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Pepey A, Souris M, Kim S, Obadia T, Chy S, Ea M, Ouk S, Remoue F, Sovannaroth S, Mueller I, Witkowski B, Vantaux A. Comparing malaria risk exposure in rural Cambodia population using GPS tracking and questionnaires. Malar J 2024; 23:75. [PMID: 38475843 DOI: 10.1186/s12936-024-04890-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Accepted: 02/23/2024] [Indexed: 03/14/2024] Open
Abstract
BACKGROUND The Great Mekong Subregion has attained a major decline in malaria cases and fatalities over the last years, but residual transmission hotspots remain, supposedly fueled by forest workers and migrant populations. This study aimed to: (i) characterize the fine-scale mobility of forest-goers and understand links between their daily movement patterns and malaria transmission, using parasites detection via real time polymerase chain reaction (RT PCR) and the individual exposure to Anopheles bites by quantification of anti-Anopheles saliva antibodies via enzyme-linked immunosorbent assay; (ii) assess the concordance of questionnaires and Global Positioning System (GPS) data loggers for measuring mobility. METHODS Two 28 day follow-ups during dry and rainy seasons, including a GPS tracking, questionnaires and health examinations, were performed on male forest goers representing the population at highest risk of infection. Their time spent in different land use categories and demographic data were analyzed in order to understand the risk factors driving malaria in the study area. RESULTS Malaria risk varied with village forest cover and at a resolution of only a few kilometers: participants from villages outside the forest had the highest malaria prevalence compared to participants from forest fringe's villages. The time spent in a specific environment did not modulate the risk of malaria, in particular the time spent in forest was not associated with a higher probability to detect malaria among forest-goers. The levels of antibody response to Anopheles salivary peptide among participants were significantly higher during the rainy season, in accordance with Anopheles mosquito density variation, but was not affected by sociodemographic and mobility factors. The agreement between GPS and self-reported data was only 61.9% in reporting each kind of visited environment. CONCLUSIONS In a context of residual malaria transmission which was mainly depicted by P. vivax asymptomatic infections, the implementation of questionnaires, GPS data-loggers and quantification of anti-saliva Anopheles antibodies on the high-risk group were not powerful enough to detect malaria risk factors associated with different mobility behaviours or time spent in various environments. The joint implementation of GPS trackers and questionnaires allowed to highlight the limitations of both methodologies and the benefits of using them together. New detection and follow-up strategies are still called for.
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Affiliation(s)
- Anaïs Pepey
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, 5 Blvd Monivong, Phnom Penh 120 210, Phnom Penh, BP983, Cambodia.
| | - Marc Souris
- UMR Unité des Virus Emergents, UVE: Aix-Marseille Univ-IRD 190-Inserm 1207-IHU 5 Méditerranée Infection, 13005, Marseille, France
| | - Saorin Kim
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, 5 Blvd Monivong, Phnom Penh 120 210, Phnom Penh, BP983, Cambodia
| | - Thomas Obadia
- Institut Pasteur, G5 Infectious Disease Epidemiology and Analytics, Université Paris Cité, 75015, Paris, France
- Institut Pasteur, Bioinformatics and Biostatistics Hub, Université Paris Cité, 75015, Paris, France
| | - Sophy Chy
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, 5 Blvd Monivong, Phnom Penh 120 210, Phnom Penh, BP983, Cambodia
| | - Malen Ea
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, 5 Blvd Monivong, Phnom Penh 120 210, Phnom Penh, BP983, Cambodia
| | - Sivkeng Ouk
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, 5 Blvd Monivong, Phnom Penh 120 210, Phnom Penh, BP983, Cambodia
| | - Franck Remoue
- UMR MIVEGEC, IRD, CNRS, University of Montpellier, Montpellier, France
| | - Siv Sovannaroth
- National Centre for Parasitology Entomology and Malaria Control (CNM), Phnom Penh 120 801, Phnom Penh, Cambodia
| | - Ivo Mueller
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia
- Department of Medical Biology, University of Melbourne, Melbourne, VIC, Australia
| | - Benoit Witkowski
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, 5 Blvd Monivong, Phnom Penh 120 210, Phnom Penh, BP983, Cambodia
- Genetic and Biology of Plasmodium Unit, Institut Pasteur de Madagascar, Antananarivo, Madagascar
| | - Amélie Vantaux
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, 5 Blvd Monivong, Phnom Penh 120 210, Phnom Penh, BP983, Cambodia
- Genetic and Biology of Plasmodium Unit, Institut Pasteur de Madagascar, Antananarivo, Madagascar
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Sa-Ngamuang C, Lawpoolsri S, Su Yin M, Barkowsky T, Cui L, Prachumsri J, Haddawy P. Assessment of malaria risk in Southeast Asia: a systematic review. Malar J 2023; 22:339. [PMID: 37940923 PMCID: PMC10631000 DOI: 10.1186/s12936-023-04772-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 10/26/2023] [Indexed: 11/10/2023] Open
Abstract
BACKGROUND Several countries in Southeast Asia are nearing malaria elimination, yet eradication remains elusive. This is largely due to the challenge of focusing elimination efforts, an area where risk prediction can play an essential supporting role. Despite its importance, there is no standard numerical method to quantify the risk of malaria infection. Thus, there is a need for a consolidated view of existing definitions of risk and factors considered in assessing risk to analyse the merits of risk prediction models. This systematic review examines studies of the risk of malaria in Southeast Asia with regard to their suitability in addressing the challenges of malaria elimination in low transmission areas. METHODS A search of four electronic databases over 2010-2020 retrieved 1297 articles, of which 25 met the inclusion and exclusion criteria. In each study, examined factors included the definition of the risk and indicators of malaria transmission used, the environmental and climatic factors associated with the risk, the statistical models used, the spatial and temporal granularity, and how the relationship between environment, climate, and risk is quantified. RESULTS This review found variation in the definition of risk used, as well as the environmental and climatic factors in the reviewed articles. GLM was widely adopted as the analysis technique relating environmental and climatic factors to malaria risk. Most of the studies were carried out in either a cross-sectional design or case-control studies, and most utilized the odds ratio to report the relationship between exposure to risk and malaria prevalence. CONCLUSIONS Adopting a standardized definition of malaria risk would help in comparing and sharing results, as would a clear description of the definition and method of collection of the environmental and climatic variables used. Further issues that need to be more fully addressed include detection of asymptomatic cases and considerations of human mobility. Many of the findings of this study are applicable to other low-transmission settings and could serve as a guideline for further studies of malaria in other regions.
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Affiliation(s)
- Chaitawat Sa-Ngamuang
- Faculty of Information and Communication Technology, Mahidol University, Nakhon Pathom, Thailand
| | - Saranath Lawpoolsri
- Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Myat Su Yin
- Faculty of Information and Communication Technology, Mahidol University, Nakhon Pathom, Thailand
| | - Thomas Barkowsky
- Bremen Spatial Cognition Center (BSCC), University of Bremen, Bremen, Germany
| | - Liwang Cui
- Division of Infectious Diseases and International Medicine, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, USA
| | - Jetsumon Prachumsri
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Peter Haddawy
- Faculty of Information and Communication Technology, Mahidol University, Nakhon Pathom, Thailand.
- Bremen Spatial Cognition Center (BSCC), University of Bremen, Bremen, Germany.
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Yu X, Fang M, Li Y, Yu J, Cheng L, Ding S, Kou Z. Epidemiological characteristics and spatio-temporal analysis of brucellosis in Shandong province, 2015-2021. BMC Infect Dis 2023; 23:669. [PMID: 37814221 PMCID: PMC10561485 DOI: 10.1186/s12879-023-08503-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 07/31/2023] [Indexed: 10/11/2023] Open
Abstract
BACKGROUND Brucellosis is one of the major public health problems in China, it not only causes huge economic losses to the society, but also threatens the human's physical and mental health. The reported cases of brucellosis in Shandong province were at a high level, therefore, it is necessary for us to understand the epidemic characteristics and distribution trend of Brucellosis in Shandong province. This study aims to describe the epidemiological characteristics and spatial clustering characteristics of brucellosis in Shandong Province, provide a reference for the scientific prevention and control. METHODS Human brucellosis data in Shandong province from 2015 to 2021 were obtained from the China Information System for Disease Control and Prevention, the data were analyzed by descriptive epidemiological methods, spatial autocorrelation analysis and spatial-temporal cluster analysis methods use ArcGIS and SaTScan software, the results were presented in ArcMap. RESULTS A total of 22,251 human cases of brucellosis were reported, the annual incidence ranged between 2.41/100,000 and 4.07/100,000 from 2015 to 2021 in Shandong province, incidence has been decreasing year by year, while there was a significant increase in 2021. The distribution of brucellosis was of a seasonal trend, mainly concentrating during March to August. The age of the cases was mainly concentrated in the 30-74 age ranges, the average annual incidence rate was significantly higher in males than in females. The spatial analysis showed that the epidemics were mainly concentrated in the north and southwest. For the spatial autocorrelation analysis, a high global autocorrelation was observed at the county level, and the high-high clusters mainly distributed in the north and southwest region. For the spatio-temporal scanning, the most likely cluster areas mainly distributed in the north area, and then gradually moved southward, and the radius of clustered narrowed. CONCLUSIONS Human brucellosis remains a common challenge, particularly in northern region in spring and summer. More disease prevention and control measures should be taken in high-risk populations, and such higher-risk susceptible areas to reduce the incidence of brucellosis and ensure the health of the people.
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Affiliation(s)
- Xiaolin Yu
- Institute for Communicable Disease Control and Prevention, Shandong provincial Center for Disease Control and Prevention, Jinan, Shandong, China
| | - Ming Fang
- Institute for Communicable Disease Control and Prevention, Shandong provincial Center for Disease Control and Prevention, Jinan, Shandong, China
| | - Yan Li
- Institute for Communicable Disease Control and Prevention, Shandong provincial Center for Disease Control and Prevention, Jinan, Shandong, China
| | - Jianmei Yu
- Institute for Communicable Disease Control and Prevention, Shandong provincial Center for Disease Control and Prevention, Jinan, Shandong, China
- Department of public health and health management, Shandong First Medical University, Jinan, Shandong, China
| | - Lixiao Cheng
- Institute for Communicable Disease Control and Prevention, Shandong provincial Center for Disease Control and Prevention, Jinan, Shandong, China
| | - Shujun Ding
- Institute for Communicable Disease Control and Prevention, Shandong provincial Center for Disease Control and Prevention, Jinan, Shandong, China
| | - Zengqiang Kou
- Institute for Communicable Disease Control and Prevention, Shandong provincial Center for Disease Control and Prevention, Jinan, Shandong, China.
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Chen I, Doum D, Mannion K, Hustedt J, Sovannaroth S, McIver D, Macdonald M, Lobo N, Tatarsky A, Handley MA, Neukom J. Applying the COM-B behaviour change model to a pilot study delivering volatile pyrethroid spatial repellents and insecticide-treated clothing to forest-exposed populations in Mondulkiri Province, Cambodia. Malar J 2023; 22:251. [PMID: 37658337 PMCID: PMC10472618 DOI: 10.1186/s12936-023-04685-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 08/22/2023] [Indexed: 09/03/2023] Open
Abstract
BACKGROUND Southeast Asia is making tremendous progress towards their 2030 malaria elimination goal but needs new interventions to stop forest malaria. This study trials two new vector control tools, a volatile pyrethroid spatial repellent (VPSR) and insecticide-treated clothing (ITC), amongst forest-exposed populations in Mondulkiri Province Cambodia to inform their potential use for eliminating forest malaria. METHODS 21 forest-exposed individuals were given a questionnaire on their perceptions of malaria and preventive practices used, after which they trialed two products sequentially. Clothes was treated with ITC by the study team. Mixed methods were used to understand their experience, attitudes, and preferences regarding the products trialed. Quantitative data was summarized and qualitative insights were analysed using thematic analysis, applying the Capability, Opportunity, and Motivation Behaviour Change (COM-B) model and Behaviour Change Wheel Framework to identify intervention functions to support tailored product rollout amongst these populations. RESULTS Study participants reported a need for protection from mosquito bites in outdoor and forest-exposed settings and perceived both products trialed to be effective for this purpose. The VPSR product was preferred when travel was not required, whereas ITC was preferred for ease of use when going to the forest, especially in rainy conditions. COM-B analysis identified that key enablers for use of both products included their perceived efficacy and ease of use, which required no skill or preparation. For barriers to use, the odour of ITC was sometimes perceived as being toxic, as well as its inability to protect uncovered skin from mosquito bites, while the perceived usefulness of the VPSR product trialed was limited by its water sensitivity in rainy forest settings. Intervention components to encourage appropriate and sustained use of these products include education about how to use these products and what to expect, persuasion to use them from community leaders and targeted channels, and enablement to facilitate convenient and affordable access. CONCLUSION The rollout of VPSRs and ITC amongst forest-exposed populations can be useful for eliminating malaria in Southeast Asia. Study findings can be applied to increase product uptake among forest exposed populations in Cambodia, while manufacturers can aim to develop products that are rainproof, easy to use in forest settings, and have favourable odour profiles to target users.
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Affiliation(s)
- Ingrid Chen
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, USA.
| | - Dyna Doum
- Health Forefront Organization, Phnom Penh, Cambodia
| | - Kylie Mannion
- Menzies School of Health Research, Charles Darwin University, Casuarina, Australia
| | - John Hustedt
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, USA
| | - Siv Sovannaroth
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - David McIver
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, USA
| | | | - Neil Lobo
- University of Notre Dame, Notre Dame, IN, USA
| | - Allison Tatarsky
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, USA
| | - Margaret A Handley
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, USA
| | - Josselyn Neukom
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, USA
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Doum D, Mclver DJ, Hustedt J, Hii J, Sovannaroth S, Lek D, Richardson JH, Tatarsky A, Lobo NF. An active and targeted survey reveals asymptomatic malaria infections among high-risk populations in Mondulkiri, Cambodia. Malar J 2023; 22:193. [PMID: 37353790 DOI: 10.1186/s12936-023-04630-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Accepted: 06/20/2023] [Indexed: 06/25/2023] Open
Abstract
BACKGROUND Malaria is a mosquito-borne disease that is one of the most serious public health issues globally and a leading cause of mortality in many developing countries worldwide. Knowing the prevalence of both symptomatic and asymptomatic malaria on a subnational scale allows for the estimation of the burden of parasitaemia present in the transmission system, enabling targeting and tailoring of resources towards greater impact and better use of available capacity. This study aimed to determine the PCR-based point prevalence of malaria infection, by parasite species, among three high-risk populations in Mondulkiri province, Cambodia: forest rangers, forest dwellers, and forest goers. METHODS A cross-sectional survey was performed during the transmission season in November and December 2021. Blood samples collected on filter paper from participants (n = 1301) from all target groups were screened for Plasmodium spp using PCR. RESULTS Malaria prevalence among all study participants was 6.7% for any Plasmodium species. Malaria prevalence in the forest ranger group was 8.1%, was 6.8% in forest goers, and 6.4% in forest dwellers; all infections were asymptomatic. Plasmodium vivax was detected in all participant groups, while the few Plasmodium falciparum infections were found in goers and dwellers. 81% of all infections were due to P. vivax, 9% were due to P. falciparum, 3% due to Plasmodium cynomolgi, and the rest (7%) remained undefined. Gender was associated with malaria infection prevalence, with male participants having higher odds of malaria infection than female participants (OR = 1.69, 95% CI 1.08-2.64). Passively collected malaria incidence data from the Cambodian government were also investigated. Health facility-reported malaria cases, based on rapid diagnostic tests, for the period Jan-Dec 2021 were 521 Plasmodium vivax (0.89% prevalence), 34 P. falciparum (0.06%) and four P. falciparum + mixed (0.01%)-a total of 559 cases (0.95%) for all of Mondulkiri. CONCLUSION This reservoir of asymptomatic parasitaemia may be perpetuating low levels of transmission, and thus, new strategies are required to realize the goal of eliminating malaria in Cambodia by 2025.
