201
|
Walker PGT, Griffin JT, Ferguson NM, Ghani AC. Estimating the most efficient allocation of interventions to achieve reductions in Plasmodium falciparum malaria burden and transmission in Africa: a modelling study. LANCET GLOBAL HEALTH 2016; 4:e474-84. [PMID: 27269393 DOI: 10.1016/s2214-109x(16)30073-0] [Citation(s) in RCA: 89] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Revised: 04/04/2016] [Accepted: 04/21/2016] [Indexed: 11/26/2022]
Abstract
BACKGROUND Reducing the burden of malaria is a global priority, but financial constraints mean that available resources must be allocated rationally to maximise their effect. We aimed to develop a model to estimate the most efficient (ie, minimum cost) ordering of interventions to reduce malaria burden and transmission. We also aimed to estimate the efficiency of different spatial scales of implementation. METHODS We combined a dynamic model capturing heterogeneity in malaria transmission across Africa with financial unit cost data for key malaria interventions. We combined estimates of patterns of malaria endemicity, seasonality in rainfall, and mosquito composition to map optimum packages of these interventions across Africa. Using non-linear optimisation methods, we examined how these optimum packages vary when control measures are deployed and assessed at national, subnational first administrative (provincial), or fine-scale (5 km(2) pixel) spatial scales. FINDINGS The most efficient package in a given setting varies depending on whether disease reduction or elimination is the target. Long-lasting insecticide-treated nets are generally the most cost-effective first intervention to achieve either goal, with seasonal malaria chemoprevention or indoor residual spraying added second depending on seasonality and vector species. These interventions are estimated to reduce malaria transmission to less than one case per 1000 people per year in 43·4% (95% CI 40·0-49·0) of the population at risk in Africa. Adding three rounds of mass drug administration per year is estimated to increase this proportion to 90·9% (95% CI 86·9-94·6). Further optimisation can be achieved by targeting policies at the provincial level, achieving an estimated 32·1% (95% CI 29·6-34·5) cost saving relative to adopting country-wide policies. Nevertheless, we predict that only 26 (95% CI 22-29) of 41 countries could reduce transmission to these levels with these approaches. INTERPRETATION These results highlight the cost-benefits of carefully tailoring malaria interventions to the ecological landscape of different areas. However, novel interventions are necessary if malaria eradication is to be achieved. FUNDING Bill & Melinda Gates Foundation, UK Medical Research Council.
Collapse
Affiliation(s)
- Patrick G T Walker
- MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Imperial College London, London, UK.
| | - Jamie T Griffin
- MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Imperial College London, London, UK
| | - Neil M Ferguson
- MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Imperial College London, London, UK
| | - Azra C Ghani
- MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Imperial College London, London, UK
| |
Collapse
|
202
|
Abstract
Supplemental Digital Content is available in the text Objective: There is evidence of substantial subnational variation in the HIV epidemic. However, robust spatial HIV data are often only available at high levels of geographic aggregation and not at the finer resolution needed for decision making. Therefore, spatial analysis methods that leverage available data to provide local estimates of HIV prevalence may be useful. Such methods exist but have not been formally compared when applied to HIV. Design/methods: Six candidate methods – including those used by the Joint United Nations Programme on HIV/AIDS to generate maps and a Bayesian geostatistical approach applied to other diseases – were used to generate maps and subnational estimates of HIV prevalence across three countries using cluster level data from household surveys. Two approaches were used to assess the accuracy of predictions: internal validation, whereby a proportion of input data is held back (test dataset) to challenge predictions; and comparison with location-specific data from household surveys in earlier years. Results: Each of the methods can generate usefully accurate predictions of prevalence at unsampled locations, with the magnitude of the error in predictions similar across approaches. However, the Bayesian geostatistical approach consistently gave marginally the strongest statistical performance across countries and validation procedures. Conclusions: Available methods may be able to furnish estimates of HIV prevalence at finer spatial scales than the data currently allow. The subnational variation revealed can be integrated into planning to ensure responsiveness to the spatial features of the epidemic. The Bayesian geostatistical approach is a promising strategy for integrating HIV data to generate robust local estimates.
Collapse
|
203
|
Quispe AM, Llanos-Cuentas A, Rodriguez H, Clendenes M, Cabezas C, Leon LM, Chuquiyauri R, Moreno M, Kaslow DC, Grogl M, Herrera S, Magill AJ, Kosek M, Vinetz JM, Lescano AG, Gotuzzo E. Accelerating to Zero: Strategies to Eliminate Malaria in the Peruvian Amazon. Am J Trop Med Hyg 2016; 94:1200-1207. [PMID: 30851016 PMCID: PMC4889734 DOI: 10.4269/ajtmh.15-0369] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
AbstractIn February 2014, the Malaria Elimination Working Group, in partnership with the Peruvian Ministry of Health (MoH), hosted its first international conference on malaria elimination in Iquitos, Peru. The 2-day meeting gathered 85 malaria experts, including 18 international panelists, 23 stakeholders from different malaria-endemic regions of Peru, and 11 MoH authorities. The main outcome was consensus that implementing a malaria elimination project in the Amazon region is achievable, but would require: 1) a comprehensive strategic plan, 2) the altering of current programmatic guidelines from control toward elimination by including symptomatic as well as asymptomatic individuals for antimalarial therapy and transmission-blocking interventions, and 3) the prioritization of community-based active case detection with proper rapid diagnostic tests to interrupt transmission. Elimination efforts must involve key stakeholders and experts at every level of government and include integrated research activities to evaluate, implement, and tailor sustainable interventions appropriate to the region.
Collapse
Affiliation(s)
- Antonio M. Quispe
- *Address correspondence to Antonio M. Quispe, Department of International Health, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, MD 21205. E-mail:
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
204
|
Gametocyte carriage in uncomplicated Plasmodium falciparum malaria following treatment with artemisinin combination therapy: a systematic review and meta-analysis of individual patient data. BMC Med 2016; 14:79. [PMID: 27221542 PMCID: PMC4879753 DOI: 10.1186/s12916-016-0621-7] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Accepted: 04/27/2016] [Indexed: 01/21/2023] Open
Abstract
BACKGROUND Gametocytes are responsible for transmission of malaria from human to mosquito. Artemisinin combination therapy (ACT) reduces post-treatment gametocyte carriage, dependent upon host, parasite and pharmacodynamic factors. The gametocytocidal properties of antimalarial drugs are important for malaria elimination efforts. An individual patient clinical data meta-analysis was undertaken to identify the determinants of gametocyte carriage and the comparative effects of four ACTs: artemether-lumefantrine (AL), artesunate/amodiaquine (AS-AQ), artesunate/mefloquine (AS-MQ), and dihydroartemisinin-piperaquine (DP). METHODS Factors associated with gametocytaemia prior to, and following, ACT treatment were identified in multivariable logistic or Cox regression analysis with random effects. All relevant studies were identified through a systematic review of PubMed. Risk of bias was evaluated based on study design, methodology, and missing data. RESULTS The systematic review identified 169 published and 9 unpublished studies, 126 of which were shared with the WorldWide Antimalarial Resistance Network (WWARN) and 121 trials including 48,840 patients were included in the analysis. Prevalence of gametocytaemia by microscopy at enrolment was 12.1 % (5887/48,589), and increased with decreasing age, decreasing asexual parasite density and decreasing haemoglobin concentration, and was higher in patients without fever at presentation. After ACT treatment, gametocytaemia appeared in 1.9 % (95 % CI, 1.7-2.1) of patients. The appearance of gametocytaemia was lowest after AS-MQ and AL and significantly higher after DP (adjusted hazard ratio (AHR), 2.03; 95 % CI, 1.24-3.12; P = 0.005 compared to AL) and AS-AQ fixed dose combination (FDC) (AHR, 4.01; 95 % CI, 2.40-6.72; P < 0.001 compared to AL). Among individuals who had gametocytaemia before treatment, gametocytaemia clearance was significantly faster with AS-MQ (AHR, 1.26; 95 % CI, 1.00-1.60; P = 0.054) and slower with DP (AHR, 0.74; 95 % CI, 0.63-0.88; P = 0.001) compared to AL. Both recrudescent (adjusted odds ratio (AOR), 9.05; 95 % CI, 3.74-21.90; P < 0.001) and new (AOR, 3.03; 95 % CI, 1.66-5.54; P < 0.001) infections with asexual-stage parasites were strongly associated with development of gametocytaemia after day 7. CONCLUSIONS AS-MQ and AL are more effective than DP and AS-AQ FDC in preventing gametocytaemia shortly after treatment, suggesting that the non-artemisinin partner drug or the timing of artemisinin dosing are important determinants of post-treatment gametocyte dynamics.
Collapse
Affiliation(s)
- WWARN Gametocyte Study Group
- />Department of Medical Microbiology 268, Radboud University Medical Center, PO Box 9101, 6500HB Nijmegen, the Netherlands
- />WorldWide Antimalarial Resistance Network (WWARN), Centre for Tropical Medicine and Global Health, Churchill Hospital, CCVTM, University of Oxford, Old Road, Oxford, OX3 7LE UK
| |
Collapse
|
205
|
Murray L, Mobegi VA, Duffy CW, Assefa SA, Kwiatkowski DP, Laman E, Loua KM, Conway DJ. Microsatellite genotyping and genome-wide single nucleotide polymorphism-based indices of Plasmodium falciparum diversity within clinical infections. Malar J 2016; 15:275. [PMID: 27176827 PMCID: PMC4865991 DOI: 10.1186/s12936-016-1324-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2016] [Accepted: 05/03/2016] [Indexed: 11/10/2022] Open
Abstract
Background In regions where malaria is endemic, individuals are often infected with multiple distinct parasite genotypes, a situation that may impact on evolution of parasite virulence and drug resistance. Most approaches to studying genotypic diversity have involved analysis of a modest number of polymorphic loci, although whole genome sequencing enables a broader characterisation of samples. Methods PCR-based microsatellite typing of a panel of ten loci was performed on Plasmodium falciparum in 95 clinical isolates from a highly endemic area in the Republic of Guinea, to characterize within-isolate genetic diversity. Separately, single nucleotide polymorphism (SNP) data from genome-wide short-read sequences of the same samples were used to derive within-isolate fixation indices (Fws), an inverse measure of diversity within each isolate compared to overall local genetic diversity. The latter indices were compared with the microsatellite results, and also with indices derived by randomly sampling modest numbers of SNPs. Results As expected, the number of microsatellite loci with more than one allele in each isolate was highly significantly inversely correlated with the genome-wide Fws fixation index (r = −0.88, P < 0.001). However, the microsatellite analysis revealed that most isolates contained mixed genotypes, even those that had no detectable genome sequence heterogeneity. Random sampling of different numbers of SNPs showed that an Fws index derived from ten or more SNPs with minor allele frequencies of >10 % had high correlation (r > 0.90) with the index derived using all SNPs. Conclusions Different types of data give highly correlated indices of within-infection diversity, although PCR-based analysis detects low-level minority genotypes not apparent in bulk sequence analysis. When whole-genome data are not obtainable, quantitative assay of ten or more SNPs can yield a reasonably accurate estimate of the within-infection fixation index (Fws). Electronic supplementary material The online version of this article (doi:10.1186/s12936-016-1324-4) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Lee Murray
- Pathogen Molecular Biology Department, London School of Hygiene and Tropical Medicine, Keppel St, London, WC1E 7HT, UK
| | - Victor A Mobegi
- Pathogen Molecular Biology Department, London School of Hygiene and Tropical Medicine, Keppel St, London, WC1E 7HT, UK.,Medical Research Council Unit, Fajara, Atlantic Road, Banjul, Gambia
| | - Craig W Duffy
- Pathogen Molecular Biology Department, London School of Hygiene and Tropical Medicine, Keppel St, London, WC1E 7HT, UK
| | - Samuel A Assefa
- Pathogen Molecular Biology Department, London School of Hygiene and Tropical Medicine, Keppel St, London, WC1E 7HT, UK
| | | | - Eugene Laman
- National Institute of Public Health, Conakry, Republic of Guinea
| | - Kovana M Loua
- National Institute of Public Health, Conakry, Republic of Guinea
| | - David J Conway
- Pathogen Molecular Biology Department, London School of Hygiene and Tropical Medicine, Keppel St, London, WC1E 7HT, UK.
| |
Collapse
|
206
|
Lalani T, Yun H, Tribble D, Ganesan A, Kunz A, Fairchok M, Schnaubelt E, Fraser J, Mitra I, Kronmann KC, Burgess T, Deiss RG, Riddle MS, Johnson MD. A comparison of compliance rates with anti-vectorial protective measures during travel to regions with dengue or chikungunya activity, and regions endemic for Plasmodium falciparum malaria. J Travel Med 2016; 23:taw043. [PMID: 27378367 PMCID: PMC4939934 DOI: 10.1093/jtm/taw043] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 05/24/2016] [Indexed: 01/05/2023]
Abstract
BACKGROUND There is limited information on compliance rates with anti-vectorial protective measures (AVPMs) during travel to countries with risk of dengue and chikungunya. We evaluated differences in mosquito exposures, and factors associated with AVPM compliance in travellers going to countries where the principal mosquito-borne infectious disease threat is falciparum malaria and those where risk of dengue or chikungunya predominates. METHODS Department of Defence beneficiaries with planned travel to regions where the predominant mosquito-borne infection is falciparum malaria, and those with predominantly dengue or chikungunya risk, were included. Regions were divided into three groups: 'high-risk falciparum malaria', 'low-risk falciparum malaria' and 'chikungunya/dengue risk'. Demographics, trip characteristics, arthropod exposure and AVPM compliance were captured using pre- and post-travel surveys. Skin repellent compliance was defined as self-reported use, categorized as 'often/every day'. A logistic regression model was used to estimate factors associated with AVPM compliance. RESULTS 183 (9%), 185 (9%) and 149 (7%) travelled to high and low falciparum malaria risk regions, and chikungunya/dengue risk regions, respectively. Overall, 53% (95% CI: 48-57%) and 16% (95% CI: 12-19%) were compliant with repellent use on skin and clothing, respectively. Daytime bites were reported more frequently in chikungunya/dengue risk regions than high malaria risk regions (37% vs. 10%), while night time bites were frequently in high malaria risk regions (53% vs 20%; P < 0.001). Compliance with skin repellents was associated with female gender [RR: 1.54 (95% CI: 1.05-2.28)], observing mosquitoes during travel [RR: 2.77 (95% CI: 1.76-4.36)] and travel during the rainy season [RR: 2.45 (95% CI: 1.66-3.71)]). CONCLUSIONS Poor AVPM compliance was observed in the overall cohort. Compliance with skin repellent use was associated with female gender, observing mosquitoes and travelling during the rainy season, and was not associated with the risk of malaria or chikungunya/dengue at the travel destination.
Collapse
Affiliation(s)
- Tahaniyat Lalani
- Department of Preventive Medicine and Biostatistics, Infectious Disease Clinical Research Program, Uniformed Services University of the Health Sciences, Bethesda, MD, USA.,Division of Infectious Diseases, Naval Medical Center Portsmouth, Portsmouth, VA, USA.,Henry M Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA
| | - Heather Yun
- San Antonio Uniformed Services Health Education, Fort Sam Houston, TX, USA
| | - David Tribble
- Department of Preventive Medicine and Biostatistics, Infectious Disease Clinical Research Program, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Anuradha Ganesan
- Department of Preventive Medicine and Biostatistics, Infectious Disease Clinical Research Program, Uniformed Services University of the Health Sciences, Bethesda, MD, USA.,Henry M Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA.,Walter Reed National Military Medical Center, Bethesda, MD, USA
| | - Anjali Kunz
- Madigan Army Medical Center, Tacoma, WA, USA
| | - Mary Fairchok
- Department of Preventive Medicine and Biostatistics, Infectious Disease Clinical Research Program, Uniformed Services University of the Health Sciences, Bethesda, MD, USA.,Henry M Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA.,Madigan Army Medical Center, Tacoma, WA, USA
| | | | - Jamie Fraser
- Department of Preventive Medicine and Biostatistics, Infectious Disease Clinical Research Program, Uniformed Services University of the Health Sciences, Bethesda, MD, USA.,Henry M Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA
| | - Indrani Mitra
- Department of Preventive Medicine and Biostatistics, Infectious Disease Clinical Research Program, Uniformed Services University of the Health Sciences, Bethesda, MD, USA.,Henry M Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA
| | - Karl C Kronmann
- Division of Infectious Diseases, Naval Medical Center Portsmouth, Portsmouth, VA, USA
| | - Timothy Burgess
- San Antonio Uniformed Services Health Education, Fort Sam Houston, TX, USA
| | - Robert G Deiss
- Department of Preventive Medicine and Biostatistics, Infectious Disease Clinical Research Program, Uniformed Services University of the Health Sciences, Bethesda, MD, USA.,Henry M Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA.,Naval Medical Center of San Diego, San Diego, CA, USA
| | - Mark S Riddle
- Enteric Diseases Department, Naval Medical Research Center, Silver Spring, MD, USA
| | - Mark D Johnson
- Naval Medical Center of San Diego, San Diego, CA, USA.,DoD HIV/AIDS Prevention Program, Naval Health Research Center, San Diego, CA, USA
| |
Collapse
|
207
|
Diboulo E, Sié A, Vounatsou P. Assessing the effects of malaria interventions on the geographical distribution of parasitaemia risk in Burkina Faso. Malar J 2016; 15:228. [PMID: 27098853 PMCID: PMC4839146 DOI: 10.1186/s12936-016-1282-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Accepted: 04/12/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Burkina Faso conducted its first nationally representative household malaria survey in 2010/2011. The survey collected among others, information on malaria interventions, treatment choices and malaria parasite prevalence in children aged 6-59 months. METHODS In this study, Bayesian geostatistical models were employed to assess the effects of health interventions related to insecticide-treated bed nets (ITN), indoor residual spray (IRS), artemisinin-based combination therapy (ACT) coverage associated with childhood malaria parasite risk at national and sub-national level, after taking into account geographical disparities of climatic/environmental and socio-economic factors. Several ITN coverage measures were calculated and Bayesian variable selection was used to identify the most important ones. Parasitaemia risk depicting spatial patterns of infections were estimated. RESULTS The results show that the predicted population-adjusted parasitaemia risk ranges from 4.04 % in Kadiogo province to 82 % in Kompienga province. The effect of ITN coverage was not important at national level; however ITNs have an important protective effect in Ouagadougou as well as in three districts in the western part of the country with high parasitaemia prevalence and low to moderate coverage. There is a large variation in ACT coverage between the districts. Although at national level the ACT effects on parasitaemia risk was not important, at sub-national level 18 districts around Ouagadougou deliver effective treatment. CONCLUSION The produced maps show great variations in parasitaemia risk across the country and identify the districts where interventions are being effective. These outputs are valuable tools that can help improve malaria control in Burkina Faso.
