Surveys of Arboviruses Vectors in Four Cities Stretching Along a Railway Transect of Burkina Faso: Risk Transmission and Insecticide Susceptibility Status of Potential Vectors

Background: A severe outbreak of dengue occurred in Burkina Faso in 2016, with the most cases reported in Ouagadougou, that highlights the necessity to implement vector surveillance system. This study aims to estimate the risk of arboviruses transmission and the insecticide susceptibility status of potential vectors in four sites in Burkina Faso.Methods: From June to September 2016, house-to-house cross sectional entomological surveys were performed in four cities stretching along a southwest-to-northeast railway transect. The household surveys analyzed the presence of Aedes spp. larvae in containers holding water and the World Health Organization (WHO) larval abundance indices were estimated. WHO tube assays was used to evaluate the insecticide susceptibility within Aedes populations from these localities.Results: A total of 31,378 mosquitoes' larvae were collected from 1,330 containers holding water. Aedes spp. was the most abundant (95.19%) followed by Culex spp. (4.75%). Aedes aegypti a key vector of arboviruses (ARBOV) in West Africa was the major Aedes species found (98.60%). The relative larval indices, house index, container and Breteau indexes were high, up to 70, 35, and 10, respectively. Aedes aegypti tended to breed mainly in discarded tires and terracotta jars. Except in Banfora the western city, Ae. aegypti populations were resistant to deltamethrin 0.05% in the other localities with low mortality rate under 20% in Ouagadougou whereas they were fully susceptible to malathion 5% whatever the site. Intermediate resistance was observed in the four sites with mortality rates varying between 78 and 94% with bendiocarb 0.1%.Conclusions: This study provided basic information on entomological indices that can help to monitor the risks of ARBOV epidemics in the main cities along the railway in Burkina Faso. In these cities, all larval indices exceeded the risk level of ARBOV outbreak. Aedes aegypti the main species collected was resistant to deltamethrin 0.05% and bendiocarb 0.1% whereas they were fully susceptible to malathion 5%. The monitoring of insecticide resistance is also important to be integrated to the vector surveillance system in Burkina Faso

Applications of Remote Sensing to the Epidemiology of Infectious Diseases: Some Examples

International audienceInfectious diseases are caused by a pathogenic microorganism (virus, bacterium, parasite or fungus) and have a significant impact on public and animal health. In public health, they are one of the leading causes of death and are priorities in the poorest countries. In animal health, they can be devastating and radical measures are taken to prevent them from spreading. Infectious diseases therefore have major economic consequences, in terms of both healthcare and livestock production losses. In recent decades, we have seen the emergence of a significant number of infectious diseases, such as chikungunya, avian influenza and Ebola. These diseases have spread around the world all the more dramatically due to the rapid movement of populations and goods. The majority of pathogenic agents responsible for these emergences are zoonotic (transmitted from animals to humans or vice versa). There has also been a significant increase in vector-borne diseases – that is diseases whose pathogenic agent is transmitted through the intermediary of a vector. Vectors are arthropods (e.g. mosquitoes, fleas, sand flies and reduviid bugs) and acarids (e.g. ticks). One example is the mosquito Aedes albopictus, more commonly known as the “tiger mosquito”, which is a vector for the chikungunya and dengue viruses. The geographical distribution of this mosquito is increasing year by year. This species was responsible for the first indigenous cases of chikungunya in France in 2010

Processus d’urbanisation et inégalités de santé : l’exemple d’une ville moyenne africaine, Bobo-Dioulasso (Burkina Faso)

International audienceA veni

Can Urbanization, Social and Spatial Disparities Help to Understand the Rise of Cardiometabolic Risk Factors in Bobo-Dioulasso ? A Study in a Secondary City of Burkina Faso, West Africa