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Affiliation(s)
- Dyna Doum
- Health Forefront Organization, Phnom Penh, Cambodia
| | - David J Mclver
- Malaria Elimination Initiative, University of California, San Francisco, CA, USA.
| | - John Hustedt
- Health Forefront Organization, Phnom Penh, Cambodia
| | - Jeffrey Hii
- Malaria Elimination Initiative, University of California, San Francisco, CA, USA
| | - Siv Sovannaroth
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Dysoley Lek
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | | | - Allison Tatarsky
- Malaria Elimination Initiative, University of California, San Francisco, CA, USA
| | - Neil F Lobo
- Malaria Elimination Initiative, University of California, San Francisco, CA, USA
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, USA
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Sandfort M, Monteiro W, Lacerda M, Nguitragool W, Sattabongkot J, Waltmann A, Salje H, Vantaux A, Witkowski B, Robinson LJ, Mueller I, White M. The spatial signature of Plasmodium vivax and Plasmodium falciparum infections: quantifying the clustering of infections in cross-sectional surveys and cohort studies. Malar J 2023; 22:75. [PMID: 36870976 PMCID: PMC9985228 DOI: 10.1186/s12936-023-04515-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Accepted: 02/25/2023] [Indexed: 03/06/2023] Open
Abstract
BACKGROUND Over the last decades, enormous successes have been achieved in reducing malaria burden globally. In Latin America, South East Asia, and the Western Pacific, many countries now pursue the goal of malaria elimination by 2030. It is widely acknowledged that Plasmodium spp. infections cluster spatially so that interventions need to be spatially informed, e.g. spatially targeted reactive case detection strategies. Here, the spatial signature method is introduced as a tool to quantify the distance around an index infection within which other infections significantly cluster. METHODS Data were considered from cross-sectional surveys from Brazil, Thailand, Cambodia, and Solomon Islands, conducted between 2012 and 2018. Household locations were recorded by GPS and finger-prick blood samples from participants were tested for Plasmodium infection by PCR. Cohort studies from Brazil and Thailand with monthly sampling over a year from 2013 until 2014 were also included. The prevalence of PCR-confirmed infections was calculated at increasing distance around index infections (and growing time intervals in the cohort studies). Statistical significance was defined as prevalence outside of a 95%-quantile interval of a bootstrap null distribution after random re-allocation of locations of infections. RESULTS Prevalence of Plasmodium vivax and Plasmodium falciparum infections was elevated in close proximity around index infections and decreased with distance in most study sites, e.g. from 21.3% at 0 km to the global study prevalence of 6.4% for P. vivax in the Cambodian survey. In the cohort studies, the clustering decreased with longer time windows. The distance from index infections to a 50% reduction of prevalence ranged from 25 m to 3175 m, tending to shorter distances at lower global study prevalence. CONCLUSIONS The spatial signatures of P. vivax and P. falciparum infections demonstrate spatial clustering across a diverse set of study sites, quantifying the distance within which the clustering occurs. The method offers a novel tool in malaria epidemiology, potentially informing reactive intervention strategies regarding radius choices of operations around detected infections and thus strengthening malaria elimination endeavours.
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Affiliation(s)
- Mirco Sandfort
- Unité Malaria : Parasites Et Hôtes, Département Parasites Et Insectes Vecteurs, Institut Pasteur, Paris, France. .,Sorbonne Université, Collège Doctoral, Paris, France.
| | - Wuelton Monteiro
- Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Brazil.,Universidade do Estado do Amazonas, Manaus, Brazil
| | - Marcus Lacerda
- Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Brazil.,Universidade do Estado do Amazonas, Manaus, Brazil.,Instituto de Pesquisas Leônidas e Maria Deane, Manaus, Brazil
| | - Wang Nguitragool
- Department of Molecular Tropical Medicine & Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Jetsumon Sattabongkot
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Andreea Waltmann
- Population Health & Immunity Division, Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.,Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Henrik Salje
- Department of Genetics, University of Cambridge, Cambridge, UK
| | - Amélie Vantaux
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Benoit Witkowski
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Leanne J Robinson
- Population Health & Immunity Division, Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.,Department of Medical Biology, University of Melbourne, Melbourne, Australia.,Burnet Institute, Melbourne, Australia
| | - Ivo Mueller
- Unité Malaria : Parasites Et Hôtes, Département Parasites Et Insectes Vecteurs, Institut Pasteur, Paris, France.,Population Health & Immunity Division, Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.,Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Michael White
- Unité Malaria : Parasites Et Hôtes, Département Parasites Et Insectes Vecteurs, Institut Pasteur, Paris, France.,G5 Épidémiologie et Analyse des Maladies Infectieuses, Département de Santé Globale, Institut Pasteur, Paris, France
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Rerolle F, Dantzer E, Phimmakong T, Lover A, Hongvanthong B, Phetsouvanh R, Marshall J, Sturrock H, Bennett A. Characterizing mobility patterns of forest goers in southern Lao PDR using GPS loggers. Malar J 2023; 22:38. [PMID: 36732769 PMCID: PMC9893532 DOI: 10.1186/s12936-023-04468-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Accepted: 01/24/2023] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND In the Greater Mekong Subregion (GMS), forest-going populations are considered high-risk populations for malaria and are increasingly targeted by national control programmes' elimination efforts. A better understanding of forest-going populations' mobility patterns and risk associated with specific types of forest-going trips is necessary for countries in the GMS to achieve their objective of eliminating malaria by 2030. METHODS Between March and November 2018, as part of a focal test and treat intervention (FTAT), 2,904 forest-goers were recruited in southern Lao PDR. A subset of forest-goers carried an "i-Got-U" GPS logger for roughly 2 months, configured to collect GPS coordinates every 15 to 30 min. The utilization distribution (UD) surface around each GPS trajectory was used to extract trips to the forest and forest-fringes. Trips with shared mobility characteristics in terms of duration, timing and forest penetration were identified by a hierarchical clustering algorithm. Then, clusters of trips with increased exposure to dominant malaria vectors in the region were further classified as high-risk. Finally, gradient boosting trees were used to assess which of the forest-goers' socio-demographic and behavioural characteristics best predicted their likelihood to engage in such high-risk trips. RESULTS A total of 122 forest-goers accepted carrying a GPS logger resulting in the collection of 803 trips to the forest or forest-fringes. Six clusters of trips emerged, helping to classify 385 (48%) trips with increased exposure to malaria vectors based on high forest penetration and whether the trip happened overnight. Age, outdoor sleeping structures and number of children were the best predictors of forest-goers' probability of engaging in high-risk trips. The probability of engaging in high-risk trips was high (~ 33%) in all strata of the forest-going population. CONCLUSION This study characterized the heterogeneity within the mobility patterns of forest-goers and attempted to further segment their role in malaria transmission in southern Lao People's Democratic Republic (PDR). National control programmes across the region can leverage these results to tailor their interventions and messaging to high-risk populations and accelerate malaria elimination.
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Affiliation(s)
- Francois Rerolle
- grid.266102.10000 0001 2297 6811Malaria Elimination Initiative, The Global Health Group, University of California, San Francisco, CA USA ,grid.266102.10000 0001 2297 6811Department of Epidemiology and Biostatistics, University of California, San Francisco, CA USA
| | - Emily Dantzer
- grid.266102.10000 0001 2297 6811Malaria Elimination Initiative, The Global Health Group, University of California, San Francisco, CA USA
| | - Toula Phimmakong
- grid.415768.90000 0004 8340 2282Center for Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Lao People’s Democratic Republic
| | - Andrew Lover
- grid.266683.f0000 0001 2166 5835Department of Biostatistics and Epidemiology, School of Public Health and Health Sciences, University of Massachusetts, Amherst, MA USA
| | - Bouasy Hongvanthong
- grid.415768.90000 0004 8340 2282Center for Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Lao People’s Democratic Republic
| | - Rattanaxay Phetsouvanh
- grid.415768.90000 0004 8340 2282Center for Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Lao People’s Democratic Republic
| | - John Marshall
- grid.47840.3f0000 0001 2181 7878Divisions of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, CA USA
| | - Hugh Sturrock
- grid.266102.10000 0001 2297 6811Malaria Elimination Initiative, The Global Health Group, University of California, San Francisco, CA USA ,grid.266102.10000 0001 2297 6811Department of Epidemiology and Biostatistics, University of California, San Francisco, CA USA
| | - Adam Bennett
- grid.266102.10000 0001 2297 6811Malaria Elimination Initiative, The Global Health Group, University of California, San Francisco, CA USA ,grid.266102.10000 0001 2297 6811Department of Epidemiology and Biostatistics, University of California, San Francisco, CA USA ,grid.415269.d0000 0000 8940 7771Malaria and Neglected Tropical Diseases, PATH, Seattle, WA USA
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Oduma CO, Ombok M, Zhao X, Huwe T, Ondigo BN, Kazura JW, Grieco J, Achee N, Liu F, Ochomo E, Koepfli C. Altitude, not potential larval habitat availability, explains pronounced variation in Plasmodium falciparum infection prevalence in the western Kenya highlands. PLOS GLOBAL PUBLIC HEALTH 2023; 3:e0001505. [PMID: 37068071 PMCID: PMC10109483 DOI: 10.1371/journal.pgph.0001505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Accepted: 03/03/2023] [Indexed: 04/18/2023]
Abstract
Progress in malaria control has stalled over the recent years. Knowledge on main drivers of transmission explaining small-scale variation in prevalence can inform targeted control measures. We collected finger-prick blood samples from 3061 individuals irrespective of clinical symptoms in 20 clusters in Busia in western Kenya and screened for Plasmodium falciparum parasites using qPCR and microscopy. Clusters spanned an altitude range of 207 meters (1077-1284 m). We mapped potential mosquito larval habitats and determined their number within 250 m of a household and distances to households using ArcMap. Across all clusters, P. falciparum parasites were detected in 49.8% (1524/3061) of individuals by qPCR and 19.5% (596/3061) by microscopy. Across the clusters, prevalence ranged from 26% to 70% by qPCR. Three to 34 larval habitats per cluster and 0-17 habitats within a 250m radius around households were observed. Using a generalized linear mixed effect model (GLMM), a 5% decrease in the odds of getting infected per each 10m increase in altitude was observed, while the number of larval habitats and their proximity to households were not statistically significant predictors for prevalence. Kitchen located indoors, open eaves, a lower level of education of the household head, older age, and being male were significantly associated with higher prevalence. Pronounced variation in prevalence at small scales was observed and needs to be taken into account for malaria surveillance and control. Potential larval habitat frequency had no direct impact on prevalence.
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Affiliation(s)
- Colins O Oduma
- Department of Biochemistry and Molecular Biology, Egerton University, Nakuru, Kenya
- Kenya Medical Research Institute, Centre for Global Health Research, Kisumu, Kenya
| | - Maurice Ombok
- Kenya Medical Research Institute, Centre for Global Health Research, Kisumu, Kenya
| | - Xingyuan Zhao
- Department of Applied and Computational Mathematics and Statistics, University of Notre Dame, Notre Dame, IN, United States of America
| | - Tiffany Huwe
- Department of Biological Sciences and Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, United States of America
| | - Bartholomew N Ondigo
- Department of Biochemistry and Molecular Biology, Egerton University, Nakuru, Kenya
- Kenya Medical Research Institute, Centre for Global Health Research, Kisumu, Kenya
| | - James W Kazura
- Case Western Reserve University, Center for Global Health and Diseases, Cleveland, OH, United States of America
| | - John Grieco
- Department of Biological Sciences and Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, United States of America
| | - Nicole Achee
- Department of Biological Sciences and Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, United States of America
| | - Fang Liu
- Department of Applied and Computational Mathematics and Statistics, University of Notre Dame, Notre Dame, IN, United States of America
- Department of Biological Sciences and Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, United States of America
| | - Eric Ochomo
- Kenya Medical Research Institute, Centre for Global Health Research, Kisumu, Kenya
| | - Cristian Koepfli
- Department of Biological Sciences and Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, United States of America
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Loeffel M, Ross A. The relative impact of interventions on sympatric Plasmodium vivax and Plasmodium falciparum malaria: A systematic review. PLoS Negl Trop Dis 2022; 16:e0010541. [PMID: 35767578 PMCID: PMC9242512 DOI: 10.1371/journal.pntd.0010541] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Accepted: 05/27/2022] [Indexed: 11/18/2022] Open
Abstract
Background
In areas with both Plasmodium vivax and Plasmodium falciparum malaria, interventions can reduce the burden of both species but the impact may vary due to their different biology. Knowing the expected relative impact on the two species over time for vector- and drug-based interventions, and the factors affecting this, could help plan and evaluate intervention strategies.
Methods
For three interventions (treated bed nets (ITN), mass drug administration (MDA) and indoor residual spraying (IRS)), we identified studies providing information on the proportion of clinical illness and patent infections attributed to P. vivax over time using a literature search. The change in the proportion of malaria attributed to P. vivax up to two years since implementation was estimated using logistic regression accounting for clustering with random effects. Potential factors (intervention type, coverage, relapse pattern, transmission intensity, seasonality, initial proportion of P. vivax and round of intervention) were assessed.
Results
In total there were 55 studies found that led to 72 series of time-points for clinical case data and 69 series for patent infection data. The main reason of study exclusion was insufficient information on interventions. There was considerable variation in the proportion of malaria attributed to P. vivax over time by study and location for all of the interventions. Overall, there was an increase apart from MDA in the short-term. The potential factors could not be ruled in or out. Although not consistently significant, coverage, transmission intensity and relapse pattern are possible factors that explain some of the variation found.
Conclusion
While there are reports of an increase in the proportion of malaria due to P. vivax following interventions in the long-term, there was substantial variation for the shorter time-scales considered in this study (up to 24 months for IRS and ITN, and up to six months for MDA). The large variability points to the need for the monitoring of both species after an intervention. Studies should report intervention timing and characteristics to allow inclusion in systematic reviews.
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Affiliation(s)
- Melanie Loeffel
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland
- University of Basel, Basel, Switzerland
| | - Amanda Ross
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland
- University of Basel, Basel, Switzerland
- * E-mail:
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10
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Pepey A, Obadia T, Kim S, Sovannaroth S, Mueller I, Witkowski B, Vantaux A, Souris M. Mobility evaluation by GPS tracking in a rural, low-income population in Cambodia. PLoS One 2022; 17:e0266460. [PMID: 35559983 PMCID: PMC9106150 DOI: 10.1371/journal.pone.0266460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 03/21/2022] [Indexed: 01/31/2023] Open
Abstract
Global Positioning System (GPS) technology is an effective tool for quantifying individuals' mobility patterns and can be used to understand their influence on infectious disease transmission. In Cambodia, mobility measurements have been limited to questionnaires, which are of limited efficacy in rural environments. In this study, we used GPS tracking to measure the daily mobility of Cambodian forest goers, a population at high risk of malaria, and developed a workflow adapted to local constraints to produce an optimal dataset representative of the participants' mobility. We provide a detailed assessment of the GPS tracking and analysis of the data, and highlight the associated difficulties to facilitate the implementation of similar studies in the future.
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Affiliation(s)
- Anaïs Pepey
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
- * E-mail:
| | - Thomas Obadia
- Department of Parasites and Insect Vectors, Infectious Diseases Epidemiology and Analytics, Institut Pasteur, Paris, France
- Département de Biologie Computationnelle, Hub de Bioinformatique et Biostatistique, Institut Pasteur, Paris, France
| | - Saorin Kim
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Siv Sovannaroth
- National Centre for Parasitology Entomology and Malaria Control (CNM), Phnom Penh, Cambodia
| | - Ivo Mueller
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Melbourne, Victoria, Australia
| | - Benoit Witkowski
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Amélie Vantaux
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Marc Souris
- UMR Unité des Virus Emergents, UVE: Aix-Marseille Univ–IRD 190–Inserm 1207–IHU 5 Méditerranée Infection, Marseille, France
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11
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Toma SA, Eneyew BW, Taye GA. Spatial Modelling of Risk Factors for Malaria Prevalence in SNNP Regional State, Ethiopia. Ethiop J Health Sci 2021; 31:731-742. [PMID: 34703172 PMCID: PMC8512951 DOI: 10.4314/ejhs.v31i4.7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 03/05/2021] [Indexed: 11/24/2022] Open
Abstract
Background Malaria is one of the most severe public health problems worldwide with 300 to 500 million cases and about one million deaths reported to date of which 90% were from world health organization (WHO) Sub Saharan Africa (SSA) countries. The purpose of this study was to explore the spatial distribution of malaria parasite prevalence (MPP) among districts of Southern Nations Nationalities and Peoples Regional State (SNNRS) in Ethiopia by using 2011 malaria indicator survey (MIS) data collected for 76 districts and to model its relationship with different covariates. Method Exploratory spatial data analysis (ESDA) was conducted followed by implementation of spatial lag model (SLM) and spatial error model (SEM) in GeoDa software. Queen contiguity second order type of spatial weight matrix was applied in order to formalize spatial interaction among districts. Results From ESDA, we found positive spatial autocorrelation in malaria prevalence rate. Hot spot areas for MPP were found in the eastern and southeast parts of the region. Relying on specification diagnostics and measures of fit, SLM was found to be the best model for explaining the geographical variation of MPP. SLM analysis demonstrated that proportion of households living in earth/local dung plastered floor house, proportion of households living under thatched roof house, average number of rooms/person in a given district, proportion of households who used anti-malaria spray in the last 12 months before the survey, percentage household using mosquito nets and average number of mosquito nets/person in a given district have positive and statistically significant effect on spatial distribution of MPP across districts of SNNPRS. Percentage of households living without access to radio and television has negative and statistically significant effect on spatial distribution of MPP across districts of MPP. Conclusion Malaria is spatially clustered in space. The implication of the spatial clustering is that, in cases where the decisions on how to allocate funds for interventions needs to have spatial dimension.