Collapse
Affiliation(s)
- Eric Diboulo
- />Swiss Tropical and Public Health Institute, Socinstrasse 57, P.O. Box, CH-4002 Basel, Switzerland
- />University of Basel, Basel, Switzerland
- />Centre de Recherche en Santé de Nouna, Nouna, Burkina Faso
| | - Ali Sié
- />Swiss Tropical and Public Health Institute, Socinstrasse 57, P.O. Box, CH-4002 Basel, Switzerland
| | - Penelope Vounatsou
- />Swiss Tropical and Public Health Institute, Socinstrasse 57, P.O. Box, CH-4002 Basel, Switzerland
- />University of Basel, Basel, Switzerland
| |
Collapse
|
208
|
Marshall JM, Touré M, Ouédraogo AL, Ndhlovu M, Kiware SS, Rezai A, Nkhama E, Griffin JT, Hollingsworth TD, Doumbia S, Govella NJ, Ferguson NM, Ghani AC. Key traveller groups of relevance to spatial malaria transmission: a survey of movement patterns in four sub-Saharan African countries. Malar J 2016; 15:200. [PMID: 27068686 PMCID: PMC4828820 DOI: 10.1186/s12936-016-1252-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 03/30/2016] [Indexed: 01/29/2023] Open
Abstract
Background As malaria prevalence declines in many parts of the world due to widescale control efforts and as drug-resistant parasites begin to emerge, a quantitative understanding of human movement is becoming increasingly relevant to malaria control. However, despite its importance, significant knowledge gaps remain regarding human movement, particularly in sub-Saharan Africa. Methods A quantitative survey of human movement patterns was conducted in four countries in sub-Saharan Africa: Mali, Burkina Faso, Zambia, and Tanzania, with three to five survey locations chosen in each country. Questions were included on demographic and trip details, malaria risk behaviour, children accompanying travellers, and mobile phone usage to enable phone signal data to be better correlated with movement. A total of 4352 individuals were interviewed and 6411 trips recorded. Results A cluster analysis of trips highlighted two distinct traveller groups of relevance to malaria transmission: women travelling with children (in all four countries) and youth workers (in Mali). Women travelling with children were more likely to travel to areas of relatively high malaria prevalence in Mali (OR = 4.46, 95 % CI = 3.42–5.83), Burkina Faso (OR = 1.58, 95 % CI = 1.23–1.58), Zambia (OR = 1.50, 95 % CI = 1.20–1.89), and Tanzania (OR = 2.28, 95 % CI = 1.71–3.05) compared to other travellers. They were also more likely to own bed nets in Burkina Faso (OR = 1.77, 95 % CI = 1.25–2.53) and Zambia (OR = 1.74, 95 % CI = 1.34 2.27), and less likely to own a mobile phone in Mali (OR = 0.50, 95 % CI = 0.39–0.65), Burkina Faso (OR = 0.39, 95 % CI = 0.30–0.52), and Zambia (OR = 0.60, 95 % CI = 0.47–0.76). Malian youth workers were more likely to travel to areas of relatively high malaria prevalence (OR = 23, 95 % CI = 17–31) and for longer durations (mean of 70 days cf 21 days, p < 0.001) compared to other travellers. Conclusions Women travelling with children were a remarkably consistent traveller group across all four countries surveyed. They are expected to contribute greatly towards spatial malaria transmission because the children they travel with tend to have high parasite prevalence. Youth workers were a significant traveller group in Mali and are expected to contribute greatly to spatial malaria transmission because their movements correlate with seasonal rains and hence peak mosquito densities. Interventions aimed at interrupting spatial transmission of parasites should consider these traveller groups. Electronic supplementary material The online version of this article (doi:10.1186/s12936-016-1252-3) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- John M Marshall
- Department of Infectious Disease Epidemiology, MRC Center for Outbreak Analysis and Modelling, Imperial College London, London, UK. .,Divisions of Biostatistics and Epidemiology, School of Public Health, University of California, Berkeley, CA, USA.
| | - Mahamoudou Touré
- Malaria Research and Training Center, University of Bamako, Bamako, Mali
| | - André Lin Ouédraogo
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso.,Institute for Disease Modeling, Bellevue, WA, USA
| | | | - Samson S Kiware
- Environmental Health and Ecological Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, Tanzania
| | - Ashley Rezai
- Department of Infectious Disease Epidemiology, MRC Center for Outbreak Analysis and Modelling, Imperial College London, London, UK
| | - Emmy Nkhama
- Chainama College of Health Sciences, Lusaka, Zambia
| | - Jamie T Griffin
- Department of Infectious Disease Epidemiology, MRC Center for Outbreak Analysis and Modelling, Imperial College London, London, UK
| | - T Deirdre Hollingsworth
- Department of Infectious Disease Epidemiology, MRC Center for Outbreak Analysis and Modelling, Imperial College London, London, UK.,School of Life Sciences, University of Warwick, Warwick, Coventry, UK
| | - Seydou Doumbia
- Malaria Research and Training Center, University of Bamako, Bamako, Mali
| | - Nicodem J Govella
- Environmental Health and Ecological Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, Tanzania
| | - Neil M Ferguson
- Department of Infectious Disease Epidemiology, MRC Center for Outbreak Analysis and Modelling, Imperial College London, London, UK
| | - Azra C Ghani
- Department of Infectious Disease Epidemiology, MRC Center for Outbreak Analysis and Modelling, Imperial College London, London, UK
| |
Collapse
|
209
|
Identifying Malaria Transmission Foci for Elimination Using Human Mobility Data. PLoS Comput Biol 2016; 12:e1004846. [PMID: 27043913 PMCID: PMC4820264 DOI: 10.1371/journal.pcbi.1004846] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Accepted: 03/03/2016] [Indexed: 11/30/2022] Open
Abstract
Humans move frequently and tend to carry parasites among areas with endemic malaria and into areas where local transmission is unsustainable. Human-mediated parasite mobility can thus sustain parasite populations in areas where they would otherwise be absent. Data describing human mobility and malaria epidemiology can help classify landscapes into parasite demographic sources and sinks, ecological concepts that have parallels in malaria control discussions of transmission foci. By linking transmission to parasite flow, it is possible to stratify landscapes for malaria control and elimination, as sources are disproportionately important to the regional persistence of malaria parasites. Here, we identify putative malaria sources and sinks for pre-elimination Namibia using malaria parasite rate (PR) maps and call data records from mobile phones, using a steady-state analysis of a malaria transmission model to infer where infections most likely occurred. We also examined how the landscape of transmission and burden changed from the pre-elimination setting by comparing the location and extent of predicted pre-elimination transmission foci with modeled incidence for 2009. This comparison suggests that while transmission was spatially focal pre-elimination, the spatial distribution of cases changed as burden declined. The changing spatial distribution of burden could be due to importation, with cases focused around importation hotspots, or due to heterogeneous application of elimination effort. While this framework is an important step towards understanding progressive changes in malaria distribution and the role of subnational transmission dynamics in a policy-relevant way, future work should account for international parasite movement, utilize real time surveillance data, and relax the steady state assumption required by the presented model. For countries considering pursuing malaria elimination, understanding where malaria transmission occurs is crucial for intervention planning. By identifying the areas that act as sources of malaria parasites, elimination programs can target efforts to end local transmission and achieve nationwide elimination. Mapping parasite sources requires a modeling framework that integrates malaria burden and human movement information, however, as human mobility facilitates parasite spread and drives source-sink disease dynamics. In this study, we present a mathematical model that can be used to identify areas with self-sustaining malaria transmission when analyzed at equilibrium. We demonstrate how this method can inform elimination planning for countries with stable low transmission using data from Namibia. The maps of sources and sinks created using this method can be used to direct policy and target areas with self-sustaining malaria transmission in countries with stable transmission. Finally, we compare the predicted extent of transmission foci with more recent maps of incidence, to determine whether local transmission likely retreated into focal areas and the potential importance of importation.
Collapse
|
210
|
Griffin JT, Bhatt S, Sinka ME, Gething PW, Lynch M, Patouillard E, Shutes E, Newman RD, Alonso P, Cibulskis RE, Ghani AC. Potential for reduction of burden and local elimination of malaria by reducing Plasmodium falciparum malaria transmission: a mathematical modelling study. THE LANCET. INFECTIOUS DISEASES 2016; 16:465-72. [PMID: 26809816 PMCID: PMC5206792 DOI: 10.1016/s1473-3099(15)00423-5] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Revised: 10/05/2015] [Accepted: 10/27/2015] [Indexed: 02/02/2023]
Abstract
BACKGROUND Rapid declines in malaria prevalence, cases, and deaths have been achieved globally during the past 15 years because of improved access to first-line treatment and vector control. We aimed to assess the intervention coverage needed to achieve further gains over the next 15 years. METHODS We used a mathematical model of the transmission of Plasmodium falciparum malaria to explore the potential effect on case incidence and malaria mortality rates from 2015 to 2030 of five different intervention scenarios: remaining at the intervention coverage levels of 2011-13 (Sustain), for which coverage comprises vector control and access to treatment; two scenarios of increased coverage to 80% (Accelerate 1) and 90% (Accelerate 2), with a switch from quinine to injectable artesunate for management of severe disease and seasonal malaria chemoprevention where recommended for both Accelerate scenarios, and rectal artesunate for pre-referral treatment at the community level added to Accelerate 2; a near-term innovation scenario (Innovate), which included longer-lasting insecticidal nets and expansion of seasonal malaria chemoprevention; and a reduction in coverage to 2006-08 levels (Reverse). We did the model simulations at the first administrative level (ie, state or province) for the 80 countries with sustained stable malaria transmission in 2010, accounting for variations in baseline endemicity, seasonality in transmission, vector species, and existing intervention coverage. To calculate the cases and deaths averted, we compared the total number of each under the five scenarios between 2015 and 2030 with the predicted number in 2015, accounting for population growth. FINDINGS With an increase to 80% coverage, we predicted a reduction in case incidence of 21% (95% credible intervals [CrI] 19-29) and a reduction in mortality rates of 40% (27-61) by 2030 compared with 2015 levels. Acceleration to 90% coverage and expansion of treatment at the community level was predicted to reduce case incidence by 59% (Crl 56-64) and mortality rates by 74% (67-82); with additional near-term innovation, incidence was predicted to decline by 74% (70-77) and mortality rates by 81% (76-87). These scenarios were predicted to lead to local elimination in 13 countries under the Accelerate 1 scenario, 20 under Accelerate 2, and 22 under Innovate by 2030, reducing the proportion of the population living in at-risk areas by 36% if elimination is defined at the first administrative unit. However, failing to maintain coverage levels of 2011-13 is predicted to raise case incidence by 76% (Crl 71-80) and mortality rates by 46% (39-51) by 2020. INTERPRETATION Our findings show that decreases in malaria transmission and burden can be accelerated over the next 15 years if the coverage of key interventions is increased. FUNDING UK Medical Research Council, UK Department for International Development, the Bill & Melinda Gates Foundation, the Swiss Development Agency, and the US Agency for International Development.
Collapse
Affiliation(s)
| | | | | | | | | | | | | | | | | | | | - Azra C Ghani
- Medical Research Council Centre for Outbreak Analysis and Modelling, Imperial College London, London, UK.
| |
Collapse
|
211
|
BROCK PM, FORNACE KM, PARMITER M, COX J, DRAKELEY CJ, FERGUSON HM, KAO RR. Plasmodium knowlesi transmission: integrating quantitative approaches from epidemiology and ecology to understand malaria as a zoonosis. Parasitology 2016; 143:389-400. [PMID: 26817785 PMCID: PMC4800714 DOI: 10.1017/s0031182015001821] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Revised: 12/01/2015] [Accepted: 12/02/2015] [Indexed: 12/12/2022]
Abstract
The public health threat posed by zoonotic Plasmodium knowlesi appears to be growing: it is increasingly reported across South East Asia, and is the leading cause of malaria in Malaysian Borneo. Plasmodium knowlesi threatens progress towards malaria elimination as aspects of its transmission, such as spillover from wildlife reservoirs and reliance on outdoor-biting vectors, may limit the effectiveness of conventional methods of malaria control. The development of new quantitative approaches that address the ecological complexity of P. knowlesi, particularly through a focus on its primary reservoir hosts, will be required to control it. Here, we review what is known about P. knowlesi transmission, identify key knowledge gaps in the context of current approaches to transmission modelling, and discuss the integration of these approaches with clinical parasitology and geostatistical analysis. We highlight the need to incorporate the influences of fine-scale spatial variation, rapid changes to the landscape, and reservoir population and transmission dynamics. The proposed integrated approach would address the unique challenges posed by malaria as a zoonosis, aid the identification of transmission hotspots, provide insight into the mechanistic links between incidence and land use change and support the design of appropriate interventions.
Collapse
Affiliation(s)
- P. M. BROCK
- Institute of Biodiversity Animal Health and Comparative Medicine, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - K. M. FORNACE
- London School of Hygiene and Tropical Medicine, London, UK
| | - M. PARMITER
- Institute of Biodiversity Animal Health and Comparative Medicine, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - J. COX
- London School of Hygiene and Tropical Medicine, London, UK
| | - C. J. DRAKELEY
- London School of Hygiene and Tropical Medicine, London, UK
| | - H. M. FERGUSON
- Institute of Biodiversity Animal Health and Comparative Medicine, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - R. R. KAO
- Institute of Biodiversity Animal Health and Comparative Medicine, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| |
Collapse
|
212
|
Tun KM, Jeeyapant A, Imwong M, Thein M, Aung SSM, Hlaing TM, Yuentrakul P, Promnarate C, Dhorda M, Woodrow CJ, Dondorp AM, Ashley EA, Smithuis FM, White NJ, Day NPJ. Parasite clearance rates in Upper Myanmar indicate a distinctive artemisinin resistance phenotype: a therapeutic efficacy study. Malar J 2016; 15:185. [PMID: 27036739 PMCID: PMC4815199 DOI: 10.1186/s12936-016-1240-7] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 03/16/2016] [Indexed: 01/23/2023] Open
Abstract
Background Artemisinin resistance in Plasmodium falciparum extends across Southeast Asia where it is associated with worsening partner drug resistance and a decline in the efficacy of frontline artemisinin-based combination therapy. Dihydroartemisinin-piperaquine (DP) is an essential component of preventive and curative treatment in the region, but its therapeutic efficacy has fallen in Cambodia. Methods A prospective clinical and parasitological evaluation of DP was conducted at two sites in Upper Myanmar between August 2013 and December 2014, enrolling 116 patients with acute uncomplicated falciparum malaria. Patients received DP orally for 3 days together with primaquine 0.25 mg/kg on admission. Parasite clearance half-lives based on 6 hourly blood smears, and day 42 therapeutic responses were assessed as well as parasite K13 genotypes. Results Median parasite clearance half-life was prolonged, and clearance half-life was greater than 5 h in 21 % of patients. Delayed parasite clearance was significantly associated with mutations in the propeller region of the parasite k13 gene. The k13 F446I mutation was found in 25.4 % of infections and was associated with a median clearance half-life of 4.7 h compared with 2.7 h for infections without k13 mutations (p < 0.001). There were no failures after 42 days of follow-up, although 18 % of patients had persistent parasitaemia on day 3. Conclusion The dominant k13 mutation observed in Upper Myanmar, F446I, appears to be associated with an intermediate rate of parasite clearance compared to other common mutations described elsewhere in the Greater Mekong Subregion. Discerning this phenotype requires relatively detailed clearance measurements, highlighting the importance of methodology in assessing artemisinin resistance. Electronic supplementary material The online version of this article (doi:10.1186/s12936-016-1240-7) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Kyaw Myo Tun
- Defence Services Medical Research Centre, Naypyitaw, Myanmar.,Myanmar Oxford Clinical Research Unit, Yangon, Myanmar
| | - Atthanee Jeeyapant
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 3rd Floor, 60th Anniversary Chalermprakiat Building, 420/6 Ratchawithi Rd., Ratchathewi District, Bangkok, 10400, Thailand
| | - Mallika Imwong
- Department of Molecular Tropical Medicine and Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Min Thein
- Defence Services Medical Research Centre, Naypyitaw, Myanmar
| | | | | | - Prayoon Yuentrakul
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 3rd Floor, 60th Anniversary Chalermprakiat Building, 420/6 Ratchawithi Rd., Ratchathewi District, Bangkok, 10400, Thailand
| | | | - Mehul Dhorda
- Nuffield Department of Clinical Medicine, Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK.,Worldwide Antimalarial Resistance Network (WWARN), Bangkok, Thailand
| | - Charles J Woodrow
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 3rd Floor, 60th Anniversary Chalermprakiat Building, 420/6 Ratchawithi Rd., Ratchathewi District, Bangkok, 10400, Thailand.,Nuffield Department of Clinical Medicine, Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
| | - Arjen M Dondorp
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 3rd Floor, 60th Anniversary Chalermprakiat Building, 420/6 Ratchawithi Rd., Ratchathewi District, Bangkok, 10400, Thailand.,Nuffield Department of Clinical Medicine, Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
| | - Elizabeth A Ashley
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 3rd Floor, 60th Anniversary Chalermprakiat Building, 420/6 Ratchawithi Rd., Ratchathewi District, Bangkok, 10400, Thailand
| | - Frank M Smithuis
- Myanmar Oxford Clinical Research Unit, Yangon, Myanmar.,Nuffield Department of Clinical Medicine, Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK.,Medical Action Myanmar, Yangon, Myanmar
| | - Nicholas J White
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 3rd Floor, 60th Anniversary Chalermprakiat Building, 420/6 Ratchawithi Rd., Ratchathewi District, Bangkok, 10400, Thailand.,Nuffield Department of Clinical Medicine, Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
| | - Nicholas P J Day
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 3rd Floor, 60th Anniversary Chalermprakiat Building, 420/6 Ratchawithi Rd., Ratchathewi District, Bangkok, 10400, Thailand. .,Nuffield Department of Clinical Medicine, Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK.
