1,720,983 research outputs found
Evaluation de l'impact d'une pulvérisation intra-domiciliaire en saison sèche sur la transmission du paludisme le long du fleuve Niger, Mali
No full textLa lutte anti-vectorielle est essentiellement basée sur l'utilisation des moustiquaires imprégnées d'insecticide à longue durée (MILD) et la pulvérisation intra-domiciliaire (PID). Mais le succès de toute méthode de lutte anti-vectorielle et son coût dépendent de son adaptation aux conditions environnementales locales. Le coût élevé de la PID peut limiter sa généralisation et sa pérennité d'où la nécessité de développer de nouvelles approches moins onéreuses adaptées aux zones d'interventions. C'est dans cet ordre d'idée que le présent travail a été entrepris dont l'objet est d'évaluer la faisabilité et l'impact possible d'une PID en saison sèche dans les hameaux riverains du fleuve Niger ainsi que dans leurs villages mères sur la transmission du paludisme. Cette étude s'est déroulée en trois volets : i) la PID, effectuée par des operateurs expérimentés du 10 au 25 Février 2010 ; ii) une évaluation de l'efficacité biologique de l'insecticide utilisé par le cône test de l'OMS 2, 4, 7 et 9 mois après la PID ; iii) un monitorage des paramètres entomologiques de la transmission dans des hameaux de pêche où eu lieu la PID (tests) et dans d'autres où il n'y a pas eu de PID (contrôle) ainsi que dans leurs villages mères respectifs (tests vs témoins) de mars à décembre 2010 par la capture au pyrèthre dans les habitations humaines. Nos résultats ont montré un taux global de couverture de 88,8 p.100 . (978/1101) des cases. La population couverte était de 2250 habitants dont 21,5 p.100 étaient des sujets à risque du paludisme (enfants de inférieur à 5 ans et femmes enceintes). L'efficacité biologique de l'insecticide a varié de 100 p.100 deux mois après la PID dans les deux types de case (tôle et paille) à 36 p.100 et 6,11 p.100 neuf mois après la PID respectivement dans les cases en tôle et en paille. La densité et l'agressivité d'An. gambiae s.l. étaient significativement plus faibles dans les hameaux tests comparés aux témoins ainsi que dans les villages mères tests comparés aux témoins jusqu'à 4 mois après la PID. Les mêmes tendances étaient observées avec les TIEs mais seulement 3 mois après la PID. Par contre aucune tendance de réduction n'a été observée avec les taux d'anthropophilie et d'infection. Une seule PID avec la lambda-cyhalothrine pendant la saison sèche le long du fleuve ne protégerait pas la population d'une transmission toute l'année, mais réduirait celle-ci de façon significative au moins quatre mois après sa mise en oeuvre
Geostatistical models of malaria and associated morbidity among preschool-aged children in Nigeria
Full text linkMalaria remains a threat to the lives of millions of children in tropical and subtropical countries. It is still a disease of public health significance, because of its role as a major cause of morbidity and mortality among the vulnerable group, specifically children under the age of five in the endemic countries. Although, substantial progress has been made in the control and prevention of the disease especially during the past 15 years due to multilateral commitment to malaria control, and this has led to reduction in the burden attributed to the disease. During the same period, financial resources for malaria prevention and control have been like up to twenty-fold increase, which led to widespread scale-up of coverage of the core malaria control interventions: insecticide-treated nets (ITNs), indoor residual spraying (IRS), and prompt treatment of clinical malaria cases with artemisinin-based combination therapy (ACT).
High resolution disease risk distribution is essential information in successful control activities, because of its versatility in cost effective planning, surveillance, and evaluation of such activities. Spatial statistical modelling provides rigorous inferential framework for high resolution disease risk mapping. It is a data-driven approach, which is used to build mathematical relationship between geo-referenced disease data and potential predictors (environmental and socio-demographic factors). Such model always includes the location specific random effect to explain the spatial correlation in the disease data that are due to common exposure in neighbouring locations. Geostatistical model are highly parameterized, nevertheless, a Bayesian geostatistical framework provides flexible and rigorous inferential methods for modelling such data. Computation tools such as simulation based Markov chain Monte Carlo (MCMC) or numerical approximation approach as integrated nested Laplace approach (INLA) are mostly engaged for such model fit.
Nigeria is one of the countries in sub-Sahara Africa with high prevalence of malaria and its related morbidity and mortality among children under the age of five years. Contemporary high resolution estimates of malaria prevalence needed for control activities are lacking. Also the precise nature of malaria transmission and all-cause mortality remains unclear. Furthermore, spatial analysis of the effect of malaria intervention on the risk of the disease at the national and sub-national level is not yet done. Moreover, anaemia prevalence in Nigeria is high; however, its relationship with malaria burden among children under the age of five is not fully understood, coupled with lack of high resolution estimates of the spatial distribution of the risk in the country.