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Affiliation(s)
- Shammena Aklilu Toma
- Department of Statistics, College of Natural and Computational Sciences, Hawassa University, Hawassa, Ethiopia
| | - Baleh Wubejig Eneyew
- Department of Statistics, College of Natural and Computational Sciences, Hawassa University, Hawassa, Ethiopia
| | - Goshu Ayele Taye
- Department of Statistics, College of Natural and Computational Sciences, Kotebe Metropolitan University, Addis Ababa, Ethiopia
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Clustering of malaria in households in the Greater Mekong Subregion: operational implications for reactive case detection. Malar J 2021; 20:351. [PMID: 34446009 PMCID: PMC8393740 DOI: 10.1186/s12936-021-03879-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Accepted: 08/15/2021] [Indexed: 11/10/2022] Open
Abstract
Background Malaria reactive case detection is the testing and, if positive, treatment of close contacts of index cases. It is included in national malaria control programmes of countries in the Greater Mekong Subregion to accelerate malaria elimination. Yet the value of reactive case detection in the control and elimination of malaria remains controversial because of the low yield, limited evidence for impact, and high demands on resources. Methods Data from the epidemiological assessments of large mass drug administration (MDA) studies in Myanmar, Vietnam, Cambodia and Laos were analysed to explore malaria infection clustering in households. The proportion of malaria positive cases among contacts screened in a hypothetical reactive case detection programme was then determined. The parasite density thresholds for rapid diagnostic test (RDT) detection was assumed to be > 50/µL (50,000/mL), for dried-blood-spot (DBS) based PCR > 5/µL (5000/mL), and for ultrasensitive PCR (uPCR) with a validated limit of detection at 0.0022/µL (22/mL). Results At baseline, before MDA, 1223 Plasmodium infections were detected by uPCR in 693 households. There was clustering of Plasmodium infections. In 637 households with asymptomatic infections 44% (278/637) had more than one member with Plasmodium infections. In the 132 households with symptomatic infections, 65% (86/132) had more than one member with Plasmodium infections. At baseline 4% of households had more than one Plasmodium falciparum infection, but three months after MDA no household had more than one P. falciparum infected member. Reactive case detection using DBS PCR would have detected ten additional cases in six households, and an RDT screen would have detected five additional cases in three households among the 169 households with at least one RDT positive case. This translates to 19 and 9 additional cases identified per 1000 people screened, respectively. Overall, assuming all febrile RDT positive patients would seek treatment and provoke reactive case detection using RDTs, then 1047 of 1052 (99.5%) Plasmodium infections in these communities would have remained undetected. Conclusion Reactive case detection in the Greater Mekong subregion is predicted to have a negligible impact on the malaria burden, but it has substantial costs in terms of human and financial resources. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-021-03879-9.
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13
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Investigating differences in village-level heterogeneity of malaria infection and household risk factors in Papua New Guinea. Sci Rep 2021; 11:16540. [PMID: 34400687 PMCID: PMC8367982 DOI: 10.1038/s41598-021-95959-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 07/27/2021] [Indexed: 11/13/2022] Open
Abstract
Malaria risk is highly heterogeneous. Understanding village and household-level spatial heterogeneity of malaria risk can support a transition to spatially targeted interventions for malaria elimination. This analysis uses data from cross-sectional prevalence surveys conducted in 2014 and 2016 in two villages (Megiar and Mirap) in Papua New Guinea. Generalised additive modelling was used to characterise spatial heterogeneity of malaria risk and investigate the contribution of individual, household and environmental-level risk factors. Following a period of declining malaria prevalence, the prevalence of P. falciparum increased from 11.4 to 19.1% in Megiar and 12.3 to 28.3% in Mirap between 2014 and 2016, with focal hotspots observed in these villages in 2014 and expanding in 2016. Prevalence of P. vivax was similar in both years (20.6% and 18.3% in Megiar, 22.1% and 23.4% in Mirap) and spatial risk heterogeneity was less apparent compared to P. falciparum. Within-village hotspots varied by Plasmodium species across time and between villages. In Megiar, the adjusted odds ratio (AOR) of infection could be partially explained by household factors that increase risk of vector exposure, such as collecting outdoor surface water as a main source of water. In Mirap, increased AOR overlapped with proximity to densely vegetated areas of the village. The identification of household and environmental factors associated with increased spatial risk may serve as useful indicators of transmission hotspots and inform the development of tailored approaches for malaria control.
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14
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Population size estimation of seasonal forest-going populations in southern Lao PDR. Sci Rep 2021; 11:14816. [PMID: 34285321 PMCID: PMC8292394 DOI: 10.1038/s41598-021-94413-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 06/02/2021] [Indexed: 11/09/2022] Open
Abstract
Forest-going populations are key to malaria transmission in the Greater Mekong Sub-region (GMS) and are therefore targeted for elimination efforts. Estimating the size of this population is essential for programs to assess, track and achieve their elimination goals. Leveraging data from three cross-sectional household surveys and one survey among forest-goers, the size of this high-risk population in a southern province of Lao PDR between December 2017 and November 2018 was estimated by two methods: population-based household surveys and capture-recapture. During the first month of the dry season, the first month of the rainy season, and the last month of the rainy season, respectively, 16.2% [14.7; 17.7], 9.3% [7.2; 11.3], and 5.3% [4.4; 6.1] of the adult population were estimated to have engaged in forest-going activities. The capture-recapture method estimated a total population size of 18,426 [16,529; 20,669] forest-goers, meaning 61.0% [54.2; 67.9] of the adult population had engaged in forest-going activities over the 12-month study period. This study demonstrates two methods for population size estimation to inform malaria research and programming. The seasonality and turnover within this forest-going population provide unique opportunities and challenges for control programs across the GMS as they work towards malaria elimination.
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15
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Khundi M, Carpenter JR, Nliwasa M, Cohen T, Corbett EL, MacPherson P. Effectiveness of spatially targeted interventions for control of HIV, tuberculosis, leprosy and malaria: a systematic review. BMJ Open 2021; 11:e044715. [PMID: 34257091 PMCID: PMC8278879 DOI: 10.1136/bmjopen-2020-044715] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Accepted: 06/15/2021] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND As infectious diseases approach global elimination targets, spatial targeting is increasingly important to identify community hotspots of transmission and effectively target interventions. We aimed to synthesise relevant evidence to define best practice approaches and identify policy and research gaps. OBJECTIVE To systematically appraise evidence for the effectiveness of spatially targeted community public health interventions for HIV, tuberculosis (TB), leprosy and malaria. DESIGN Systematic review. DATA SOURCES We searched Medline, Embase, Global Health, Web of Science and Cochrane Database of Systematic Reviews between 1 January 1993 and 22 March 2021. STUDY SELECTION The studies had to include HIV or TB or leprosy or malaria and spatial hotspot definition, and community interventions. DATA EXTRACTION AND SYNTHESIS A data extraction tool was used. For each study, we summarised approaches to identifying hotpots, intervention design and effectiveness of the intervention. RESULTS Ten studies, including one cluster randomised trial and nine with alternative designs (before-after, comparator area), satisfied our inclusion criteria. Spatially targeted interventions for HIV (one USA study), TB (three USA) and leprosy (two Brazil, one Federated States of Micronesia) each used household location and disease density to define hotspots followed by community-based screening. Malaria studies (one each from India, Indonesia and Kenya) used household location and disease density for hotspot identification followed by complex interventions typically combining community screening, larviciding of stagnant water bodies, indoor residual spraying and mass drug administration. Evidence of effect was mixed. CONCLUSIONS Studies investigating spatially targeted interventions were few in number, and mostly underpowered or otherwise limited methodologically, affecting interpretation of intervention impact. Applying advanced epidemiological methodologies supporting more robust hotspot identification and larger or more intensive interventions would strengthen the evidence-base for this increasingly important approach. PROSPERO REGISTRATION NUMBER CRD42019130133.
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Affiliation(s)
- McEwen Khundi
- Public Health, Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
- Medical Statistics, London School of Hygiene and Tropical Medicine, London, UK
| | - James R Carpenter
- Medical Statistics, London School of Hygiene and Tropical Medicine, London, UK
- MRC Clinical Trials Unit, University College London, London, UK
| | - Marriott Nliwasa
- Helse Nord Tuberculosis Initiative, University of Malawi College of Medicine, Blantyre, Malawi
| | - Ted Cohen
- School of Public Health, Yale University, New Haven, Connecticut, USA
| | - Elizabeth L Corbett
- Public Health, Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
- Department of Clinical Research, London School of Hygiene & Tropical Medicine, London, UK
| | - Peter MacPherson
- Public Health, Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
- Medical Statistics, London School of Hygiene and Tropical Medicine, London, UK
- Department of Clinical Sciences, Liverpool School of Tropical Medicine, Liverpool, UK
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16
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Vantaux A, Riehle MM, Piv E, Farley EJ, Chy S, Kim S, Corbett AG, Fehrman RL, Pepey A, Eiglmeier K, Lek D, Siv S, Mueller I, Vernick KD, Witkowski B. Anopheles ecology, genetics and malaria transmission in northern Cambodia. Sci Rep 2021; 11:6458. [PMID: 33742030 PMCID: PMC7979810 DOI: 10.1038/s41598-021-85628-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 03/04/2021] [Indexed: 12/20/2022] Open
Abstract
In the Greater Mekong Subregion, malaria cases have significantly decreased but little is known about the vectors or mechanisms responsible for residual malaria transmission. We analysed a total of 3920 Anopheles mosquitoes collected during the rainy and dry seasons from four ecological settings in Cambodia (villages, forested areas near villages, rubber tree plantations and forest sites). Using odor-baited traps, 81% of the total samples across all sites were collected in cow baited traps, although 67% of the samples attracted by human baited traps were collected in forest sites. Overall, 20% of collected Anopheles were active during the day, with increased day biting during the dry season. 3131 samples were identified morphologically as 14 different species, and a subset was also identified by DNA amplicon sequencing allowing determination of 29 Anopheles species. The investigation of well characterized insecticide mutations (ace-1, kdr, and rdl genes) indicated that individuals carried mutations associated with response to all the different classes of insecticides. There also appeared to be a non-random association between mosquito species and insecticide resistance with Anopheles peditaeniatus exhibiting nearly fixed mutations. Molecular screening for Plasmodium sp. presence indicated that 3.6% of collected Anopheles were positive, most for P. vivax followed by P. falciparum. These results highlight some of the key mechanisms driving residual human malaria transmission in Cambodia, and illustrate the importance of diverse collection methods, sites and seasons to avoid bias and better characterize Anopheles mosquito ecology in Southeast Asia.
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Affiliation(s)
- Amélie Vantaux
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia.
| | - Michelle M Riehle
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Eakpor Piv
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Elise J Farley
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Sophy Chy
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Saorin Kim
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Anneli G Corbett
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Rachel L Fehrman
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Anais Pepey
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Karin Eiglmeier
- Unit of Insect Vector Genetics and Genomics, Department of Parasites and Insect Vectors, Institut Pasteur, Paris, France.,CNRS Unit of Evolutionary Genomics, Modeling, and Health (UMR2000), Institut Pasteur, Paris, France
| | - Dysoley Lek
- National Center for Parasitology, Entomology and Malaria Control Program, Phnom Penh, Cambodia.,School of Public Health, National Institute of Public Health, Phnom Penh, Cambodia
| | - Sovannaroth Siv
- National Center for Parasitology, Entomology and Malaria Control Program, Phnom Penh, Cambodia
| | - Ivo Mueller
- Malaria: Parasites and Hosts Unit, Institut Pasteur, Paris, France
| | - Kenneth D Vernick
- Unit of Insect Vector Genetics and Genomics, Department of Parasites and Insect Vectors, Institut Pasteur, Paris, France.,CNRS Unit of Evolutionary Genomics, Modeling, and Health (UMR2000), Institut Pasteur, Paris, France
| | - Benoit Witkowski
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
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17
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Malaria in Cambodia: A Retrospective Analysis of a Changing Epidemiology 2006-2019. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:ijerph18041960. [PMID: 33670471 PMCID: PMC7922556 DOI: 10.3390/ijerph18041960] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 01/22/2021] [Accepted: 02/12/2021] [Indexed: 11/17/2022]
Abstract
Background: In Cambodia, malaria persists with changing epidemiology and resistance to antimalarials. This study aimed to describe how malaria has evolved spatially from 2006 to 2019 in Cambodia. Methods: We undertook a secondary analysis of existing malaria data from all government healthcare facilities in Cambodia. The epidemiology of malaria was described by sex, age, seasonality, and species. Spatial clusters at the district level were identified with a Poisson model. Results: Overall, incidence decreased from 7.4 cases/1000 population in 2006 to 1.9 in 2019. The decrease has been drastic for females, from 6.7 to 0.6/1000. Adults aged 15–49 years had the highest malaria incidence among all age groups. The proportion of Plasmodium (P.) falciparum + Mixed among confirmed cases declined from 87.9% (n = 67,489) in 2006 to 16.6% (n = 5290) in 2019. Clusters of P. falciparum + Mixed and P. vivax + Mixed were detected in forested provinces along all national borders. Conclusions: There has been a noted decrease in P. falciparum cases in 2019, suggesting that an intensification plan should be maintained. A decline in P. vivax cases was also noted, although less pronounced. Interventions aimed at preventing new infections of P. vivax and relapses should be prioritized. All detected malaria cases should be captured by the national surveillance system to avoid misleading trends.
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18
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Sandfort M, Vantaux A, Kim S, Obadia T, Pepey A, Gardais S, Khim N, Lek D, White M, Robinson LJ, Witkowski B, Mueller I. Forest malaria in Cambodia: the occupational and spatial clustering of Plasmodium vivax and Plasmodium falciparum infection risk in a cross-sectional survey in Mondulkiri province, Cambodia. Malar J 2020; 19:413. [PMID: 33213471 PMCID: PMC7678315 DOI: 10.1186/s12936-020-03482-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 11/04/2020] [Indexed: 02/24/2023] Open
Abstract
Background After a marked reduction in malaria burden in Cambodia over the last decades, case numbers increased again in 2017–2018. In light of the national goal of malaria elimination by 2025, remaining pockets of high risk need to be well defined and strategies well-tailored to identify and target the persisting burden cost-effectively. This study presents species-specific prevalence estimates and risk stratification for a remote area in Cambodia. Methods A cross-sectional survey was conducted in 17 villages in the high-incidence province Mondulkiri in the dry season (December 2017 to April 2018). 4200 randomly selected participants (2–80 years old) were tested for Plasmodium infection by PCR. Risk of infection was associated with questionnaire-derived covariates and spatially stratified based on household GPS coordinates. Results The prevalence of PCR-detectable Plasmodium infection was 8.3% (349/4200) and was more than twice as high for Plasmodium vivax (6.4%, 268) than for Plasmodium falciparum (3.0%, 125, p < 0.001). 97.8% (262/268) of P. vivax and 92.8% (116/125, p < 0.05) of P. falciparum infections were neither accompanied by symptoms at the time of the interview nor detected by microscopy or RDT. Recent travels to forest sites (aOR 2.17, p < 0.01) and forest work (aOR 2.88, p < 0.001) were particularly strong risk factors and risk profiles for both species were similar. Large village-level differences in prevalence of Plasmodium infection were observed, ranging from 0.6% outside the forest to 40.4% inside. Residing in villages at the forest fringe or inside the forest compared to outside was associated with risk of infection (aOR 2.14 and 12.47, p < 0.001). Villages inside the forest formed spatial hotspots of infection despite adjustment for the other risk factors. Conclusions Persisting pockets of high malaria risk were detected in forested areas and in sub-populations engaging in forest-related activities. High levels of asymptomatic infections suggest the need of better case detection plans and the predominance of P. vivax the implementation of radical cure. In villages inside the forest, within-village exposure was indicated in addition to risk due to forest activities. Village-level stratification of targeted interventions based on forest proximity could render the elimination efforts more cost-effective and successful.
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Affiliation(s)
- Mirco Sandfort
- Malaria: Parasites and Hosts Unit, Institut Pasteur, Paris, France. .,Sorbonne Université, Collège doctoral, Paris, France.
| | - Amélie Vantaux
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Saorin Kim
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Thomas Obadia
- Malaria: Parasites and Hosts Unit, Institut Pasteur, Paris, France.,Hub de Bioinformatique et Biostatistique, Département Biologie Computationnelle, Institut Pasteur, USR 3756 CNRS, Paris, France
| | - Anaïs Pepey
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Soazic Gardais
- Malaria: Parasites and Hosts Unit, Institut Pasteur, Paris, France
| | - Nimol Khim
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Dysoley Lek
- National Centre for Parasitology, Entomology, and Malaria Control, Phnom Penh, Cambodia.,School of Public Health, National Institute of Public Health, Phnom Penh, Cambodia
| | - Michael White
- Malaria: Parasites and Hosts Unit, Institut Pasteur, Paris, France.,Population Health & Immunity, Walter and Eliza Hall Institute, Melbourne, Australia
| | - Leanne J Robinson
- Population Health & Immunity, Walter and Eliza Hall Institute, Melbourne, Australia.,University of Melbourne, Melbourne, Australia.,Burnet Institute, Melbourne, Australia
| | - Benoit Witkowski
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Ivo Mueller
- Malaria: Parasites and Hosts Unit, Institut Pasteur, Paris, France.,Population Health & Immunity, Walter and Eliza Hall Institute, Melbourne, Australia.,University of Melbourne, Melbourne, Australia
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19
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Matin MA, Sarkar NDP, Phru CS, Ley B, Thriemer K, Price RN, Peeters Grietens K, Ali Khan W, Alam MS, Gryseels C. Precarity at the Margins of Malaria Control in the Chittagong Hill Tracts in Bangladesh: A Mixed-Methods Study. Pathogens 2020; 9:pathogens9100840. [PMID: 33066621 PMCID: PMC7602388 DOI: 10.3390/pathogens9100840] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 10/05/2020] [Accepted: 10/13/2020] [Indexed: 01/12/2023] Open
Abstract
Bangladesh has achieved significant progress towards malaria elimination, although health service delivery for malaria remains challenging in remote forested areas such as the Chittagong Hill Tracts (CHT). The aim of this study was to investigate perceptions of malaria and its treatment among the local population to inform contextualized strategies for rolling out radical cure for P. vivax in Bangladesh. The study comprised two sequential strands whereby the preliminary results of a qualitative strand informed the development of a structured survey questionnaire used in the quantitative strand. Results show that ethnic minority populations in the CHT live in precarious socio-economic conditions which increase their exposure to infectious diseases, and that febrile patients often self-treat, including home remedies and pharmaceuticals, before attending a healthcare facility. Perceived low quality of care and lack of communication between Bengali health providers and ethnic minority patients also affects access to public healthcare. Malaria is viewed as a condition that affects vulnerable people weakened by agricultural work and taking away blood is perceived to increase such vulnerability. Healthcare providers that initiate and sustain a dialogue about these issues with ethnic minority patients may foster the trust that is needed for local malaria elimination efforts.