| |
Collapse
|
213
|
Kamel MM, Attia SS, Emam GD, Al Sherbiny NAEK. The Validity of Rapid Malaria Test and Microscopy in Detecting Malaria in a Preelimination Region of Egypt. SCIENTIFICA 2016; 2016:4048032. [PMID: 27088038 PMCID: PMC4819100 DOI: 10.1155/2016/4048032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 03/09/2016] [Indexed: 05/07/2023]
Abstract
Background. Malaria is a leading cause of morbidity and mortality worldwide. Rapid and accurate diagnosis of malaria would improve control measures and reduce morbidity and mortality. Objective. The aim of this study was to assess the prevalence of malaria in high risk foci in Egypt and the effectiveness of rapid diagnostic tests in diagnosis and subsequently control of malaria. Methodology. A total number of 600 cases of both sexes with different ages were included in the present study. Cases were included in 2 groups; first group (500 cases) were randomly selected from households in Fayoum Governorate and second group (100 cases) were admitted to Fayoum Fever Hospital with signs suggestive of malaria. Cases were subjected to detailed history taking, clinical examination, microscopic examination of thin and thick blood films, and immunological test to detect plasmodial antigens. Results. A total of 3 positive cases were detected by rapid diagnostic tests (RDTs). Out of these 3 cases, one case was positive for malaria parasite by microscopic examination of blood films. All positive cases in the study had history of travel to malaria endemic areas. Conclusion. RDTs are simple and effective for rapid diagnosis of malaria to help in implication of control measures in different localities.
Collapse
Affiliation(s)
- Maysa Mohamed Kamel
- Medical Parasitology Department, Faculty of Medicine, Cairo University, Cairo, Egypt
| | - Samar Sayed Attia
- Medical Parasitology Department, Faculty of Medicine, Cairo University, Cairo, Egypt
| | - Gomaa Desoky Emam
- Medical Parasitology Department, Faculty of Medicine, Fayoum University, Fayoum, Egypt
| | | |
Collapse
|
214
|
Pulice G, Pelaz S, Matías-Hernández L. Molecular Farming in Artemisia annua, a Promising Approach to Improve Anti-malarial Drug Production. FRONTIERS IN PLANT SCIENCE 2016; 7:329. [PMID: 27047510 PMCID: PMC4796020 DOI: 10.3389/fpls.2016.00329] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 03/03/2016] [Indexed: 05/03/2023]
Abstract
Malaria is a parasite infection affecting millions of people worldwide. Even though progress has been made in prevention and treatment of the disease; an estimated 214 million cases of malaria occurred in 2015, resulting in 438,000 estimated deaths; most of them occurring in Africa among children under the age of five. This article aims to review the epidemiology, future risk factors and current treatments of malaria, with particular focus on the promising potential of molecular farming that uses metabolic engineering in plants as an effective anti-malarial solution. Malaria represents an example of how a health problem may, on one hand, influence the proper development of a country, due to its burden of the disease. On the other hand, it constitutes an opportunity for lucrative business of diverse stakeholders. In contrast, plant biofarming is proposed here as a sustainable, promising, alternative for the production, not only of natural herbal repellents for malaria prevention but also for the production of sustainable anti-malarial drugs, like artemisinin (AN), used for primary parasite infection treatments. AN, a sesquiterpene lactone, is a natural anti-malarial compound that can be found in Artemisia annua. However, the low concentration of AN in the plant makes this molecule relatively expensive and difficult to produce in order to meet the current worldwide demand of Artemisinin Combination Therapies (ACTs), especially for economically disadvantaged people in developing countries. The biosynthetic pathway of AN, a process that takes place only in glandular secretory trichomes of A. annua, is relatively well elucidated. Significant efforts have been made using plant genetic engineering to increase production of this compound. These include diverse genetic manipulation approaches, such as studies on diverse transcription factors which have been shown to regulate the AN genetic pathway and other biological processes. Results look promising; however, further efforts should be addressed toward optimization of the most cost-effective biofarming approaches for synthesis and production of medicines against the malaria parasite.
Collapse
Affiliation(s)
- Giuseppe Pulice
- Sequentia Biotech, Parc Científic de BarcelonaBarcelona, Spain
| | - Soraya Pelaz
- Plant Development and Signal Transduction Department, Centre for Research in Agricultural GenomicsBarcelona, Spain
- Institució Catalana de Recerca i Estudis AvançatsBarcelona, Spain
| | - Luis Matías-Hernández
- Sequentia Biotech, Parc Científic de BarcelonaBarcelona, Spain
- Plant Development and Signal Transduction Department, Centre for Research in Agricultural GenomicsBarcelona, Spain
| |
Collapse
|
215
|
Bushman M, Morton L, Duah N, Quashie N, Abuaku B, Koram KA, Dimbu PR, Plucinski M, Gutman J, Lyaruu P, Kachur SP, de Roode JC, Udhayakumar V. Within-host competition and drug resistance in the human malaria parasite Plasmodium falciparum. Proc Biol Sci 2016; 283:20153038. [PMID: 26984625 PMCID: PMC4810865 DOI: 10.1098/rspb.2015.3038] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 02/16/2016] [Indexed: 11/12/2022] Open
Abstract
Infections with the malaria parasite Plasmodium falciparum typically comprise multiple strains, especially in high-transmission areas where infectious mosquito bites occur frequently. However, little is known about the dynamics of mixed-strain infections, particularly whether strains sharing a host compete or grow independently. Competition between drug-sensitive and drug-resistant strains, if it occurs, could be a crucial determinant of the spread of resistance. We analysed 1341 P. falciparum infections in children from Angola, Ghana and Tanzania and found compelling evidence for competition in mixed-strain infections: overall parasite density did not increase with additional strains, and densities of individual chloroquine-sensitive (CQS) and chloroquine-resistant (CQR) strains were reduced in the presence of competitors. We also found that CQR strains exhibited low densities compared with CQS strains (in the absence of chloroquine), which may underlie observed declines of chloroquine resistance in many countries following retirement of chloroquine as a first-line therapy. Our observations support a key role for within-host competition in the evolution of drug-resistant malaria. Malaria control and resistance-management efforts in high-transmission regions may be significantly aided or hindered by the effects of competition in mixed-strain infections. Consideration of within-host dynamics may spur development of novel strategies to minimize resistance while maximizing the benefits of control measures.
Collapse
Affiliation(s)
- Mary Bushman
- Department of Biology, Emory University, Atlanta, GA 30322, USA Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA
| | - Lindsay Morton
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA
| | - Nancy Duah
- Epidemiology Department, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Neils Quashie
- Epidemiology Department, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana Centre for Tropical Clinical Pharmacology and Therapeutics, University of Ghana Medical School, Accra, Ghana
| | - Benjamin Abuaku
- Epidemiology Department, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Kwadwo A Koram
- Epidemiology Department, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | | | - Mateusz Plucinski
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA Epidemic Intelligence Service, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA
| | - Julie Gutman
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA
| | - Peter Lyaruu
- Ifakara Health Institute, Dar es Salaam, Tanzania
| | - S Patrick Kachur
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA
| | | | - Venkatachalam Udhayakumar
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA
| |
Collapse
|
216
|
Assessing the Role of Climate Change in Malaria Transmission in Africa. Malar Res Treat 2016; 2016:7104291. [PMID: 27066290 PMCID: PMC4811621 DOI: 10.1155/2016/7104291] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 01/22/2016] [Accepted: 02/23/2016] [Indexed: 11/18/2022] Open
Abstract
The sensitivity of vector borne diseases like malaria to climate continues to raise considerable concern over the implications of climate change on future disease dynamics. The problem of malaria vectors shifting from their traditional locations to invade new zones is of important concern. A mathematical model incorporating rainfall and temperature is constructed to study the transmission dynamics of malaria. The reproduction number obtained is applied to gridded temperature and rainfall datasets for baseline climate and future climate with aid of GIS. As a result of climate change, malaria burden is likely to increase in the tropics, the highland regions, and East Africa and along the northern limit of falciparum malaria. Falciparum malaria will spread into the African highlands; however it is likely to die out at the southern limit of the disease.
Collapse
|
217
|
Kepha S, Nikolay B, Nuwaha F, Mwandawiro CS, Nankabirwa J, Ndibazza J, Cano J, Matoke-Muhia D, Pullan RL, Allen E, Halliday KE, Brooker SJ. Plasmodium falciparum parasitaemia and clinical malaria among school children living in a high transmission setting in western Kenya. Malar J 2016; 15:157. [PMID: 26969283 PMCID: PMC4788950 DOI: 10.1186/s12936-016-1176-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 02/17/2016] [Indexed: 01/24/2023] Open
Abstract
Background Malaria among school children is increasingly receiving attention, yet the burden of malaria in this age group is poorly defined. This study presents data on malaria morbidity among school children in Bungoma county, western Kenya. Method This study investigated the burden and risk factors of Plasmodium falciparum infection, clinical malaria, and anaemia among 2346 school children aged 5–15 years, who were enrolled in an individually randomized trial evaluating the effect of anthelmintic treatment on the risks of malaria. At baseline, children were assessed for anaemia and nutritional status and information on household characteristics was collected. Children were followed-up for 13 months to assess the incidence of clinical malaria by active detection, and P. falciparum infection and density evaluated using repeated cross-sectional surveys over 15 months. Results On average prevalence of P. falciparum infection was 42 % and ranged between 32 and 48 % during the five cross-sectional surveys. Plasmodium falciparum prevalence was significantly higher among boys than girls. The overall incidence of clinical malaria was 0.26 episodes per person year (95 % confidence interval, 0.24–0.29) and was significantly higher among girls (0.23 versus 0.31, episodes per person years). Both infection prevalence and clinical disease varied by season. In multivariable analysis, P. falciparum infection was associated with being male, lower socioeconomic status and stunting. The risk of clinical malaria was associated with being female. Conclusion These findings show that the burden of P. falciparum parasitaemia, clinical malaria and anaemia among school children is not insignificant, and suggest that malaria control programmes should be expanded to include this age group. Electronic supplementary material The online version of this article (doi:10.1186/s12936-016-1176-y) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Stella Kepha
- School of Public Health, Makerere University College of Health Sciences, Kampala, Uganda.
| | - Birgit Nikolay
- London School of Hygiene and Tropical Medicine, London, UK
| | - Fred Nuwaha
- School of Public Health, Makerere University College of Health Sciences, Kampala, Uganda
| | - Charles S Mwandawiro
- Eastern and Southern Africa Centre of International Parasite Control, Kenya Medical Research Institute (KEMRI), Nairobi, Kenya
| | - Joaniter Nankabirwa
- Department of Internal Medicine, Makerere University College of Health Sciences, Kampala, Uganda
| | - Juliet Ndibazza
- Department of Internal Medicine, Makerere University College of Health Sciences, Kampala, Uganda
| | - Jorge Cano
- London School of Hygiene and Tropical Medicine, London, UK
| | | | | | | | | | - Simon J Brooker
- London School of Hygiene and Tropical Medicine, London, UK.,KEMRI-Wellcome Trust Research Programme, Nairobi, Kenya
| |
Collapse
|
218
|
Kinyoki DK, Kandala NB, Manda SO, Krainski ET, Fuglstad GA, Moloney GM, Berkley JA, Noor AM. Assessing comorbidity and correlates of wasting and stunting among children in Somalia using cross-sectional household surveys: 2007 to 2010. BMJ Open 2016; 6:e009854. [PMID: 26962034 PMCID: PMC4785320 DOI: 10.1136/bmjopen-2015-009854] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE Wasting and stunting may occur together at the individual child level; however, their shared geographic distribution and correlates remain unexplored. Understanding shared and separate correlates may inform interventions. We aimed to assess the spatial codistribution of wasting, stunting and underweight and investigate their shared correlates among children aged 6-59 months in Somalia. SETTING Cross-sectional nutritional assessments surveys were conducted using structured interviews among communities in Somalia biannually from 2007 to 2010. A two-stage cluster sampling methodology was used to select children aged 6-59 months from households across three livelihood zones (pastoral, agropastoral and riverine). Using these data and environmental covariates, we implemented a multivariate spatial technique to estimate the codistribution and divergence of the risks and correlates of wasting and stunting at the 1 × 1 km spatial resolution. PARTICIPANTS 73,778 children aged 6-59 months from 1066 survey clusters in Somalia. RESULTS Observed pairwise child level empirical correlations were 0.30, 0.70 and 0.73 between weight-for-height and height-for-age; height-for-age and weight-for-age, and weight-for-height and weight-for-age, respectively. Access to foods with high protein content and vegetation cover, a proxy of rainfall or drought, were associated with lower risk of wasting and stunting. Age, gender, illness, access to carbohydrates and temperature were correlates of all three indicators. The spatial codistribution was highest between stunting and underweight with relative risk values ranging between 0.15 and 6.20, followed by wasting and underweight (range: 0.18-5.18) and lowest between wasting and stunting (range: 0.26-4.32). CONCLUSIONS The determinants of wasting and stunting are largely shared, but their correlation is relatively variable in space. Significant hotspots of different forms of malnutrition occurred in the South Central regions of the country. Although nutrition response in Somalia has traditionally focused on wasting rather than stunting, integrated programming and interventions can effectively target both conditions to alleviate common risk factors.
