This dissertation examined risk factors for hypertensive disorders of pregnancy (HDP) — specifically whether neighborhood socioeconomic deprivation exacerbates individual socioeconomic disadvantage (deprivation amplification) to increase the likelihood of developing HDP. To select the optimal areal unit at which to investigate HDP, geographic proxies for neighborhoods were explored. A thematic review qualitatively examined nontraditional neighborhood boundaries identified through internet sources. Data from 2008–2012 Miami-Dade County, Florida birth records (n=121,421) and the U.S. Census Bureau were used for the remaining analyses. Ordinary least squares (OLS) and geographically weighted regression (GWR) analysis empirically compared the proportion of HDP prevalence explained by six areal units: census block groups, census tracts, ZIP code tabulation areas (ZCTAs), and three types of natural neighborhood — census units clustered based on an eight-item Neighborhood Deprivation Index. Multilevel logistic regression examined relationships between HDP, neighborhood deprivation, and individual-level factors. Odds ratios (OR) and adjusted odds ratios (aOR) were calculated. The thematic review found 22 potential alternatives to census boundaries developed through techniques such as crowd-sourcing and qualitative research. In the sensitivity analysis, census tracts aggregated at the scale of ZCTAs performed twice as well as any other model (GWR2 = 0.27) and were used as the Aim 3 unit of analysis. In the multilevel logistic regression, HDP was associated with moderate (aOR=1.13; CI: 1.05, 1.21) and high neighborhood deprivation (aOR=1.16; CI: 1.07, 1.26). Compared with mothers with private insurance, uninsured women (aOR=1.69; CI: 1.56, 1.84) and Medicaid recipients (aOR=1.12; CI: 1.05, 1.18) had higher HDP odds. Non-Hispanic Black women’s HDP odds were 1.58 times those of non-Hispanic White women. Cross-level interactions — between neighborhood deprivation and educational attainment and neighborhood deprivation and insurance status — did not reach statistical significance. Private sector neighborhood boundaries hold promise for developing new public health tools. Because they are relatively easy to generate from census data, natural neighborhoods may balance tradition and innovation. While no evidence of deprivation amplification was found, results suggested that individual-level and neighborhood deprivation are HDP risk factors. Interventions that target expectant mothers in deprived neighborhoods — particularly non-Hispanic Black and Hispanic women who lack health insurance — may help reduce HDP prevalence and disparities.

Background South Africa has experienced the most severe consequences of the HIV/AIDS pandemic. Every community has been affected in some way, many experiencing huge increases in mortality,particularly before antiretroviral therapies (ART) were readily available. However, the micro-level understanding of the HIV epidemic in South Africa is weak, because of a lack of detailed data for most of the population. This thesis is based on detailed individual follow-up in the Agincourt Health and Demographic Surveillance Site (HDSS) located in the Agincourt subdistrict of Mpumalanga Province and investigates micro-level determinants of HIV epidemiology and the impact of treatment provided. Methods The Agincourt HDSS has followed a geographically defined population since 1992,approximately the time when the HIV/AIDS epidemic first became apparent. This population based surveillance has included capturing details of all deaths, with cause of death determined by verbal autopsy, as well as the geographical location of individual households within the overall Agincourt area. Background information on the roll-out of ART over time was also recorded. Results A comparison immediately before and after the major roll-out of ART showed a substantial decrease in HIV-related mortality, greater in some local communities within the area than others. Individual determinants associated with a decreased risk of HIV/AIDS mortality included proximity to ART services, as well as being female, younger, and in higher socioeconomic and educational strata. There was a decrease in the use of traditional healthcare sources and an increase in the use of biomedical healthcare amongst those dying of HIV/AIDS between periods before and after the roll-out of ART. Conclusions Understanding micro-level determinants of HIV/AIDS infection and mortality was very important in terms of characterising the overall epidemic in this community. This approach will enable public health interventions to be more effectively targeted towards those who need them most in the continuing evolution of the HIV/AIDS epidemic.

