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Association of sub-microscopic malaria parasite carriage with transmission intensity in north-eastern Tanzania

BACKGROUND: In malaria endemic areas, individuals are frequently asymptomatic and may be undetected by conventional microscopy or newer, rapid diagnostic tests. Molecular techniques allow a more accurate assessment of this asymptomatic parasite burden, the extent of which is important for malaria co...

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Autores principales: Manjurano, Alphaxard, Okell, Lucy, Lukindo, Tedson, Reyburn, Hugh, Olomi, Raimos, Roper, Cally, Clark, Taane G, Joseph, Sarah, Riley, Eleanor M, Drakeley, Chris
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2011
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3276450/
https://www.ncbi.nlm.nih.gov/pubmed/22177014
http://dx.doi.org/10.1186/1475-2875-10-370
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author Manjurano, Alphaxard
Okell, Lucy
Lukindo, Tedson
Reyburn, Hugh
Olomi, Raimos
Roper, Cally
Clark, Taane G
Joseph, Sarah
Riley, Eleanor M
Drakeley, Chris
author_facet Manjurano, Alphaxard
Okell, Lucy
Lukindo, Tedson
Reyburn, Hugh
Olomi, Raimos
Roper, Cally
Clark, Taane G
Joseph, Sarah
Riley, Eleanor M
Drakeley, Chris
author_sort Manjurano, Alphaxard
collection PubMed
description BACKGROUND: In malaria endemic areas, individuals are frequently asymptomatic and may be undetected by conventional microscopy or newer, rapid diagnostic tests. Molecular techniques allow a more accurate assessment of this asymptomatic parasite burden, the extent of which is important for malaria control. This study examines the relative prevalence of sub-microscopic level parasite carriage and clonal complexity of infections (multiplicity of infection) over a range of endemicities in a region of north-eastern Tanzania where altitude is an established proxy of malaria transmission. The PCR prevalence was then compared against other measures of transmission intensity collected in the same area. METHODS: This study used 1,121 blood samples collected from a previously conducted cross-sectional malario-metric survey during the short rainy season in 2001 from 13 villages (three at < 600 m, four at 600-1,200 m and six at > 1,200 m in altitude above sea level). Samples were analysed by PCR for carriage of parasites and multiplicity of infection. These data were compared with other measures of transmission intensity collected from the same area. RESULTS: Parasite prevalence was 34.7% by PCR and 13.6% by microscopy; a 2.5-fold difference in line with other recent observations. This fold difference was relatively consistent at the different altitude bands despite a marked decrease in parasite prevalence with altitude: < 600 m 70.9 vs 28.6, 600-1,200 m 35.5 vs 9.9, > 1,200 m 15.8 vs 5.9. The difference between parasite prevalence by PCR was 3.2 in individuals aged between 15 and 45 years (34.5 vs 10.9) compared with 2.5 in those aged 1-5 (34.0 vs 13.5) though this was not statistically significant. Multiplicity of infection (MOI) ranged from 1.2 to 3.7 and was positively associated with parasite prevalence assessed by both PCR and microscopy. There was no association of MOI and age. Village level PCR parasite prevalence was strongly correlated with altitude, sero-conversion rate and predicted entomological inoculation rate. CONCLUSIONS: Asymptomatic, low density, multi-clone malaria infection was common in this study area. These infections are important as potential contributors to the infectious reservoir of parasites and need to be identified by control programmes especially in this era where malaria elimination is a focus. High throughput standardized PCR approaches are needed to identify individuals who are malaria carriers.
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spelling pubmed-32764502012-02-10 Association of sub-microscopic malaria parasite carriage with transmission intensity in north-eastern Tanzania Manjurano, Alphaxard Okell, Lucy Lukindo, Tedson Reyburn, Hugh Olomi, Raimos Roper, Cally Clark, Taane G Joseph, Sarah Riley, Eleanor M Drakeley, Chris Malar J Research BACKGROUND: In malaria endemic areas, individuals are frequently asymptomatic and may be undetected by conventional microscopy or newer, rapid diagnostic tests. Molecular techniques allow a more accurate assessment of this asymptomatic parasite burden, the extent of which is important for malaria control. This study examines the relative prevalence of sub-microscopic level parasite carriage and clonal complexity of infections (multiplicity of infection) over a range of endemicities in a region of north-eastern Tanzania where altitude is an established proxy of malaria transmission. The PCR prevalence was then compared against other measures of transmission intensity collected in the same area. METHODS: This study used 1,121 blood samples collected from a previously conducted cross-sectional malario-metric survey during the short rainy season in 2001 from 13 villages (three at < 600 m, four at 600-1,200 m and six at > 1,200 m in altitude above sea level). Samples were analysed by PCR for carriage of parasites and multiplicity of infection. These data were compared with other measures of transmission intensity collected from the same area. RESULTS: Parasite prevalence was 34.7% by PCR and 13.6% by microscopy; a 2.5-fold difference in line with other recent observations. This fold difference was relatively consistent at the different altitude bands despite a marked decrease in parasite prevalence with altitude: < 600 m 70.9 vs 28.6, 600-1,200 m 35.5 vs 9.9, > 1,200 m 15.8 vs 5.9. The difference between parasite prevalence by PCR was 3.2 in individuals aged between 15 and 45 years (34.5 vs 10.9) compared with 2.5 in those aged 1-5 (34.0 vs 13.5) though this was not statistically significant. Multiplicity of infection (MOI) ranged from 1.2 to 3.7 and was positively associated with parasite prevalence assessed by both PCR and microscopy. There was no association of MOI and age. Village level PCR parasite prevalence was strongly correlated with altitude, sero-conversion rate and predicted entomological inoculation rate. CONCLUSIONS: Asymptomatic, low density, multi-clone malaria infection was common in this study area. These infections are important as potential contributors to the infectious reservoir of parasites and need to be identified by control programmes especially in this era where malaria elimination is a focus. High throughput standardized PCR approaches are needed to identify individuals who are malaria carriers. BioMed Central 2011-12-16 /pmc/articles/PMC3276450/ /pubmed/22177014 http://dx.doi.org/10.1186/1475-2875-10-370 Text en Copyright ©2011 Manjurano et al; licensee BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 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.
spellingShingle Research
Manjurano, Alphaxard
Okell, Lucy
Lukindo, Tedson
Reyburn, Hugh
Olomi, Raimos
Roper, Cally
Clark, Taane G
Joseph, Sarah
Riley, Eleanor M
Drakeley, Chris
Association of sub-microscopic malaria parasite carriage with transmission intensity in north-eastern Tanzania
title Association of sub-microscopic malaria parasite carriage with transmission intensity in north-eastern Tanzania
title_full Association of sub-microscopic malaria parasite carriage with transmission intensity in north-eastern Tanzania
title_fullStr Association of sub-microscopic malaria parasite carriage with transmission intensity in north-eastern Tanzania
title_full_unstemmed Association of sub-microscopic malaria parasite carriage with transmission intensity in north-eastern Tanzania
title_short Association of sub-microscopic malaria parasite carriage with transmission intensity in north-eastern Tanzania
title_sort association of sub-microscopic malaria parasite carriage with transmission intensity in north-eastern tanzania
topic Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3276450/
https://www.ncbi.nlm.nih.gov/pubmed/22177014
http://dx.doi.org/10.1186/1475-2875-10-370
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