Collapse
Affiliation(s)
- Damaris K Kinyoki
- Spatial Health Metris Group, INFORM Project, Kenya Medical Research Institute/Wellcome Trust Research Programme, Nairobi, Kenya
| | - Ngianga-Bakwin Kandala
- Warwick Medical School, Health Sciences Research Institute, University of Warwick, Warwick Evidence, Coventry, UK
- Department of Mathematics and Information sciences, Faculty of Engineering and Environment, Northumbria University, Newcastle upon Tyne, UK
- Department of Population Health, Luxembourg Institute of Health (LIH), Strassen, Luxembourg
| | - Samuel O Manda
- Biostatistics Research Unit, South African Medical Research Council, Pretoria, South Africa
- Division of Epidemiology and Biostatistics, School of Public Health, University of Witwatersrand, Johannesburg, South Africa
| | - Elias T Krainski
- Department of Mathematical Sciences, Norwegian University of Science and Technology, Trondheim, Norway
- Department of Statistics, Federal University of Paraná, Curitiba, Brazil
| | - Geir-Arne Fuglstad
- Department of Mathematical Sciences, Norwegian University of Science and Technology, Trondheim, Norway
| | - Grainne M Moloney
- Nutrition Section, United Nations Children's Fund (UNICEF), Kenya Country Office, UN Complex Gigiri, Nairobi, Kenya
| | - James A Berkley
- Kenya Medical Research Institute/Wellcome Trust Research Programme, Centre for Geographic Medicine Research (coast), Kilifi, Kenya
- Nuffield Department of Clinical Medicine, Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
| | - Abdisalan M Noor
- Spatial Health Metris Group, INFORM Project, Kenya Medical Research Institute/Wellcome Trust Research Programme, Nairobi, Kenya
- Nuffield Department of Clinical Medicine, Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
| |
Collapse
|
219
|
Sinka ME, Golding N, Massey NC, Wiebe A, Huang Z, Hay SI, Moyes CL. Modelling the relative abundance of the primary African vectors of malaria before and after the implementation of indoor, insecticide-based vector control. Malar J 2016; 15:142. [PMID: 26945997 PMCID: PMC4779559 DOI: 10.1186/s12936-016-1187-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 02/23/2016] [Indexed: 11/16/2022] Open
Abstract
Background Malaria remains a heavy burden across sub-Saharan Africa where transmission is maintained by some of the world’s most efficient vectors. Indoor insecticide-based control measures have significantly reduced transmission, yet elimination remains a distant target. Knowing the relative abundance of the primary vector species can provide transmission models with much needed information to guide targeted control measures. Moreover, understanding how existing interventions are impacting on these relative abundances highlights where alternative control (e.g., larval source management) is needed. Methods Using the habitat suitability probabilities generated by predictive species distribution models combined with data collated from the literature, a multinomial generalized additive model was applied to produce relative abundance estimates for Anopheles arabiensis, Anopheles funestus and Anopheles gambiae/Anopheles coluzzii. Using pre- and post-intervention abundance data, estimates of the effect of indoor insecticide-based interventions on these relative abundances were made and are illustrated in post-intervention maps. Results Conditional effect plots and relative abundance maps illustrate the individual species’ predicted habitat suitability and how they interact when in sympatry. Anopheles arabiensis and An. funestus show an affinity in habitat preference at the expense of An. gambiae/An. coluzzii, whereas increasing habitat suitability for An. gambiae/An. coluzzii is conversely less suitable for An. arabiensis but has little effect on An. funestus. Indoor insecticide-based interventions had a negative impact on the relative abundance of An. funestus, and a lesser effect on An. arabiensis. Indoor residual spraying had the greatest impact on the relative abundance of An. funestus, and a lesser effect on An. gambiae/An. coluzzii. Insecticide-treated bed nets reduced the relative abundance of both species equally. These results do not indicate changes in the absolute abundance of these species, which may be reduced for all species overall. Conclusions The maps presented here highlight the interactions between the primary vector species in sub-Saharan Africa and demonstrate that An. funestus is more susceptible to certain indoor-based insecticide interventions than An. gambiae/An. coluzzii, which in turn, is more susceptible than An. arabiensis. This may provide An. arabiensis with a competitive advantage where it is found in sympatry with other more endophilic vectors, and potentially increase the need for outdoor-based vector interventions to deal with any residual transmission barring the way to malaria elimination. Electronic supplementary material The online version of this article (doi:10.1186/s12936-016-1187-8) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Marianne E Sinka
- Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Oxford, OX1 3PS, UK.
| | - Nick Golding
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK.
| | - N Claire Massey
- Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Oxford, OX1 3PS, UK.
| | - Antoinette Wiebe
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK.
| | - Zhi Huang
- Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Oxford, OX1 3PS, UK.
| | - Simon I Hay
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK. .,Institute for Health Metrics and Evaluation, University of Washington, Seattle, WA, 98121, USA. .,Fogarty International Center, National Institutes of Health, Bethesda, MD, 20892-2220, USA.
| | - Catherine L Moyes
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK.
| |
Collapse
|
220
|
Awab GR, Imwong M, Pukrittayakamee S, Alim F, Hanpithakpong W, Tarning J, Dondorp AM, Day NPJ, White NJ, Woodrow CJ. Clinical trials of artesunate plus sulfadoxine-pyrimethamine for Plasmodium falciparum malaria in Afghanistan: maintained efficacy a decade after introduction. Malar J 2016; 15:121. [PMID: 26917051 PMCID: PMC4766631 DOI: 10.1186/s12936-016-1167-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Accepted: 02/11/2016] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND Combination therapy with artesunate plus sulfadoxine-pyrimethamine (SP) was adopted as recommended treatment for Plasmodium falciparum infection in Afghanistan in 2003. METHODS A series of prospective clinical studies examining the efficacy of artesunate plus sulfadoxine-pyrimethamine (AS + SP) against P. falciparum were undertaken in sentinel sites in Afghanistan from 2007 to 2014, accompanied by relevant molecular studies. The first study was a randomized trial of AS + SP versus dihydroartemisinin-piperaquine, while two subsequent studies were standard therapeutic efficacy studies of AS + SP. RESULTS Three hundred and three patients were enrolled across four provinces in the north and east of the country. Curative efficacy was high in all the trials, with an adequate clinical and parasitological response (ACPR) of more than 95 % in all groups and trial stages. Genotyping for drug-resistance alleles at dhfr indicated fixation of the S108 N mutation and a prevalence of the C59R mutation of approximately 95 % across all sites. Other mutations in dhfr and dhps remained rare or absent entirely, although five isolates from the first trial carried the dhps triple mutant SGEGA haplotype. In the last study undertaken in 2012-2014 the K13 artemisinin resistance marker was examined; only two of 60 successfully sequenced samples carried a K13-propeller mutation. CONCLUSIONS These data confirm maintained efficacy 10 years after introduction of artesunate plus SP as combination treatment of P. falciparum in Afghanistan. The molecular data indicate that despite a substantial fall in incidence, resistance has not developed to artemisinins, or intensified to the ACT partner drug components. Trial Registration http://www.clinicaltrials.gov/ct NCT00682578, NCT01115439 and NCT01707199.
Collapse
Affiliation(s)
- Ghulam Rahim Awab
- Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
- Ministry of Public Health, Kabul, Afghanistan.
| | - Mallika Imwong
- Department of Molecular Tropical Medicine and Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
- Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
| | - Sasithon Pukrittayakamee
- Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
| | - Fazel Alim
- Ministry of Public Health, Kabul, Afghanistan.
| | - Warunee Hanpithakpong
- Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
| | - Joel Tarning
- Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
| | - Arjen M Dondorp
- Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
| | - Nicholas P J Day
- Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
| | - Nicholas J White
- Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
| | - Charles J Woodrow
- Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
| |
Collapse
|
221
|
Win AA, Imwong M, Kyaw MP, Woodrow CJ, Chotivanich K, Hanboonkunupakarn B, Pukrittayakamee S. K13 mutations and pfmdr1 copy number variation in Plasmodium falciparum malaria in Myanmar. Malar J 2016; 15:110. [PMID: 26911145 PMCID: PMC4765153 DOI: 10.1186/s12936-016-1147-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2015] [Accepted: 02/04/2016] [Indexed: 11/11/2022] Open
Abstract
Background Artemisinin-based combination therapy has been first-line treatment for falciparum malaria in Myanmar since 2005. The wide extent of artemisinin resistance in the Greater Mekong sub-region and the presence of mefloquine resistance at the Myanmar-Thailand border raise concerns over resistance patterns in Myanmar. The availability of molecular markers for resistance to both drugs enables assessment even in remote malaria-endemic areas. Methods A total of 250 dried blood spot samples collected from patients with Plasmodium falciparum malarial infection in five malaria-endemic areas across Myanmar were analysed for kelch 13 sequence (k13) and pfmdr1 copy number variation. K13 mutations in the region corresponding to amino acids 210–726 (including the propeller region of the protein) were detected by nested PCR amplification and sequencing, and pfmdr1 copy number variation by real-time PCR. In two sites, a sub-set of patients were prospectively followed up for assessment of day-3 parasite clearance rates after a standard course of artemether-lumefantrine. Results K13 mutations and pfmdr1 amplification were successfully analysed in 206 and 218 samples, respectively. Sixty-nine isolates (33.5 %) had mutations within the k13 propeller region with 53 of these (76.8 %) having mutations already known to be associated with artemisinin resistance. F446I (32 isolates) and P574L (15 isolates) were the most common examples. K13 mutation was less common in sites in western border regions (29 of 155 isolates) compared to samples from the east and north (40 of 51 isolates; p < 0.0001). The overall proportion of parasites with multiple pfmdr1 copies (greater than 1.5) was 5.5 %. Seven samples showed both k13 mutation and multiple copies of pfmdr1. Only one of 36 patients followed up after artemether-lumefantrine treatment still had parasites at day 3; molecular analysis indicated wild-type k13 and single copy pfmdr1. Conclusion The proportion of P. falciparum isolates with mutations in the propeller region of k13 indicates that artemisinin resistance extends across much of Myanmar. There is a low prevalence of parasites with multiple pfmdr1 copies across the country. The efficacy of artemisinin-based combination therapy containing mefloquine and lumefantrine is, therefore, expected to be high, although regular monitoring of efficacy will be important. Electronic supplementary material The online version of this article (doi:10.1186/s12936-016-1147-3) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Aye A Win
- Department of Medicine, Institute of Medicine 1, Yangon, Myanmar.
| | - Mallika Imwong
- Department of Molecular Tropical Medicine and Genetics, Mahidol University, Bangkok, Thailand. .,Mahidol Oxford Tropical Medicine Research Unit, Bangkok, Thailand.
| | - Myat P Kyaw
- Department of Medical Research (Lower Myanmar), Yangon, Myanmar.
| | - Charles J Woodrow
- Mahidol Oxford Tropical Medicine Research Unit, Bangkok, Thailand. .,Nuffield Department of Clinical Medicine, Centre for Tropical Medicine & Global Health, University of Oxford, Oxford, UK.
| | - Kesinee Chotivanich
- Mahidol Oxford Tropical Medicine Research Unit, Bangkok, Thailand. .,Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
| | - Borimas Hanboonkunupakarn
- Mahidol Oxford Tropical Medicine Research Unit, Bangkok, Thailand. .,Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
| | - Sasithon Pukrittayakamee
- Mahidol Oxford Tropical Medicine Research Unit, Bangkok, Thailand. .,Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
| |
Collapse
|
222
|
Abstract
PURPOSE OF REVIEW Limitations of blood smear microscopy contributed to failure of the 1950-1960s WHO Global Programme to Eliminate Malaria. All diagnostic methods encounter limits of detection (LOD) beyond which it will not be possible to identify infected individuals. When this occurs, it becomes difficult to continue evaluating progress of malaria elimination. The purpose of this review is to compare available diagnostic technologies, factors that underlie their LOD, and their potential roles related to the goal of elimination. RECENT FINDINGS Parasite-containing cells, parasite proteins, hemozoin, nucleic acids, and parasite-specific human antibodies are targets of diagnosis. Many studies report advantages of technologies to detect these diagnostic targets. Nucleic acid amplification tests and strategies for enriching capture of malaria diagnostic targets have consistently identified a parasite reservoir not detected by methods focused on the other biological targets. Exploiting magnetic properties of hemozoin may open new strategies for noninvasive malaria diagnosis. SUMMARY Microscopy and rapid diagnostic tests provide effective surveillance for malaria control. Strategies that detect a reservoir of submicroscopic infection must be developed and standardized to guide malaria elimination.
Collapse
|
223
|
Cadavid Restrepo AM, Yang YR, McManus DP, Gray DJ, Giraudoux P, Barnes TS, Williams GM, Soares Magalhães RJ, Hamm NAS, Clements ACA. The landscape epidemiology of echinococcoses. Infect Dis Poverty 2016; 5:13. [PMID: 26895758 PMCID: PMC4759770 DOI: 10.1186/s40249-016-0109-x] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Accepted: 02/15/2016] [Indexed: 12/29/2022] Open
Abstract
Echinococcoses are parasitic diseases of major public health importance globally. Human infection results in chronic disease with poor prognosis and serious medical, social and economic consequences for vulnerable populations. According to recent estimates, the geographical distribution of Echinococcus spp. infections is expanding and becoming an emerging and re-emerging problem in several regions of the world. Echinococcosis endemicity is geographically heterogeneous and over time it may be affected by global environmental change. Therefore, landscape epidemiology offers a unique opportunity to quantify and predict the ecological risk of infection at multiple spatial and temporal scales. Here, we review the most relevant environmental sources of spatial variation in human echinococcosis risk, and describe the potential applications of landscape epidemiological studies to characterise the current patterns of parasite transmission across natural and human-altered landscapes. We advocate future work promoting the use of this approach as a support tool for decision-making that facilitates the design, implementation and monitoring of spatially targeted interventions to reduce the burden of human echinococcoses in disease-endemic areas.
Collapse
Affiliation(s)
- Angela M Cadavid Restrepo
- Research School of Population Health, The Australian National University, Canberra, New South Wales, Australia.
| | - Yu Rong Yang
- Ningxia Medical University, Yinchuan, Ningxia Hui Autonomous Region, P. R. China.
- Molecular Parasitology Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia.
| | - Donald P McManus
- Molecular Parasitology Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia.
| | - Darren J Gray
- Research School of Population Health, The Australian National University, Canberra, New South Wales, Australia.
- Molecular Parasitology Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia.
| | - Patrick Giraudoux
- Chrono-environment lab, UMR6249, University of Bourgogne Franche-Comté/CNRS, Besançon, France.
- Institut Universitaire de France, Paris, France.
| | - Tamsin S Barnes
- The University of Queensland, School of Veterinary Science, Gatton, Queensland, Australia.
- The University of Queensland, Queensland Alliance for Agriculture and Food Innovation, Gatton, Queensland, Australia.
| | - Gail M Williams
- School of Public Health, The University of Queensland, Brisbane, Queensland, Australia.
| | - Ricardo J Soares Magalhães
- The University of Queensland, School of Veterinary Science, Gatton, Queensland, Australia.
- Child Health Research Centre, The University of Queensland, Brisbane, Queensland, Australia.
| | - Nicholas A S Hamm
- Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, Enschede, The Netherlands.
| | - Archie C A Clements
- Research School of Population Health, The Australian National University, Canberra, New South Wales, Australia.
| |
Collapse
|
224
|
Frank C, Krumkamp R, Sarpong N, Sothmann P, Fobil JN, Foli G, Jaeger A, Ehlkes L, Owusu-Dabo E, Adu-Sarkodie Y, Marks F, Schumann RR, May J, Kreuels B. Spatial heterogeneity of malaria in Ghana: a cross-sectional study on the association between urbanicity and the acquisition of immunity. Malar J 2016; 15:84. [PMID: 26867774 PMCID: PMC4751679 DOI: 10.1186/s12936-016-1138-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 01/29/2016] [Indexed: 11/30/2022] Open
Abstract
Background Malaria incidence has declined considerably over the last decade. This is partly due to a scale-up of control measures but is also attributed to increasing urbanization. This study aimed to analyse the association between malaria and urbanization and the effect of urbanicity on the acquisition of semi-immunity. Methods In 2012, children with fever presenting to St Michael’s Hospital Pramso/Ghana were recruited. The malaria-positive-fraction (MPF) of fever cases was calculated on community-level to approximate the malaria risk. The mean age of malaria cases was calculated for each community to estimate the acquisition of semi-immunity. The level of urbanicity for the communities was calculated and associations between MPF, urbanicity and immunity were modelled using linear regression. Results Twenty-six villages were included into the study with a mean MPF of 35 %. A linear decrease of 5 % (95 % CI: 4–6 %) in MPF with every ten-point increase in urbanicity was identified. The mean age of malaria patients increased by 2.9 months (95 % CI: 1.0–4.8) with every ten-point increase in urbanicity. Discussion The results confirm an association between an increase in urbanicity and declining malaria risk and demonstrate that the acquisition of semi-immunity is heterogeneous on a micro-epidemiological scale and is associated with urbanicity. Electronic supplementary material The online version of this article (doi:10.1186/s12936-016-1138-4) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Clemens Frank
- Research Group Infectious Disease Epidemiology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany. .,Institute of Microbiology and Hygiene, Charité-University Medicine, Berlin, Germany.
| | - Ralf Krumkamp
- Research Group Infectious Disease Epidemiology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany. .,German Centre for Infection Research (DZIF), Partner Site Hamburg-Borstel-Lübeck, Hamburg, Germany.
| | - Nimako Sarpong
- Kumasi Centre for Collaborative Research in Tropical Medicine, College of Health Sciences, KNUST, Kumasi, Ghana.
| | - Peter Sothmann
- Research Group Infectious Disease Epidemiology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany. .,Division of Tropical Medicine, 1st Department of Medicine, University Medical Centre Hamburg Eppendorf, Hamburg, Germany.
| | - Julius N Fobil
- School of Public Health, University of Ghana, Accra, Ghana.
| | - Geoffrey Foli
- Kumasi Centre for Collaborative Research in Tropical Medicine, College of Health Sciences, KNUST, Kumasi, Ghana.
| | - Anna Jaeger
- Research Group Infectious Disease Epidemiology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.
| | - Lutz Ehlkes
- Research Group Infectious Disease Epidemiology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.
| | - Ellis Owusu-Dabo
- Kumasi Centre for Collaborative Research in Tropical Medicine, College of Health Sciences, KNUST, Kumasi, Ghana.
| | - Yaw Adu-Sarkodie
- School of Medical Sciences, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.
| | | | - Ralf R Schumann
- Institute of Microbiology and Hygiene, Charité-University Medicine, Berlin, Germany.
| | - Jürgen May
- Research Group Infectious Disease Epidemiology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany. .,German Centre for Infection Research (DZIF), Partner Site Hamburg-Borstel-Lübeck, Hamburg, Germany.
| | - Benno Kreuels
- Research Group Infectious Disease Epidemiology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany. .,German Centre for Infection Research (DZIF), Partner Site Hamburg-Borstel-Lübeck, Hamburg, Germany. .,Division of Tropical Medicine, 1st Department of Medicine, University Medical Centre Hamburg Eppendorf, Hamburg, Germany.
| |
Collapse
|
225
|
Ba H, Duffy CW, Ahouidi AD, Deh YB, Diallo MY, Tandia A, Conway DJ. Widespread distribution of Plasmodium vivax malaria in Mauritania on the interface of the Maghreb and West Africa. Malar J 2016; 15:80. [PMID: 26861780 PMCID: PMC4748559 DOI: 10.1186/s12936-016-1118-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Accepted: 01/22/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Plasmodium vivax is very rarely seen in West Africa, although specific detection methods are not widely applied in the region, and it is now considered to be absent from North Africa. However, this parasite species has recently been reported to account for most malaria cases in Nouakchott, the capital of Mauritania, which is a large country at the interface of sub-Saharan West Africa and the Maghreb region in northwest Africa. METHODS To determine the distribution of malaria parasite species throughout Mauritania, malaria cases were sampled in 2012 and 2013 from health facilities in 12 different areas. These sampling sites were located in eight major administrative regions of the country, within different parts of the Sahara and Sahel zones. Blood spots from finger-prick samples of malaria cases were processed to identify parasite DNA by species-specific PCR. RESULTS Out of 472 malaria cases examined, 163 (34.5 %) had P. vivax alone, 296 (62.7 %) Plasmodium falciparum alone, and 13 (2.8 %) had mixed P. falciparum and P. vivax infection. All cases were negative for Plasmodium malariae and Plasmodium ovale. The parasite species distribution showed a broad spectrum, P. vivax being detected at six of the different sites, in five of the country's major administrative regions (Tiris Zemmour, Tagant, Brakna, Assaba, and the capital Nouakchott). Most cases in Nouakchott were due to P. vivax, although proportions vary significantly among different health facilities in the city. In the northern town of Zouérat, all cases were due to P. vivax, whereas almost all cases in the south of the country were due to P. falciparum. All P. vivax cases tested were Duffy blood group positive. CONCLUSIONS It is important that P. vivax is recognized to be a widespread cause of malaria in Mauritania, occurring in diverse regions. This should be noted by the World Health Organization, as it has significant implications for diagnosis, treatment and control of malaria in the northwestern part of Africa.