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Affiliation(s)
- Mohammad Abdul Matin
- International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), 68, Shaheed Tajuddin Ahmed Sarani Mohakhali, Dhaka 1212, Bangladesh; (M.A.M.); (C.S.P.); (W.A.K.); (M.S.A.)
| | - Nandini D. P. Sarkar
- Department of Public Health, Institute of Tropical Medicine (ITM), Nationalestraat 155, 2000 Antwerp, Belgium; (N.D.P.S.); (K.P.G.)
| | - Ching Swe Phru
- International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), 68, Shaheed Tajuddin Ahmed Sarani Mohakhali, Dhaka 1212, Bangladesh; (M.A.M.); (C.S.P.); (W.A.K.); (M.S.A.)
| | - Benedikt Ley
- Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Rocklands Drive Casuarina, Darwin Northern Territory 0810, Australia; (B.L.); (K.T.); (R.N.P.)
| | - Kamala Thriemer
- Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Rocklands Drive Casuarina, Darwin Northern Territory 0810, Australia; (B.L.); (K.T.); (R.N.P.)
| | - Ric N. Price
- Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Rocklands Drive Casuarina, Darwin Northern Territory 0810, Australia; (B.L.); (K.T.); (R.N.P.)
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford OX3 7LG, UK
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvith Road, Tungphyathai, Bangkok 10400, Thailand
| | - Koen Peeters Grietens
- Department of Public Health, Institute of Tropical Medicine (ITM), Nationalestraat 155, 2000 Antwerp, Belgium; (N.D.P.S.); (K.P.G.)
| | - Wasif Ali Khan
- International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), 68, Shaheed Tajuddin Ahmed Sarani Mohakhali, Dhaka 1212, Bangladesh; (M.A.M.); (C.S.P.); (W.A.K.); (M.S.A.)
| | - Mohammad Shafiul Alam
- International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), 68, Shaheed Tajuddin Ahmed Sarani Mohakhali, Dhaka 1212, Bangladesh; (M.A.M.); (C.S.P.); (W.A.K.); (M.S.A.)
| | - Charlotte Gryseels
- Department of Public Health, Institute of Tropical Medicine (ITM), Nationalestraat 155, 2000 Antwerp, Belgium; (N.D.P.S.); (K.P.G.)
- Correspondence: ; Tel.: +324-8561-8475
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20
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Liang PF, Zhao Y, Zhao JH, Pan DF, Guo ZQ. Human distribution and spatial-temporal clustering analysis of human brucellosis in China from 2012 to 2016. Infect Dis Poverty 2020; 9:142. [PMID: 33050950 PMCID: PMC7557093 DOI: 10.1186/s40249-020-00754-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 09/10/2020] [Indexed: 12/19/2022] Open
Abstract
Background Brucellosis is a major public health issue in China, while its temporal and spatial distribution have not been studied in depth. This study aims to better understand the epidemiology of brucellosis in the mainland of China, by investigating the human, temporal and spatial distribution and clustering characteristics of the disease. Methods Human brucellosis data from the mainland of China between 2012 and 2016 were obtained from the China Information System for Disease Control and Prevention. The spatial autocorrelation analysis of ArcGIS10.6 and the spatial-temporal scanning analysis of SaTScan software were used to identify potential changes in the spatial and temporal distribution of human brucellosis in the mainland of China during the study period. Results A total of 244 348 human brucellosis cases were reported during the study period of 2012–2016. The average incidence of human brucellosis was higher in the 40–65 age group. The temporal clustering analysis showed that the high incidence of brucellosis occurred between March and July. The spatial clustering analysis showed that the location of brucellosis clustering in the mainland of China remained relatively fixed, mainly concentrated in most parts of northern China. The results of the spatial-temporal clustering analysis showed that Heilongjiang represents a primary clustering area, and the Tibet, Shanxi and Hubei provinces represent three secondary clustering areas. Conclusions Human brucellosis remains a widespread challenge, particularly in northern China. The clustering analysis highlights potential high-risk human groups, time frames and areas, which may require special plans and resources to monitor and control the disease.
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Affiliation(s)
- Pei-Feng Liang
- Department of medical record and statistics, People's hospital of Ningxia Hui Autonomous region, Yinchuan, 750004, China.,Xiangya Medical College, Central South University, Changsha, 410013, China
| | - Yuan Zhao
- Department of Epidemiology and Biostatistics, School of Public Health and management, Ningxia Medical University, Yinchuan, 750001, China
| | - Jian-Hua Zhao
- Ningxia Center for Diseases Prevention and Control, Yinchuan, 750001, China
| | - Dong-Feng Pan
- Department of Emergency, People's hospital of Ningxia Hui Autonomous region, Yinchuan, 750004, China
| | - Zhong-Qin Guo
- Department of Epidemiology and Biostatistics, School of Public Health and management, Ningxia Medical University, Yinchuan, 750001, China.
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21
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Kotepui M, Kotepui KU, Milanez GD, Masangkay FR. Prevalence and proportion of Plasmodium spp. triple mixed infections compared with double mixed infections: a systematic review and meta-analysis. Malar J 2020; 19:224. [PMID: 32580721 PMCID: PMC7315477 DOI: 10.1186/s12936-020-03292-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Accepted: 06/17/2020] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Although mixed infection by two Plasmodium species has been recognized, mixed infection by three different Plasmodium species within one individual has not been clarified. This study sought to determine the pooled prevalence and proportion of triple mixed Plasmodium spp. infection compared with double mixed infection. METHODS Articles from PubMed, Scopus, and Web of Science were searched for cross-sectional studies of triple mixed infection by Plasmodium species and then were retrieved and extracted. The pooled proportion and prevalence of triple mixed infection by Plasmodium species were subjected to random-effects analysis. The secondary outcomes were differences in the pooled proportion between triple mixed infection and double mixed infection by Plasmodium species reported in the included studies. RESULTS Of 5621 identified studies, triple mixed infection data were available for 35 records, including 601 patients from 22 countries. The overall pooled prevalence of triple mixed infection was 4% (95% Confidence Interval (CI) 3-5%; I2 = 92.5%). The pooled proportion of triple mixed infection compared with double mixed infection was 12% (95% CI 9-18; I2 = 91%). Most of the included studies (29/35; 82.9%) presented a lower proportion of triple mixed infection than double mixed infection. Subgroup analysis demonstrated that the proportion of triple mixed infection was the highest in Oceania (23%; 95% CI 15-36%) and Europe (21%; 95% CI 5-86%), but the lowest in the USA (3%; 95% CI 2-4%). Moreover, the proportion of triple mixed infection was higher in residents (20%; 95% CI 14-29%) than in febrile patients (7%; 95% CI 4-13%), when compared with the proportion of double mixed infection. Subgroup analysis of the age groups demonstrated that, compared with the proportion of double mixed infection, triple mixed infection was lower in patients aged ≤ 5 years (OR = 0.27; 95% CI 0.13-0.56; I2 = 31%) and > 5 years (OR = 0.09; 95% CI 0.04-0.25, I2 = 78%). CONCLUSIONS The present study suggested that, in areas where triple mixed infection were endemic, PCR or molecular diagnosis for all residents in communities where malaria is submicroscopic can provide prevalence data and intervention measures, as well as prevent disease transmission and enhance malaria elimination efforts.
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Affiliation(s)
- Manas Kotepui
- Medical Technology, School of Allied Health Sciences, Walailak University, Tha Sala, Nakhon Si Thammarat, Thailand.
| | - Kwuntida Uthaisar Kotepui
- Medical Technology, School of Allied Health Sciences, Walailak University, Tha Sala, Nakhon Si Thammarat, Thailand
| | - Giovanni D Milanez
- Department of Medical Technology, Far Eastern University-Manila, Manila, Philippines
| | - Frederick R Masangkay
- Department of Medical Technology, Far Eastern University-Manila, Manila, Philippines
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22
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Bannister-Tyrrell M, Krit M, Sluydts V, Tho S, Sokny M, Mean V, Kim S, Menard D, Grietens KP, Abrams S, Hens N, Coosemans M, Bassat Q, van Hensbroek MB, Durnez L, Van Bortel W. Households or Hotspots? Defining Intervention Targets for Malaria Elimination in Ratanakiri Province, Eastern Cambodia. J Infect Dis 2020; 220:1034-1043. [PMID: 31028393 PMCID: PMC6688056 DOI: 10.1093/infdis/jiz211] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Accepted: 04/25/2019] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Malaria "hotspots" have been proposed as potential intervention units for targeted malaria elimination. Little is known about hotspot formation and stability in settings outside sub-Saharan Africa. METHODS Clustering of Plasmodium infections at the household and hotspot level was assessed over 2 years in 3 villages in eastern Cambodia. Social and spatial autocorrelation statistics were calculated to assess clustering of malaria risk, and logistic regression was used to assess the effect of living in a malaria hotspot compared to living in a malaria-positive household in the first year of the study on risk of malaria infection in the second year. RESULTS The crude prevalence of Plasmodium infection was 8.4% in 2016 and 3.6% in 2017. Living in a hotspot in 2016 did not predict Plasmodium risk at the individual or household level in 2017 overall, but living in a Plasmodium-positive household in 2016 strongly predicted living in a Plasmodium-positive household in 2017 (Risk Ratio, 5.00 [95% confidence interval, 2.09-11.96], P < .0001). There was no consistent evidence that malaria risk clustered in groups of socially connected individuals from different households. CONCLUSIONS Malaria risk clustered more clearly in households than in hotspots over 2 years. Household-based strategies should be prioritized in malaria elimination programs in this region.
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Affiliation(s)
| | | | - Vincent Sluydts
- Institute of Tropical Medicine, Antwerp.,University of Antwerp, Belgium
| | - Sochantha Tho
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh
| | - Mao Sokny
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh
| | - Vanna Mean
- Ratanakiri Provincial Health Department, Banlung
| | | | | | | | - Steven Abrams
- University of Antwerp, Belgium.,University of Hasselt, Belgium
| | - Niel Hens
- University of Antwerp, Belgium.,University of Hasselt, Belgium
| | | | - Quique Bassat
- ISGlobal, Hospital Clínic-Universitat de Barcelona, Spain.,Centro de Investigação em Saúde de Manhiça, Maputo, Mozambique.,Catalan Institution for Research and Advanced Studies, Barcelona, Spain
| | | | - Lies Durnez
- Institute of Tropical Medicine, Antwerp.,University of Antwerp, Belgium
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23
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Li Y, Shetty AC, Lon C, Spring M, Saunders DL, Fukuda MM, Hien TT, Pukrittayakamee S, Fairhurst RM, Dondorp AM, Plowe CV, O’Connor TD, Takala-Harrison S, Stewart K. Detecting geospatial patterns of Plasmodium falciparum parasite migration in Cambodia using optimized estimated effective migration surfaces. Int J Health Geogr 2020; 19:13. [PMID: 32276636 PMCID: PMC7149848 DOI: 10.1186/s12942-020-00207-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Accepted: 04/01/2020] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND Understanding the genetic structure of natural populations provides insight into the demographic and adaptive processes that have affected those populations. Such information, particularly when integrated with geospatial data, can have translational applications for a variety of fields, including public health. Estimated effective migration surfaces (EEMS) is an approach that allows visualization of the spatial patterns in genomic data to understand population structure and migration. In this study, we developed a workflow to optimize the resolution of spatial grids used to generate EEMS migration maps and applied this optimized workflow to estimate migration of Plasmodium falciparum in Cambodia and bordering regions of Thailand and Vietnam. METHODS The optimal density of EEMS grids was determined based on a new workflow created using density clustering to define genomic clusters and the spatial distance between genomic clusters. Topological skeletons were used to capture the spatial distribution for each genomic cluster and to determine the EEMS grid density; i.e., both genomic and spatial clustering were used to guide the optimization of EEMS grids. Model accuracy for migration estimates using the optimized workflow was tested and compared to grid resolutions selected without the optimized workflow. As a test case, the optimized workflow was applied to genomic data generated from P. falciparum sampled in Cambodia and bordering regions, and migration maps were compared to estimates of malaria endemicity, as well as geographic properties of the study area, as a means of validating observed migration patterns. RESULTS Optimized grids displayed both high model accuracy and reduced computing time compared to grid densities selected in an unguided manner. In addition, EEMS migration maps generated for P. falciparum using the optimized grid corresponded to estimates of malaria endemicity and geographic properties of the study region that might be expected to impact malaria parasite migration, supporting the validity of the observed migration patterns. CONCLUSIONS Optimized grids reduce spatial uncertainty in the EEMS contours that can result from user-defined parameters, such as the resolution of the spatial grid used in the model. This workflow will be useful to a broad range of EEMS users as it can be applied to analyses involving other organisms of interest and geographic areas.
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Affiliation(s)
- Yao Li
- Center for Geospatial Information Science, Department of Geographical Sciences, University of Maryland, College Park, 20742 MD USA
| | - Amol C. Shetty
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, 21201 MD USA
| | - Chanthap Lon
- Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Michele Spring
- Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - David L. Saunders
- Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Mark M. Fukuda
- Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Tran Tinh Hien
- Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam
| | | | | | - Arjen M. Dondorp
- Mahidol-Oxford Tropical Medicine Research Unit, Bangkok, Thailand
| | | | - Timothy D. O’Connor
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, 21201 MD USA
| | - Shannon Takala-Harrison
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, 21201 MD USA
| | - Kathleen Stewart
- Center for Geospatial Information Science, Department of Geographical Sciences, University of Maryland, College Park, 20742 MD USA
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24
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Bannister-Tyrrell M, Gryseels C, Sokha S, Dara L, Sereiboth N, James N, Thavrin B, Ly P, Soy Ty K, Peeters Grietens K, Sovannaroth S, Yeung S. Forest Goers and Multidrug-Resistant Malaria in Cambodia: An Ethnographic Study. Am J Trop Med Hyg 2020; 100:1170-1178. [PMID: 30860021 PMCID: PMC6493920 DOI: 10.4269/ajtmh.18-0662] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Multidrug-resistant Plasmodium falciparum malaria on the Cambodia-Thailand border is associated with working in forested areas. Beyond broad recognition of "forest-going" as a risk factor for malaria, little is known about different forest-going populations in this region. In Oddar Meanchey Province in northwestern Cambodia, qualitative ethnographic research was conducted to gain an in-depth understanding of how different populations, mobility and livelihood patterns, and activities within the forest intersect with potentiate malaria risk and impact on the effectiveness of malaria control and elimination strategies. We found that most forest-going in this area is associated with obtaining precious woods, particularly Siamese rosewood. In the past, at-risk populations included large groups of temporary migrants. As timber supplies have declined, so have these large migrant groups. However, groups of local residents continue to go to the forest and are staying for longer. Most forest-goers had experienced multiple episodes of malaria and were well informed about malaria risk. However, economic realities mean that local residents continue to pursue forest-based livelihoods. Severe constraints of available vector control methods mean that forest-goers have limited capacity to prevent vector exposure. As forest-goers access the forest using many different entry and exit points, border screening and treatment interventions will not be feasible. Once in the forest, groups often converge in the same areas; therefore, interventions targeting the mosquito population may have a potential role. Ultimately, a multisectoral approach as well as innovative and flexible malaria control strategies will be required if malaria elimination efforts are to be successful.
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Affiliation(s)
| | | | - Suon Sokha
- Center for Health and Social Development, Phnom Penh, Cambodia
| | - Lim Dara
- Center for Health and Social Development, Phnom Penh, Cambodia
| | - Noan Sereiboth
- Center for Health and Social Development, Phnom Penh, Cambodia
| | - Nicola James
- London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Boukheng Thavrin
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Po Ly
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Kheang Soy Ty
- Center for Health and Social Development, Phnom Penh, Cambodia
| | | | - Siv Sovannaroth
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Shunmay Yeung
- London School of Hygiene and Tropical Medicine, London, United Kingdom
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25
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Gryseels C, Bannister-Tyrrell M, Uk S, Set S, Suon S, Gerrets R, Peeters Grietens K. A Critical Enquiry into Variability of Insecticidal Net Use in Cambodia: Implications for Assessing Appropriateness of Malaria Elimination Interventions. Am J Trop Med Hyg 2020; 100:1424-1432. [PMID: 30994087 PMCID: PMC6553892 DOI: 10.4269/ajtmh.18-0730] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Distributing long-lasting insecticidal nets (LLINs) to individuals living in malaria-endemic regions is a cornerstone of global malaria control. National malaria control programs aim to achieve "universal coverage" of at-risk populations to reach LLINs' full potential to reduce malaria, progress of which is then measured by indicators constructed from standardized questionnaires. Through an exploration of variability in LLIN use in Cambodia, we argue that indicators of universal coverage of LLINs are not sufficiently commensurate with the realities they are intended to measure, limiting the suitability of the data to serve program and policy purposes in a malaria elimination era. Reflecting on the various sources of variability in LLIN use, we apply and extend the concept of "appropriateness" as a third prong to the widely used "efficacy" and "effectiveness" criteria for evaluating LLINs as a tool for malaria prevention. Describing first the different dimensions of the intervention and the sociocultural context separately, we will further show how the variability underlying both is affected and induced by inappropriate aspects of the intervention and the measurements of its impact. We consider the gap between "net use" and the numerical representations of such local net use justifies further exploration of potential strategies to improve LLIN use in subgroups where persisting malaria transmission clusters.