International audienceBackground: Unplanned urbanization plays a key role in chronic disease growth. This population-based cross-sectional study assessed the occurrence of cardiometabolic risk factors in Bobo-Dioulasso and their association with urbanization conditions.Methods: Through spatial sampling, four Bobo-Dioulasso sub-spaces were selected for a population survey to measure the adult health status. Yéguéré, Dogona, Tounouma and Secteur 25 had very different urbanization conditions (position within the city; time of creation and healthcare structure access). The sample size was estimated at 1000 households (250 for each sub-space) in which one adult (35 to 59-year-old) was randomly selected. Finally, 860 adults were surveyed. Anthropometric, socioeconomic and clinical data were collected. Arterial blood pressure was measured and blood samples were collected to assess glycemia.Results: Weight, body mass index and waist circumference (mean values) and serum glycemia (83.4 mg/dL ± 4.62 mmol/L) were significantly higher in Tounouma, Dogona, and Secteur 25 than in Yéguéré; the poorest and most rural-like sub-space (p = 0.001). Overall, 43.2%, 40.5%, 5.3% and 60.9% of participants had overweight, hypertension, hyperglycemia and one or more cardiometabolic risk markers, respectively.Conclusions: Bobo-Dioulasso is unprepared to face this public health issue and urgent responses are needed to reduce the health risks associated with unplanned urbanization

Analyse de la distribution socio-spatiale du paludisme dans une ville moyenne ouest africaine, Bobo-Dioulasso (Burkina Faso)

International audienceOccurring with a time delay compared to what was observed elsewhere in the world, urbanization is expanding in Africa. Incontrast to what happened in Europe, the decline of infectious diseases is not perceived, although non communicable diseasesincrease. Thus, malaria which should disappear from the cities because of environment pollution persists in cities. The adaptation ofthe vectors to water pollution could explain its persistence, with also some practices like urban agriculture. Under these conditions,transmission of the disease could be unequal and populations may be exposed to a different risk. The study conducted in Bobo-Dioulasso, second city of Burkina Faso, aimed to analyze the distribution of malaria in differently urbanized districts, and to identifythe risk factors which may explain its spatial distribution. It appeared that the old central districts were more exposed to malaria thanthe recent peripheral ones. Moreover, spatial disparities could be observed inside districts. The determinants of malaria emphasizedthe importance of the environment (proximity of lowlands) and social factors like education level of the mother and socio-economiclevel of the household. This kind of study allowed defining health patterns of areas and populations according to methodologiesadapted to the urban context. Beyond the demonstration of the importance of studies crossing urban diversity and health, ourambition was to underline the need for a dialogue between health and urban policies for a better control of diseases like malaria,at the time of the implementation of their elimination.ce que l’on avait pu observer en Europe, elle ne s’accompagne pas de la disparition des maladies de type infectieux ou parasitaire,bien que le poids des maladies non transmissibles se fasse largement sentir. Ainsi, le paludisme dont on prédisait la disparition dansles villes souvent perçues comme délétères du fait notamment de la pollution de l’environnement, y persiste. L’adaptation desmoustiques vecteurs de la maladie à la pollution est une des causes de ce maintien mais aussi certaines pratiques spatiales dela population comme la persistance d’une agriculture périurbaine, voire même intra urbaine. Dans ces conditions, la transmissionde la maladie pourrait être inégale et les populations ne seraient donc pas soumises au même risque. L’étude conduite à Bobo-Dioulasso, seconde ville du Burkina Faso, avait pour objectif d’analyser la distribution du paludisme dans des quartiers différemmenturbanisés et d’identifier les facteurs de risque permettant d’expliquer sa transmission. Il apparaît que la distribution du paludismedans les quartiers étudiés est inégale : les quartiers centraux et anciennement urbanisés sont plus exposés au paludisme que lesquartiers périphériques et plus récents. Cependant, il existe au sein de chaque quartier des sous espaces au sein desquels les enfantssont plus exposés à la maladie. Les déterminants du paludisme font ressortir l’importance de l’environnement (proximité des basfonds) mais également des facteurs sociaux comme le niveau d’éducation de la mère des enfants et le niveau socio-économiquedes ménages. Au-delà de la démonstration de l’importance d’études croisant la diversité urbaine et la santé permettant dedéfinir des profils sanitaires d’espaces et de populations, passant par l’élaboration de méthodologies adaptées au contexte urbain,notre ambition était de souligner le besoin d’une concertation entre politiques de santé et de la ville pour un meilleur contrôle demaladies comme le paludisme, à l’heure de la mise en oeuvre de leur élimination

