ORCID Profile
0000-0003-3725-6088
Current Organisations
KEMRI/Wellcome Trust Programme
,
University of Oxford
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Publisher: Elsevier
Date: 2013
Publisher: F1000 Research Ltd
Date: 26-07-2017
DOI: 10.12688/WELLCOMEOPENRES.12187.1
Abstract: Background : Understanding the distribution of anopheline vectors of malaria is an important prelude to the design of national malaria control and elimination programmes. A single, geo-coded continental inventory of anophelines using all available published and unpublished data has not been undertaken since the 1960s. Methods : We have searched African, European and World Health Organization archives to identify unpublished reports on anopheline surveys in 48 sub-Saharan Africa countries. This search was supplemented by identification of reports that formed part of post-graduate theses, conference abstracts, regional insecticide resistance databases and more traditional bibliographic searches of peer-reviewed literature. Finally, a check was made against two recent repositories of dominant malaria vector species locations ( circa 2,500). Each report was used to extract information on the survey dates, village locations (geo-coded to provide a longitude and latitude), s ling methods, species identification methods and all anopheline species found present during the survey. Survey records were collapsed to a single site over time. Results : The search strategy took years and resulted in 13,331 unique, geo-coded survey locations of anopheline vector occurrence between 1898 and 2016. A total of 12,204 (92%) sites reported the presence of 10 dominant vector species/sibling species 4,473 (37%) of these sites were s led since 2005. 4,442 (33%) sites reported at least one of 13 possible secondary vector species 1,107 (25%) of these sites were s led since 2005. Distributions of dominant and secondary vectors conform to previous descriptions of the ecological ranges of these vectors. Conclusion : We have assembled the largest ever geo-coded database of anophelines in Africa, representing a legacy dataset for future updating and identification of knowledge gaps at national levels. The geo-coded database is available on Harvard Dataverse as a reference source for African national malaria control programmes planning their future control and elimination strategies.
Publisher: Elsevier BV
Date: 02-2005
Publisher: Public Library of Science (PLoS)
Date: 06-06-2006
Publisher: Public Library of Science (PLoS)
Date: 15-06-2010
Publisher: Wiley
Date: 17-03-2008
Publisher: Springer Science and Business Media LLC
Date: 05-2010
DOI: 10.1038/NATURE09098
Publisher: Springer Science and Business Media LLC
Date: 2009
Publisher: Springer Science and Business Media LLC
Date: 10-2017
DOI: 10.1038/NATURE24059
Publisher: Springer Science and Business Media LLC
Date: 23-09-2011
Abstract: Following the development of resistance to anti-malarial mono-therapies, malaria endemic countries in Africa now use artemisinin-based combination therapy (ACT) as recommended first-line treatment for uncomplicated malaria. Patients' adherence to ACT is an important factor to ensure treatment efficacy, as well as to reduce the likelihood of parasite resistance to these drugs. This study reports adherence to a specific ACT, artemether-lumefantrine (AL), under conditions of routine clinical practice in Kenya. The study was undertaken in Garissa and Bunyala districts among outpatients of five government health facilities. Patients treated with AL were visited at home four days after having been prescribed the drug. Respondents (patients ≥ 15 years and caregivers of patients 15 years) were interviewed using a standardized questionnaire, AL blister packs were physically inspected and the adherence status of patients was then recorded. Multivariate logistic regression modelling was used to determine predictors of adherence. Of the 918 patients included in the study, 588 (64.1%) were 'probably adherent', 291 (31.7%) were 'definitely non-adherent' and 39 (4.2%) were 'probably non-adherent'. Six factors were found to be significant predictors of adherence: patient knowledge of the ACT dosing regimen (odds ratio (OR) = 1.76 95% CI = 1.32-2.35), patient age (OR = 1.65 95% CI = 1.02-1.85), respondent age (OR = 1.37 95% CI = 1.10-2.48), whether a respondent had seen AL before (OR = 1.46 95% CI = 1.08-1.98), whether a patient had reported dislikes to AL (OR = 0.62 95% CI = 0.47-0.82) and whether a respondent had waited more than 24 hours to seek treatment (OR = 0.73 95% CI = 0.54-0.99). Overall, adherence to AL was found to be low in both Garissa and Bunyala districts, with patient knowledge of the AL dosing regimen found to be the strongest predictor of adherence. Interventions aimed at increasing community awareness of the AL dosing regimen, use of child friendly formulations and improving health workers' prescribing practices are likely to ensure higher adherence to AL and eventual treatment success.