This thesis aims to address these knowledge gaps by developing data driven Bayesian geostatistical models for analyzing spatially referenced data and also to provide tools for malaria and its related morbidity control programmes in the country. The analysis in this work is based on data from the contemporary nationwide survey which are malaria indicator survey (MIS) and demography and health survey (DHS). Roll back malaria initiative in its global effort of coordinating malaria control developed the MIS to collect malaria related burden data on children under the age of five, and it is always conducted during the high transmission season. MIS is standardized in terms of survey design, questionnaire and implementation time.
In chapter 2, we implemented a Bayesian geo-statistical model to analyze the first nationally representative malaria parasitaemia prevalence data in Nigeria to produce high resolution risk estimates of spatial distribution of malaria prevalence in the country, and also derived number of infected children at the sub-national level. Rigorous Bayesian variable selections were incorporated in the spatial models in order to select the best environmental predictors of malaria and its functional form. The approach identifies important risk factor to build Bayesian model of malaria risk in Nigeria. Also, various interventions coverage indicators were derived to assess their effect on malaria risk. The high resolution estimates show that malaria risk varies between 19.6% and 47.7% in Lagos and Osun state, respectively. However, household coverage indicators of intervention did not indicates association with malaria risk.
Chapter 3, present the assessment of the spatial effect of ITN use by children less than five years on the malaria parasitaemia prevalence at the first administrative, after adjusting for climatic and socio-demographic factors. Bayesian geostatistical model with spatial varying coefficient at the sub-national level was used to explore the malaria risk-intervention relationship. Smooth map of intervention effect was produced based on the parameter estimates of ITN use at the first administrative level.
In chapter 4, we employed a joint Bayesian geo-statistical Cox model with log constant baseline hazard and binomial geostatistical logistic regression models to relate mortality with malaria prevalence, and take into account spatial misalignment between DHS and MIS datasets, to evaluate the contribution of malaria prevalence to all-cause mortality among children less than five year of age. The mortality model was implemented separately for infant 0-6 months, 7-11 months, and older children. The model adjusted for socio-demographic factors known to be associated with risk of death among this vulnerable group. We also produced smooth map of residual variation not accounted for by the factors in our model.
Chapter 5 presents the geostatistical analysis of haemoglobin level/anaemia risk. The study assessed malaria burden on anaemia risk among the children after adjusting for helminthiasis and schistosomiasis, and socio-demographic factors. We make use of some of these factors as available at individual level, and also use the predicted prevalence of those that were not directly obtained with the haemoglobin data, which led to the implementation of Bayesian geostatistical models (Gaussian and logistic) with measurement error, to incorporate the uncertainty in the predicted estimates. The predictive models were used to obtain high resolution estimates of geographical distribution of anaemia risk/haemoglobin level concentration in the country. The population adjusted prevalence show that approximately every 7 out of 10 children under the age of five years are anaemic in the country.
The work in this thesis contributes improved Bayesian statistical methods for generating reliable estimate of disease burden (malaria parasitaemia prevalence, anaemia prevalence and number of infected children) at high spatial resolution. It also adds to the evidence of improve method of evaluating the effect of malaria interventions on disease prevalence. Furthermore, the generated model based risk maps constitute important information to national malaria control programme, because of its resourcefulness in right targeting of high risk area to achieve disease reduction, and eventually elimination. Finally, our work provides essential yardstick on which newer estimates could be compared as new data becomes available and control efforts continue
Spatial distribution of malaria transmission in relationship to "Anopheles gambiae" complex members in Sudan savanna and irrigated rice cultivation areas of Mali
Full text linkMalaria remains a major public health problem that is exacerbated by poor
implementation of control measures, and by the spread of drug-resistant parasites and
insecticide resistant vectors. Preventive measures, including those targeted at vectors, are one
of the four basic elements of the global malaria control strategy. The control methods to use
should be selective and specific to the control area. The success of the approach of selective
and targeted interventions requires a good stratification of control areas, which should be
based on mapping of malaria risk and vector species distribution.
The goal of this thesis was to enhance our understanding of the relationship between
the distribution of members of Anopheles gambiae complex and climatic and environmental
conditions, to describe their spatial and temporal distribution, to quantify their unique
contribution to malaria transmission, and to produce attributed malaria risk maps of Mali. We
used Bayesian geostatistical modeling, implemented via Markov chain Monte Carlo
simulation (MCMC), which can quantify the relationship between environmental factors and
the species distribution by taking into account the spatial dependence present in the data in a
flexible way that allows simultaneous estimation of all model parameters. In addition,
Bayesian kriging enables model-based prediction together with the prediction error, a feature which is not possible in the classical kriging.