Spatial modelling of malaria prevalence associated with geographical factors in Houet province of Burkina Faso, West Africa

International audienceMalaria is a permanent threat to health in western Burkina Faso. Research has shown that geographical variables contribute to the spatial distribution in its transmission. The objective of this study is to assess the relationship between malaria prevalence and potential explanatory geographical variables in the Houet province in Burkina Faso. Statistics on malaria prevalence registered by health centres in the Houet province in 2017 and potential geographical variables identified through a literature review were collected. An Ordinary Least Squares (OLS) regression was used to identify key geographical variables and to measure their association with malaria while the Getis Ord Gi* index was used to locate malaria hotspots. The results showed that average annual temperature, vegetation density, percentage of clay in the soil, total annual rainfall and distance to the nearest waterbody are the main variables associated with malaria prevalence. These variables account for two-thirds of the spatial variability of malaria prevalence observed in Houet province. The intensity and direction of the relationship between malaria prevalence and geographical factors vary according to the variable. Hence, only vegetation density is positively correlated with malaria prevalence. Average temperature, for soil clay content, annual rainfall and for distance to the nearest water body are negatively correlated with the disease prevalence. These results show that even in an endemic area, malaria prevalence has significant spatial variation. The results could contribute to the choice of intervention sites, as this choice is crucial for reducing the malaria burden

Spatial Risk Of Urban Exposure To <em>Anopheles</em> And <em>Aedes</em> Mosquito Bites In Africa Using Salivary Antibody-Based Biomarkers

International audienceUrban settings often present low densities of mosquito vectors which do not allow to accurately assess the risk of arthropod-borne diseases based on entomological parameters. This study aims to evaluate the spatial risk of both malaria and arbovirus transmission in a northern urban area of Senegal, West-Africa, using antibody-based biomarkers of human exposure to Anopheles and Aedes mosquito bites. A cross-sectional study was undertaken between August and September 2014 (rainy season) in four urban districts (UDs) of the city of Saint-Louis, Senegal: Leona (LEO), Ndioloffene (NDI), Guet Ndar (GND) and Pi kine Sor Diagne (PSD). In each UD, dry blood spots were performed in 809 children aged 6-59 months and ELISA method was used to evaluate lgG antibody (Ab) responses to both gSG6-P1 (Anopheles) and Nterm-34kDa (Aedes) peptides of respective mosquito saliva. The median of lgG response levels to both gSG6-P1 and Nterm-34kDa salivary peptide varied significantly according to UDs and were lower in LEO compared to PSD, GND and NDI (p<0.0001 ). Heat maps of lgG responses to both salivary peptides indicated variations in the spatial distribution of the intensity of Ab responses inside UDs. There were no hot spots of malaria transmission risk (areas with children presenting a high lgG intensity) in LEO. Hot spots of malaria were mainly located in the northern part of NDI and GND, and in the southern part of PSD. As for the risk of arbovirus transmission, there were no hot spots in LEO and PSD. Hot spots of arbovirus transmission risk were located in some patch in the north of NDI and were dispersed throughout the UD of GND. Our results demonstrate that hot spots of both malaria and arbovirus transmission risk actually exist in northern parts of NDI and GND. This highlights that a targeted fight against mosquitoes in these hot spots could be effective against all mosquito-borne diseases. Antibody-based biomarkers could then help national control programs to target and prioritize vector control strategies in areas with common risk of malaria and arbovirus transmission