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Affiliation(s)
| | | | - Sambunny Uk
- National Center for Parasitology Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Srun Set
- National Center for Parasitology Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Sokha Suon
- National Center for Parasitology Entomology and Malaria Control, Phnom Penh, Cambodia
| | - René Gerrets
- Amsterdam Institute for Social Science Research, University of Amsterdam, Amsterdam, The Netherlands
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26
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Canavati SE, Kelly GC, Quintero CE, Vo TH, Tran LK, Ohrt C, Ngo TD, Tran DT, Martin NJ. Risk factor assessment for clinical malaria among forest-goers in a pre-elimination setting in Phu Yen Province, Vietnam. Malar J 2019; 18:435. [PMID: 31861988 PMCID: PMC6923829 DOI: 10.1186/s12936-019-3068-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2019] [Accepted: 12/09/2019] [Indexed: 11/13/2022] Open
Abstract
Background The transition from malaria control to elimination requires understanding and targeting interventions among high-risk populations. In Vietnam, forest-goers are often difficult to test, treat and follow-up for malaria because they are highly mobile. If undiagnosed, forest-goers can maintain parasite reservoirs and contribute to ongoing malaria transmission. Methods A case–control study was conducted to identify malaria risk factors associated with forest-goers in three communes in Phu Yen Province, Vietnam. Cases (n = 81) were residents from the study area diagnosed with malaria and known to frequent forest areas. Controls (n = 94) were randomly selected forest-going residents from within the study area with no identified malaria infection. Participants were interviewed face-to-face using a standard questionnaire to identify malaria risk factors. Logistic regression was used to calculate odds ratios (ORs) and 95% CI for risk factors after adjusting for socio-demographic characteristics. Results Among the cases, malaria infection varied by species: 66.7% were positive for Plasmodium falciparum, 29.6% for Plasmodium vivax, and 3.7% were diagnosed as mixed infection. Cases were less likely than controls to use treated nets (aOR = 0.31; 95% CI 0.12–0.80), work after dark (aOR = 2.93; 95% CI 1.35, 6.34), bath in a stream after dark (aOR = 2.44; 95% CI 1.02–5.88), and collect water after dark (aOR = 1.99; 95% CI 1.02–3.90). Conclusions As Vietnam moves toward malaria elimination, these findings can inform behaviour change communication and malaria prevention strategies, incorporating the risk of after-dark and water-related activities, in this priority and difficult-to-access population group.
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Affiliation(s)
- Sara E Canavati
- Vysnova Partners, Inc., 4915 St. Elmo Ave., Bethesda, 20814, USA
| | - Gerard C Kelly
- Vysnova Partners, Inc., 4915 St. Elmo Ave., Bethesda, 20814, USA
| | - Cesia E Quintero
- Vysnova Partners, Inc., 4915 St. Elmo Ave., Bethesda, 20814, USA
| | - Thuan Huu Vo
- Vysnova Partners, Inc., 4915 St. Elmo Ave., Bethesda, 20814, USA
| | - Long Khanh Tran
- Vysnova Partners, Inc., 4915 St. Elmo Ave., Bethesda, 20814, USA
| | - Colin Ohrt
- Vysnova Partners, Inc., 4915 St. Elmo Ave., Bethesda, 20814, USA
| | - Thang Duc Ngo
- National Institute of Malariology, Parasitology and Entomology, 35 Trung Van, Hanoi, Vietnam
| | - Duong Thanh Tran
- National Institute of Malariology, Parasitology and Entomology, 35 Trung Van, Hanoi, Vietnam
| | - Nicholas J Martin
- Naval Medical Research Unit TWO, PSA Sembawang Deptford Rd., Building 7-4, Singapore, 759657, Singapore.
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27
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Thomson R, Sochea P, Sarath M, MacDonald A, Pratt A, Poyer S, Allen H, Kunthy S, Chamroeun S, Daro K, Samean S, Panharith N, Ra S, Sovottha C, Mundy G, Yeung S. Rubber plantations and drug resistant malaria: a cross-sectional survey in Cambodia. Malar J 2019; 18:379. [PMID: 31775755 PMCID: PMC6882203 DOI: 10.1186/s12936-019-3000-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 11/11/2019] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND The ongoing spread of artemisinin resistant Plasmodium falciparum malaria is a major threat to global health. In response, countries in the Greater Mekong Sub-region, including Cambodia, have declared ambitious goals to eliminate malaria. Major challenges include the lack of information on the at-risk population-individuals who live or work in or near the forest where the malaria vectors are found, including plantation workers. This study aimed to address this knowledge gap through a cross-sectional survey conducted in rubber plantations in Cambodia in 2014. METHODS The survey was conducted in two rounds in four provinces and included a malaria prevalence survey, analysis for the K13 genetic mutation, and a comprehensive behavioural questionnaire. Forty plantations were included in each round, and 4201 interviews were conducted. An additional 701 blood samples were collected from family members of plantation workers. RESULTS Overall malaria prevalence was relatively low with adjusted PCR prevalence rate of 0.6% for P. falciparum and 0.3% for Plasmodium vivax, and was very heterogenous between plantations. There was little difference in risk between permanent residents and temporary workers, and between the two rounds. The main risk factors for P. falciparum infection were smaller plantations, age under 30 years, lack of self-reported use of a treated net and recent travel, especially to the Northeastern provinces. Proximity of plantations to the forest was also a risk factor for malaria in round one, while male gender was also a risk factor for malaria by either species. CONCLUSIONS With Cambodia's P. falciparum elimination target on the horizon, identifying every single malaria case will become increasingly important. Plantations workers are relatively accessible compared to some other at-risk groups and will likely remain a high priority. Ongoing surveillance and adaptive strategies will be critical if malaria elimination is to be achieved in this setting.
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Affiliation(s)
- Rebecca Thomson
- Department of Global Health and Development, Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, London, UK
| | - Phok Sochea
- Population Services Khmer, Phnom Penh, Cambodia
| | - Mak Sarath
- Population Services Khmer, Phnom Penh, Cambodia
| | | | - Abigail Pratt
- Population Services International, Washington, DC, USA
| | - Steve Poyer
- Population Services International, Washington, DC, USA
| | | | - Sok Kunthy
- Partners for Development-LSHTM Partnership, Phnom Penh, Cambodia
| | - Sok Chamroeun
- Partners for Development-LSHTM Partnership, Phnom Penh, Cambodia
| | - Kim Daro
- Partners for Development-LSHTM Partnership, Phnom Penh, Cambodia
| | - Sourn Samean
- Partners for Development-LSHTM Partnership, Phnom Penh, Cambodia
| | - Nou Panharith
- Partners for Development-LSHTM Partnership, Phnom Penh, Cambodia
| | - Sok Ra
- Partners for Development-LSHTM Partnership, Phnom Penh, Cambodia
| | - Chan Sovottha
- Partners for Development-LSHTM Partnership, Phnom Penh, Cambodia
| | - Gary Mundy
- Helen Keller International, New York, USA
| | - Shunmay Yeung
- Department of Global Health and Development, Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, London, UK.
- Clinical Research Department, Faculty of Infectious and Tropical Disease, London School of Hygiene and Tropical Medicine, London, UK.
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Popovici J, Pierce-Friedrich L, Kim S, Bin S, Run V, Lek D, Hee KHD, Lee Soon-U L, Cannon MV, Serre D, Menard D. Recrudescence, Reinfection, or Relapse? A More Rigorous Framework to Assess Chloroquine Efficacy for Plasmodium vivax Malaria. J Infect Dis 2019; 219:315-322. [PMID: 30102351 DOI: 10.1093/infdis/jiy484] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 08/07/2018] [Indexed: 11/14/2022] Open
Abstract
Background Plasmodium vivax resistance to chloroquine (CQ) has been reported worldwide, although the World Health Organization clinical drug efficacy studies protocol does not permit classification of patient outcomes. Methods We enrolled 40 patients with P. vivax malaria in northeastern Cambodia, where >17% treatment failures were previously reported. Patients were treated with CQ (30 mg/kg) and followed for 2 months, with frequent clinical examination and capillary blood sample collection for microscopy, molecular parasite detection and genotyping, and drug concentration measurements. Reinfections were prevented by relocating patients to a transmission-free area. Results P. vivax parasites were eliminated in all patients by day 3. Genomic analyses revealed that all clones in polyclonal infections were cleared at the same rate, indicating their equal susceptibility to CQ. CQ blood concentrations were below the therapeutic level in all recurrent infections (24 of 40 patients), which were efficiently cleared by a second course of CQ treatment. Genotyping (128 SNPs barcode) and sequences of entire parasite genome (Whole-Genome Sequencing, Illumina) indicated that two thirds (6 of 8) of the recurrent parasites resulted from heterologous relapses whose 50% are from by sibling/recombinant clones. Conclusions No evidence of CQ resistance was observed. Our data suggest that P. vivax antimalarial drug resistance is likely overestimated and that the current guidelines for clinical drug studies of P. vivax malaria need to be revised.
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Affiliation(s)
- Jean Popovici
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh
| | | | - Saorin Kim
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh
| | - Sophalai Bin
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh
| | - Vorleak Run
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh
| | - Dysoley Lek
- National Center for Malaria Control, Phnom Penh, Cambodia
| | | | | | - Matthew V Cannon
- Genomic Medicine Institute, Cleveland Clinic, Ohio.,Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore
| | - David Serre
- Genomic Medicine Institute, Cleveland Clinic, Ohio.,Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore
| | - Didier Menard
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh.,Malaria Genetics and Resistance Group, Biology of Host-Parasite Interactions Unit, Institut Pasteur, France
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29
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Rossi G, Vernaeve L, Van den Bergh R, Nguon C, Debackere M, Abello Peiri C, Van V, Khim N, Kim S, Eam R, Ken M, Khean C, De Smet M, Menard D, Kindermans JM. Closing in on the Reservoir: Proactive Case Detection in High-Risk Groups as a Strategy to Detect Plasmodium falciparum Asymptomatic Carriers in Cambodia. Clin Infect Dis 2019; 66:1610-1617. [PMID: 29361021 DOI: 10.1093/cid/cix1064] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 12/19/2017] [Indexed: 12/11/2022] Open
Abstract
Background In the frame of elimination strategies of Plasmodium falciparum (Pf), active case detection has been recommended as complementary approach to the existing passive case detection programs. We trialed a polymerase chain reaction (PCR)-based active detection strategy targeting asymptomatic individuals, named proactive case detection (PACD), with the aim of assessing its feasibility, the extra yield of Pf infections, and the at-risk population for Pf carriage status. Methods A pilot of PACD was conducted in 3 villages in Chey Saen district (Preah Vihear province, Cambodia), from December 2015 to March 2016. Voluntary screening and treatment, following health promotion sensitization, was used as mobilization strategy. Results A total of 2802 persons were tested, representing 54% of the population. PACD (n = 30) and the respective reactive case detection (RACD) (n = 3) identified 33 Pf carriers, approximately twice as many as the Pf infections (n = 17) diagnosed in passive case detection and respective RACD, by health centers and village malaria workers using PCR, in the same villages/period. Final positivity rate was 1.07% (30/2802). People spending nighttime in forests and plantations were found to be at increased risk for Pf infection (odds ratio [OR], 3.4 [95% CI, 1.6-7.2], P = .002 and OR, 2.3 [95% CI, 1.1-4.9], P = .03, respectively). Conclusions We demonstrated the usefulness of the PACD component in identifying Pf asymptomatic carriers. Social mobilization and promotion led to good attendance of specific risk groups, identified to be, in the Cambodian context, individuals spending nighttime in forest and plantations.
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Affiliation(s)
| | | | | | - Chea Nguon
- Centre for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | | | | | - Vuthea Van
- Médecins Sans Frontières, Phnom Penh, Cambodia
| | - Nimol Khim
- Malaria Molecular Epidemiology Unit, Institut Pasteur, Phnom Penh, Cambodia
| | - Saorin Kim
- Malaria Molecular Epidemiology Unit, Institut Pasteur, Phnom Penh, Cambodia
| | - Rotha Eam
- Malaria Molecular Epidemiology Unit, Institut Pasteur, Phnom Penh, Cambodia
| | - Malen Ken
- Malaria Molecular Epidemiology Unit, Institut Pasteur, Phnom Penh, Cambodia
| | - Chanra Khean
- Malaria Molecular Epidemiology Unit, Institut Pasteur, Phnom Penh, Cambodia
| | - Martin De Smet
- Médecins Sans Frontières Operational Center, Brussels, Belgium
| | - Didier Menard
- Malaria Molecular Epidemiology Unit, Institut Pasteur, Phnom Penh, Cambodia.,Unité Biologie des Interactions Hôte-Parasite, Institut Pasteur, Paris, France
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30
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Rossi G, Van den Bergh R, Nguon C, Debackere M, Vernaeve L, Khim N, Kim S, Menard D, De Smet M, Kindermans JM. Adapting Reactive Case Detection Strategies for falciparum Malaria in a Low-Transmission Area in Cambodia. Clin Infect Dis 2019; 66:296-298. [PMID: 29020325 DOI: 10.1093/cid/cix781] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 08/26/2017] [Indexed: 12/26/2022] Open
Abstract
Reactive case detection around falciparum malaria cases in Cambodia presents a low output. We improved it by including individuals occupationally coexposed with index case patients and using polymerase chain reaction-based diagnosis. The positivity rate increased from 0.16% to 3.9%.
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Affiliation(s)
| | | | - Chea Nguon
- Centre for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | | | | | | | | | | | - Martin De Smet
- Médecins Sans Frontières Operational Center Brussels, Belgium
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31
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Vantaux A, Samreth R, Piv E, Khim N, Kim S, Berne L, Chy S, Lek D, Siv S, Taylor WR, Ménard D. Contribution to Malaria Transmission of Symptomatic and Asymptomatic Parasite Carriers in Cambodia. J Infect Dis 2019; 217:1561-1568. [PMID: 29394367 DOI: 10.1093/infdis/jiy060] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 01/26/2018] [Indexed: 12/14/2022] Open
Abstract
Background Eliminating falciparum malaria in Cambodia is a top priority, requiring the implementation of novel tools and strategies to interrupt its transmission. To date, few data are available regarding the contributions to malaria transmission of symptomatic and asymptomatic carriers. Methods Direct-membrane and skin feeding assays (DMFAs, SFAs) were performed, using Anopheles minimus and Anopheles dirus, to determine infectivity of symptomatic falciparum-infected patients and malaria asymptomatic carriers; a subset of the latter were followed up for 2 months to assess their transmission potential. Results By microscopy and real-time polymerase chain reaction, Plasmodium falciparum gametocyte prevalence rates were, respectively, 19.3% (n = 21/109) and 44% (n = 47/109) on day (D) 0 and 17.9% (n = 5/28) and 89.3% (n = 25/28) in recrudescent patients (Drec) (RT-PCR Drec vs D0 P = .002). Falciparum malaria patient infectivity was low on D0 (6.2%; n = 3/48) and in Drec (8.3%; n = 1/12). Direct-membrane feeding assays and SFAs gave similar results. None of the falciparum (n = 0/19) and 3 of 28 Plasmodium vivax asymptomatic carriers were infectious to mosquitoes, including those that were followed up for 2 months. Overall, P. falciparum gametocytemias were low except in a few symptomatic carriers. Conclusions Only symptomatic falciparum malaria patients were infectious to mosquito vectors at baseline and recrudescence, highlighting the need to detect promptly and treat effectively P. falciparum patients.