The analyses described in chapters 2 and 3 identified environmental factors related to
the distribution of a) the two major species (An. arabiensis and An. gambiae s.s.) which
compose the An. gambiae complex and b) the chromosomal (Bamako, Mopti, Savanna
Hybrids) forms of An. gambiae s.s., and produced maps of the geographical distribution of the
species and chromosomal forms. Estimation of the contribution of species and chromosomal
forms to malaria transmission in Mali is described in Chapter 4; the spatio-temporal
distribution of An. gambiae complex densities and its chromosomal (Mopti, Bamako, Savanna, Hybrids) forms in a Sudan savanna village is examined in Chapter 5; the
investigation of malaria vector ecology during the dry season and its implication for vector
control is described in Chapter 6, and Chapter 7 presents the spatial pattern of malaria
transmission in the rice cultivation area of the Office du Niger.
The maps produced in chapters 2 & 3 showed higher frequencies of An. arabiensis in
the drier Savanna areas and An. gambiae s.s. in the flooded/irrigated areas of the inner delta of
Niger river, the southern Savanna, along rivers and in the Sahel. The Mopti form was found in
the same ecological area as An. arabiensis. In addition, it occupied the flooded/irrigated areas
of the inner delta of Niger River. The Savanna form prefers the Sudan Savanna areas and the
Bamako form was confined around Bamako city and in part of Sikasso region (South of
Mali). Analyses in Chapter 4 indicated that high malaria risk was associated with insecticide
resistance gene (kdr) carriers (Bamako/Savanna chromosomal) and Hybrids compared to the
non-carriers An. arabiensis and the Mopti chromosomal form, although the association was
not significant. The attributed risk maps of the different species and subspecies indicated that
in the middle West and South East part of the country malaria transmission risk is mainly due
to An. arabiensis, in the irrigated/flooded areas malaria risk is attributed to the Mopti form, in the southern part to the Savanna/Bamako forms and in the southern areas of the region of
Kayes to the hybrids. Thus these results suggest that insecticide control measures must be
strengthened in the Sahelian (epidemic prone area) and irrigated/flooded areas where An.
arabiensis and the Mopti chromosomal form, which have no or lower frequency of insecticide
resistance gene, prevail. Any vector control by means of insecticides in the Southern part of
the country, where the S molecular form (Savanna and Bamako) predominates, must be
accompanied by a close insecticide resistance monitoring system. The analyses carried out in Chapter 5 and 6 on the spatial distribution of the sibling
species of An. gambiae complex in a savanna village showed that the distribution of mosquito
densities was concentric with higher densities clustering at the periphery of the village at the
beginning of the rainy season and during the dry season. This distribution was patchy during
the middle and the end of the rainy season. The chromosomal forms were sympatric
throughout the seasons. There was a spatial clustering in their relative frequency distribution
changing over time in the village. The Mopti chromosomal form was the most abundant at the
beginning and middle of the rainy season and the Bamako form at the end of the rainy season.
Larval habitats monitoring showed that in the main village of Bancoumana nearly all larval
habitats were human-made, rain-dependent and dried out 10-12 weeks after the end of the
rainy season. At the same time, numerous natural puddles highly productive for anopheline
larvae even during the dry season were located in the fishermen’s hamlets. These were
adjacent to the receding Niger River bed and 5 km away from the main village. Larval
habitats in Bancoumana were re-colonized shortly after rainfall suggesting that mosquitoes
emerging from the riverbed are an important source for the rain-fed water bodies of
Bancoumana. This observation indicates that control interventions targeting the Mopti form
should be implemented at the beginning and middle of the rainy season, while those targeting the Bamako form should be done at the end of the rainy season. In addition, appropriate
vector control implemented in the fishermen’s hamlet during the dry season and at the
periphery of the main village at the beginning of the rainy season may be feasible, sustainable
at low cost and may ameliorate malaria transmission in this area.
In chapter 7, the analyses of malaria transmission parameters in the rice cultivation
area of the Office du Niger indicated a strong spatial correlation in mosquito densities, which
is related to the rice cultivation environment. However, the spatial correlation observed in the
parous rate (PR) and human blood index (HBI) was weak suggesting that these parameters are more closely related to local conditions such as population behavior and economic status,
and/or the presence of animals rather than similar environment over large areas. Since both
the PR and HBI measure the vector-human contact rate, and hence the potential for malaria
transmission intensity, attention must be paid to the local variations when implementing
control strategies in rice cultivation areas.
This work makes a substantial contribution to the mapping of the spatial distribution
of malaria vector species and subspecies which was previously limited by the lack of field
data and appropriate statistical analyses. It also provides valuable information for
conventional vector control as well as future implementation for genetically manipulated
mosquitoes control method
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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