La campylobactériose représente la principale cause de gastro-entérite bactérienne dans les pays industrialisés. L’épidémiologie de la maladie est complexe, impliquant plusieurs sources et voies de transmission. L’objectif principal de ce projet était d’étudier les facteurs environnementaux impliqués dans le risque de campylobactériose et les aspects méthodologiques pertinents à cette problématique à partir des cas humains déclarés au Québec (Canada) entre 1996 et 2006. Un schéma conceptuel des sources et voies de transmission de Campylobacter a d’abord été proposé suivant une synthèse des connaissances épidémiologiques tirées d’une revue de littérature extensive. Le risque d’une récurrence de campylobactériose a ensuite été décrit selon les caractéristiques des patients à partir de tables de survie et de modèles de régression logistique. Comparativement au risque de campylobactériose dans la population générale, le risque d’un épisode récurrent était plus élevé pour les quatre années suivant un épisode. Ce risque était similaire entre les genres, mais plus élevé pour les personnes de régions rurales et plus faible pour les enfants de moins de quatre ans. Ces résultats suggèrent une absence d’immunité durable ou de résilience clinique suivant un épisode déclaré et/ou une ré-exposition périodique. L’objectif suivant portait sur le choix de l’unité géographique dans les études écologiques. Neuf critères mesurables ont été proposés, couvrant la pertinence biologique, la communicabilité, l’accès aux données, la distribution des variables d’exposition, des cas et de la population, ainsi que la forme de l’unité. Ces critères ont été appliqués à des unités géographiques dérivées de cadre administratif, sanitaire ou naturel. La municipalité affichait la meilleure performance, étant donné les objectifs spécifiques considérés. Les associations entre l’incidence de campylobactériose et diverses variables (densité de volailles, densité de ruminants, abattoirs, température, précipitations, densité de population, pourcentage de diplomation) ont ensuite été comparées pour sept unités géographiques différentes en utilisant des modèles conditionnels autorégressifs. Le nombre de variables statistiquement significatives variait selon le degré d’agrégation, mais la direction des associations était constante. Les unités plus agrégées tendaient à démontrer des forces d’association plus élevées, mais plus variables, à l’exception de l’abattoir. Cette étude a souligné l’importance du choix de l’unité géographique d’analyse lors d’une utilisation d’un devis d’étude écologique. Finalement, les associations entre l’incidence de campylobactériose et des caractéristiques environnementales ont été décrites selon quatre groupes d’âge et deux périodes saisonnières d’après une étude écologique. Un modèle de Poisson multi-niveau a été utilisé pour la modélisation, avec la municipalité comme unité. Une densité de ruminant élevée était positivement associée avec l’incidence de campylobactériose, avec une force d’association diminuant selon l’âge. Une densité de volailles élevée et la présence d’un abattoir de volailles à fort volume d’abattage étaient également associées à une incidence plus élevée, mais seulement pour les personnes de 16 à 34 ans. Des associations ont également été détectées avec la densité de population et les précipitations. À l’exception de la densité de population, les associations étaient constantes entre les périodes saisonnières. Un contact étroit avec les animaux de ferme explique le plus vraisemblablement les associations trouvées. La spécificité d’âge et de saison devrait être considérée dans les études futures sur la campylobactériose et dans l’élaboration de mesures préventives. / Campylobacteriosis is a leading cause of acute bacterial gastro-enteritis in industrialized countries. The epidemiology of the disease is complex, involving many sources and transmission pathways. The principal objective of this project was to study environmental factors and methodological aspects pertinent to the spatial epidemiology of human campylobacteriosis using cases reported in Quebec (Canada) between 1996 and 2006. A conceptual diagram of sources and transmission pathways of Campylobacter was first proposed following a synthesis of current epidemiological knowledge based on a comprehensive literature review. The risk of recurrent episodes in relation to patient characteristics was described. Life table estimates and logistic regression were used for modeling. Compared to campylobacteriosis risk in the general population, the risk for a recurrent disease event was higher for a period of four years with a decreasing trend. This increased risk was similar across gender but higher for people from rural areas and lower for children under four years old. These results may suggest the absence of durable immunity or clinical resilience following a first episode and/or