Heckman-type selection models to obtain unbiased estimates with missing measures outcome: theoretical considerations and an application to missing birth weight data

In low-income settings, key outcomes such as biomarkers or clinical assessments are often missing for a substantial proportion of the study population. The aim of this study was to assess the extent to which Heckman-type selection models can create unbiased estimates in such settings.; We introduce the basic Heckman model in a first stage, and then use simulation models to compare the performance of the model to alternative approaches used in the literature for missing outcome data, including complete case analysis (CCA), multiple imputations by chained equations (MICE) and pattern imputation with delta adjustment (PIDA). Last, we use a large population-representative data set on antenatal supplementation (AS) and birth outcomes from Côte d'Ivoire to illustrate the empirical relevance of this method.; All models performed well when data were missing at random. When missingness in the outcome data was related to unobserved determinants of the outcome, large and systematic biases were found for CCA and MICE, while Heckman-style selection models yielded unbiased estimates. Using Heckman-type selection models to correct for missingness in our empirical application, we found supplementation effect sizes that were very close to those reported in the most recent systematic review of clinical AS trials.; Missingness in health outcome can lead to substantial bias. Heckman-selection models can correct for this selection bias and yield unbiased estimates, even when the proportion of missing data is substantial

Caractérisation saisonnière des eaux de puits à usage maraîchère et domestique de Korhogo (Côte d’Ivoire)

Cette étude a été conduite afin de déterminer les caractéristiques physico-chimiques etmicrobiologiques des eaux de puits à usages domestiques et agricoles du département de Korhogo. Les paramètres physico-chimiques et microbiologiques ont été analysés suivants les techniques décrites par AFNOR. 18 puits ont été échantillonnés durant les saisons pluvieuse et sèche. Les résultats des analyses physico-chimiques montrent que les eaux sont légèrement acides et faiblement minéralisées avec des valeurs de conductivités comprises entre 59,5 et 225 μS/cm. Les concentrations en oxygène dissous sont comprises entre 0,78 mg/l et 4,93 mg/l. Par ailleurs, les teneurs en nitrate et ammonium de ces eaux prouvent qu'elles ne sont pas assujetties à une pollution azotée. En outre, la présence de pesticides tels que le chlorpyriphos-éthyle, le parathion-éthyle, le thiaméthoxame, le spirodiclofen, le deltamethrine, le zoxamide et le carbaryl a été souligné dans 16 puits prospectés. La teneur résiduelle des pesticides atteint 3,61 μg/l dans certains puits. La concentration totale des pesticides décelés dans les puits varie entre 0,01 μg/l et 6,36 μg/l. L’analyse microbiologique a mis en évidence la présence de coliformes totaux à des teneurs significativement élevées (2,3.103 UFC/ml). Aussi, la consommation de ces eaux présente t- elle des risques sanitaires pour les populations.Mots clés : Eaux souterraines, pollution, microorganismes, pesticides, Côte d’Ivoire

Typology, technical efficiency and scale economy of dibiteries in Dakar, Senegal

In recent years, a profound transformation has been observed in the eating habits of the populations of African cities, induced by accelerated socioeconomic and demographic growth. In Senegal, these changes have manifested in the proliferation of collective informal catering enterprises, such as the '; dibiteries; ', where the roasted meat of sheep is prepared and sold. The rise of the average household income has contributed substantially to increasing levels of meat consumption, leading to the expansion of the; dibiteries; . The purpose of the current work was to evaluate the managerial performance of these establishments in Dakar, Senegal.; To achieve this, a cross-sectional study was conducted among 152 ; dibiteries; using a questionnaire. Efficiency scores were determined via the data envelopment analysis method. The pure technical scores thereby obtained were subsequently used as dependent variables in a Tobit model to identify the socioeconomic determinants of; dibiterie; efficiency.; The resulting average score of the; dibiteries; suggests that the majority are operating inefficiently (79.6%). Moreover, it was demonstrated that this inefficiency seems to be related to scale rather than technical issues. However, few of the; dibiteries; assessed (20.4%) were nevertheless in a situation of constant scale economy. Among the socioeconomic variables tested, experience, leadership (family or individual-run), the ownership status of the restaurant building (own or lease) and the type of workforce (family, recruited, mixed or without) had a significant impact on the efficiency of the establishments.; The scale economy and waste reduction in food production can result in economic gains that can in turn be used in the safety of finished products. Indeed, by following best practices,; dibiteries; can make gains which could be used to invest in good hygiene practices on handwashing, cleaning and disinfecting grilling tools, optimizing work space and training staff

