Identification and characterization of areas of high and low risk for asymptomatic malaria infections at sub-village level in Ratanakiri, Cambodia
Abstract Background Malaria elimination needs a concentration of activities towards identification of residual transmission foci and intensification of efforts to eliminate the last few infections, located in so-called ‘malaria hotspots’. Previous work on characterizing malaria transmission hotspots...
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doaj-0641631a93be486d9452ef7d66972ddf2020-11-25T00:51:48ZengBMCMalaria Journal1475-28752018-01-0117111410.1186/s12936-017-2169-1Identification and characterization of areas of high and low risk for asymptomatic malaria infections at sub-village level in Ratanakiri, CambodiaLies Durnez0Myrthe Pareyn1Vanna Mean2Saorin Kim3Nimol Khim4Didier Menard5Marc Coosemans6Tho Sochantha7Vincent Sluydts8Institute of Tropical MedicineInstitute of Tropical MedicineNational Center for Parasitology, Entomology and Malaria ControlInstitut Pasteur du CambodgeInstitut Pasteur du CambodgeInstitut Pasteur du CambodgeInstitute of Tropical MedicineNational Center for Parasitology, Entomology and Malaria ControlInstitute of Tropical MedicineAbstract Background Malaria elimination needs a concentration of activities towards identification of residual transmission foci and intensification of efforts to eliminate the last few infections, located in so-called ‘malaria hotspots’. Previous work on characterizing malaria transmission hotspots has mainly focused on falciparum malaria and especially on symptomatic cases, while the malaria reservoir is expected to be mainly concentrated in the asymptomatic human population when transmission is low. For Plasmodium vivax, there has been less effort in identifying transmission hotspots. The main aim of this study was to uncover micro-epidemiological mechanisms of clustering of malaria infections at a sub-village level, based on geographical or behavioural features. Methods A cross-sectional survey was performed in three villages within the highest malaria endemic province of Cambodia. The survey took place in the dry season, when the malaria reservoir is expected to be low and residing in the asymptomatic part of the population. Village and field locations of households were georeferenced, blood samples were taken from as many residents as possible and a short questionnaire probing for individual risk factors was taken. Asymptomatic malaria carriers were detected by PCR, and geographical clustering analysis (SaTScan) as well as risk factor analysis were performed. Results A total of 1540 out of 1792 (86%) individuals were sampled. Plasmodial DNA was detected in 129 individuals (8.4%). P. vivax was most prevalent (5.5%) followed by Plasmodium malariae (2.1%) and Plasmodium falciparum (1.6%). Mixed infection occurred in 12 individuals. In two out of three villages geographical clustering of high and low malaria infection risk was clearly present. Cluster location and risk factors associated with the infection differed between the parasite species. Age was an important risk factor for the combined Plasmodium infections, while watching television at evenings was associated with increased odds of P. vivax infections [OR (CI): 1.86 (0.95–3.64)] and bed net use was associated with reduced odds of P. falciparum infections [OR (CI): 0.25 (0.077–0.80)]. Conclusions Clusters of malaria carriers were malaria species specific and often located remotely, outside village centres. As such, at micro-epidemiological level, malaria is not a single disease. Further unravelling the micro-epidemiology of malaria can enable programme managers to define the interventions likely to contribute to halt transmission in a particular hotspot location.http://link.springer.com/article/10.1186/s12936-017-2169-1MalariaHotspotsAsymptomatic carriersRisk factorsClusters |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Lies Durnez Myrthe Pareyn Vanna Mean Saorin Kim Nimol Khim Didier Menard Marc Coosemans Tho Sochantha Vincent Sluydts |
spellingShingle |
Lies Durnez Myrthe Pareyn Vanna Mean Saorin Kim Nimol Khim Didier Menard Marc Coosemans Tho Sochantha Vincent Sluydts Identification and characterization of areas of high and low risk for asymptomatic malaria infections at sub-village level in Ratanakiri, Cambodia Malaria Journal Malaria Hotspots Asymptomatic carriers Risk factors Clusters |
author_facet |
Lies Durnez Myrthe Pareyn Vanna Mean Saorin Kim Nimol Khim Didier Menard Marc Coosemans Tho Sochantha Vincent Sluydts |
author_sort |
Lies Durnez |
title |
Identification and characterization of areas of high and low risk for asymptomatic malaria infections at sub-village level in Ratanakiri, Cambodia |
title_short |
Identification and characterization of areas of high and low risk for asymptomatic malaria infections at sub-village level in Ratanakiri, Cambodia |
title_full |
Identification and characterization of areas of high and low risk for asymptomatic malaria infections at sub-village level in Ratanakiri, Cambodia |
title_fullStr |
Identification and characterization of areas of high and low risk for asymptomatic malaria infections at sub-village level in Ratanakiri, Cambodia |
title_full_unstemmed |
Identification and characterization of areas of high and low risk for asymptomatic malaria infections at sub-village level in Ratanakiri, Cambodia |
title_sort |
identification and characterization of areas of high and low risk for asymptomatic malaria infections at sub-village level in ratanakiri, cambodia |
publisher |
BMC |
series |
Malaria Journal |
issn |
1475-2875 |
publishDate |
2018-01-01 |
description |
Abstract Background Malaria elimination needs a concentration of activities towards identification of residual transmission foci and intensification of efforts to eliminate the last few infections, located in so-called ‘malaria hotspots’. Previous work on characterizing malaria transmission hotspots has mainly focused on falciparum malaria and especially on symptomatic cases, while the malaria reservoir is expected to be mainly concentrated in the asymptomatic human population when transmission is low. For Plasmodium vivax, there has been less effort in identifying transmission hotspots. The main aim of this study was to uncover micro-epidemiological mechanisms of clustering of malaria infections at a sub-village level, based on geographical or behavioural features. Methods A cross-sectional survey was performed in three villages within the highest malaria endemic province of Cambodia. The survey took place in the dry season, when the malaria reservoir is expected to be low and residing in the asymptomatic part of the population. Village and field locations of households were georeferenced, blood samples were taken from as many residents as possible and a short questionnaire probing for individual risk factors was taken. Asymptomatic malaria carriers were detected by PCR, and geographical clustering analysis (SaTScan) as well as risk factor analysis were performed. Results A total of 1540 out of 1792 (86%) individuals were sampled. Plasmodial DNA was detected in 129 individuals (8.4%). P. vivax was most prevalent (5.5%) followed by Plasmodium malariae (2.1%) and Plasmodium falciparum (1.6%). Mixed infection occurred in 12 individuals. In two out of three villages geographical clustering of high and low malaria infection risk was clearly present. Cluster location and risk factors associated with the infection differed between the parasite species. Age was an important risk factor for the combined Plasmodium infections, while watching television at evenings was associated with increased odds of P. vivax infections [OR (CI): 1.86 (0.95–3.64)] and bed net use was associated with reduced odds of P. falciparum infections [OR (CI): 0.25 (0.077–0.80)]. Conclusions Clusters of malaria carriers were malaria species specific and often located remotely, outside village centres. As such, at micro-epidemiological level, malaria is not a single disease. Further unravelling the micro-epidemiology of malaria can enable programme managers to define the interventions likely to contribute to halt transmission in a particular hotspot location. |
topic |
Malaria Hotspots Asymptomatic carriers Risk factors Clusters |
url |
http://link.springer.com/article/10.1186/s12936-017-2169-1 |
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