periodic re-exposure, at least among reported cases. Next, criteria were proposed and applied to ascertain the best geographical unit to use. Nine measurable criteria were proposed, including biological relevance, communicability of results, ease of data access, distribution of exposure variables, cases and population, and unit shape. These criteria were applied to various geographical units derived from administrative, health services and natural frameworks. Ultimately, the municipal geographical unit performed the best, given the specific objectives of the study. Future research areas for optimizing the choice of geographical unit were discussed. Another objective was to estimate and compare the associations between incidence and various environmental characteristics (poultry density, ruminant density, slaughterhouse, temperature, and precipitation) and demographic characteristics (population density, diploma) using seven different geographical units. Conditional autoregressive models were used for statistical modeling. In general, the number of significant predictors decreased as the aggregation level increased but directions of associations were consistent. More aggregated scales tended to show larger but more variable estimates for all variables, with the exception of the presence of slaughterhouses. This study highlighted the need for careful selection and analysis of geographical units when using ecological designs in epidemiological studies. Finally, the association between environmental characteristics and incidence in relation to four age groups and deux seasonal periods was studied. A multi-level Poisson regression model was used for modeling at the municipal level. High ruminant density was positively associated with incidence but decreased with age. High poultry density and presence of a large poultry slaughterhouse were also associated with higher incidence for people aged 16-34. Associations were also detected with population density and average daily precipitation. Except for population density, associations were constant across seasonal periods. Close contact with farm animals is most likely involved in the associations observed. Clearly, age and season must be considered in future studies on campylobacteriosis and in the design of preventive measures.

Los objetivos de la tesis son:1.- Estudiar la relación entre la incidencia y mortalidad por cáncer y los factores medioambientales, en particular la contaminación atmosférica, controlando por factores socioeconómicos.2.- Utilizar aquellos métodos de estadística espacial apropiados para cada tipo de diseño.3.- Distinguir en los modelos las diferentes fuentes de extra-variabilidad espacial.4.- Controlar el problema de exceso de ceros inherente a alguna de las neoplasias de interés medioambientales.Conclusiones:- Tanto la incidencia como la mortalidad de las neoplasias, presentaron dos fuentes de extravariación. La extravariaicón espacial, por la que unidades vecinas tienden a presentar razones de incidencia/mortalidad similares, y la heterogeneidad no espacial. En general la extravariabilidad espacial ha resultado ser mucho mayor que la no espacial.- Para suavizar las RIE/RME correspondientes a variables con un porcentaje de ceros superior al40-50% debe utilizarse un modelo que capture este comportamiento.- El mejor modelo en términos de ajuste para recoger el exceso de ceros en las variables de interés ha resultado ser el modelo mixto de riesgo relativo.- Las RIE/RME suavizadas presentan un patrón geográfico claro sólo en algunas neoplasias de interés medioambiental.- Parte de la variabilidad remanente en las RIE/RME suavizadas pudo ser explicada mediante la introducción de variables explicativas, en particular la contaminación atmosférica y variables socioeconómicas.-Como los contaminantes atmosféricos fueron observados en un diseño geoestadístico y las neoplasias de interés mediambiental lo fueron en un diseño en rejilla se modelizó la superficie de exposición.- El efecto del contaminante en cada municipio/sección censal se aproximó introduciendo en el modelo el valor promedio en cada área y la variabilidad intra-área.- El efecto del contaminante se consideró aleatorio, en el sentido de que podría ser diferente en cada una de las áreas.- Las condiciones socioeconómicas fueron otra de las variables que redujeron la variabilidad remanente en las RIE/RME suavizadas.-Las variables explicativas observadas con un diseño en rejilla, como el índice de privación, se introdujeron en el modelo como efectos fijos.- El efecto de la privación sobre la incidencia y/o mortalidad por cáncer de tráquea, bronquios y pulmón, controlando por contaminantes atmosféricos, fue mayor en las mujeres que en los hombres.-Altas concentraciones de contaminantes atmosféricos aumentan el riesgo de padecer neoplasias de interés medioambiental, controlando por condiciones socioeconómicas. / The objectives of the Thesis are:1.