Publisher: Springer Science and Business Media LLC
Date: 22-02-2021
Publisher: Springer Science and Business Media LLC
Date: 04-05-2021
DOI: 10.1186/S12916-021-01974-X
Abstract: During the millennium development goals period, reduction in under-five mortality (U5M) and increases in child health intervention coverage were characterised by sub-national disparities and inequities across Kenya. The contribution of changing risk factors and intervention coverage on the sub-national changes in U5M remains poorly defined. Sub-national county-level data on U5M and 43 factors known to be associated with U5M spanning 1993 and 2014 were assembled. Using a Bayesian ecological mixed-effects regression model, the relationships between U5M and significant intervention and infection risk ecological factors were quantified across 47 sub-national counties. The coefficients generated were used within a counterfactual framework to estimate U5M and under-five deaths averted (U5-DA) for every county and year (1993–2014) associated with changes in the coverage of interventions and disease infection prevalence relative to 1993. Nationally, the stagnation and increase in U5M in the 1990s were associated with rising human immunodeficiency virus (HIV) prevalence and reduced maternal autonomy while improvements after 2006 were associated with a decline in the prevalence of HIV and malaria, increase in access to better sanitation, fever treatment-seeking rates and maternal autonomy. Reduced stunting and increased coverage of early breastfeeding and institutional deliveries were associated with a smaller number of U5-DA compared to other factors while a reduction in high parity and fully immunised children were associated with under-five lives lost. Most of the U5-DA occurred after 2006 and varied spatially across counties. The highest number of U5-DA was recorded in western and coastal Kenya while northern Kenya recorded a lower number of U5-DA than western. Central Kenya had the lowest U5-DA. The deaths averted across the different regions were associated with a unique set of factors. Contributions of interventions and risk factors to changing U5M vary sub-nationally. This has important implications for targeting future interventions within decentralised health systems such as those operated in Kenya. Targeting specific factors where U5M has been high and intervention coverage poor would lead to the highest likelihood of sub-national attainment of sustainable development goal (SDG) 3.2 on U5M in Kenya.
Publisher: Elsevier BV
Date: 10-2010
Publisher: Public Library of Science (PLoS)
Date: 03-08-2010
Publisher: Elsevier BV
Date: 08-2004
Publisher: Springer Science and Business Media LLC
Date: 31-07-2009
Publisher: BMJ
Date: 04-2021
DOI: 10.1136/BMJGH-2020-004544
Abstract: To improve child survival, it is necessary to describe and understand the spatial and temporal variation of factors associated with child survival beyond national aggregates, anchored at decentralised health planning units. Therefore, we aimed to provide subnational estimates of factors associated with child survival while elucidating areas of progress, stagnation and decline in Kenya. Twenty household surveys and three population censuses conducted since 1989 were assembled and spatially aligned to 47 subnational Kenyan county boundaries. Bayesian spatio-temporal Gaussian process regression models accounting for inadequate s le size and spatio-temporal relatedness were fitted for 43 factors at county level between 1993 and 2014. Nationally, the coverage and prevalence were highly variable with 38 factors recording an improvement. The absolute percentage change (1993–2014) was heterogeneous ranging between 1% and 898%. At the county level, the estimates varied across space and over time with a majority showing improvements after 2008 which was preceded by a period of deterioration (late-1990 to early-2000). Counties in Northern Kenya were consistently observed to have lower coverage of interventions and remained disadvantaged in 2014 while areas around Central Kenya had and historically have had higher coverage across all intervention domains. Most factors in Western and South-East Kenya recorded moderate intervention coverage although having a high infection prevalence of both HIV and malaria. The heterogeneous estimates necessitates prioritisation of the marginalised counties to achieve health equity and improve child survival uniformly across the country. Efforts are required to narrow the gap between counties across all the drivers of child survival. The generated estimates will facilitate improved benchmarking and establish a baseline for monitoring child development goals at subnational level.
Publisher: Springer Science and Business Media LLC
Date: 20-11-2009
Publisher: Springer Science and Business Media LLC
Date: 11-05-2011
Publisher: Elsevier BV
Date: 12-2002
DOI: 10.1016/S1471-4922(02)02374-7
Abstract: Climate has a significant impact on malaria incidence and we have predicted that forecast climate changes might cause some modifications to the present global distribution of malaria close to its present boundaries. However, it is quite another matter to attribute recent resurgences of malaria in the highlands of East Africa to climate change. Analyses of malaria time-series at such sites have shown that malaria incidence has increased in the absence of co-varying changes in climate. We find the widespread increase in resistance of the malaria parasite to drugs and the decrease in vector control activities to be more likely driving forces behind the malaria resurgence.