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Affiliation(s)
- Amélie Vantaux
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia
| | - Reingsey Samreth
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia
| | - Eakpor Piv
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia
| | - Nimol Khim
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia
| | - Saorin Kim
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia
| | - Laura Berne
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia.,Xeno Cell Innovations, Plzen, Czech Republic
| | - Sophy Chy
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia
| | - Dysoley Lek
- National Center for Parasitology, Entomology and Malaria Control Program, Phnom Penh, Cambodia.,School of Public Health, National Institute of Public Health, Phnom Penh, Cambodia
| | - Sovannaroth Siv
- National Center for Parasitology, Entomology and Malaria Control Program, Phnom Penh, Cambodia
| | - Walter R Taylor
- Mahidol Oxford Tropical Medicine Research Unit, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, United Kingdom
| | - Didier Ménard
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia.,Unité Biologie des Interactions Hôte-Parasite, Institut Pasteur, Paris, France
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32
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Alves LS, Dos Santos DT, Arcoverde MAM, Berra TZ, Arroyo LH, Ramos ACV, de Assis IS, de Queiroz AAR, Alonso JB, Alves JD, Popolin MP, Yamamura M, de Almeida Crispim J, Dessunti EM, Palha PF, Chiaraval-Neto F, Nunes C, Arcêncio RA. Detection of risk clusters for deaths due to tuberculosis specifically in areas of southern Brazil where the disease was supposedly a non-problem. BMC Infect Dis 2019; 19:628. [PMID: 31315568 PMCID: PMC6637579 DOI: 10.1186/s12879-019-4263-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 07/04/2019] [Indexed: 01/06/2023] Open
Abstract
Background Tuberculosis (TB) is the infectious disease that kills the most people worldwide. The use of geoepidemiological techniques to demonstrate the dynamics of the disease in vulnerable communities is essential for its control. Thus, this study aimed to identify risk clusters for TB deaths and their variation over time. Methods This ecological study considered cases of TB deaths in residents of Londrina, Brazil between 2008 and 2015. We used standard, isotonic scan statistics for the detection of spatial risk clusters. The Poisson discrete model was adopted with the high and low rates option used for 10, 30 and 50% of the population at risk, with circular format windows and 999 replications considered the maximum cluster size. Getis-Ord Gi* (Gi*) statistics were used to diagnose hotspot areas for TB mortality. Kernel density was used to identify whether the clusters changed over time. Results For the standard version, spatial risk clusters for 10, 30 and 50% of the exposed population were 4.9 (95% CI 2.6–9.4), 3.2 (95% CI: 2.1–5.7) and 3.2 (95% CI: 2.1–5.7), respectively. For the isotonic spatial statistics, the risk clusters for 10, 30 and 50% of the exposed population were 2.8 (95% CI: 1.5–5.1), 2.7 (95% CI: 1.6–4.4), 2.2 (95% CI: 1.4–3.9), respectively. All risk clusters were located in the eastern and northern regions of the municipality. Additionally, through Gi*, hotspot areas were identified in the eastern and western regions. Conclusions There were important risk areas for tuberculosis mortality in the eastern and northern regions of the municipality. Risk clusters for tuberculosis deaths were observed in areas where TB mortality was supposedly a non-problem. The isotonic and Gi* statistics were more sensitive for the detection of clusters in areas with a low number of cases; however, their applicability in public health is still restricted.
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Affiliation(s)
- Luana Seles Alves
- Nursing Graduate Program in Public Health Nursing, University of São Paulo at Ribeirão Preto Nursing College, 3900 Avenida dos Bandeirantes, São Paulo, Brazil. .,Maternal-Infant and Public Health Nursing Department, University of São Paulo at Ribeirão Preto College of Nursing, Av dos Bandeirantes 3900, Ribeirão Preto, São Paulo, 14040-902, Brazil.
| | - Danielle Talita Dos Santos
- Inter-institutions Doctoral Program in Nursing, University of São Paulo at Ribeirão Preto Nursing College, São Paulo, Brazil
| | - Marcos Augusto Moraes Arcoverde
- Nursing Graduate Program in Public Health Nursing, University of São Paulo at Ribeirão Preto Nursing College, 3900 Avenida dos Bandeirantes, São Paulo, Brazil
| | - Thais Zamboni Berra
- Nursing Graduate Program in Public Health Nursing, University of São Paulo at Ribeirão Preto Nursing College, 3900 Avenida dos Bandeirantes, São Paulo, Brazil
| | - Luiz Henrique Arroyo
- Inter-institutions Doctoral Program in Nursing, University of São Paulo at Ribeirão Preto Nursing College, São Paulo, Brazil
| | - Antônio Carlos Vieira Ramos
- Nursing Graduate Program in Public Health Nursing, University of São Paulo at Ribeirão Preto Nursing College, 3900 Avenida dos Bandeirantes, São Paulo, Brazil
| | - Ivaneliza Simionato de Assis
- Nursing Graduate Program in Public Health Nursing, University of São Paulo at Ribeirão Preto Nursing College, 3900 Avenida dos Bandeirantes, São Paulo, Brazil
| | | | | | - Josilene Dália Alves
- Inter-institutions Doctoral Program in Nursing, University of São Paulo at Ribeirão Preto Nursing College, São Paulo, Brazil
| | | | - Mellina Yamamura
- Inter-institutions Doctoral Program in Nursing, University of São Paulo at Ribeirão Preto Nursing College, São Paulo, Brazil
| | - Juliane de Almeida Crispim
- Inter-institutions Doctoral Program in Nursing, University of São Paulo at Ribeirão Preto Nursing College, São Paulo, Brazil
| | | | | | - Francisco Chiaraval-Neto
- Department of Epidemiology, School of Public Health, University of São Paulo, São Paulo, São Paulo, Brazil
| | - Carla Nunes
- National School of Public Health, Nova University of Lisbon, Lisboa, Portugal
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Gryseels C, Kuijpers LMF, Jacobs J, Peeters Grietens K. When ‘substandard’ is the standard, who decides what is appropriate? Exploring healthcare provision in Cambodia. CRITICAL PUBLIC HEALTH 2019. [DOI: 10.1080/09581596.2019.1591614] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Charlotte Gryseels
- Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium
| | | | - Jan Jacobs
- Department of Clinical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
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Dalmat R, Naughton B, Kwan-Gett TS, Slyker J, Stuckey EM. Use cases for genetic epidemiology in malaria elimination. Malar J 2019; 18:163. [PMID: 31064369 PMCID: PMC6503548 DOI: 10.1186/s12936-019-2784-0] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Accepted: 04/22/2019] [Indexed: 12/22/2022] Open
Abstract
Background While traditional epidemiological approaches have supported significant reductions in malaria incidence across many countries, higher resolution information about local and regional malaria epidemiology will be needed to efficiently target interventions for elimination. The application of genetic epidemiological methods for the analysis of parasite genetics has, thus far, primarily been confined to research settings. To illustrate how these technical methods can be used to advance programmatic and operational needs of National Malaria Control Programmes (NMCPs), and accelerate global progress to eradication, this manuscript presents seven use cases for which genetic epidemiology approaches to parasite genetic data are informative to the decision-making of NMCPs. Methods The use cases were developed through a highly iterative process that included an extensive review of the literature and global guidance documents, including the 2017 World Health Organization’s Framework for Malaria Elimination, and collection of stakeholder input. Semi-structured interviews were conducted with programmatic and technical experts about the needs and opportunities for genetic epidemiology methods in malaria elimination. Results Seven use cases were developed: Detect resistance, Assess drug resistance gene flow, Assess transmission intensity, Identify foci, Determine connectivity of parasite populations, Identify imported cases, and Characterize local transmission chains. The method currently used to provide the information sought, population unit for implementation, the pre-conditions for using these approaches, and post-conditions intended as a product of the use case were identified for each use case. Discussion This framework of use cases will prioritize research and development of genetic epidemiology methods that best achieve the goals of NMCPs, and ultimately, inform the establishment of normative policy guidance for their uses. With significant engagement of stakeholders from malaria endemic countries and collaboration with local programme experts to ensure strategic implementation, genetic epidemiological approaches have tremendous potential to accelerate global malaria elimination efforts. Electronic supplementary material The online version of this article (10.1186/s12936-019-2784-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ronit Dalmat
- Department of Epidemiology, University of Washington, Seattle, WA, USA.,Strategic Analysis Research and Training Center, University of Washington, Seattle, WA, USA
| | - Brienna Naughton
- Department of Global Health, University of Washington, Seattle, WA, USA.,Strategic Analysis Research and Training Center, University of Washington, Seattle, WA, USA
| | - Tao Sheng Kwan-Gett
- Department of Health Services, University of Washington, Seattle, WA, USA.,Strategic Analysis Research and Training Center, University of Washington, Seattle, WA, USA
| | - Jennifer Slyker
- Department of Epidemiology, University of Washington, Seattle, WA, USA.,Department of Global Health, University of Washington, Seattle, WA, USA.,Strategic Analysis Research and Training Center, University of Washington, Seattle, WA, USA
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Dhewantara PW, Ipa M, Widawati M. Individual and contextual factors predicting self-reported malaria among adults in eastern Indonesia: findings from Indonesian community-based survey. Malar J 2019; 18:118. [PMID: 30947730 PMCID: PMC6449936 DOI: 10.1186/s12936-019-2758-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2019] [Accepted: 03/30/2019] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND Malaria is still an important parasitic infectious disease that affecting poor and vulnerable communities in many developing countries, including Indonesia. During the period of 2010-2017, there have been approximately 2.2 million confirmed malaria cases reported across Indonesia. This study aimed to identify individual, household and village-level factors associated with self-reported malaria among adults more than 15 years of age in Maluku, West Papua and Papua province. METHODS This study analysed a subset of the data from nationally representative population-based Indonesian National Basic Health Research (Riset Kesehatan Dasar) (N = 1,027,763 in 294,959 households in 33 provinces) in 2013. Total of 41,079 individuals (20,326 males and 20,753 females) aged ≥ 15 years in 19,269 households in Maluku, West Papua and Papua provinces were included. Participants were interviewed if they ever had been diagnosed and laboratory confirmed of having malaria by physician in the past 12 months. A mixed effects multilevel logistic regression models were developed to assess the associations between socio-demographical variables at individual, household and village level and self-reported malaria. RESULTS Individuals aged ≥ 15 years in 701 villages in Maluku (n = 11,919), West Papua (n = 8003) and Papua (n = 21,157) were analysed. In all provinces, gender distribution was equally-represented. The prevalence of self-reported malaria was 4.1% (Maluku), 12.4% (West Papua) and 18.8% (Papua). At the individual level, primary industry workers (OR 1.29, 95% CI 1.15-1.46 [Maluku]; OR 1.17, 95% CI 1.09-1.25 [Papua]) and having higher education were associated with self-reporting malaria (OR 0.67, 95% CI 0.53-0.83 [Maluku]; OR 1.27, 95% CI 1.15-1.40 [Papua]). Household level factors include having bed net and better off wealth index were associated with increased self-reporting malaria among West Papua (OR 1.21; 95% CI 1.09-1.34 and OR 1.38; 95% CI 1.17-1.65, respectively) and Papuan (OR 1.12; 95% CI 1.02-1.23 and OR 1.33; 95% CI 1.11-1.57, respectively) adults. Increased odds of self-reporting malaria was associated with time required to reach healthcare facility (OR 1.30, 95% CI 1.01-1.67 [Maluku]). Contextual village-level characteristics such as living in rural (OR 1.31, 95% CI 1.12-1.54 [Maluku]; OR 1.56, 95% CI 1.17-2.07 [West Papua]), higher community education level (OR 1.28, 95% CI 1.02-1.63 [West Papua]; OR 1.45, 95% CI 1.23-1.72 [Papua]), higher community bed net ownerships (OR 0.59 95% CI 0.45-0.77 [West Papua]) were associated with self-reported malaria. CONCLUSIONS Factors associated with self-reported malaria were varied between provinces suggesting locally-specific determinants were exist at individual, household and community-level. This study highlights the need for specific interventions by taking into consideration the contextual factors within the region and involving multi-sectoral collaboration between health authorities and related stakeholders (e.g., bureau of education, bureau of public works and infrastructure) to improve designs in planning and intervention strategies to succesfully eliminate malaria in Maluku and Papua.
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Affiliation(s)
- Pandji Wibawa Dhewantara
- Pangandaran Unit for Health Research and Development, National Institute of Health Research and Development, Ministry of Health of Indonesia, Pangandaran, West Java, 46396, Indonesia. .,School of Veterinary Science, University of Queensland, Gatton, QLD, 4343, Australia.
| | - Mara Ipa
- Pangandaran Unit for Health Research and Development, National Institute of Health Research and Development, Ministry of Health of Indonesia, Pangandaran, West Java, 46396, Indonesia
| | - Mutiara Widawati
- Pangandaran Unit for Health Research and Development, National Institute of Health Research and Development, Ministry of Health of Indonesia, Pangandaran, West Java, 46396, Indonesia
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Osei FB, Stein A. Temporal trend and spatial clustering of cholera epidemic in Kumasi-Ghana. Sci Rep 2018; 8:17848. [PMID: 30552392 PMCID: PMC6294804 DOI: 10.1038/s41598-018-36029-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Accepted: 11/10/2018] [Indexed: 12/02/2022] Open
Abstract
Knowledge of the temporal trends and spatial patterns will have significant implications for effective preparedness in future epidemics. Our objective was to investigate the temporal trends and the nature of the spatial interaction of cholera incidences, dwelling on an outbreak in the Kumasi Metropolis, Ghana. We developed generalized nonparametric and segmented regression models to describe the epidemic curve. We used the pair correlation function to describe the nature of spatial clustering parameters such as the maximum scale of interaction and the scale of maximal interaction. The epidemic rose suddenly to a peak with 40% daily increments of incidences. The decay, however, was slower with 5% daily reductions. Spatial interaction occurred within 1 km radius. Maximal interaction occurred within 0.3 km, suggesting a household level of interactions. Significant clustering during the first week suggests secondary transmissions sparked the outbreak. The nonparametric and segmented regression models, together with the pair correlation function, contribute to understanding the transmission dynamics. The issue of underreporting remains a challenge we seek to address in future. These findings, however, will have innovative implications for developing preventive measures during future epidemics.
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Affiliation(s)
- Frank Badu Osei
- Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, Enschede, Netherlands.
| | - Alfred Stein
- Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, Enschede, Netherlands
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Yasuoka J, Kikuchi K, Nanishi K, Ly P, Thavrin B, Omatsu T, Mizutani T. Malaria knowledge, preventive actions, and treatment-seeking behavior among ethnic minorities in Ratanakiri Province, Cambodia: a community-based cross-sectional survey. BMC Public Health 2018; 18:1206. [PMID: 30367615 PMCID: PMC6203989 DOI: 10.1186/s12889-018-6123-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Accepted: 10/15/2018] [Indexed: 12/13/2022] Open
Abstract
Background Malaria incidence has been steadily declining in Cambodia, where the government is aiming to eliminate malaria by 2025. Successful malaria elimination requires active engagement and participation of communities to recognize malaria symptoms and the development of prompt treatment-seeking behavior for early diagnosis and appropriate treatment. This study examined malaria knowledge, preventive actions, and treatment-seeking behavior among different groups of ethnic minorities and Khmer in Ratanakiri Province, Cambodia. Methods Face-to-face interviews were conducted in December 2015, targeting 388 mothers with children under 2 years old, who belonged to ten ethnic minority groups or the Khmer group living in 62 rural villages in Ratanakiri. In addition to describing mothers’ knowledge and actions for malaria prevention, logistic regression analysis was performed to identify determinants of fever during the most recent pregnancy and among children under two. Results Overall 388 mothers were identified for enrollment into the study of which 377 (97.2%) were included in analyses. The majority of mothers slept under bed nets at home (95.8%) and wore long-sleeved clothes (83.8%) for malaria prevention. However, knowledge of malaria was limited: 44.6% were aware of malaria symptoms, 40.6% knew the malaria transmission route precisely, and 29.2% knew of mosquito breeding places. Staying overnight at a farm hut was significantly associated with having fever during the most recent pregnancy (adjusted odds ratio [AOR] 2.008, 95% confidence interval [CI]: 1.215–3.321) and a child having fever (AOR 3.681, 95% CI 1.943–6.972). Mothers’ partaking in a variety of malaria preventive actions was protective against fever in children (AOR 0.292, 95% CI: 0.136–0.650). Among those who had fever during pregnancy, 39.4% did not seek treatment. Conclusion Although the majority of mothers took malaria preventive actions, knowledge of malaria epidemiology and vector ecology and treatment-seeking behavior for fever were limited. Staying overnight at farm huts, regardless of the differences in socio-demographic and socio-cultural characteristics, was strongly associated with fever episodes during pregnancy and childhood. This study indicates the necessity of spreading accurate malaria knowledge, raising awareness of health risks related to agricultural practices, and promoting treatment-seeking behavior among ethnic minorities to strengthen their engagement in malaria elimination.
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Affiliation(s)
- Junko Yasuoka
- Research and Education Center for Prevention of Global Infectious Diseases of Animals, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8508, Japan.
| | - Kimiyo Kikuchi
- Graduate Education and Research Training Program in Decision Science for Sustainable Society, Kyushu University, Motooka 744, Nishi-ku, Fukuoka-shi, Fukuoka, 819-0395, Japan
| | - Keiko Nanishi
- Office of International Academic Affairs, Graduate School of Medicine and Faculty of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Po Ly
- National center for Parasitology, Entomology & Malaria Control (CNM), Ministry of Health, #477 Betong Street (Corner St.92), Village Trapangsvay, Sanakat Phnom Penh Thmey, Khan Sen Sok, Phnom Penh, Cambodia
| | - Boukheng Thavrin
- National center for Parasitology, Entomology & Malaria Control (CNM), Ministry of Health, #477 Betong Street (Corner St.92), Village Trapangsvay, Sanakat Phnom Penh Thmey, Khan Sen Sok, Phnom Penh, Cambodia
| | - Tsutomu Omatsu
- Research and Education Center for Prevention of Global Infectious Diseases of Animals, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8508, Japan
| | - Tetsuya Mizutani
- Research and Education Center for Prevention of Global Infectious Diseases of Animals, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8508, Japan
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Zemene E, Koepfli C, Tiruneh A, Yeshiwondim AK, Seyoum D, Lee MC, Yan G, Yewhalaw D. Detection of foci of residual malaria transmission through reactive case detection in Ethiopia. Malar J 2018; 17:390. [PMID: 30367636 PMCID: PMC6203988 DOI: 10.1186/s12936-018-2537-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 10/20/2018] [Indexed: 12/18/2022] Open
Abstract
Background Sub-microscopic and asymptomatic infections could be bottlenecks to malaria elimination efforts in Ethiopia. This study determined the prevalence of malaria, and individual and household-level factors associated with Plasmodium infections obtained following detection of index cases in health facilities in Jimma Zone. Methods Index malaria cases were passively detected and tracked in health facilities from June to November 2016. Moreover, family members of the index houses and neighbours located within approximately 200 m from the index houses were also screened for malaria. Results A total of 39 index cases initiated the reactive case detection of 726 individuals in 116 households. Overall, the prevalence of malaria using microscopy and PCR was 4.0% and 8.96%, respectively. Seventeen (43.6%) of the index cases were from Doyo Yaya kebele, where parasite prevalence was higher. The majority of the malaria cases (90.74%) were asymptomatic. Fever (AOR = 12.68, 95% CI 3.34–48.18) and history of malaria in the preceding 1 year (AOR = 3.62, 95% CI 1.77–7.38) were significant individual-level factors associated with detection of Plasmodium infection. Moreover, living in index house (AOR = 2.22, 95% CI 1.16–4.27), house with eave (AOR = 2.28, 95% CI 1.14–4.55), area of residence (AOR = 6.81, 95% CI 2.49–18.63) and family size (AOR = 3.35, 95% CI 1.53–7.33) were main household-level predictors for residual malaria transmission. Conclusion The number of index cases per kebele may enhance RACD efforts to detect additional malaria cases in low transmission settings. Asymptomatic and sub-microscopic infections were high in the study area, which need new or improved surveillance tools for malaria elimination efforts.