- To study the relationship between incidence and cancer mortality and environmental factors, particularly atmospheric pollutio, using socioeconomic factors as control.2.- To use those methods of spatial statistics suitable for each type of design.3.- To distinguish different sources of spatial extra-variability between the models.4.- To control the problem of excess zeros inherent in some of the environment-related neoplasias.5.- To correctly introduce explanatory variables (according to the design oberved in them) of the geographical variability of the environment-related neoplasias in order to avoid possible biases.The conclusions are:-Both the incidence and mortality of environment-related neoplasias showed two wources of extra-variation: spatil extra-variation, in which neighbouring units tend to show similar incidence/mortality ratios, and non-spatial heterogeneity.-To smooth the SIR/SMR corresponding to variables with a precentage of zeros higher than 40-50% a model that captures this behaviour must be used.-The best model, in terms of fit, which recognises excess zeros in the variables of interest was the mixture relative risk model.-Smoothed SIR/SMR only showed a clear geographical pattern in some of the environment-related neoplasias.-Part of the remaining variability in the smoothed SIR/SMR could be explained by introducing explanatory variables, in particular atmospheric pollution and socieconomic variables.-As the atmospheric pollutants were observed in a geostatistical design and the environment-related neoplasias were studied in a lattice design, the exposure surface was modelled.-The effect of the pollutant in each municipality/electoral district as approached in the model by introducing the average value in each area and the intra-area variability.-Socioeconomic conditions were another of the variables that reduced the remaining variability in the smoothed SIR/SMR.-Explanatory variables observed with a lattice design, such as the privation index, were introduced in the model as fixed effects.-Greater privation, using atmospheric pollutans as control, implied a greater risk of suffering/dying from some of the environment-realted neoplasias in the three areas and periods studies.-The effect of privation on the incidence and/or mortality form throat, bronchial and lung cancer, using atmospheric pollutans as control, was greater in women than in men.

Type 1 diabetes (T1D) is an autoimmune disease that destroys the bodies’ insulin producing beta-cells. The disease is understood to be triggered in genetically susceptible individuals by environmental factors. While the genetic side of the etiological model has to some degree been uncovered, there is no clear understanding of which environmental factors play a role in the disease process. Several hypotheses claim to explain the development of T1D, of which enteroviral infections show the most promise. According to this hypothesis high prevalence of enteroviral infections would also mean high incidence rates of T1D. This study focused on four Nordic countries (Denmark, Finland, Norway and Sweden) that as late as 2017 were found in the top 10 countries for incidence rate of childhood-onset T1D in the world. Incidence rates of T1D and prevalence of enteroviruses were mapped and geographically analyzed according to the principles of spatial epidemiology, after which correlation coefficients were calculated. In doing so the study tried to answer to which extent the prevalence of enteroviruses could explain the regional variations in T1D. For all countries no significant correlation was found, but increasing sample size, by grouping countries, showed considerably different outcomes with a small positive correlation in the case of Norway and Finland.

Le virus du Nil occidental (VNO) est un flavivirus présent au Canada depuis 2001, affectant principalement les oiseaux, les chevaux et les humains. En 2003, l’Agence canadienne d’inspection des aliments (ACIA) a inscrit le VNO sur la liste des maladies à notification immédiate (MANI) et depuis, les cas chez les animaux domestiques sont rapportés dès l’obtention d’un résultat positif à l’autorité fédérale. Aucune étude au Canada n’a encore colligé tous les cas de VNO chez une espèce animale afin d’améliorer la compréhension de la distribution du VNO au pays et de formuler des recommandations pour la prévention de futures infections. Dans le cadre de cette étude, tous les cas de VNO rapportés à l’ACIA chez les chevaux ont été analysés afin de décrire, dans un premier temps, l’incidence des cas rapportés de VNO au Canada (2003 à 2019) et les caractéristiques principales des cas récents (2015 à 2019). Dans un second temps, une analyse géospatiale a été effectuée afin de décrire les patrons spatiotemporels de la distribution des cas de VNO rapportés de 2003 à 2020 chez les chevaux. Au cours de la période d’étude, 848 cas de VNO chez les