Spatial Assessment of Contact Between Humans and Anopheles and Aedes Mosquitoes in a Medium-Sized African Urban Setting, Using Salivary Antibody-Based Biomarkers

International audienceBACKGROUND: Anarchic and poorly controlled urbanization led to an increased risk of mosquito-borne diseases (MBD) in many African cities. Here, we evaluate the spatial heterogeneity of human exposure to malaria and arboviral disease vectors in an urban area of northern Senegal, using antibody-based biomarkers of exposure to Anopheles and Aedes mosquito bites.METHODS: A cross-sectional study was undertaken during the rainy season of 2014 in 4 neighborhoods of Saint-Louis, a city in northern Senegal. Among children aged 6-59 months in each neighborhood, the dried blood spot technique was used to evaluate immunoglobulin G (IgG) responses to both gSG6-P1 (Anopheles) and Nterm-34-kDa (Aedes) salivary peptides as validated biomarkers of respective mosquito bite exposure.RESULTS: IgG response levels to gSG6-P1 and Nterm-34-kDa salivary peptides varied significantly between the 4 neighborhoods (P < .0001). The level of exposure to Aedes bites also varied according to household access to sanitation services (P = .027), whereas that of exposure to Anopheles bites varied according to insecticide-treated bed net use (P = .006). In addition, spatial clusters of high contact between humans and mosquitoes were identified inside 3 neighborhoods.CONCLUSIONS: Antibody-based biomarkers of exposure to Anopheles and Aedes mosquito bites could be helpful tools for evaluating the heterogeneity of exposure to malaria and arboviral disease vectors by national control program

Observar a Terra para analisar a distribuição espacial das desigualdades da saúde: um olhar histórico e prospectivo sobre o uso do sensoriamento remoto no campo da saúde

International audienceBy providing a wide view of territories, satellite images and aerial photographs allow to capture the environmental factors that can affect the health of populations. Since the development of satellite remote sensing in the 1970s, its use in the health field has had moderate success. Although its potential was widely mentioned in the literature until the 2000s, its operational contribution was not obvious. It is only recently that health applications have been enriched and multiplied by the development of interdisciplinary approaches. This article aims to question the uses of remote sensing applied to health issues according to technical, historical, and thematic aspects in order to identify the bottlenecks. First, it offers a didactic view of theoretical principles, available data and possible uses. Through a bibliographic study, it offers a retrospective look at the evolution of its implementation in the field of health, which allows synthesizing current contributions: for operational mapping, for surveillance and analysis of the dynamics of infectious diseases or, to a lesser extent, to apprehend the vulnerabilities of populations such as difficulties in accessing healthcare. Finally, the article concludes on the limits, recommendations and perspectives for optimizing these uses, which are often constrained by technical and structural issues and for which methodologies still need to be developed.En prenant de la hauteur et en offrant une vue élargie des territoires, les images satellite et les photographies aériennes permettent d'appréhender les facteurs environnementaux qui peuvent conditionner la santé des populations. Depuis l'essor de la télédétection satellite à partir des années 1970, son usage dans le domaine de la santé a connu des succès modérés. Si son potentiel a été largement évoqué dans la littérature jusqu'aux années 2000, son apport opérationnel ne s'est pas imposé. Ce n'est que récemment que les applications en santé se sont enrichies et multipliées par le développement d'approches interdisciplinaires. Cet article vise à questionner les usages de la télédétection appliquée aux questions de santé selon les aspects techniques, historiques, et thématiques afin d'identifier les verrous. Il propose tout d'abord une vue didactique des principes théoriques, des données disponibles et des usages possibles. A travers une étude bibliographique, il offre un regard rétrospectif sur l'évolution de sa mise en ½uvre dans le domaine la santé, qui permet de synthétiser les contributions actuelles : pour la cartographie opérationnelle, pour la surveillance et l'analyse des dynamiques des maladies infectieuses ou, dans une moindre de mesure, pour appréhender les vulnérabilités des populations comme les difficultés d'accès aux soins. Enfin, l'article conclut sur les limites, les recommandations et les perspectives pour optimiser ces usages dont les verrous sont souvent techniques et structurels mais pour lesquels des méthodologies doivent encore être développées.Ao fornecer uma visão ampla dos territórios, as imagens de sensoriamento remoto orbital e fotografias aéreas permitem analisar os fatores ambientais que podem condicionar a saúde das populações. Desde o surgimento do sensoriamento remoto orbital na década de 1970, seu uso no campo da saúde teve um sucesso moderado. Embora seu potencial tenha sido amplamente mencionado na literatura até a década de 2000, sua contribuição operacional era óbvia. Apenas recentemente as aplicações em saúde foram enriquecidas e multiplicadas pelo desenvolvimento de abordagens interdisciplinares. Este artigo tem como objetivo questionar os usos do sensoriamento remoto aplicados às questões de saúde, de acordo com os aspectos técnicos, históricos e temáticos, a fim de identificar os seus gargalos. Primeiramente propõe uma visão didática dos princípios teóricos, dados disponíveis e possíveis usos. Através de um estudo bibliográfico, oferece uma retrospectiva da evolução de sua implementação no campo da saúde, permitindo sintetizar as contribuições atuais: para o mapeamento operacional, para a vigilância e a análise da dinâmica de doenças infecciosas ou, em menor grau, para compreender as vulnerabilidades das populações, tais como as dificuldades de acesso aos serviços de saúde. Por fim, o artigo conclui sobre os limites, as recomendações e as perspectivas para otimizar esses usos, que muitas vezes são limitados por questões técnicas e estruturais e para as quais as metodologias ainda precisam ser desenvolvidas