Publisher: Elsevier BV
Date: 08-2021
Publisher: Springer Science and Business Media LLC
Date: 12-2002
DOI: 10.1038/420628A
Publisher: Springer Science and Business Media LLC
Date: 05-08-2009
Abstract: Clinical malaria has proven an elusive burden to enumerate. Many cases go undetected by routine disease recording systems. Epidemiologists have, therefore, frequently defaulted to actively measuring malaria in population cohorts through time. Measuring the clinical incidence of malaria longitudinally is labour-intensive and impossible to undertake universally. There is a need, therefore, to define a relationship between clinical incidence and the easier and more commonly measured index of infection prevalence: the "parasite rate". This relationship can help provide an informed basis to define malaria burdens in areas where health statistics are inadequate. Formal literature searches were conducted for Plasmodium falciparum malaria incidence surveys undertaken prospectively through active case detection at least every 14 days. The data were abstracted, standardized and geo-referenced. Incidence surveys were time-space matched with modelled estimates of infection prevalence derived from a larger database of parasite prevalence surveys and modelling procedures developed for a global malaria endemicity map. Several potential relationships between clinical incidence and infection prevalence were then specified in a non-parametric Gaussian process model with minimal, biologically informed, prior constraints. Bayesian inference was then used to choose between the candidate models. The suggested relationships with credible intervals are shown for the Africa and a combined America and Central and South East Asia regions. In both regions clinical incidence increased slowly and smoothly as a function of infection prevalence. In Africa, when infection prevalence exceeded 40%, clinical incidence reached a plateau of 500 cases per thousand of the population per annum . In the combined America and Central and South East Asia regions, this plateau was reached at 250 cases per thousand of the population per annum . A temporal volatility model was also incorporated to facilitate a closer description of the variance in the observed data. It was possible to model a relationship between clinical incidence and P. falciparum infection prevalence but the best-fit models were very noisy reflecting the large variance within the observed opportunistic data s le. This continuous quantification allows for estimates of the clinical burden of P. falciparum of known confidence from wherever an estimate of P. falciparum prevalence is available.
Publisher: Springer Science and Business Media LLC
Date: 12-2007
Publisher: Springer Science and Business Media LLC
Date: 02-2002
DOI: 10.1038/415905A
Publisher: Public Library of Science (PLoS)
Date: 06-07-2010
Publisher: Public Library of Science (PLoS)
Date: 24-03-2009
Publisher: Public Library of Science (PLoS)
Date: 15-09-2011
Publisher: Wiley
Date: 02-2006
Publisher: Elsevier BV
Date: 11-2010
Publisher: Centers for Disease Control and Prevention (CDC)
Date: 09-2005
Abstract: Records from tea estates in the Kericho district in Kenya show that malaria reemerged in the 1980s. Renewed epidemic activity coincided with the emergence of chloroquine-resistant Plasmodium falciparum malaria and may have been triggered by the failure of antimalarial drugs. Meteorologic changes, population movements, degradation of health services, and changes in Anopheles vector populations are possible contributing factors. The highland malaria epidemics of the 1940s were stopped largely by sporontocidal drugs, and combination chemotherapy has recently limited transmission. Antimalarial drugs can limit the pool of gametocytes available to infect mosquitoes during the brief transmission season.
Publisher: Elsevier BV
Date: 03-2011
Publisher: Elsevier BV
Date: 11-2010
Publisher: Centers for Disease Control and Prevention (CDC)
Date: 12-2002
Abstract: Recent epidemics of Plasmodium falciparum malaria have been observed in high-altitude areas of East Africa. Increased malaria incidence in these areas of unstable malaria transmission has been attributed to a variety of changes including global warming. To determine whether the reemergence of malaria in western Kenya could be attributed to changes in meteorologic conditions, we tested for trends in a continuous 30-year monthly malaria incidence dataset (1966-1995) obtained from complete hospital registers at a Kenyan tea plantation. Contemporary monthly meteorologic data (1966-1995) that originated from the tea estate meteorologic station and from global climatology records were also tested for trends. We found that total hospital admissions (malaria and nonmalaria) remained unchanged while malaria admissions increased significantly during the period. We also found that all meteorologic variables showed no trends for significance, even when combined into a monthly suitability index for malaria transmission. We conclude that climate changes have not caused the highland malaria resurgence in western Kenya.
Publisher: Oxford University Press (OUP)
Date: 06-01-2016
Publisher: Springer Science and Business Media LLC
Date: 26-05-2011
Publisher: Springer Science and Business Media LLC
Date: 21-08-2008
Publisher: Springer Science and Business Media LLC
Date: 21-10-2008
Publisher: Elsevier
Date: 2012
Publisher: Springer Science and Business Media LLC
Date: 07-02-2011
Publisher: Oxford University Press (OUP)
Date: 2005
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Robert Snow.