chevaux ont été rapportés à l’ACIA. Ces cas étaient répartis dans toutes les provinces, à l’exception des quatre provinces de l’Atlantique (Nouveau-Brunswick, Nouvelle-Écosse, Île-du-Prince-Édouard, Terre-Neuve-et-Labrador). La région de l’Ouest (Colombie-Britannique, Alberta, Saskatchewan, Manitoba) a déclaré un plus haut taux d’incidence (15,4 cas/100 000 chevaux-année) que la région de l’Est (8,3 cas/100 000 chevaux-année) (Ontario, Québec, Atlantique). Les taux d’incidence étaient particulièrement élevés en Saskatchewan avec en moyenne 33,2 cas/100 000 chevaux-année entre 2003 et 2019. L’analyse descriptive des caractéristiques des cas a démontré que 96 % de ceux-ci n’étaient pas vaccinés et que le taux de létalité était de 31,9 %. La distribution spatiotemporelle des cas a été décrite par région en analysant d’abord la récurrence annuelle des cas dans les divisions de recensement et ensuite la présence d’agrégats spatiotemporels pour investiguer les excès de risque. L’analyse des patrons spatiotemporels a révélé une dispersion vaste et rapide ainsi qu’une récurrence élevée du VNO dans la région de l’Ouest. En revanche, pour la région de l’Est, la dispersion du VNO a été plus lente et graduelle. Les agrégats spatiotemporels identifiés ont permis de démontrer que, malgré la présence répétée des cas dans certaines divisions de recensement, des excès de risque spatiotemporels peuvent être observés. Ces patrons indiquent que les cas de fièvre du VNO peuvent être anticipés dans les endroits où la récurrence annuelle est plus élevée et, parfois, conduire à des éclosions de la maladie. En somme, cette étude a mis en évidence l’importance de la surveillance du VNO chez les chevaux en décrivant notamment la saisonnalité du VNO et en délimitant des zones avec une forte récurrence de cas. Ces caractéristiques illustrent l’apport considérable de la surveillance chez les chevaux à un système de surveillance intégrée. Les résultats pourront aussi aider les autorités sanitaires et les médecins vétérinaires praticiens à cibler leurs efforts de prévention et de contrôle dans les zones les plus touchées. / West Nile virus (WNV) is a flavivirus which has been present in Canada since 2001, affecting mostly birds, horses and humans. In 2003, the Canadian Food Inspection Agency (CFIA) included WNV on its list of immediately notifiable diseases (INDs), and since then, cases in domestic animals are reported to the federal authority as soon as positive samples are obtained from diagnostic laboratories. To date, no study in Canada has compiled all reported WNV cases in an animal species to describe the distribution of this virus in the country and formulate recommendations for future prevention strategies. In this study, all WNV cases reported to the CFIA in horses were analyzed to describe their incidence in Canada (2003 to 2019) and the main characteristics of the recent ones (2015 to 2019). A geospatial analysis was also conducted to describe the spatiotemporal patterns of reported WNV cases in horses from 2003 to 2020. Over the study period, 848 cases of WNV in horses were reported to the CFIA. These cases were distributed in all provinces, except for the Atlantic provinces (New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland and Labrador). The western region of Canada (British Columbia, Alberta, Saskatchewan, Manitoba) reported a higher incidence rate (15.4 cases/100,000 horse-year) than the eastern region (8.3 cases/100,000 horse-year) (Ontario, Quebec, Atlantic). The reported incidence rates were particularly high in Saskatchewan, with an average of 33.2 cases/100,000 horse-year between 2003 and 2019. The descriptive analysis of case characteristics showed that 96% of cases were not vaccinated, and the case fatality rate was 31.9%. The regional spatiotemporal distribution of cases was described by first analyzing the annual recurrence of cases in census divisions and then the presence of spatiotemporal high-risk clusters. The analysis of spatiotemporal patterns revealed a swift spread and a high recurrence of WNV cases in the western region. In contrast, in the eastern region, the dispersion was slower and more gradual. The identified clusters showed that, despite the repeated presence of cases in some census divisions, excess in spatiotemporal risk can be observed. These patterns indicate that cases of WNV fever can be anticipated in areas with higher annual recurrence, and in some instances, can result in disease outbreaks. This study highlights the importance of WNV surveillance in horses, enabling a better understanding of the seasonality of WNV in horses and the identification of areas with a high recurrence of cases. The findings are a considerable contribution in an integrated surveillance system. The results can also assist health authorities and veterinary practitioners in targeting prevention and control efforts to the most affected areas.