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Affiliation(s)
- Endalew Zemene
- School of Medical Laboratory Sciences, Faculty of Health Sciences, Jimma University, Jimma, Ethiopia.
| | - Cristian Koepfli
- Program in Public Health, College of Health Sciences, University of California at Irvine, Irvine, CA, 92697, USA
| | - Abebaw Tiruneh
- School of Medical Laboratory Sciences, Faculty of Health Sciences, Jimma University, Jimma, Ethiopia
| | | | - Dinberu Seyoum
- Department of Statistics, College of Natural Sciences, Jimma University, Jimma, Ethiopia
| | - Ming-Chieh Lee
- Program in Public Health, College of Health Sciences, University of California at Irvine, Irvine, CA, 92697, USA
| | - Guiyun Yan
- Program in Public Health, College of Health Sciences, University of California at Irvine, Irvine, CA, 92697, USA
| | - Delenasaw Yewhalaw
- School of Medical Laboratory Sciences, Faculty of Health Sciences, Jimma University, Jimma, Ethiopia.,Tropical and Infectious Diseases Research Centre, Jimma University, Jimma, Ethiopia
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Bannister-Tyrrell M, Srun S, Sluydts V, Gryseels C, Mean V, Kim S, Sokny M, Peeters Grietens K, Coosemans M, Menard D, Tho S, Van Bortel W, Durnez L. Importance of household-level risk factors in explaining micro-epidemiology of asymptomatic malaria infections in Ratanakiri Province, Cambodia. Sci Rep 2018; 8:11643. [PMID: 30076361 PMCID: PMC6076298 DOI: 10.1038/s41598-018-30193-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 07/20/2018] [Indexed: 11/09/2022] Open
Abstract
Heterogeneity in malaria risk is considered a challenge for malaria elimination. A cross-sectional study was conducted to describe and explain micro-epidemiological variation in Plasmodium infection prevalence at household and village level in three villages in Ratanakiri Province, Cambodia. A two-level logistic regression model with a random intercept fitted for each household was used to model the odds of Plasmodium infection, with sequential adjustment for individual-level then household-level risk factors. Individual-level risk factors for Plasmodium infection included hammock net use and frequency of evening outdoor farm gatherings in adults, and older age in children. Household-level risk factors included house wall material, crop types, and satellite dish and farm machine ownership. Individual-level risk factors did not explain differences in odds of Plasmodium infection between households or between villages. In contrast, once household-level risk factors were taken into account, there was no significant difference in odds of Plasmodium infection between households and between villages. This study shows the importance of ongoing indoor and peridomestic transmission in a region where forest workers and mobile populations have previously been the focus of attention. Interventions targeting malaria risk at household level should be further explored.
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Affiliation(s)
| | - Set Srun
- National Centre for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Vincent Sluydts
- Institute of Tropical Medicine, Nationalestraat 155, Antwerp, Belgium
- University of Antwerp, Antwerpm, Belgium
| | | | - Vanna Mean
- Ratanakiri Provincial Health Department, Banlung, Cambodia
| | - Saorin Kim
- Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Mao Sokny
- National Centre for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | | | - Marc Coosemans
- Institute of Tropical Medicine, Nationalestraat 155, Antwerp, Belgium
| | | | - Sochantha Tho
- National Centre for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Wim Van Bortel
- Institute of Tropical Medicine, Nationalestraat 155, Antwerp, Belgium
| | - Lies Durnez
- Institute of Tropical Medicine, Nationalestraat 155, Antwerp, Belgium
- University of Antwerp, Antwerpm, Belgium
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Lover AA, Dantzer E, Hongvanthong B, Chindavongsa K, Welty S, Reza T, Khim N, Menard D, Bennett A. Prevalence and risk factors for asymptomatic malaria and genotyping of glucose 6-phosphate (G6PD) deficiencies in a vivax-predominant setting, Lao PDR: implications for sub-national elimination goals. Malar J 2018; 17:218. [PMID: 29859089 PMCID: PMC5984820 DOI: 10.1186/s12936-018-2367-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Accepted: 05/23/2018] [Indexed: 12/27/2022] Open
Abstract
Background Lao People Democratic Republic (PDR; Laos), a landlocked country in Southeast Asia, has made important progress in reducing malaria morbidity and mortality in the past 5–6 years, and the northern provinces have very low reported incidence. To support national progress towards elimination, it is critical to verify and understand these changes in disease burden. Methods A two-stage cluster cross-sectional survey was conducted in four districts within four northern provinces (Khua, Phongsaly Province; Paktha, Bokeo Province; Nambak, Luang Prabang, and Muang Et, Huaphanh Province). During September and October 2016, demographics and malaria risk factors were collected from a total of 1492 households. A total of 5085 persons consented to collection of blood samples for testing, by rapid diagnostic test (RDT) and polymerase chain reaction (PCR)-based testing. Risk factors for infection were examined using logistic regression; and a randomized subset of males was tested for glucose-6-phosphate dehydrogenase (G6PD) deficiencies using a combined PCR and sequencing approach. Results There were zero positives by RDT, and PCR detected Plasmodium infections in 39 (0.77%; 95% CI 0.40–1.47%) of 5082 analysable samples. The species distribution was Plasmodium vivax (28 total); Plasmodium falciparum/P. vivax (5); P. falciparum (3), Plasmodium malariae (2), and P. vivax/P. malariae (1). In multivariable analysis, the main risk factors included having any other cases within the household [aOR 12.83 (95% CI 4.40 to 37.38), p < 0.001]; and lack of bed net ownership within the household [aOR 10.91 (95% 5.42–21.94), p < 0.001]; age, sex and forest-travel were not associated with parasitaemia. A total of 910 males were tested for the six most common G6PDd in SE Asia; and 30 (3.3%; 95% CI 2.1–5.1%) had a G6PD variant allele associated with G6PD deficiency, with the majority being the Union (14) and Viangchan (11) polymorphisms, with smaller numbers of Canton and Mahidol. Conclusion This is the first rigorous PCR-based population survey for malaria infection in Northern Lao PDR, and found a very low prevalence of asymptomatic Plasmodium infections by standard PCR methods, with P. vivax predominating in the surveyed districts. Clustering of cases within households, and lack of a bed nets suggest reactive case detection, and scale-up of coverage should be prioritized. The predominance of infections with P. vivax, combined with moderate levels of serious G6PD deficiencies highlight the need for careful rollout of primaquine towards elimination goals. Electronic supplementary material The online version of this article (10.1186/s12936-018-2367-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Andrew A Lover
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, CA, USA.
| | - Emily Dantzer
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, CA, USA
| | - Bouasy Hongvanthong
- Center for Malariology, Parasitology and Entomology (CMPE), Ministry of Health, Vientiane, Lao PDR
| | | | - Susie Welty
- Global Strategic Information, Institute for Global Health Sciences, University of California, San Francisco, CA, USA
| | - Tania Reza
- Global Strategic Information, Institute for Global Health Sciences, University of California, San Francisco, CA, USA
| | | | - Didier Menard
- Malaria Genetic and Resistance Group, Institut Pasteur, Paris, France
| | - Adam Bennett
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, CA, USA
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Taffon P, Rossi G, Kindermans JM, Van den Bergh R, Nguon C, Debackere M, Vernaeve L, De Smet M, Venables E. 'I could not join because I had to work for pay.': A qualitative evaluation of falciparum malaria pro-active case detection in three rural Cambodian villages. PLoS One 2018; 13:e0195809. [PMID: 29649317 PMCID: PMC5897025 DOI: 10.1371/journal.pone.0195809] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 03/29/2018] [Indexed: 11/19/2022] Open
Abstract
Background Pro-active case detection (Pro-ACD), in the form of voluntary screening and treatment (VSAT) following community mobilisation about ‘asymptomatic malaria’, is currently being evaluated as a tool for Plasmodium falciparum elimination in Preah Vihear Province, Cambodia. Methods A qualitative study was conducted to explore community understanding, perceptions, expectations and acceptability of the Pro-ACD intervention in order to identify aspects that could be improved in future Pro-ACD activities. This was ancillary to a three-round VSAT campaign, carried out in three villages between December 2015 and March 2016. Qualitative data collection began shortly after the end of the three rounds of screening. Purposive sampling was used to select participants. Nine focus group discussions with participants (n = 46) and non-participants (n = 40) in the Pro-ACD screening were conducted, in addition to in-depth interviews with key village figures (n = 9). Results Health promotion messages were well delivered and received, but it was difficult for many villagers to understand the messages around ‘asymptomatic malaria’. Overall, villagers and village leaders had a positive opinion about the VSAT intervention. Acceptability was high, as a direct consequence of favourable perceptions towards the screening activity: the Pro-ACD intervention was seen by the local population as an effective, inexpensive, reliable and readily available tool to protect individuals and the community from the insurgence of malaria. Physical absence and lack of time (both linked to work-related activities) were the main reasons for non-participation. Conclusions Although VSAT was generally well perceived and accepted, the ‘time factor’ related to the need to satisfy essential daily subsistence requirements played a significant role in determining participation in the screening. More well-adapted and meaningful Pro-ACD approaches could be implemented by improving the timing of the testing activites, and strengthening community participation and engagement to increase acceptability.
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Affiliation(s)
| | | | | | | | - Chea Nguon
- Centre for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | | | | | - Martin De Smet
- Médecins Sans Frontières, Operational Centre Belgium, Brussels, Belgium
| | - Emilie Venables
- Médecins Sans Frontières, Operational Centre Belgium, Brussels, Belgium
- Division of Social and Behavioural Sciences, School of Public Health and Family Medicine, University of Cape Town, Cape Town, South Africa
- * E-mail:
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Durnez L, Pareyn M, Mean V, Kim S, Khim N, Menard D, Coosemans M, Sochantha T, Sluydts V. Identification and characterization of areas of high and low risk for asymptomatic malaria infections at sub-village level in Ratanakiri, Cambodia. Malar J 2018; 17:27. [PMID: 29334956 PMCID: PMC5769347 DOI: 10.1186/s12936-017-2169-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 12/29/2017] [Indexed: 01/08/2023] Open
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.
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Affiliation(s)
- Lies Durnez
- Institute of Tropical Medicine, Antwerp, Belgium. .,University of Antwerp, Antwerp, Belgium.
| | - Myrthe Pareyn
- Institute of Tropical Medicine, Antwerp, Belgium.,University of Antwerp, Antwerp, Belgium
| | - Vanna Mean
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Saorin Kim
- Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Nimol Khim
- Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | | | - Marc Coosemans
- Institute of Tropical Medicine, Antwerp, Belgium.,University of Antwerp, Antwerp, Belgium
| | - Tho Sochantha
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Vincent Sluydts
- Institute of Tropical Medicine, Antwerp, Belgium. .,University of Antwerp, Antwerp, Belgium.
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Platt A, Obala AA, MacIntyre C, Otsyula B, Meara WPO. Dynamic malaria hotspots in an open cohort in western Kenya. Sci Rep 2018; 8:647. [PMID: 29330454 PMCID: PMC5766583 DOI: 10.1038/s41598-017-13801-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 10/02/2017] [Indexed: 11/14/2022] Open
Abstract
Malaria hotspots, defined as areas where transmission intensity exceeds the average level, become more pronounced as transmission declines. Targeting hotspots may accelerate reductions in transmission and could be pivotal for malaria elimination. Determinants of hotspot location, particularly of their movement, are poorly understood. We used spatial statistical methods to identify foci of incidence of self-reported malaria in a large census population of 64,000 people, in 8,290 compounds over a 2.5-year study period. Regression models examine stability of hotspots and identify static and dynamic correlates with their location. Hotspot location changed over short time-periods, rarely recurring in the same area. Hotspots identified in spring versus fall season differed in their stability. Households located in a hotspot in the fall were more likely to be located in a hotspot the following fall (RR = 1.77, 95% CI: 1.66-1.89), but the opposite was true for compounds in spring hotspots (RR = 0.15, 95% CI: 0.08-0.28). Location within a hotspot was related to environmental and static household characteristics such as distance to roads or rivers. Human migration into a household was correlated with risk of hotspot membership, but the direction of the association differed based on the origin of the migration event.
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Affiliation(s)
- Alyssa Platt
- Duke Global Health Institute, Durham, North Carolina, United States of America.
- Department of Biostatistics and Bioinformatics, Duke University, Eldoret, North Carolina, United States of America.
| | - Andrew A Obala
- College of Health Sciences, Moi University, Eldoret, Kenya
| | - Charlie MacIntyre
- Duke Global Health Institute, Durham, North Carolina, United States of America
- Campbell University School of Osteopathic Medicine, Buies Creek, North Carolina, United States of America
| | - Barasa Otsyula
- College of Health Sciences, Moi University, Eldoret, Kenya
| | - Wendy Prudhomme O' Meara
- Duke Global Health Institute, Durham, North Carolina, United States of America
- Department of Biostatistics and Bioinformatics, Duke University, Eldoret, North Carolina, United States of America
- Department of Medicine, Duke University, Durham, North Carolina, United States of America
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Björkman A, Cook J, Sturrock H, Msellem M, Ali A, Xu W, Molteni F, Gosling R, Drakeley C, Mårtensson A. Spatial Distribution of Falciparum Malaria Infections in Zanzibar: Implications for Focal Drug Administration Strategies Targeting Asymptomatic Parasite Carriers. Clin Infect Dis 2018; 64:1236-1243. [PMID: 28431115 PMCID: PMC5399945 DOI: 10.1093/cid/cix136] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Indexed: 12/30/2022] Open
Abstract
Background. Optimal use of mass/targeted screen-and-treat or mass or focal drug administration as malaria elimination strategies remains unclear. We therefore studied spatial distribution of Plasmodium falciparum infections to compare simulated effects of these strategies on reducing the parasite reservoir in a pre-elimination setting. Methods. P. falciparum rapid diagnostic tests (RDTs) and molecular (polymerase chain reaction [PCR]) and serological (enzyme-linked immunosorbent assay) analyses were performed on finger-prick blood samples from a population-based survey in 3 adjacent communities. Results. Among 5278 persons screened, 13 (0.2%) were positive by RDT and 123 (2.3%) by PCR. PCR-positive individuals were scattered over the study area, but logistic regression analysis suggested a propensity of these infections to cluster around RDT-positive individuals. The odds ratios for being PCR positive was 7.4 (95% confidence interval, 2.8–19.9) for those living in the household of an RDT-positive individual and 1.64 (1.0–2.8; P = .06) for those living within <300 m, compared with >1000 m. Treating everyone within households of RDT-positive individuals (1% population) would target 13% of those who are PCR positive. Treating all living within a radius of <300 or <1000 m (14% or 58% population) would target 30% or 66% of infections, respectively. Among 4431 serologically screened individuals, 26% were seropositive. Treating everyone within seropositive households (63% population) would target 77% of PCR-positive individuals. Conclusions. Presumptive malaria treatment seemed justified within RDT-positive households and potentially worth considering within, for example, a radius of <300 m. Serology was not discriminative enough in identifying ongoing infections for improving focal interventions in this setting but may rather be useful to detect larger transmission foci.