Collapse
Affiliation(s)
- Hampâté Ba
- Institut National de Recherches en Santé Publique (INRSP), Nouakchott, Mauritania.
| | - Craig W Duffy
- Department of Pathogen Molecular Biology, London School of Hygiene and Tropical Medicine, London, UK.
| | | | - Yacine Boubou Deh
- Institut National de Recherches en Santé Publique (INRSP), Nouakchott, Mauritania.
| | - Mamadou Yero Diallo
- Institut National de Recherches en Santé Publique (INRSP), Nouakchott, Mauritania.
| | - Abderahmane Tandia
- Institut National de Recherches en Santé Publique (INRSP), Nouakchott, Mauritania.
| | - David J Conway
- Department of Pathogen Molecular Biology, London School of Hygiene and Tropical Medicine, London, UK.
| |
Collapse
|
226
|
Pothin E, Ferguson NM, Drakeley CJ, Ghani AC. Estimating malaria transmission intensity from Plasmodium falciparum serological data using antibody density models. Malar J 2016; 15:79. [PMID: 26861862 PMCID: PMC4748547 DOI: 10.1186/s12936-016-1121-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Accepted: 01/22/2016] [Indexed: 12/21/2022] Open
Abstract
Background Serological data are increasingly being used to monitor malaria transmission intensity and have been demonstrated to be particularly useful in areas of low transmission where traditional measures such as EIR and parasite prevalence are limited. The seroconversion rate (SCR) is usually estimated using catalytic models in which the measured antibody levels are used to categorize individuals as seropositive or seronegative. One limitation of this approach is the requirement to impose a fixed cut-off to distinguish seropositive and negative individuals. Furthermore, the continuous variation in antibody levels is ignored thereby potentially reducing the precision of the estimate. Methods An age-specific density model which mimics antibody acquisition and loss was developed to make full use of the information provided by serological measures of antibody levels. This was fitted to blood-stage antibody density data from 12 villages at varying transmission intensity in Northern Tanzania to estimate the exposure rate as an alternative measure of transmission intensity. Results The results show a high correlation between the exposure rate estimates obtained and the estimated SCR obtained from a catalytic model (r = 0.95) and with two derived measures of EIR (r = 0.74 and r = 0.81). Estimates of exposure rate obtained with the density model were also more precise than those derived from catalytic models. Conclusion This approach, if validated across different epidemiological settings, could be a useful alternative framework for quantifying transmission intensity, which makes more complete use of serological data.
Collapse
Affiliation(s)
- Emilie Pothin
- Department of Infectious Disease Epidemiology, MRC Centre for Outbreak Analysis and Modelling, Imperial College London, London, UK. .,Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland. .,University of Basel, Basel, Switzerland.
| | - Neil M Ferguson
- Department of Infectious Disease Epidemiology, MRC Centre for Outbreak Analysis and Modelling, Imperial College London, London, UK.
| | - Chris J Drakeley
- Department of Immunology, London School of Hygiene and Tropical Medicine, London, UK.
| | - Azra C Ghani
- Department of Infectious Disease Epidemiology, MRC Centre for Outbreak Analysis and Modelling, Imperial College London, London, UK.
| |
Collapse
|
227
|
Community knowledge and perceptions on the management of non-malarial fevers under reduced malaria burden and implications on the current malaria treatment policy in Morogoro, Tanzania. ASIAN PACIFIC JOURNAL OF TROPICAL DISEASE 2016. [DOI: 10.1016/s2222-1808(15)61005-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
228
|
Brady OJ, Godfray HCJ, Tatem AJ, Gething PW, Cohen JM, McKenzie FE, Perkins TA, Reiner RC, Tusting LS, Sinka ME, Moyes CL, Eckhoff PA, Scott TW, Lindsay SW, Hay SI, Smith DL. Vectorial capacity and vector control: reconsidering sensitivity to parameters for malaria elimination. Trans R Soc Trop Med Hyg 2016; 110:107-17. [PMID: 26822603 PMCID: PMC4731004 DOI: 10.1093/trstmh/trv113] [Citation(s) in RCA: 109] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Major gains have been made in reducing malaria transmission in many parts of the world, principally by scaling-up coverage with long-lasting insecticidal nets and indoor residual spraying. Historically, choice of vector control intervention has been largely guided by a parameter sensitivity analysis of George Macdonald's theory of vectorial capacity that suggested prioritizing methods that kill adult mosquitoes. While this advice has been highly successful for transmission suppression, there is a need to revisit these arguments as policymakers in certain areas consider which combinations of interventions are required to eliminate malaria. METHODS AND RESULTS Using analytical solutions to updated equations for vectorial capacity we build on previous work to show that, while adult killing methods can be highly effective under many circumstances, other vector control methods are frequently required to fill effective coverage gaps. These can arise due to pre-existing or developing mosquito physiological and behavioral refractoriness but also due to additive changes in the relative importance of different vector species for transmission. Furthermore, the optimal combination of interventions will depend on the operational constraints and costs associated with reaching high coverage levels with each intervention. CONCLUSIONS Reaching specific policy goals, such as elimination, in defined contexts requires increasingly non-generic advice from modelling. Our results emphasize the importance of measuring baseline epidemiology, intervention coverage, vector ecology and program operational constraints in predicting expected outcomes with different combinations of interventions.
Collapse
Affiliation(s)
- Oliver J Brady
- The Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
| | | | - Andrew J Tatem
- Department of Geography and Environment, University of Southampton, Southampton, UK Fogarty International Center, NIH, Bethesda, MD, USA Flowminder Foundation, Stockholm, Sweden
| | - Peter W Gething
- Spatial Ecology and Epidemiology Group, Department of Zoology, Oxford University, Oxford, UK
| | | | | | - T Alex Perkins
- Fogarty International Center, NIH, Bethesda, MD, USA Department of Biological Sciences & Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, USA
| | - Robert C Reiner
- Fogarty International Center, NIH, Bethesda, MD, USA Department of Epidemiology & Biostatistics, Indiana University, Bloomington, IN, USA
| | - Lucy S Tusting
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
| | - Marianne E Sinka
- The Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK Department of Zoology, University of Oxford, Oxford, UK
| | - Catherine L Moyes
- The Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
| | | | - Thomas W Scott
- Fogarty International Center, NIH, Bethesda, MD, USA Department of Entomology and Nematology, University of California, Davis, CA, USA
| | - Steven W Lindsay
- School of Biological & Biomedical Sciences, Durham University, Durham, UK
| | - Simon I Hay
- The Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK Fogarty International Center, NIH, Bethesda, MD, USA Institute for Health Metrics and Evaluation, University of Washington, Seattle, WA, USA
| | - David L Smith
- Department of Zoology, University of Oxford, Oxford, UK Fogarty International Center, NIH, Bethesda, MD, USA Institute for Health Metrics and Evaluation, University of Washington, Seattle, WA, USA Sanaria Institute for Global Health and Tropical Medicine, Rockville, MD, USA
| |
Collapse
|
229
|
Kinyoki DK, Berkley JA, Moloney GM, Odundo EO, Kandala NB, Noor AM. Space-time mapping of wasting among children under the age of five years in Somalia from 2007 to 2010. Spat Spatiotemporal Epidemiol 2016; 16:77-87. [PMID: 26919757 PMCID: PMC4813094 DOI: 10.1016/j.sste.2015.12.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 10/15/2015] [Accepted: 12/31/2015] [Indexed: 11/06/2022]
Abstract
OBJECTIVE To determine the sub-national seasonal prevalence and trends in wasting from 2007 to 2010 among children aged 6-59 months in Somalia using remote sensing and household survey data from nutritional surveys. METHODS Bayesian hierarchical space-time model was implemented using a stochastic partial differential equation (SPDE) approach in integrated nested Laplace approximations (INLA) to produce risk maps of wasting at 1 × 1 km(2) spatial resolution and predict to seasons in each year of study from 2007 to 2010. RESULTS The prevalence of wasting was generally at critical levels throughout the country, with most of the areas remaining in the upper classes of critical and very critical levels. There was minimal variation in wasting from year-to-year, but a well-defined seasonal variation was observed. The mean difference of the prevalence of wasting between the dry and wet season ranges from 0% to 5%. The risks of wasting in the South Central zone were highest in the Gedo (37%) and Bay (32%) regions. In North East zone the risk was highest in Nugaal (25%) and in the North West zone the risk was high in Awdal and Woqooyi Galbeed regions with 23%. CONCLUSION There was a clear seasonal variation in wasting with minimal year-to-year variability from 2007 to 2010 in Somalia. The prevalence was high during the long dry season, which affects the prevalence in the preceding long rainy season. Understanding the seasonal fluctuations of wasting in different locations and at different times is important to inform timely interventions.
Collapse
Affiliation(s)
- Damaris K Kinyoki
- Spatial Health Metrics Group, INFORM Project, Kenya Medical Research Institute/Wellcome Trust Research Programme, Nairobi P.O. Box 43640-00100, Kenya.
| | - James A Berkley
- Kenya Medical Research Institute/Wellcome Trust Research Programme, Centre for Geographic Medicine Research (coast), Kilifi, Kenya; Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, CCVTM, Oxford OX3 7LJ, UK.
| | - Grainne M Moloney
- Nutrition Section, United Nations Children's Fund (UNICEF), Kenya Country Office, UN Complex Gigiri, Nairobi, Kenya.
| | - Elijah O Odundo
- Food Security and Nutrition Analysis Unit (FSNAU) - Somalia, United Nations Food and Agricultural Organization, Ngecha Road Campus, Nairobi, Kenya .
| | - Ngianga-Bakwin Kandala
- Warwick Medical School, Health Sciences Research Institute, University of Warwick, Warwick Evidence, Gibbet Hill, CV4 7AL Coventry, UK; Department of Mathematics and Information sciences Faculty of Engineering and Environment, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK; Health Economics and Evidence Synthesis Research Unit, Department of Population Health, Luxembourg Institute of Health L-1445 Strassen, Luxembourg.
| | - Abdisalan M Noor
- Spatial Health Metrics Group, INFORM Project, Kenya Medical Research Institute/Wellcome Trust Research Programme, Nairobi P.O. Box 43640-00100, Kenya; Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, CCVTM, Oxford OX3 7LJ, UK.
| |
Collapse
|
230
|
Kwizera A, Festic E, Dünser MW. What's new in sepsis recognition in resource-limited settings? Intensive Care Med 2016; 42:2030-2033. [PMID: 26825954 PMCID: PMC5106488 DOI: 10.1007/s00134-016-4222-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 01/10/2016] [Indexed: 02/04/2023]
Affiliation(s)
- Arthur Kwizera
- Department of Anaesthesia, Makerere University College of Health Sciences, Mulago National Referral Hospital, Kampala, Uganda
| | - Emir Festic
- Pulmonary and Critical Care Medicine, Mayo Clinic, Jacksonville, FL USA
| | - Martin W. Dünser
- Interdisciplinary Intensive Care Units, Department of Anesthesiology, Perioperative and General Intensive Care Medicine, University Hospital Salzburg and Paracelsus Private Medical University, Müllner Hauptstrasse 48, 5020 Salzburg, Austria
| |
Collapse
|
231
|
The Kynurenine Pathway of Tryptophan Catabolism and AIDS-Associated Kaposi Sarcoma in Africa. J Acquir Immune Defic Syndr 2016; 70:296-303. [PMID: 26181812 DOI: 10.1097/qai.0000000000000747] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND Other than Kaposi sarcoma (KS)-associated herpesvirus and CD4 T-cell lymphopenia, the mechanisms responsible for KS in the context of HIV are poorly understood. One recently explored pathway of HIV pathogenesis involves induction of the enzyme indoleamine 2,3-dioxygenase-1 (IDO), which catabolizes tryptophan into kynurenine and several other immunologically active metabolites that suppress T-cell proliferation. We investigated the role of IDO in the development of KS in HIV disease. METHODS In a case-control study among untreated HIV-infected Ugandans, cases were adults with KS and controls were without KS. IDO activity was assessed by the ratio of plasma kynurenine to tryptophan levels (KT ratio), measured by liquid chromatography-tandem mass spectrometry. RESULTS We studied 631 HIV-infected subjects: 222 KS cases and 409 controls. Non-KS controls had a higher median plasma KT ratio (130, interquartile range: 90 to 190 nM/μM) than KS cases (110, interquartile range: 90 to 150 nM/μM) (P = 0.004). After adjustment for age, sex, CD4 count, and plasma HIV RNA level, subjects with the highest (fourth quartile) plasma KT ratios had a 59% reduction (95% confidence interval: 27% to 77%) in the odds of KS compared with those with the lowest (first quartile) levels. KS was also independently associated with lower CD4 count, higher plasma HIV RNA, and men. CONCLUSIONS Among HIV-infected individuals, greater activity of the kynurenine pathway of tryptophan catabolism, as evidenced by higher levels of plasma KT ratio, was associated with lower occurrence of KS. Some consequences of immune activation in HIV infection might actually suppress certain cancers.
Collapse
|
232
|
Ali IM, Bigoga JD, Forsah DA, Cho-Ngwa F, Tchinda V, Moor VA, Fogako J, Nyongalema P, Nkoa T, Same-Ekobo A, Mbede J, Fondjo E, Mbacham WF, Leke RGF. Field evaluation of the 22 rapid diagnostic tests for community management of malaria with artemisinin combination therapy in Cameroon. Malar J 2016; 15:31. [PMID: 26791422 PMCID: PMC4721050 DOI: 10.1186/s12936-016-1085-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2015] [Accepted: 01/08/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND All suspected cases of malaria should receive a diagnostic test prior to treatment with artemisinin-based combinations based on the new WHO malaria treatment guidelines. This study compared the accuracy and some operational characteristics of 22 different immunochromatographic antigen capture point-of- malaria tests (RDTs) in Cameroon to inform test procurement prior to deployment of artemisinin-based combinations for malaria treatment. METHODS One hundred human blood samples (50 positive and 50 negative) collected from consenting febrile patients in two health centres at Yaoundé were used for evaluation of the 22 RDTs categorized as "Pf Only" (9) or "Pf + PAN" (13) based on parasite antigen captured [histidine rich protein II (HRP2) or lactate dehydrogenase (pLDH) or aldolase]. RDTs were coded to blind technicians performing the tests. The sensitivity, specificity, and predictive values of the positive and negative tests (PPV and NPV) as well as the likelihood ratios were assessed. The reliability and some operational characteristics were determined as the mean values from two assessors, and the Cohen's kappa statistic was then used to compare agreement. Light microscopy was the referent. RESULTS Of all RDTs tested, 94.2 % (21/22) had sensitivity values greater than 90% among which 14 (63.6%) were 'Pf + PAN' RDTs. The specificity was generally lower than the sensitivity for all RDTs and poorer for "Pf Only" RDTs. The predictive values and likelihood ratios were better for non-HRP2 analytes for "Pf + PAN" RDTs. The Kappa value for most of the tests obtained was around 67% (95% CI 50-69%), corresponding to a moderate agreement. CONCLUSION Overall, 94.2% (21/22) of RDTs tested had accuracy within the range recommended by the WHO, while one performed poorly, below acceptable levels. Seven "Pf + PAN" and 3 "Pf Only" RDTs were selected for further assessment based on performance characteristics. Harmonizing RDT test presentation and procedures would prevent mistakes of test performance and interpretation.
