A large proportion of asymptomatic Plasmodium infections with low and sub-microscopic parasite densities in the low transmission setting of Temotu Province, Solomon Islands: challenges for malaria diagnostics in an elimination setting

Malaria Journal

Research

Darren Krause¹  Ivor Harris¹  Ken Lilley¹  Lisa M Bain²  Wesley W Sharrock²  Qin Cheng²  G Dennis Shanks³  Karen-Ann Gray³  Marie-Louise Johnson³  Michelle L Gatton⁴  Andrew Vallely⁵  Leonard Boaz⁶  Albino Bobogare⁶ 

[1] Australian Army Malaria Institute, Weary Dunlop Drive, Gallipoli Barracks Enoggera, 4051, Qld, Australia;Australian Army Malaria Institute, Weary Dunlop Drive, Gallipoli Barracks Enoggera, 4051, Qld, Australia;Malaria Drug Resistance and Chemotherapy, Queensland Institute of Medical Research, Brisbane, Australia;Pacific Malaria Initiative Support Centre, School of Population Health, University of Queensland, Brisbane, Australia;Australian Army Malaria Institute, Weary Dunlop Drive, Gallipoli Barracks Enoggera, 4051, Qld, Australia;Pacific Malaria Initiative Support Centre, School of Population Health, University of Queensland, Brisbane, Australia;Malaria Drug Resistance and Chemotherapy, Queensland Institute of Medical Research, Brisbane, Australia;Pacific Malaria Initiative Support Centre, School of Population Health, University of Queensland, Brisbane, Australia;Vector Borne Disease Control Programme, Ministry of Health, Solomon Islands;

关键词: Malaria;    Parasite Density;    Mass Drug Administration;    Solomon Island;    Malaria Elimination;   

DOI  :  10.1186/1475-2875-9-254

 received in 2010-06-23, accepted in 2010-09-07,  发布年份 2010

来源: Springer

【 摘 要 】

BackgroundMany countries are scaling up malaria interventions towards elimination. This transition changes demands on malaria diagnostics from diagnosing ill patients to detecting parasites in all carriers including asymptomatic infections and infections with low parasite densities. Detection methods suitable to local malaria epidemiology must be selected prior to transitioning a malaria control programme to elimination. A baseline malaria survey conducted in Temotu Province, Solomon Islands in late 2008, as the first step in a provincial malaria elimination programme, provided malaria epidemiology data and an opportunity to assess how well different diagnostic methods performed in this setting.MethodsDuring the survey, 9,491 blood samples were collected and examined by microscopy for Plasmodium species and density, with a subset also examined by polymerase chain reaction (PCR) and rapid diagnostic tests (RDTs). The performances of these diagnostic methods were compared.ResultsA total of 256 samples were positive by microscopy, giving a point prevalence of 2.7%. The species distribution was 17.5% Plasmodium falciparum and 82.4% Plasmodium vivax. In this low transmission setting, only 17.8% of the P. falciparum and 2.9% of P. vivax infected subjects were febrile (≥38°C) at the time of the survey. A significant proportion of infections detected by microscopy, 40% and 65.6% for P. falciparum and P. vivax respectively, had parasite density below 100/μL. There was an age correlation for the proportion of parasite density below 100/μL for P. vivax infections, but not for P. falciparum infections. PCR detected substantially more infections than microscopy (point prevalence of 8.71%), indicating a large number of subjects had sub-microscopic parasitemia. The concordance between PCR and microscopy in detecting single species was greater for P. vivax (135/162) compared to P. falciparum (36/118). The malaria RDT detected the 12 microscopy and PCR positive P. falciparum, but failed to detect 12/13 microscopy and PCR positive P. vivax infections.ConclusionAsymptomatic malaria infections and infections with low and sub-microscopic parasite densities are highly prevalent in Temotu province where malaria transmission is low. This presents a challenge for elimination since the large proportion of the parasite reservoir will not be detected by standard active and passive case detection. Therefore effective mass screening and treatment campaigns will most likely need more sensitive assays such as a field deployable molecular based assay.

【 授权许可】

Unknown   
© Harris et al; licensee BioMed Central Ltd. 2010. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.