Uneven malaria transmission in geographically distinct districts of Bobo-Dioulasso, Burkina Faso

Abstract Background Urbanization is a main trend in developing countries and leads to health transition. Although non-communicable diseases are increasing in cities of low-income countries, vector-borne diseases such as malaria, are still present. In the case of malaria, transmission is lower than in rural areas, but is uneven and not well documented. In this study, we wanted to evaluate intra-urban malaria transmission in a West African country (Burkina Faso). Methods A cross-sectional study on 847 adults (35 to 59 year-old) and 881 children (6 months to 5 year-old) living in 1045 households of four districts (Dogona, Yeguere, Tounouma and Secteur 25) of Bobo-Dioulasso was performed between October and November 2013. The districts were selected according to a geographical approach that took into account the city heterogeneity. Malaria prevalence was evaluated using thick and thin blood smears. Human exposure to Anopheles bites was measured by assessing the level of IgG against the Anopheles gSG6-P1 salivary peptide. Adult mosquitoes were collected using CDC traps and indoor insecticide spraying in some houses of the four neighbourhoods. The Anopheles species and Plasmodium falciparum infection rate were determined using PCR assays. Results In this study, 98.5% of the malaria infections were due to Plasmodium falciparum. Malaria transmission occurred in the four districts. Malaria prevalence was higher in children than in adults (19.2 vs 4.4%), and higher in the central districts than in the peripheral ones (P = 0.001). The median IgG level was more elevated in P. falciparum-infected than in non-infected individuals (P < 0.001). Anopheles arabiensis was the main vector identified (83.2%; 227 of the 273 tested mosquito specimens). Five P. falciparum-infected mosquitoes were caught, and they were all caught in the central district of Tounouma where 28.6% (14/49) of the tested blood-fed mosquito specimens had a human blood meal. Conclusions This study showed that urban malaria transmission occurred in Bobo-Dioulasso, in all the four studied areas, but mainly in central districts. Environmental determinants primarily explain this situation, which calls for better urban management