Collapse
Affiliation(s)
- Innocent M Ali
- The Biotechnology Centre, University of Yaoundé 1, BP 8094, Yaoundé, Cameroon. .,Department of Biochemistry, University of Dschang, Dschang, Cameroon.
| | - Jude D Bigoga
- The Biotechnology Centre, University of Yaoundé 1, BP 8094, Yaoundé, Cameroon.
| | - Dorothy A Forsah
- National Malaria Control Program, Ministry of Public Health, Yaoundé, Cameroon.
| | - Fidelis Cho-Ngwa
- Department of Biochemistry and Molecular Biology, University of Buea, Buea, Cameroon.
| | - Vivian Tchinda
- Medical Research Centre, Institute of Medical Research and Medicinal Plant Study, Yaoundé, Cameroon.
| | - Vicky Ama Moor
- Faculty of Medicine and Biomedical Sciences, University of Yaoundé 1, Yaoundé, Cameroon.
| | - Josephine Fogako
- The Biotechnology Centre, University of Yaoundé 1, BP 8094, Yaoundé, Cameroon.
| | | | | | - Albert Same-Ekobo
- Faculty of Health Sciences, Université des Montagnes, Bangante, Cameroon.
| | - Joseph Mbede
- Paediatrics Unit, University Teaching Hospital, Faculty of Medicine and Biomedical Sciences, University of Yaoundé 1, Yaoundé, Cameroon.
| | - Etienne Fondjo
- Department of Biochemistry, University of Dschang, Dschang, Cameroon.
| | - Wilfred F Mbacham
- The Biotechnology Centre, University of Yaoundé 1, BP 8094, Yaoundé, Cameroon.
| | - Rose G F Leke
- Laboratory of Immunology and Parasitology, The Biotechnology Centre, University of Yaoundé 1, BP 8094, Yaoundé, Cameroon.
| |
Collapse
|
233
|
Battle KE, Bisanzio D, Gibson HS, Bhatt S, Cameron E, Weiss DJ, Mappin B, Dalrymple U, Howes RE, Hay SI, Gething PW. Treatment-seeking rates in malaria endemic countries. Malar J 2016; 15:20. [PMID: 26754795 PMCID: PMC4709965 DOI: 10.1186/s12936-015-1048-x] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2015] [Accepted: 12/11/2015] [Indexed: 11/25/2022] Open
Abstract
Background The proportion of individuals who seek treatment for fever is an important quantity in understanding access to and use of health systems, as well as for interpreting data on disease incidence from routine surveillance systems. For many malaria endemic countries (MECs), treatment-seeking information is available from national household surveys. The aim of this paper was to assemble sub-national estimates of treatment-seeking behaviours and to predict national treatment-seeking measures for all MECs lacking household survey data. Methods Data on treatment seeking for fever were obtained from Demographic and Health Surveys, Malaria Indicator Surveys and Multiple Cluster Indicator Surveys for every MEC and year that data were available. National-level social, economic and health-related variables were gathered from the World Bank as putative covariates of treatment-seeking rates. A generalized additive mixed model (GAMM) was used to estimate treatment-seeking behaviours for countries where survey data were unavailable. Two separate models were developed to predict the proportion of fever cases that would seek treatment at (1) a public health facility or (2) from any kind of treatment provider. Results Treatment-seeking data were available for 74 MECs and modelled for the remaining 24. GAMMs found that the percentage of pregnant women receiving prenatal care, vaccination rates, education level, government health expenditure, and GDP growth were important predictors for both categories of treatment-seeking outcomes. Treatment-seeking rates, which varied both within and among regions, revealed that public facilities were not always the primary facility type used. Conclusions Estimates of treatment-seeking rates show how health services are utilized and help correct reported malaria case numbers to obtain more accurate measures of disease burden. The assembled and modelled data demonstrated that while treatment-seeking rates have overall increased over time, access remains low in some malaria endemic regions and utilization of government services is in some areas limited. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-1048-x) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Katherine E Battle
- Spatial Ecology and Epidemiology Group, Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford, UK.
| | - Donal Bisanzio
- Spatial Ecology and Epidemiology Group, Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford, UK.
| | - Harry S Gibson
- Spatial Ecology and Epidemiology Group, Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford, UK.
| | - Samir Bhatt
- Spatial Ecology and Epidemiology Group, Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford, UK.
| | - Ewan Cameron
- Spatial Ecology and Epidemiology Group, Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford, UK.
| | - Daniel J Weiss
- Spatial Ecology and Epidemiology Group, Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford, UK.
| | - Bonnie Mappin
- Spatial Ecology and Epidemiology Group, Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford, UK.
| | - Ursula Dalrymple
- Spatial Ecology and Epidemiology Group, Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford, UK.
| | - Rosalind E Howes
- Spatial Ecology and Epidemiology Group, Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford, UK.
| | - Simon I Hay
- Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford, UK. .,Fogarty International Center, National Institutes of Health, Bethesda, MD, USA. .,Institute for Health Metrics and Evaluation, University of Washington, Seattle, WA, USA.
| | - Peter W Gething
- Spatial Ecology and Epidemiology Group, Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford, UK.
| |
Collapse
|
234
|
Abstract
With increasing malaria control and goals of malaria elimination, many endemic areas are transitioning from high-to-low-to-no malaria transmission. Reductions in transmission will impact on the development of naturally acquired immunity to malaria, which develops after repeated exposure to Plasmodium spp. However, it is currently unclear how declining transmission and malaria exposure will affect the development and maintenance of naturally acquired immunity. Here we review the key processes which underpin this knowledge; the amount of Plasmodium spp. exposure required to generate effective immune responses, the longevity of antibody responses and the ability to mount an effective response upon re-exposure through memory responses. Lastly we identify research priorities which will increase our understanding of how changing transmission will impact on malarial immunity.
Collapse
|
235
|
Slater HC, Griffin JT, Ghani AC, Okell LC. Assessing the potential impact of artemisinin and partner drug resistance in sub-Saharan Africa. Malar J 2016; 15:10. [PMID: 26739092 PMCID: PMC4704433 DOI: 10.1186/s12936-015-1075-7] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Accepted: 12/23/2015] [Indexed: 12/26/2022] Open
Abstract
Background Artemisinin and partner drug resistant malaria parasites have emerged in Southeast Asia. If resistance were to emerge in Africa it could have a devastating impact on malaria-related morbidity and mortality. This study estimates the potential impact of artemisinin and partner drug resistance on disease burden in Africa if it were to emerge. Methods Using data from Asia and Africa, five possible artemisinin and partner drug resistance scenarios are characterized. An individual-based malaria transmission model is used to estimate the impact of each resistance scenario on clinical incidence and parasite prevalence across Africa. Artemisinin resistance is characterized by slow parasite clearance and partner drug resistance is associated with late clinical failure or late parasitological failure. Results Scenarios with high levels of recrudescent infections resulted in far greater increases in clinical incidence compared to scenarios with high levels of slow parasite clearance. Across Africa, it is estimated that artemisinin and partner drug resistance at levels similar to those observed in Oddar Meanchey province in Cambodia could result in an additional 78 million cases over a 5 year period, a 7 % increase in cases compared to a scenario with no resistance. A scenario with high levels of slow clearance but no recrudescence resulted in an additional 10 million additional cases over the same period. Conclusion Artemisinin resistance is potentially a more pressing concern than partner drug resistance due to the lack of viable alternatives. However, it is predicted that a failing partner drug will result in greater increases in malaria cases and morbidity than would be observed from artemisinin resistance only. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-1075-7) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Hannah C Slater
- Department of Infectious Disease Epidemiology, MRC Centre for Outbreak Analysis and Modelling, Imperial College London, London, W2 1PG, UK.
| | - Jamie T Griffin
- Department of Infectious Disease Epidemiology, MRC Centre for Outbreak Analysis and Modelling, Imperial College London, London, W2 1PG, UK.
| | - Azra C Ghani
- Department of Infectious Disease Epidemiology, MRC Centre for Outbreak Analysis and Modelling, Imperial College London, London, W2 1PG, UK.
| | - Lucy C Okell
- Department of Infectious Disease Epidemiology, MRC Centre for Outbreak Analysis and Modelling, Imperial College London, London, W2 1PG, UK.
| |
Collapse
|
236
|
ÇİZMECİ EA, KELEBEK GİRGİN N, CEYLAN I, TUNCEL T, ALVER O, AKALIN EH. Cerebral Malaria Treated with Artemisinin in the Intensive Care Unit: A Case Report. IRANIAN JOURNAL OF PARASITOLOGY 2016; 11:116-20. [PMID: 27095978 PMCID: PMC4835461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Malaria is a parasitic disease that is starting to be encountered in intensive care units (ICU) worldwide, owing to increasing globalisation. Severe malaria caused by Plasmodium falciparum, is characterised by cerebral malaria, acute renal failure, hypoglycaemia, severe anaemia, splenomegaly and alveolar oedema. We present the case of a 25-yr old male patient who presented to the Emergency Department of Uludag University in Bursa, Turkey in the winter of 2014 with complaints of fever for three days. His medical history revealed a 14-month stay in Tanzania. Staining of blood smears revealed characteristic gametocytes in accordance with P. falciparum infection. The day after admission, he had an epileptic seizure after which his Glasgow Coma Scale was 6, so he was intubated and transferred to the ICU. A computerized tomography scan revealed findings of cerebral oedema. Intravenous mannitol was administered for 6 days. Intravenous artemisinin was continued for 10 days. Due to refractory fevers, anti-malarial treatment was switched to quinine and doxycycline on the 14th day and on the 16th day the fevers ceased. This case emphasizes that cerebral malaria should be suspected in cases of seizures accompanying malaria, and treatment should be initiated in the ICU. Furthermore, resistance of P. falciparum to artemisinin should be in mind when a response to therapy is lacking.
Collapse
Affiliation(s)
- Elif Ayşe ÇİZMECİ
- Department of Anesthesiology and Intensive Care, School of Medicine, Uludag University, Bursa, Turkey,Correspondence
| | - Nermin KELEBEK GİRGİN
- Department of Anesthesiology and Intensive Care, School of Medicine, Uludag University, Bursa, Turkey
| | - Ilkay CEYLAN
- Department of Anesthesiology and Intensive Care, School of Medicine, Uludag University, Bursa, Turkey
| | - Tekin TUNCEL
- Department of Infectious Diseases, School of Medicine, Uludag University, Bursa, Turkey
| | - Oktay ALVER
- Department of Microbiology, School of Medicine, Uludag University, Bursa, Turkey
| | - Emin Halis AKALIN
- Department of Infectious Diseases, School of Medicine, Uludag University, Bursa, Turkey
| |
Collapse
|
237
|
O’Hanlon SJ, Slater HC, Cheke RA, Boatin BA, Coffeng LE, Pion SDS, Boussinesq M, Zouré HGM, Stolk WA, Basáñez MG. Model-Based Geostatistical Mapping of the Prevalence of Onchocerca volvulus in West Africa. PLoS Negl Trop Dis 2016; 10:e0004328. [PMID: 26771545 PMCID: PMC4714852 DOI: 10.1371/journal.pntd.0004328] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 12/04/2015] [Indexed: 12/04/2022] Open
Abstract
BACKGROUND The initial endemicity (pre-control prevalence) of onchocerciasis has been shown to be an important determinant of the feasibility of elimination by mass ivermectin distribution. We present the first geostatistical map of microfilarial prevalence in the former Onchocerciasis Control Programme in West Africa (OCP) before commencement of antivectorial and antiparasitic interventions. METHODS AND FINDINGS Pre-control microfilarial prevalence data from 737 villages across the 11 constituent countries in the OCP epidemiological database were used as ground-truth data. These 737 data points, plus a set of statistically selected environmental covariates, were used in a Bayesian model-based geostatistical (B-MBG) approach to generate a continuous surface (at pixel resolution of 5 km x 5km) of microfilarial prevalence in West Africa prior to the commencement of the OCP. Uncertainty in model predictions was measured using a suite of validation statistics, performed on bootstrap samples of held-out validation data. The mean Pearson's correlation between observed and estimated prevalence at validation locations was 0.693; the mean prediction error (average difference between observed and estimated values) was 0.77%, and the mean absolute prediction error (average magnitude of difference between observed and estimated values) was 12.2%. Within OCP boundaries, 17.8 million people were deemed to have been at risk, 7.55 million to have been infected, and mean microfilarial prevalence to have been 45% (range: 2-90%) in 1975. CONCLUSIONS AND SIGNIFICANCE This is the first map of initial onchocerciasis prevalence in West Africa using B-MBG. Important environmental predictors of infection prevalence were identified and used in a model out-performing those without spatial random effects or environmental covariates. Results may be compared with recent epidemiological mapping efforts to find areas of persisting transmission. These methods may be extended to areas where data are sparse, and may be used to help inform the feasibility of elimination with current and novel tools.
Collapse
Affiliation(s)
- Simon J. O’Hanlon
- Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine (St Mary’s Campus), Imperial College London, London, United Kingdom
| | - Hannah C. Slater
- Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine (St Mary’s Campus), Imperial College London, London, United Kingdom
- MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | - Robert A. Cheke
- Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine (St Mary’s Campus), Imperial College London, London, United Kingdom
- Natural Resources Institute, University of Greenwich at Medway, Chatham, Kent, United Kingdom
| | - Boakye A. Boatin
- Lymphatic Filariasis Support Centre, Department of Parasitology, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Luc E. Coffeng
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Sébastien D. S. Pion
- UMI 233, Institut de Recherche pour le Développement (IRD) and University of Montpellier 1, Montpellier, France
| | - Michel Boussinesq
- UMI 233, Institut de Recherche pour le Développement (IRD) and University of Montpellier 1, Montpellier, France
| | - Honorat G. M. Zouré
- African Programme for Onchocerciasis Control (APOC), World Health Organization (WHO), Ouagadougou, Burkina Faso
| | - Wilma A. Stolk
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - María-Gloria Basáñez
- Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine (St Mary’s Campus), Imperial College London, London, United Kingdom
- London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| |
Collapse
|
238
|
Sepúlveda N, Paulino CD, Drakeley C. Sample size and power calculations for detecting changes in malaria transmission using antibody seroconversion rate. Malar J 2015; 14:529. [PMID: 26715538 PMCID: PMC4696297 DOI: 10.1186/s12936-015-1050-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2015] [Accepted: 12/12/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Several studies have highlighted the use of serological data in detecting a reduction in malaria transmission intensity. These studies have typically used serology as an adjunct measure and no formal examination of sample size calculations for this approach has been conducted. METHODS A sample size calculator is proposed for cross-sectional surveys using data simulation from a reverse catalytic model assuming a reduction in seroconversion rate (SCR) at a given change point before sampling. This calculator is based on logistic approximations for the underlying power curves to detect a reduction in SCR in relation to the hypothesis of a stable SCR for the same data. Sample sizes are illustrated for a hypothetical cross-sectional survey from an African population assuming a known or unknown change point. RESULTS Overall, data simulation demonstrates that power is strongly affected by assuming a known or unknown change point. Small sample sizes are sufficient to detect strong reductions in SCR, but invariantly lead to poor precision of estimates for current SCR. In this situation, sample size is better determined by controlling the precision of SCR estimates. Conversely larger sample sizes are required for detecting more subtle reductions in malaria transmission but those invariantly increase precision whilst reducing putative estimation bias. CONCLUSIONS The proposed sample size calculator, although based on data simulation, shows promise of being easily applicable to a range of populations and survey types. Since the change point is a major source of uncertainty, obtaining or assuming prior information about this parameter might reduce both the sample size and the chance of generating biased SCR estimates.
Collapse
Affiliation(s)
- Nuno Sepúlveda
- London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK. .,Center of Statistics and Applications of University of Lisbon, Faculdade de Ciências da Universidade de Lisboa, Bloco C6-Piso 4, 1749-1016, Lisbon, Portugal.
| | - Carlos Daniel Paulino
- Center of Statistics and Applications of University of Lisbon, Faculdade de Ciências da Universidade de Lisboa, Bloco C6-Piso 4, 1749-1016, Lisbon, Portugal. .,Instituto Superior Técnico, Universidade Técnica de Lisboa, Avenida Rovisco Pais, 1049-001, Lisbonn, Portugal.
| | - Chris Drakeley
- London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK.
| |
Collapse
|
239
|
Slater HC, Ross A, Ouédraogo AL, White LJ, Nguon C, Walker PGT, Ngor P, Aguas R, Silal SP, Dondorp AM, La Barre P, Burton R, Sauerwein RW, Drakeley C, Smith TA, Bousema T, Ghani AC. Assessing the impact of next-generation rapid diagnostic tests on Plasmodium falciparum malaria elimination strategies. Nature 2015; 528:S94-101. [PMID: 26633771 DOI: 10.1038/nature16040] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Mass-screen-and-treat and targeted mass-drug-administration strategies are being considered as a means to interrupt transmission of Plasmodium falciparum malaria. However, the effectiveness of such strategies will depend on the extent to which current and future diagnostics are able to detect those individuals who are infectious to mosquitoes. We estimate the relationship between parasite density and onward infectivity using sensitive quantitative parasite diagnostics and mosquito feeding assays from Burkina Faso. We find that a diagnostic with a lower detection limit of 200 parasites per microlitre would detect 55% of the infectious reservoir (the combined infectivity to mosquitoes of the whole population weighted by how often each individual is bitten) whereas a test with a limit of 20 parasites per microlitre would detect 83% and 2 parasites per microlitre would detect 95% of the infectious reservoir. Using mathematical models, we show that increasing the diagnostic sensitivity from 200 parasites per microlitre (equivalent to microscopy or current rapid diagnostic tests) to 2 parasites per microlitre would increase the number of regions where transmission could be interrupted with a mass-screen-and-treat programme from an entomological inoculation rate below 1 to one of up to 4. The higher sensitivity diagnostic could reduce the number of treatment rounds required to interrupt transmission in areas of lower prevalence. We predict that mass-screen-and-treat with a highly sensitive diagnostic is less effective than mass drug administration owing to the prophylactic protection provided to uninfected individuals by the latter approach. In low-transmission settings such as those in Southeast Asia, we find that a diagnostic tool with a sensitivity of 20 parasites per microlitre may be sufficient for targeted mass drug administration because this diagnostic is predicted to identify a similar village population prevalence compared with that currently detected using polymerase chain reaction if treatment levels are high and screening is conducted during the dry season. Along with other factors, such as coverage, choice of drug, timing of the intervention, importation of infections, and seasonality, the sensitivity of the diagnostic can play a part in increasing the chance of interrupting transmission.