Relations sociales et influence économique dans la chaîne de valeur du lait local au Sénégal

Despite its socio-economic importance, the local milk sector in Senegal is struggling to overcome the factors that determine its development. The milk value chain study took place in the Kaolack region with 349 stakeholders and assessed the market risk factors and the level of socio-economic influence of the stakeholders. Results show that the overall added value is significant according to the income structure, relatively unequal and captured mostly by women with traditional processing of local milk. The regional economic exchange network is almost absent and the gap is filled by a sparse social network. Thus, the development of the local milk value chain requires a mobilization of both economic and social networks and a better redistribution of the added value to the different stakeholders. Keywords: Value chain, Added value, milk, social network, economic integrationMalgré son importance socio-économique, la filière lait local au Sénégal peine à maîtriser les déterminants de son développement. Une étude de cette chaîne de valeur s’est déroulée dans la région de Kaolack auprès de 349 acteurs et a permis d’évaluer les facteurs de risque du marché et le niveau d’influence socio-économique des acteurs. Les résultats montrent que la valeur ajoutée globale est forte selon la structure du revenu, inégalitaire et captée en majorité par les transformatrices artisanales du lait local. Le réseau d’échange économique régional est quasi-absent et comblé par un réseau social peu dense. Ainsi, le développement de la chaîne de valeur du lait local doit passer par une mobilisation à la fois des relations économiques et sociales et une meilleure redistribution de la valeur ajoutée aux différents acteurs. Mots-clés: Chaîne de valeur, Valeur ajoutée, lait, réseau social, intégration économiqu

Relations sociales et influence économique dans la chaîne de valeur du lait local au Sénégal

Malgré son importance socio-économique, la filière lait local au Sénégal peine à maîtriser les déterminants de son développement. Une étude de cette chaîne de valeur s’est déroulée dans la région de Kaolack auprès de 349 acteurs et a permis d’évaluer les facteurs de risque du marché et le niveau d’influence socio-économique des acteurs. Les résultats montrent que la valeur ajoutée globale est forte selon la structure du revenu, inégalitaire et captée en majorité par les transformatrices artisanales du lait local. Le réseau d’échange économique régional est quasi-absent et comblé par un réseau social peu dense. Ainsi, le développement de la chaîne de valeur du lait local doit passer par une mobilisation à la fois des relations économiques et sociales et une meilleure redistribution de la valeur ajoutée aux différents acteurs. Mots-clés: Chaîne de valeur, Valeur ajoutée, lait, réseau social, intégration économiqu

Pregnancy-related morbidity and risk factors for fatal foetal outcomes in the Taabo health and demographic surveillance system, Côte d'Ivoire

Reliable, population-based data on pregnancy-related morbidity and mortality, and risk factors for fatal foetal outcomes are scarce for low- and middle-income countries. Yet, such data are essential for understanding and improving maternal and neonatal health and wellbeing.; Within the 4-monthly surveillance rounds of the Taabo health and demographic surveillance system (HDSS) in south-central Côte d'Ivoire, all women of reproductive age identified to be pregnant between 2011 and 2014 were followed-up. A questionnaire pertaining to antenatal care, pregnancy-related morbidities, delivery circumstances, and birth outcome was administered to eligible women. Along with sociodemographic information retrieved from the Taabo HDSS repository, these data were subjected to penalized maximum likelihood logistic regression analysis, to determine risk factors for fatal foetal outcomes.; A total of 2976 pregnancies were monitored of which 118 (4.0%) resulted in a fatal outcome. Risk factors identified by multivariable logistic regression analysis included sociodemographic factors of the expectant mother, such as residency in a rural area (adjusted odds ratio (aOR) = 2.87; 95% confidence interval (CI) 1.31-6.29) and poorest wealth tertile (aOR = 1.79; 95% CI 1.02-3.14), a history of miscarriage (aOR = 23.19; 95% CI 14.71-36.55), non-receipt of preventive treatment such as iron/folic acid supplementation (aOR = 3.15; 95% CI 1.71-5.80), only two doses of tetanus vaccination (aOR = 2.59; 95% CI 1.56-4.30), malaria during pregnancy (aOR = 1.94; 95% CI 1.21-3.11), preterm birth (aOR = 4.45; 95% CI 2.82-7.01), and delivery by caesarean section (aOR = 13.03; 95% CI 4.24-40.08) or by instrumental delivery (aOR = 5.05; 95% CI 1.50-16.96). Women who paid for delivery were at a significantly lower odds of a fatal foetal outcome (aOR = 0.39; 95% CI 0.25-0.74).; We identified risk factors for fatal foetal outcomes in a mainly rural HDSS site of Côte d'Ivoire. Our findings call for public health action to improve access to, and use of, quality services of ante- and perinatal care