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Affiliation(s)
- Anders Björkman
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Jackie Cook
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.,MRC Tropical Epidemiology Group, Faculty of Epidemiology and Population Health
| | - Hugh Sturrock
- Global Health Group, University of California, San Francisco, CA, USA
| | - Mwinyi Msellem
- Zanzibar Malaria Elimination Programme, Zanzibar Ministry of Health, Stone Town, Zanzibar, United Republic of Tanzania
| | - Abdullah Ali
- Zanzibar Malaria Elimination Programme, Zanzibar Ministry of Health, Stone Town, Zanzibar, United Republic of Tanzania
| | - Weiping Xu
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Fabrizio Molteni
- Swiss Tropical and Public Health Institute, Dar es Salaam, Tanzania
| | - Roly Gosling
- Global Health Group, University of California, San Francisco, CA, USA
| | - Chris Drakeley
- Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Andreas Mårtensson
- Department of Women's and Children's Health, International Maternal and Child Health, Uppsala University, Sweden
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Kesteman T, Randrianarivelojosia M, Rogier C. The protective effectiveness of control interventions for malaria prevention: a systematic review of the literature. F1000Res 2017; 6:1932. [PMID: 29259767 PMCID: PMC5721947 DOI: 10.12688/f1000research.12952.1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 10/27/2017] [Indexed: 12/22/2022] Open
Abstract
Background: Thanks to a considerable increase in funding, malaria control interventions (MCI) whose efficacy had been demonstrated by controlled trials have been largely scaled up during the last decade. Nevertheless, it was not systematically investigated whether this efficacy had been preserved once deployed on the field. Therefore, we sought the literature to assess the disparities between efficacy and effectiveness and the effort to measure the protective effectiveness (PE) of MCI. Methods: The PubMed database was searched for references with keywords related to malaria, to control interventions for prevention and to study designs that allow for the measure of the PE against parasitemia or against clinical outcomes. Results: Our search retrieved 1423 references, and 162 articles were included in the review. Publications were scarce before the year 2000 but dramatically increased afterwards. Bed nets was the MCI most studied (82.1%). The study design most used was a cross-sectional study (65.4%). Two thirds (67.3%) were conducted at the district level or below, and the majority (56.8%) included only children even if the MCI didn’t target only children. Not all studies demonstrated a significant PE from exposure to MCI: 60.6% of studies evaluating bed nets, 50.0% of those evaluating indoor residual spraying, and 4/8 showed an added PE of using both interventions as compared with one only; this proportion was 62.5% for intermittent preventive treatment of pregnant women, and 20.0% for domestic use of insecticides. Conclusions: This review identified numerous local findings of low, non-significant PE –or even the absence of a protective effect provided by these MCIs. The identification of such failures in the effectiveness of MCIs advocates for the investigation of the causes of the problem found. Ideal evaluations of the PE of MCIs should incorporate both a large representativeness and an evaluation of the PE stratified by subpopulations.
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Affiliation(s)
- Thomas Kesteman
- Fondation Mérieux, Lyon, France.,Malaria Research Unit, Institut Pasteur de Madagascar, Antananarivo, Madagascar
| | | | - Christophe Rogier
- Malaria Research Unit, Institut Pasteur de Madagascar, Antananarivo, Madagascar.,Ecole doctorale Sciences de la vie et de l'environnement, Université d'Antananarivo, Antananarivo, Madagascar.,Institute for Biomedical Research of the French Armed Forces (IRBA), Brétigny-Sur-Orge , France.,Unité de recherche sur les maladies infectieuses et tropicales émergentes - (URMITE), Marseille, France
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SCMDOT: Spatial Clustering with Multiple Density-Ordered Trees. ISPRS INTERNATIONAL JOURNAL OF GEO-INFORMATION 2017. [DOI: 10.3390/ijgi6070217] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
With the rapid explosion of information based on location, spatial clustering plays an increasingly significant role in this day and age as an important technique in geographical data analysis. Most existing spatial clustering algorithms are limited by complicated spatial patterns, which have difficulty in discovering clusters with arbitrary shapes and uneven density. In order to overcome such limitations, we propose a novel clustering method called Spatial Clustering with Multiple Density-Ordered Trees (SCMDOT). Motivated by the idea of the Density-Ordered Tree (DOT), we firstly represent the original dataset by the means of constructing Multiple Density-Ordered Trees (MDOT). In the constructing process, we impose additional constraints to control the growth of each Density-Ordered Tree, ensuring that they all have high spatial similarity. Furthermore, a series of MDOT can be successively generated from regions of sparse areas to the dense areas, where each Density-Ordered Tree, also treated as a sub-tree, represents a cluster. In the merging process, the final clusters are obtained by repeatedly merging a suitable pair of clusters until they satisfy the expected clustering result. In addition, a heuristic strategy is applied during the process of our algorithm for suitability for special applications. The experiments on synthetic and real-world spatial databases are utilised to demonstrate the performance of our proposed method.
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Gómez-Barroso D, García-Carrasco E, Herrador Z, Ncogo P, Romay-Barja M, Ondo Mangue ME, Nseng G, Riloha M, Santana MA, Valladares B, Aparicio P, Benito A. Spatial clustering and risk factors of malaria infections in Bata district, Equatorial Guinea. Malar J 2017; 16:146. [PMID: 28403879 PMCID: PMC5389164 DOI: 10.1186/s12936-017-1794-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 03/31/2017] [Indexed: 11/22/2022] Open
Abstract
Background The transmission of malaria is intense in the majority of the countries of sub-Saharan Africa, particularly in those that are located along the Equatorial strip. The present study aimed to describe the current distribution of malaria prevalence among children and its environment-related factors as well as to detect malaria spatial clusters in the district of Bata, in Equatorial Guinea. Methods From June to August 2013 a representative cross-sectional survey using a multistage, stratified, cluster-selected sample was carried out of children in urban and rural areas of Bata District. All children were tested for malaria using rapid diagnostic tests (RDTs). Results were linked to each household by global position system data. Two cluster analysis methods were used: hot spot analysis using the Getis-Ord Gi statistic, and the SaTScan™ spatial statistic estimates, based on the assumption of a Poisson distribution to detect spatial clusters. In addition, univariate associations and Poisson regression model were used to explore the association between malaria prevalence at household level with different environmental factors. Results A total of 1416 children aged 2 months to 15 years living in 417 households were included in this study. Malaria prevalence by RDTs was 47.53%, being highest in the age group 6–15 years (63.24%, p < 0.001). Those children living in rural areas were there malaria risk is greater (65.81%) (p < 0.001). Malaria prevalence was higher in those houses located <1 km from a river and <3 km to a forest (IRR: 1.31; 95% CI 1.13–1.51 and IRR: 1.44; 95% CI 1.25–1.66, respectively). Poisson regression analysis also showed a decrease in malaria prevalence with altitude (IRR: 0.73; 95% CI 0.62–0.86). A significant cluster inland of the district, in rural areas has been found. Conclusions This study reveals a high prevalence of RDT-based malaria among children in Bata district. Those households situated in inland rural areas, near to a river, a green area and/or at low altitude were a risk factor for malaria. Spatial tools can help policy makers to promote new recommendations for malaria control.
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Affiliation(s)
- Diana Gómez-Barroso
- CIBERESP, National Centre of Epidemiology, Carlos III Institute of Health (ISCIII), Madrid, Spain.
| | - Emely García-Carrasco
- RICET, National Center of Tropical Medicine, Carlos III Institute of Health (ISCIII), Madrid, Spain
| | - Zaida Herrador
- RICET, National Center of Tropical Medicine, Carlos III Institute of Health (ISCIII), Madrid, Spain
| | - Policarpo Ncogo
- Reference Centre for Endemic Control of Equatorial Guinea (CRCE), Malabo, Equatorial Guinea
| | - María Romay-Barja
- RICET, National Center of Tropical Medicine, Carlos III Institute of Health (ISCIII), Madrid, Spain
| | | | - Gloria Nseng
- Ministry of Health and Social Welfare, Malabo, Equatorial Guinea
| | - Matilde Riloha
- Ministry of Health and Social Welfare, Malabo, Equatorial Guinea
| | - Maria Angeles Santana
- University Institute for Tropical Diseases and Public Health of Canarias, Tenerife, Spain
| | - Basilio Valladares
- University Institute for Tropical Diseases and Public Health of Canarias, Tenerife, Spain
| | - Pilar Aparicio
- RICET, National Center of Tropical Medicine, Carlos III Institute of Health (ISCIII), Madrid, Spain
| | - Agustín Benito
- RICET, National Center of Tropical Medicine, Carlos III Institute of Health (ISCIII), Madrid, Spain
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Heng S, Durnez L, Mao S, Siv S, Tho S, Mean V, Sluydts V, Coosemans M. Passive case detection of malaria in Ratanakiri Province (Cambodia) to detect villages at higher risk for malaria. Malar J 2017; 16:104. [PMID: 28264678 PMCID: PMC5340042 DOI: 10.1186/s12936-017-1758-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 02/28/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Cambodia reduced malaria incidence by more than 75% between 2000 and 2015, a target of the Millennium Development Goal 6. The Cambodian Government aims to eliminate all forms of malaria by 2025. The country's malaria incidence is highly variable at provincial level, but less is known at village level. This study used passive case detection (PCD) data at village level in Ratanakiri Province from 2010 to 2014 to describe incidence trends and identify high-risk areas of malaria to be primarily targeted towards malaria elimination. METHODS In 2010, the Cambodian malaria programme created a Malaria Information System (MIS) to capture malaria information at village level through PCD by village malaria workers and health facilities. The MIS data of Ratanakiri Province 2010-2014 were used to calculate annual incidence rates by Plasmodium species at province and commune levels. For estimating the trend at provincial level only villages reporting each year were selected. The communal incidences and the number of cases per village were visualized on a map per Plasmodium species and per year. Analysis of spatial clustering of village malaria cases by Plasmodium species was performed by year. RESULTS Overall, malaria annual incidence rates per 1000 inhabitants decreased from 86 (2010) to 30 (2014). Falciparum incidence decreased (by 79% in 2014 compared to 2010; CI 95% 76-82%) more rapidly than vivax incidence (by 19% in 2014 compared to 2010; CI 95% 5-32%). There were ten to 16 significant spatial clusters each year. Big clusters tended to extend along the Cambodian-Vietnamese border and along the Sesan River. Three clusters appeared throughout all years (2010-2014): one with 21 villages appeared each year, the second shrunk progressively from 2012 to 2014 and the third was split into two smaller clusters in 2013 and 2014. CONCLUSION The decline of malaria burden can be attributed to intensive malaria control activities implemented in the areas: distribution of a long-lasting insecticidal net per person and early diagnosis and prompt treatment. Dihydro-artemisinin piperaquine was the only first-line treatment for all malaria cases. No radical treatment with primaquine was provided for Plasmodium vivax cases, which could explain the slow decrease of P. vivax due to relapses. To achieve malaria elimination by 2025, priority should be given to the control of stable malaria clusters appearing over time.
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Affiliation(s)
- Somony Heng
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia. .,Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium. .,Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium.
| | - Lies Durnez
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Sokny Mao
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Sovannaroth Siv
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Sochantha Tho
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Vanna Mean
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Vincent Sluydts
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.,Department of Biology, University of Antwerp, Antwerp, Belgium
| | - Marc Coosemans
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.,Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium
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49
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Explaining changes in child health inequality in the run up to the 2015 Millennium Development Goals (MDGs): The case of Zambia. PLoS One 2017; 12:e0170995. [PMID: 28170442 PMCID: PMC5295677 DOI: 10.1371/journal.pone.0170995] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 01/13/2017] [Indexed: 12/18/2022] Open
Abstract
Background Child health interventions were drastically scaled up in the period leading up to 2015 as countries aimed at meeting the 2015 target of the Millennium Development Goals (MDGs). MDGs were defined in terms of achieving improvements in average health. Significant improvements in average child health are documented, but evidence also points to rising inequality. It is important to investigate factors that drive the increasing disparities in order to inform the post-2015 development agenda of reducing inequality, as captured in the Sustainable Development Goals (SDGs). We investigated changes in socioeconomic inequality in stunting and fever in Zambia in 2007 and 2014. Unlike the huge literature that seeks to quantify the contribution of different determinants on the observed inequality at any given time, we quantify determinants of changes in inequality. Methods Data from the 2007 and 2014 waves of the Zambia Demographic and Health Survey (DHS) were utilized. Our sample consisted of children aged 0–5 years (n = 5,616 in 2007 and n = 12,714 in 2014). We employed multilevel models to assess the determinants of stunting and fever, which are two important child health indicators. The concentration index (CI) was used to measure the magnitude of inequality. Changes in inequality of stunting and fever were investigated using Oaxaca-type decomposition of the CI. In this approach, the change in the CI for stunting/fever is decomposed into changes in CI for each determinant and changes in the effect—measured as an elasticity—of each determinant on stunting/fever. Results While average rates of stunting reduced in 2014 socioeconomic inequality in stunting increased significantly. Inequality in fever incidence also increased significantly, but average rates of fever did not reduce. The increase in the inequality (CI) of determinants accounted for the largest part (42.5%) of the increase in inequality of stunting, while the increase in the effect of determinants explained 35% of the increase. The determinants with the greatest total contribution (change in CI plus change in effect) to the increase in inequality of stunting were mother’s height and weight, wealth, birth order, facility delivery, duration of breastfeeding, and maternal education. For fever, almost all (86%) the increase in inequality was accounted for by the increase in the effect of determinants of fever, while the distribution of determinants mattered less. The determinants with the greatest total contribution to the increase in inequality of fever were wealth, maternal education, birth order and breastfeeding duration. In the multilevel model, we found that the likelihood of a child being stunted or experiencing fever depends on the community in which they live. Conclusions To curb the increase in inequality of stunting and fever, policy may focus on improving levels of, and reducing inequality in, access to facility deliveries, maternal nutrition (which may be related to maternal weight and height), complementary feeding (for breastfed children), wealth, maternal education, and child care (related to birth order effects). Improving overall levels of these determinants contribute to the persistence of inequality if these determinants are unequally concentrated on the well off to begin with.
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50
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Tripura R, Peto TJ, Veugen CC, Nguon C, Davoeung C, James N, Dhorda M, Maude RJ, Duanguppama J, Patumrat K, Imwong M, von Seidlein L, Grobusch MP, White NJ, Dondorp AM. Submicroscopic Plasmodium prevalence in relation to malaria incidence in 20 villages in western Cambodia. Malar J 2017; 16:56. [PMID: 28143518 PMCID: PMC5282880 DOI: 10.1186/s12936-017-1703-5] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2016] [Accepted: 01/19/2017] [Indexed: 11/10/2022] Open
Abstract
Background Cambodia has seen a marked reduction in the incidence of Plasmodium falciparum over the past decade without a corresponding decline in Plasmodium vivax incidence. It is unknown to what extent local transmission is sustained by a chain of clinical and sub-clinical infections or by continued re-introduction via migration. Using an ultrasensitive molecular technique, 20 villages in western Cambodia were surveyed to detect the low season prevalence of P. falciparum and P. vivax and local treatment records were reviewed. Methods During March to May 2015 cross-sectional surveys were conducted in 20 villages in Battambang, western Cambodia. Demographic and epidemiological data and venous blood samples were collected from 50 randomly selected adult volunteers in each village. Blood was tested for Plasmodium infections by rapid diagnostic test (RDT), microscopy and high volume (0.5 ml packed red blood cell) quantitative polymerase chain reaction (uPCR). Positive samples were analysed by nested PCR to determine the Plasmodium species. Malaria case records were collected from the Provincial Health Department and village malaria workers to determine incidence and migration status. Results Among the 1000 participants, 91 (9.1%) were positive for any Plasmodium infection by uPCR, seven (0.7%) by microscopy, and two (0.2%) by RDT. uPCR P. vivax prevalence was 6.6%, P. falciparum 0.7%, and undetermined Plasmodium species 1.8%. Being male (adjusted OR 2.0; 95% CI 1.2-3.4); being a young adult <30 years (aOR 2.1; 95% CI 1.3–3.4); recent forest travel (aOR 2.8; 95% CI 1.6–4.8); and, a history of malaria (aOR 5.2; 95% CI 2.5–10.7) were independent risk factors for parasitaemia. Of the clinical malaria cases diagnosed by village malaria workers, 43.9% (297/634) and 38.4% (201/523) were among migrants in 2013 and in 2014, respectively. Plasmodium vivax prevalence determined by uPCR significantly correlated with vivax malaria incidences in both 2014 and 2015 (p = 0.001 and 0.002, respectively), whereas no relationship was observed in falciparum malaria (p = 0.36 and p = 0.59, respectively). Discussion There was heterogeneity in the malaria parasite reservoir between villages, and Plasmodium prevalence correlated with subsequent malaria incidence. The association was attributable chiefly to P. vivax infections, which were nine-fold more prevalent than P. falciparum infections. In the absence of a radical cure with 8-aminoquinolines, P. vivax transmission will continue even as P. falciparum prevalence declines. Migration was associated with over a third of incident cases of clinical malaria. Trial registration clinicaltrials.gov (NCT01872702). Registered 4 June 2013 Electronic supplementary material The online version of this article (doi:10.1186/s12936-017-1703-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Rupam Tripura
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Rd, Rajthevee, Bangkok, 10400, Thailand. .,Center of Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
| | - Thomas J Peto
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Rd, Rajthevee, Bangkok, 10400, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Christianne C Veugen
- Center of Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Chea Nguon
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | | | - Nicola James
- Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, London, UK
| | - Mehul Dhorda
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Rd, Rajthevee, Bangkok, 10400, Thailand.,World-Wide Antimalarial Resistance Network, Mahidol University, Bangkok, Thailand
| | - Richard J Maude
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Rd, Rajthevee, Bangkok, 10400, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK.,Department of Epidemiology, Harvard T. H. Chan School of Public Health, Harvard University, Boston, USA
| | - Jureeporn Duanguppama
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Rd, Rajthevee, Bangkok, 10400, Thailand.,Department of Molecular Tropical Medicine and Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Krittaya Patumrat
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Rd, Rajthevee, Bangkok, 10400, Thailand.,Department of Molecular Tropical Medicine and Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Mallika Imwong
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Rd, Rajthevee, Bangkok, 10400, Thailand.,Department of Molecular Tropical Medicine and Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Lorenz von Seidlein
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Rd, Rajthevee, Bangkok, 10400, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Martin P Grobusch
- Center of Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Nicholas J White
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Rd, Rajthevee, Bangkok, 10400, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Arjen M Dondorp
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Rd, Rajthevee, Bangkok, 10400, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
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