Collapse
Affiliation(s)
- Hannah C Slater
- MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, Norfolk Place, London W2 1PG, UK
| | - Amanda Ross
- Swiss Tropical and Public Health Institute, Socinstrasse 57, 4002 Basel, Switzerland.,University of Basel, Petersplatz 1, 4001 Basel, Switzerland
| | - André Lin Ouédraogo
- Institute for Disease Modelling, Bellevue, Washington 98005, USA.,Department of Biomedical Sciences, Centre National de Recherche et de Formation sur le Paludisme, 01 B.P. 2208, Ouagadougou, Burkina Faso
| | - Lisa J White
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok 10400, Thailand.,Centre for Tropical Medicine, Nuffield Department of Medicine, University of Oxford, Oxford OX3 7LJ, UK
| | - Chea Nguon
- National Malaria Center, Ministry of Health, Phnom Penh 12302, Cambodia
| | - Patrick G T Walker
- MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, Norfolk Place, London W2 1PG, UK
| | - Pengby Ngor
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok 10400, Thailand.,National Malaria Center, Ministry of Health, Phnom Penh 12302, Cambodia
| | - Ricardo Aguas
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok 10400, Thailand
| | - Sheetal P Silal
- Department of Statistical Sciences, University of Cape Town, Rondebosch 7701, Cape Town, South Africa
| | - Arjen M Dondorp
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok 10400, Thailand.,Centre for Tropical Medicine, Nuffield Department of Medicine, University of Oxford, Oxford OX3 7LJ, UK
| | - Paul La Barre
- PATH, 2201 Westlake Avenue, Seattle, Washington 98121, USA
| | - Robert Burton
- PATH, 2201 Westlake Avenue, Seattle, Washington 98121, USA
| | | | - Chris Drakeley
- London School of Hygiene &Tropical Medicine, Keppel St, London WC1E 7HT, UK
| | - Thomas A Smith
- Swiss Tropical and Public Health Institute, Socinstrasse 57, 4002 Basel, Switzerland.,University of Basel, Petersplatz 1, 4001 Basel, Switzerland
| | - Teun Bousema
- Radboud University Medical Center, 6525 HP Nijmegen, the Netherlands.,London School of Hygiene &Tropical Medicine, Keppel St, London WC1E 7HT, UK
| | - Azra C Ghani
- MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, Norfolk Place, London W2 1PG, UK
| |
Collapse
|
240
|
Alimi TO, Fuller DO, Quinones ML, Xue RD, Herrera SV, Arevalo-Herrera M, Ulrich JN, Qualls WA, Beier JC. Prospects and recommendations for risk mapping to improve strategies for effective malaria vector control interventions in Latin America. Malar J 2015; 14:519. [PMID: 26694047 PMCID: PMC4689006 DOI: 10.1186/s12936-015-1052-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 12/12/2015] [Indexed: 11/10/2022] Open
Abstract
With malaria control in Latin America firmly established in most countries and a growing number of these countries in the pre-elimination phase, malaria elimination appears feasible. A review of the literature indicates that malaria elimination in this region will be difficult without locally tailored strategies for vector control, which depend on more research on vector ecology, genetics and behavioural responses to environmental changes, such as those caused by land cover alterations, and human population movements. An essential way to bridge the knowledge gap and improve vector control is through risk mapping. Malaria risk maps based on statistical and knowledge-based modelling can elucidate the links between environmental factors and malaria vectors, explain interactions between environmental changes and vector dynamics, and provide a heuristic to demonstrate how the environment shapes malaria transmission. To increase the utility of risk mapping in guiding vector control activities, definitions of malaria risk for mapping purposes must be standardized. The maps must also possess appropriate scale and resolution in order to become essential tools in integrated vector management (IVM), so that planners can target areas in greatest need of control measures. Fully integrating risk mapping into vector control programmes will make interventions more evidence-based, making malaria elimination more attainable.
Collapse
Affiliation(s)
- Temitope O Alimi
- Abess Center for Ecosystem Science and Policy, University of Miami, Coral Gables, FL, USA.
| | - Douglas O Fuller
- Department of Geography and Regional Studies, University of Miami, Coral Gables, FL, USA.
| | - Martha L Quinones
- Department of Public Health, Universidad Nacional de Colombia, Bogota, Colombia.
| | - Rui-De Xue
- Anastasia Mosquito Control District, 500 Old Beach Road, St. Augustine, FL, USA.
| | - Socrates V Herrera
- Centro de Investigacion Cientifica Caucaseco, Universidad del Valle, Cali, Colombia. .,School of Health, Valle State University, Cali, Colombia.
| | - Myriam Arevalo-Herrera
- Centro de Investigacion Cientifica Caucaseco, Universidad del Valle, Cali, Colombia. .,School of Health, Valle State University, Cali, Colombia.
| | - Jill N Ulrich
- Abess Center for Ecosystem Science and Policy, University of Miami, Coral Gables, FL, USA.
| | - Whitney A Qualls
- Department of Public Health Sciences, Miller School of Medicine, University of Miami, Miami, FL, USA.
| | - John C Beier
- Department of Public Health Sciences, Miller School of Medicine, University of Miami, Miami, FL, USA.
| |
Collapse
|
241
|
Sauboin CJ, Van Bellinghen LA, Van De Velde N, Van Vlaenderen I. Potential public health impact of RTS,S malaria candidate vaccine in sub-Saharan Africa: a modelling study. Malar J 2015; 14:524. [PMID: 26702637 PMCID: PMC4690265 DOI: 10.1186/s12936-015-1046-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 12/09/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Adding malaria vaccination to existing interventions could help to reduce the health burden due to malaria. This study modelled the potential public health impact of the RTS,S candidate malaria vaccine in 42 malaria-endemic countries in sub-Saharan Africa. METHODS An individual-based Markov cohort model was constructed with three categories of malaria transmission intensity and six successive malaria immunity levels. The cycle time was 5 days. Vaccination was assumed to reduce the risk of infection, with no other effects. Vaccine efficacy was assumed to wane exponentially over time. Malaria incidence and vaccine efficacy data were taken from a Phase III trial of the RTS,S vaccine with 18 months of follow-up (NCT00866619). The model was calibrated to reproduce the malaria incidence in the control arm of the trial in each transmission category and published age distribution data. Individual-level heterogeneity in malaria exposure and vaccine protection was accounted for. Parameter uncertainty and variability were captured by using stochastic model transitions. The model followed a cohort from birth to 10 years of age without malaria vaccination, or with RTS,S malaria vaccination administered at age 6, 10 and 14 weeks or at age 6, 7-and-a-half and 9 months. Median and 95% confidence intervals were calculated for the number of clinical malaria cases, severe cases, malaria hospitalizations and malaria deaths expected to be averted by each vaccination strategy. Univariate sensitivity analysis was conducted by varying the values of key input parameters. RESULTS Vaccination assuming the coverage of diphtheria-tetanus-pertussis (DTP3) at age 6, 10 and 14 weeks is estimated to avert over five million clinical malaria cases, 119,000 severe malaria cases, 98,600 malaria hospitalizations and 31,000 malaria deaths in the 42 countries over the 10-year period. Vaccination at age 6, 7-and-a-half and 9 months with 75% of DTP3 coverage is estimated to avert almost 12.5 million clinical malaria cases, 250,000 severe malaria cases, 208,000 malaria hospitalizations and 65,400 malaria deaths in the 42 countries. Univariate sensitivity analysis indicated that for both vaccination strategies, the parameters with the largest impact on the malaria mortality estimates were waning of vaccine efficacy and malaria case-fatality rate. CONCLUSIONS Addition of RTS,S malaria vaccination to existing malaria interventions is estimated to reduce substantially the incidence of clinical malaria, severe malaria, malaria hospitalizations and malaria deaths across 42 countries in sub-Saharan Africa.
Collapse
|
242
|
Hamm NAS, Soares Magalhães RJ, Clements ACA. Earth Observation, Spatial Data Quality, and Neglected Tropical Diseases. PLoS Negl Trop Dis 2015; 9:e0004164. [PMID: 26678393 PMCID: PMC4683053 DOI: 10.1371/journal.pntd.0004164] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Earth observation (EO) is the use of remote sensing and in situ observations to gather data on the environment. It finds increasing application in the study of environmentally modulated neglected tropical diseases (NTDs). Obtaining and assuring the quality of the relevant spatially and temporally indexed EO data remain challenges. Our objective was to review the Earth observation products currently used in studies of NTD epidemiology and to discuss fundamental issues relating to spatial data quality (SDQ), which limit the utilization of EO and pose challenges for its more effective use. We searched Web of Science and PubMed for studies related to EO and echinococossis, leptospirosis, schistosomiasis, and soil-transmitted helminth infections. Relevant literature was also identified from the bibliographies of those papers. We found that extensive use is made of EO products in the study of NTD epidemiology; however, the quality of these products is usually given little explicit attention. We review key issues in SDQ concerning spatial and temporal scale, uncertainty, and the documentation and use of quality information. We give examples of how these issues may interact with uncertainty in NTD data to affect the output of an epidemiological analysis. We conclude that researchers should give careful attention to SDQ when designing NTD spatial-epidemiological studies. This should be used to inform uncertainty analysis in the epidemiological study. SDQ should be documented and made available to other researchers.
Collapse
Affiliation(s)
- Nicholas A. S. Hamm
- Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, Enschede, The Netherlands
- * E-mail:
| | - Ricardo J. Soares Magalhães
- School of Veterinary Science, University of Queensland, Brisbane, Australia
- Child Health Research Centre, University of Queensland, Brisbane, Australia
| | - Archie C. A. Clements
- Research School of Population Health, The Australian National University, Canberra, Australia
| |
Collapse
|
243
|
Sedda L, Qi Q, Tatem AJ. A geostatistical analysis of the association between armed conflicts and Plasmodium falciparum malaria in Africa, 1997-2010. Malar J 2015; 14:500. [PMID: 26670739 PMCID: PMC4681145 DOI: 10.1186/s12936-015-1024-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2015] [Accepted: 11/27/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The absence of conflict in a country has been cited as a crucial factor affecting the operational feasibility of achieving malaria control and elimination, yet mixed evidence exists on the influence that conflicts have had on malaria transmission. Over the past two decades, Africa has seen substantial numbers of armed conflicts of varying length and scale, creating conditions that can disrupt control efforts and impact malaria transmission. However, very few studies have quantitatively assessed the associations between conflicts and malaria transmission, particularly in a consistent way across multiple countries. METHODS In this analysis an explicit geostatistical, autoregressive, mixed model is employed to quantitatively assess the association between conflicts and variations in Plasmodium falciparum parasite prevalence across a 13-year period in sub-Saharan Africa. RESULTS Analyses of geolocated, malaria prevalence survey variations against armed conflict data in general showed a wide, but short-lived impact of conflict events geographically. The number of countries with decreased P. falciparum parasite prevalence (17) is larger than the number of countries with increased transmission (12), and notably, some of the countries with the highest transmission pre-conflict were still found with lower transmission post-conflict. For four countries, there were no significant changes in parasite prevalence. Finally, distance from conflicts, duration of conflicts, violence of conflict, and number of conflicts were significant components in the model explaining the changes in P. falciparum parasite rate. CONCLUSIONS The results suggest that the maintenance of intervention coverage and provision of healthcare in conflict situations to protect vulnerable populations can maintain gains in even the most difficult of circumstances, and that conflict does not represent a substantial barrier to elimination goals.
Collapse
Affiliation(s)
- Luigi Sedda
- CHICAS, Lancaster Medical School, Lancaster University, Furness Building, Lancaster, LA1 4YG, UK.
| | - Qiuyin Qi
- Department of Geography, University of Florida, Gainesville, FL, 32611-7315, USA.
| | - Andrew J Tatem
- Fogarty International Center, National Institutes of Health, Bethesda, MD, 20892, USA. .,Flowminder Foundation, Roslagsgatan 17, 113 55, Stockholm, Sweden. .,Geography and Environment, University of Southampton, University Road, Southampton, SO17 1BJ, UK.
| |
Collapse
|
244
|
Lakkam M, Wein LM. Analysing the nutrition-disease nexus: the case of malaria. Malar J 2015; 14:479. [PMID: 26619943 PMCID: PMC4665912 DOI: 10.1186/s12936-015-0894-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 08/24/2015] [Indexed: 12/02/2022] Open
Abstract
Background Motivated by the observation that children suffering from undernutrition are more likely to experience disease and are more likely to die if they do contract a disease, mathematical modelling is used to explore the ramifications of targeting preventive disease measures to undernutritioned children. Methods A malaria model is constructed with superinfection and heterogeneous susceptibility, where a portion of this susceptibility is due to undernutrition (as measured by weight-for-age z scores); so as to isolate the impact of supplementary food on malaria from the influence of confounding factors, the portion of the total susceptibility that is due to undernutrition is estimated from a large randomized trial of supplementary feeding. Logistic regression is used to estimate mortality given malaria infection as a function of weight-for-age z scores. The clinical malaria morbidity and malaria mortality are analytically computed for a variety of policies involving supplementary food and insecticide-treated bed nets. Results The portion of heterogeneity in susceptibility that is due to undernutrition is estimated to be 90.3 %. Targeting insecticide-treated bed nets to undernutritioned children leads to fewer malaria deaths than the random distribution of bed nets in the hypoendemic and mesoendemic settings. When baseline bed net coverage for children is 20 %, supplementary food given to underweight children is estimated to reduce malaria mortality by 7.2–22.9 % as the entomological inoculation rate ranges from 500 to 1.0. In the hyperendemic setting, supplementary food has a bigger impact than bed nets, particularly when baseline bed net coverage is high. Conclusions Although the results are speculative (e.g., they are based on parameter estimates that do not possess the traditional statistical significance level), the biological plausibility of the modelling assumptions and the high price-sensitivity of demand for bed nets suggest that free bed net distribution targeted to undernutritioned children in areas suffering from both undernutrition and malaria (e.g., sub-Saharan Africa) should be the subject of a randomized trial in a hypoendemic or mesoendemic setting. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-0894-x) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Milinda Lakkam
- Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA, 94305, USA.
| | - Lawrence M Wein
- Graduate School of Business, Stanford University, Stanford, CA, 94305, USA.
| |
Collapse
|
245
|
Howes RE, Reiner Jr. RC, Battle KE, Longbottom J, Mappin B, Ordanovich D, Tatem AJ, Drakeley C, Gething PW, Zimmerman PA, Smith DL, Hay SI. Plasmodium vivax Transmission in Africa. PLoS Negl Trop Dis 2015; 9:e0004222. [PMID: 26587988 PMCID: PMC4654493 DOI: 10.1371/journal.pntd.0004222] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Accepted: 10/19/2015] [Indexed: 12/22/2022] Open
Abstract
Malaria in sub-Saharan Africa has historically been almost exclusively attributed to Plasmodium falciparum (Pf). Current diagnostic and surveillance systems in much of sub-Saharan Africa are not designed to identify or report non-Pf human malaria infections accurately, resulting in a dearth of routine epidemiological data about their significance. The high prevalence of Duffy negativity provided a rationale for excluding the possibility of Plasmodium vivax (Pv) transmission. However, review of varied evidence sources including traveller infections, community prevalence surveys, local clinical case reports, entomological and serological studies contradicts this viewpoint. Here, these data reports are weighted in a unified framework to reflect the strength of evidence of indigenous Pv transmission in terms of diagnostic specificity, size of individual reports and corroboration between evidence sources. Direct evidence was reported from 21 of the 47 malaria-endemic countries studied, while 42 countries were attributed with infections of visiting travellers. Overall, moderate to conclusive evidence of transmission was available from 18 countries, distributed across all parts of the continent. Approximately 86.6 million Duffy positive hosts were at risk of infection in Africa in 2015. Analysis of the mechanisms sustaining Pv transmission across this continent of low frequency of susceptible hosts found that reports of Pv prevalence were consistent with transmission being potentially limited to Duffy positive populations. Finally, reports of apparent Duffy-independent transmission are discussed. While Pv is evidently not a major malaria parasite across most of sub-Saharan Africa, the evidence presented here highlights its widespread low-level endemicity. An increased awareness of Pv as a potential malaria parasite, coupled with policy shifts towards species-specific diagnostics and reporting, will allow a robust assessment of the public health significance of Pv, as well as the other neglected non-Pf parasites, which are currently invisible to most public health authorities in Africa, but which can cause severe clinical illness and require specific control interventions.
