmission in Ngella exhibits strong heterogeneity and is characterized by a high proportion of submicroscopic and asymptomatic P. vivax infections, alongside sporadic P. falciparum infections. Implementing an appropriate primaquine treatment policy to prevent P. vivax relapses and specific targeting of control interventions to high risk areas will be required to accelerate ongoing control and elimination activities.

Item ID: 58122
Item Type: Article (Research - C1)
ISSN: 1475-2875
Keywords: Plasmodium vivax, Solomon Islands, asymptomatic, cohort, heterogeneity
Copyright Information: © The Author(s) 2019. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.
Funders: Melbourne International Fee Remission Scholarship (MIFRS), Melbourne International Research Scholarship (MIRS), National Health and Medical Research Council (NHMRC), National Institutes of Health (NIH), Transmission Epidemiology Consortium (TEC), Bill and Melinda Gates Foundation (BMGF), Victorian State Government Operational Infrastructure Support (VSGOIS)
Projects and Grants: NHMRC Early Career Fellowship GNT1052760, NHMRC Senior Research Fellowship GNT1403345, NIH 1 U19 AI089686-01, NIH 1 U19 AI129392-01, NHMRC GNT1003825, NHMRC GNT1102297, NHMRC GNT1092789
Date Deposited: 22 Apr 2019 23:44
FoR Codes: 42 HEALTH SCIENCES > 4202 Epidemiology > 420299 Epidemiology not elsewhere classified @ 60%
32 BIOMEDICAL AND CLINICAL SCIENCES > 3207 Medical microbiology > 320704 Medical parasitology @ 40%
SEO Codes: 92 HEALTH > 9204 Public Health (excl. Specific Population Health) > 920404 Disease Distribution and Transmission (incl. Surveillance and Response) @ 80%
92 HEALTH > 9204 Public Health (excl. Specific Population Health) > 920401 Behaviour and Health @ 20%
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