Traditional milk transformation schemes in Côte d'Ivoire and their impact on the prevalence of Streptococcus bovis complex bacteria in dairy products

The Streptococcus bovis/Streptococcus equinus complex (SBSEC) and possibly Streptococcus infantarius subsp. infantarius (Sii) are associated with human and animal diseases. Sii predominate in spontaneously fermented milk products with unknown public health effects. Sii/SBSEC prevalence data from West Africa in correlation with milk transformation practices are limited. Northern Côte d'Ivoire served as study area due to its importance in milk production and consumption and to link a wider Sudano-Sahelian pastoral zone of cross-border trade. We aimed to describe the cow milk value chain and determine Sii/SBSEC prevalence with a cross-sectional study. Dairy production practices were described as non-compliant with basic hygiene standards. The system is influenced by secular sociocultural practices and environmental conditions affecting product properties. Phenotypic and molecular analyses identified SBSEC in 27/43 (62.8%) fermented and 26/67 (38.8%) unfermented milk samples. Stratified by collection stage, fermented milk at producer and vendor levels featured highest SBSEC prevalence of 71.4% and 63.6%, respectively. Sii with 62.8% and 38.8% as well as Streptococcus gallolyticus subsp. macedonicus with 7.0% and 7.5% were the predominant SBSEC species identified among fermented and unfermented milk samples, respectively. The population structure of Sii/SBSEC isolates seems to reflect evolving novel dairy-adapted, non-adapted and potentially pathogenic lineages. Northern Côte d'Ivoire was confirmed as area with high Sii presence in dairy products. The observed production practices and the high diversity of Sii/SBSEC supports in-depth investigations on Sii ecology niche, product safety and related technology in the dairy value chain potentially affecting large population groups across sub-Saharan Africa

Health & Demographic Surveillance System Profile: The Taabo Health and Demographic Surveillance System, Côte d'Ivoire

The Taabo Health and Demographic Surveillance System (HDSS) is located in south-central Côte d'Ivoire, approximately 150 km north-west of Abidjan. The Taabo HDSS started surveillance activities in early 2009 and the man-made Lake Taabo is a key eco-epidemiological feature. Since inception, there has been a strong interest in research and integrated control of water-associated diseases such as schistosomiasis and malaria. The Taabo HDSS has generated setting-specific evidence on the impact of targeted interventions against malaria, schistosomiasis and other neglected tropical diseases. The Taabo HDSS consists of a small town, 13 villages and over 100 hamlets. At the end of 2013, a total population of 42 480 inhabitants drawn from 6707 households was under surveillance. Verbal autopsies have been conducted to determine causes of death. Repeated cross-sectional epidemiological surveys on approximately 5-7% of the population and specific, layered-on haematological, parasitological and questionnaire surveys have been conducted. The Taabo HDSS provides a database for surveys, facilitates interdisciplinary research, as well as surveillance, and provides a platform for the evaluation of health interventions. Requests to collaborate and to access data are welcome and should be addressed to the secretariat of the Centre Suisse de Recherches Scientifiques en Côte d'Ivoire: [[email protected]