Collapse
Affiliation(s)
- Rosalind E. Howes
- Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Oxford, United Kingdom
- Center for Global Health and Diseases, Case Western Reserve University, Cleveland, Ohio, United States of America
- * E-mail:
| | - Robert C. Reiner Jr.
- Department of Epidemiology and Biostatistics, School of Public Health, Indiana University, Bloomington, Indiana, United States of America
- Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Katherine E. Battle
- Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Oxford, United Kingdom
| | - Joshua Longbottom
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Bonnie Mappin
- Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Oxford, United Kingdom
| | - Dariya Ordanovich
- Department of Geography and Environment, University of Southampton, Highfield, Southampton, United Kingdom
| | - Andrew J. Tatem
- Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America
- Department of Geography and Environment, University of Southampton, Highfield, Southampton, United Kingdom
- Flowminder Foundation, Stockholm, Sweden
| | - Chris Drakeley
- Malaria Centre, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Peter W. Gething
- Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Oxford, United Kingdom
| | - Peter A. Zimmerman
- Center for Global Health and Diseases, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - David L. Smith
- Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Oxford, United Kingdom
- Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America
- Sanaria Institute for Global Health and Tropical Medicine, Rockville, Maryland, United States of America
- Institute for Health Metrics and Evaluation, University of Washington, Seattle, United States of America
| | - Simon I. Hay
- Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
- Institute for Health Metrics and Evaluation, University of Washington, Seattle, United States of America
| |
Collapse
|
246
|
Alegana VA, Atkinson PM, Pezzulo C, Sorichetta A, Weiss D, Bird T, Erbach-Schoenberg E, Tatem AJ. Fine resolution mapping of population age-structures for health and development applications. J R Soc Interface 2015; 12:rsif.2015.0073. [PMID: 25788540 PMCID: PMC4387535 DOI: 10.1098/rsif.2015.0073] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The age-group composition of populations varies considerably across the world, and obtaining accurate, spatially detailed estimates of numbers of children under 5 years is important in designing vaccination strategies, educational planning or maternal healthcare delivery. Traditionally, such estimates are derived from population censuses, but these can often be unreliable, outdated and of coarse resolution for resource-poor settings. Focusing on Nigeria, we use nationally representative household surveys and their cluster locations to predict the proportion of the under-five population in 1 × 1 km using a Bayesian hierarchical spatio-temporal model. Results showed that land cover, travel time to major settlements, night-time lights and vegetation index were good predictors and that accounting for fine-scale variation, rather than assuming a uniform proportion of under 5 year olds can result in significant differences in health metrics. The largest gaps in estimated bednet and vaccination coverage were in Kano, Katsina and Jigawa. Geolocated household surveys are a valuable resource for providing detailed, contemporary and regularly updated population age-structure data in the absence of recent census data. By combining these with covariate layers, age-structure maps of unprecedented detail can be produced to guide the targeting of interventions in resource-poor settings.
Collapse
Affiliation(s)
- V A Alegana
- Centre for Geographical Health Research, Geography and Environment, University of Southampton, Highfield Southampton, UK
| | - P M Atkinson
- Centre for Geographical Health Research, Geography and Environment, University of Southampton, Highfield Southampton, UK
| | - C Pezzulo
- Centre for Geographical Health Research, Geography and Environment, University of Southampton, Highfield Southampton, UK
| | - A Sorichetta
- Centre for Geographical Health Research, Geography and Environment, University of Southampton, Highfield Southampton, UK
| | - D Weiss
- Department of Zoology, University of Oxford, Oxford, UK
| | - T Bird
- Centre for Geographical Health Research, Geography and Environment, University of Southampton, Highfield Southampton, UK
| | - E Erbach-Schoenberg
- Centre for Geographical Health Research, Geography and Environment, University of Southampton, Highfield Southampton, UK
| | - A J Tatem
- Centre for Geographical Health Research, Geography and Environment, University of Southampton, Highfield Southampton, UK Fogarty International Center, National Institutes of Health, Bethesda, MD, USA Flowminder Foundation, Stockholm, Sweden
| |
Collapse
|
247
|
Mappin B, Cameron E, Dalrymple U, Weiss DJ, Bisanzio D, Bhatt S, Gething PW. Standardizing Plasmodium falciparum infection prevalence measured via microscopy versus rapid diagnostic test. Malar J 2015; 14:460. [PMID: 26577805 PMCID: PMC4650290 DOI: 10.1186/s12936-015-0984-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 11/03/2015] [Indexed: 11/21/2022] Open
Abstract
Background Large-scale mapping of Plasmodium falciparum infection
prevalence relies on opportunistic assemblies of infection prevalence data arising from thousands of P. falciparum parasite rate (PfPR) surveys conducted worldwide. Variance in these data is driven by both signal, the true underlying pattern of infection prevalence, and a range of factors contributing to ‘noise’, including sampling error, differing age ranges of subjects and differing parasite detection methods. Whilst the former two noise components have been addressed in previous studies, the effect of different diagnostic methods used to determine PfPR in different studies has not. In particular, the majority of PfPR data are based on positivity rates determined by either microscopy or rapid diagnostic test (RDT), yet these approaches are not equivalent; therefore a method is needed for standardizing RDT and microscopy-based prevalence estimates prior to use in mapping. Methods Twenty-five recent Demographic and Health surveys (DHS) datasets from sub-Saharan Africa provide child diagnostic test results derived using both RDT and microscopy for each individual. These prevalence estimates were aggregated across level one administrative zones and a Bayesian probit regression model fit to the microscopy- versus RDT-derived prevalence relationship. An errors-in-variables approach was employed to account for sampling error in both the dependent and independent variables. In addition to the diagnostic outcome, RDT type, fever status and recent anti-malarial treatment were extracted from the datasets in order to analyse their effect on observed malaria prevalence. Results A strong non-linear relationship between the microscopy and RDT-derived prevalence was found. The results of regressions stratified by the additional diagnostic variables (RDT type, fever status and recent anti-malarial treatment) indicate that there is a distinct and consistent difference in the relationship when the data are stratified by febrile status and RDT brand. Conclusions The relationships defined in this research can be applied to RDT-derived PfPR data to effectively convert them to an estimate of the parasite prevalence expected using microscopy (or vice versa), thereby standardizing the dataset and improving the signal-to-noise ratio. Additionally, the results provide insight on the importance of RDT brands, febrile status and recent anti-malarial treatment for explaining inconsistencies between observed prevalence derived from different diagnostics.
Collapse
Affiliation(s)
- Bonnie Mappin
- Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Tinbergen Building, Oxford, OX1 3PS, UK.
| | - Ewan Cameron
- Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Tinbergen Building, Oxford, OX1 3PS, UK.
| | - Ursula Dalrymple
- Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Tinbergen Building, Oxford, OX1 3PS, UK.
| | - Daniel J Weiss
- Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Tinbergen Building, Oxford, OX1 3PS, UK.
| | - Donal Bisanzio
- Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Tinbergen Building, Oxford, OX1 3PS, UK.
| | - Samir Bhatt
- Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Tinbergen Building, Oxford, OX1 3PS, UK.
| | - Peter W Gething
- Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Tinbergen Building, Oxford, OX1 3PS, UK.
| |
Collapse
|
248
|
Chitunhu S, Musenge E. Spatial and socio-economic effects on malaria morbidity in children under 5 years in Malawi in 2012. Spat Spatiotemporal Epidemiol 2015; 16:21-33. [PMID: 26919752 DOI: 10.1016/j.sste.2015.11.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Revised: 10/22/2015] [Accepted: 11/04/2015] [Indexed: 11/19/2022]
Abstract
BACKGROUND Malaria is a major health challenge in sub-Saharan Africa with children under 5 being most vulnerable. Identifying regions of greater malarial burden is vital in targeting interventions. METHODS This study analysed malaria morbidity using data from the Malawi 2012 Malaria Indicator Survey that were obtained from Demographic and Health Survey (DHS) program website. These data captured malaria related information on children under 5. Poisson regression was done to determine associations between outcome (number of children under 5 with malaria in household) and explanatory variables. A Bayesian smoothing approach was employed to adjust for spatial random effects on child related variables. RESULTS There were 1878 households in 140 clusters. The number of children under five was 1900. Spatially structured effects accounted for more than 90% of random effects as these had a mean of 1.32 (95% Credible Interval (CI)=0.37, 2.50) whilst spatially unstructured had a mean of 0.10 (CI=9.0 × 10(-4), 0.38). Spatially adjusted significant variables were; type of place of residence (urban or rural) [posterior odds ratio (POR)=2.06; CI= 1.27, 3.34], not owning land [POR=1.77; CI=1.19, 2.64], not staying in a slum [POR=0.52; CI=0.33, 0.83] and enhanced vegetation index [POR=0.02; CI=0.00, 1.08]. A trend was observed on usage of insecticide treated mosquito nets [POR=0.80; CI=0.63, 1.03]. CONCLUSION This study showed that malaria is a disease of poverty. Enhanced vegetation index was an important factor in malaria morbidity. The central region was identified as the area with greatest disease burden.
Collapse
Affiliation(s)
- Simangaliso Chitunhu
- Division of Epidemiology and Biostatistics, School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, 27 St Andrews' Road, Parktown, Johannesburg 2193, South Africa.
| | - Eustasius Musenge
- Division of Epidemiology and Biostatistics, School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, 27 St Andrews' Road, Parktown, Johannesburg 2193, South Africa.
| |
Collapse
|
249
|
Ncogo P, Herrador Z, Romay-Barja M, García-Carrasco E, Nseng G, Berzosa P, Santana-Morales MA, Riloha M, Aparicio P, Valladares B, Benito A. Malaria prevalence in Bata district, Equatorial Guinea: a cross-sectional study. Malar J 2015; 14:456. [PMID: 26573911 PMCID: PMC4647797 DOI: 10.1186/s12936-015-0986-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2015] [Accepted: 11/04/2015] [Indexed: 11/10/2022] Open
Abstract
Background Malaria has traditionally been a leading public health problem in Equatorial Guinea. After completion, in September 2011, of the integrated set of interventions against malaria launched by the Global Fund Malaria Programme in the mainland area, the epidemiological situation of malaria remains unknown. The aim of this study was to investigate the prevalence rate of malaria and associated factors based on the rapid diagnosis test (RDT) in Bata district, in order to provide evidence that will reinforce the National Malaria Control Programme. Methods From June to August 2013, a representative cross sectional survey using a multistage, stratified, cluster-selected sample was carried out in urban zones and rural villages from Bata district. Data on socio-demographic, health status and malaria-related behaviours was collected. Malaria diagnosis was performed by RDT. Bivariate and multivariable statistical methods were employed to assess malaria prevalence and its association with different factors. Results Prevalence of malaria was higher in rural settings (58.9 %; CI 95 % 55.2–62.5 %) than in the sampled urban communities (33.9 %; CI 95 % 31.1–36.9 %). Presence of anaemia was also high, especially in rural sites (89.6 vs. 82.8 %, p < 0.001). The analyses show that a positive RDT result was significantly associated with age group, the most affected age range being 13 months–14 years old. Other significant covariates were ethnic group (only in urban sites), number of adults living in the house (only in rural villages) previous history of fever, anaemia (only in urban sites) and sleeping under a bed net. Moreover, those who never slept under a bed net were two times more likely to have malaria. Conclusion The prevalence of malaria was high in Bata district, especially in rural villages. The National Programme to fight malaria in Equatorial Guinea should take into account the differences found between rural and urban communities and age groups to target appropriately those worst affected. The findings of this study will assist in planning and undertaking regional policy and other preventive initiatives. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-0986-7) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Policarpo Ncogo
- Reference Centre for Epidemics Control of Equatorial Guinea (CRCE), Ministry of Health and Social Welfare, Malabo, Equatorial Guinea.
| | - Zaida Herrador
- National Centre of Tropical Medicine, Instituto de Salud Carlos III (ISCIII) C/Sinesio Delgado, 6-Pabellón 13, 28029, Madrid, Spain. .,The Spanish Tropical Diseases Research Network (RICET in Spanish), Madrid, Spain.
| | - Maria Romay-Barja
- National Centre of Tropical Medicine, Instituto de Salud Carlos III (ISCIII) C/Sinesio Delgado, 6-Pabellón 13, 28029, Madrid, Spain. .,The Spanish Tropical Diseases Research Network (RICET in Spanish), Madrid, Spain.
| | - Emely García-Carrasco
- Department of Preventive Medicine, University Hospital of Albacete, Albacete, Spain.
| | - Gloria Nseng
- Ministry of Health and Social Welfare, Malabo, Equatorial Guinea.
| | - Pedro Berzosa
- National Centre of Tropical Medicine, Instituto de Salud Carlos III (ISCIII) C/Sinesio Delgado, 6-Pabellón 13, 28029, Madrid, Spain.
| | - Maria A Santana-Morales
- The Spanish Tropical Diseases Research Network (RICET in Spanish), Madrid, Spain. .,Instituto Universitario de Enfermedades Tropicales y Salud Pública de Canarias, Universidad de la Laguna, La Laguna, Canary Islands, Spain.
| | - Matilde Riloha
- Ministry of Health and Social Welfare, Malabo, Equatorial Guinea.
| | - Pilar Aparicio
- National Centre of Tropical Medicine, Instituto de Salud Carlos III (ISCIII) C/Sinesio Delgado, 6-Pabellón 13, 28029, Madrid, Spain. .,The Spanish Tropical Diseases Research Network (RICET in Spanish), Madrid, Spain.
| | - Basilio Valladares
- The Spanish Tropical Diseases Research Network (RICET in Spanish), Madrid, Spain. .,Instituto Universitario de Enfermedades Tropicales y Salud Pública de Canarias, Universidad de la Laguna, La Laguna, Canary Islands, Spain.
| | - Agustín Benito
- National Centre of Tropical Medicine, Instituto de Salud Carlos III (ISCIII) C/Sinesio Delgado, 6-Pabellón 13, 28029, Madrid, Spain. .,The Spanish Tropical Diseases Research Network (RICET in Spanish), Madrid, Spain.
| |
Collapse
|
250
|
Penny MA, Pemberton-Ross P, Smith TA. The time-course of protection of the RTS,S vaccine against malaria infections and clinical disease. Malar J 2015; 14:437. [PMID: 26537608 PMCID: PMC4634589 DOI: 10.1186/s12936-015-0969-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Accepted: 10/27/2015] [Indexed: 01/08/2023] Open
Abstract
Background Recent publications have reported follow-up of the RTS,S/AS01 malaria vaccine candidate Phase III trials at 11 African sites for 32 months (or longer). This includes site- and time-specific estimates of incidence and efficacy against clinical disease with four different vaccination schedules. These data allow estimation of the time-course of protection against infection associated with two different ages of vaccination, both with and without a booster dose. Methods Using an ensemble of individual-based stochastic models, each trial cohort in the Phase III trial was simulated assuming many different hypothetical profiles for the vaccine efficacy against infection in time, for both the primary course and boosting dose and including the potential for either exponential or non-exponential decay. The underlying profile of protection was determined by Bayesian fitting of these model predictions to the site- and time-specific incidence of clinical malaria over 32 months (or longer) of follow-up. Using the same stochastic models, projections of clinical efficacy in each of the sites were modelled and compared to available observed trial data. Results The initial protection of RTS,S immediately following three doses is estimated as providing an efficacy against infection of 65 % (when immunizing infants aged 6–12 weeks old) and 91 % (immunizing children aged 5–17 months old at first vaccination). This protection decays relatively rapidly, with an approximately exponential decay for the 6–12 weeks old cohort (with a half-life of 7.2 months); for the 5–17 months old cohort a biphasic decay with a similar half-life is predicted, with an initial rapid decay followed by a slower decay. The boosting dose was estimated to return protection to an efficacy against infection of 50–55 % for both cohorts. Estimates of clinical efficacy by trial site are consistent with those reported in the trial for all cohorts. Conclusions The site- and time-specific clinical observations from the RTS,S/AS01 trial data allowed a reasonably precise estimation of the underlying vaccine protection against infection which is consistent with common underlying efficacy and decay rates across the trial sites. This calibration suggests that the decay in efficacy against clinical disease is more rapid than that against infection because of age-shifts in the incidence of disease. The dynamical models predict that clinical effectiveness will continue to decay and that likely effects beyond the time-scale of the trial will be small. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-0969-8) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Melissa A Penny
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, 4051, Basel, Switzerland. .,University of Basel, Petersplatz 1, Basel, Switzerland.
| | - Peter Pemberton-Ross
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, 4051, Basel, Switzerland. .,University of Basel, Petersplatz 1, Basel, Switzerland.
| | - Thomas A Smith
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, 4051, Basel, Switzerland. .,University of Basel, Petersplatz 1, Basel, Switzerland.
| |
Collapse
|