Field deployment of loop-mediated isothermal amplification for centralized mass-screening of asymptomatic malaria in Zanzibar: a pre-elimination setting.

Ulrika Morris,Mwinyi I Msellem,Anders Björkman,Jackie Cook,Iveth J González,Mwinyi Khamis,Andreas Mårtensson,Abdullah S Ali,Berit Aydin-Schmidt,Ali K Abass,Majda H Nassor

doi:10.1186/s12936-015-0731-2

Abstract

BackgroundMolecular tools for detection of low-density asymptomatic Plasmodium infections are needed in malaria elimination efforts. This study reports results from the hitherto largest implementation of loop-mediated isothermal amplification (LAMP) for centralized mass screening of asymptomatic malaria in Zanzibar.MethodsHealthy individuals present and willing to participate in randomly selected households in 60 villages throughout Zanzibar were screened for malaria by rapid diagnostic tests (RDT). In 50 % of the study households, participants were asked to provide 60 μL of finger-prick blood for additional LAMP screening. LAMP was conducted in two centralized laboratories in Zanzibar, by trained technicians with limited or no previous experience of molecular methods. The LAMP assay was performed with LoopampTM MALARIA Pan/Pf Detection Kit (Eiken Chemical Company, Japan). Samples positive for Plasmodium genus (Pan)-LAMP were re-tested using Plasmodium falciparum-specific LAMP kits.ResultsPaired RDT and LAMP samples were available from 3983 individuals. The prevalence of asymptomatic malaria was 0.5 % (CI 95 % 0.1-0.8) and 1.6 % (CI 95 % 1.1-2.2) by RDT and Pan-LAMP, respectively. LAMP detected 3.4 (CI 95 % 2.2-5.2) times more Plasmodium positive samples than RDT. DNA contamination was experienced, but solved by repetitive decontamination of all equipment and reagents.ConclusionsLAMP is a simple and sensitive molecular tool, and has potential in active surveillance and mass-screening programmes for detection of low-density asymptomatic malaria in pre-elimination settings. However, in order to deploy LAMP more effectively in field settings, protocols may need to be adapted for processing larger numbers of samples. A higher throughput, affordable closed system would be ideal to avoid contamination.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-015-0731-2) contains supplementary material, which is available to authorized users.

Highlights

Molecular tools for detection of low-density asymptomatic Plasmodium infections are needed in malaria elimination efforts
Asymptomatic Plasmodium infections are an important reservoir for continued malaria transmission that needs to be addressed in the context of malaria elimination [1]
This study reports results from the hitherto largest implementation of loop-mediated isothermal amplification (LAMP) in the field, for scaled-up, centralized mass screening of asymptomatic malaria in Zanzibar, a pre-elimination setting

Summary

Introduction

Molecular tools for detection of low-density asymptomatic Plasmodium infections are needed in malaria elimination efforts. This study reports results from the hitherto largest implementation of loop-mediated isothermal amplification (LAMP) for centralized mass screening of asymptomatic malaria in Zanzibar. Asymptomatic Plasmodium infections are an important reservoir for continued malaria transmission that needs to be addressed in the context of malaria elimination [1]. Detection of asymptomatic infections, which are often sub-patent, i.e., fall beneath the threshold of detection of Morris et al Malaria Journal (2015) 14:205. This study reports results from the hitherto largest implementation of LAMP in the field, for scaled-up, centralized mass screening of asymptomatic malaria in Zanzibar, a pre-elimination setting The kit has been evaluated both in laboratory and field settings [6,7,8], and was piloted on a small scale in Zanzibar as a health facility-based, point-of-care, diagnostic tool for mass screening and treatment in 2013 [9].

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Results

Discussion

Conclusion