Phytophthora lateralis is the causal agent of cedar root rot, a fatal forest pathogen whose principal host is Chamaecyparis lawsoniana (Port-Orford-cedar), a predominantly riparian-restricted endemic tree species of ecological, economical, and cultural importance to coastal Oregon and California. Local scale distribution of P. lateralis is thought to be associated with timber harvest and road-building disturbances. However, knowledge of the landscape-scale factors that contribute to successful invasions of P. lateralis is also important for effective land management of Port-Orford-cedar. P. lateralis is able to infest in wet conditions via stream networks (zoospore) and dry conditions via road networks (resting spore). This study tested the hypothesis that vehicles spread P. lateralis by relating its distribution to traffic intensive, anthropogenic disturbances (i.e. a road network, timber harvest) over a 31-yr period in a 3,910-km² portion of the Rogue River-Siskiyou National Forest in the Siskiyou Mountains of Oregon. Indices of road disturbance (presence/absence, configuration, length, density, road-stream network connectivity) and timber harvest (presence/absence, area, density, frequency) were related to locations of infested cedar populations from a USFS survey dataset using a geographic information system (GIS). About 40% of 934 7th-field catchments were infested with the pathogen. Total road length of the study site was 5,070 km; maximum road density was 8.2 km/km2 and averaged 1.6 km/km² in roaded catchments (n = 766). Timber activities extracted 17,370 ha (2,338 cutting units) of forest across 509 catchments; 345 catchments were cut ≥ twice. Maximum harvest density was 0.92 km²/km² ([mean] = 0.04). Both road networks and timber harvest patchworks were significantly related to cedar root rot heterogeneity. Chi-squared contingency tables showed that infestation rates were 2.2 times higher in catchments with roads compared to roadless catchments and 1.4 times higher in catchments with road-stream intersections compared to those that were unconnected. Infestation was twice as likely in catchments with both harvest and road presence than road presence alone. Single-variable logistic regression showed that a one percent increase in harvest density increased infestation odds 25% and a one-unit (km/km²) increase in road density increased infestation odds 80%. Road and stream network configuration was also important to pathogen distribution: 1) uninfested catchments are most likely to be spatially removed from infested, roaded catchments, 2) only 11% of 287 roaded catchments downstream of infested, roaded catchments were uninfested, and 3) only 12% of 319 catchments downstream of infested catchments were uninfested. Road networks and timber harvest patchworks appear to reduce landscape heterogeneity by providing up-catchment and down-catchment access to host populations by linking pathogenic materials to the stream network. Timber harvest data suggest that while infestation risk to Port-Orford-cedar populations remains high, management policies may have curbed infestation risk in timber-harvested catchments; if this is a result of specific P. lateralis mitigation policies adopted in the late 1980's or broader, region-wide conservation policies (i.e. the Northwest Forest Plan) is yet unclear. / Graduation date: 2012

Abstract :Bluetongue (BT) is a vector-borne infectious disease primarily transmitted to even- toed ungulates by the bite of several Culicoides species. The global distribution of BT can be attributed to the ubiquity of its vectors and its rapid spread, likely to the enhancement of human activities (intensification of animal production, trans- port, changing habitat). During the last decades, BT established in Southern Europe and more recently emerged in Northern Europe, causing the death of millions of domestic ruminants. On the same time, a Belgian research project has been set up to develop remote-sensing tools to study the EPidemiology and Space-TIme dynamicS of infectious diseases (EPISTIS). In that general framework, this thesis aimed to study the space-time distribution of the main Culicoides vectors occurring in Italy and Belgium, at two different scales. Firstly, we aimed to clarify the role of several eco-climatic factors on the regional-scale distribution of C. imicola in time, based on weekly samplings achieved throughout Italy from 2001 to 2006 and to develop an easy-to-use and reproducible tool, which could be widely validated on the basis of former vector sampling and freely accessible remote-sensing data. Secondly, we aimed to investigate how Culicoides species were distributed in the fine-scale habitat encountered throughout the agro-ecological landscapes of Belgium, while recent studies have suggested that the landscapes configuration could explain the spatial distribution of BT. In the first part, we showed that an autoregressive model where the observed monthly growth rate is predicted by monthly temperature, allowed predicting >70% of the seasonal variability in C. imicola trap catches. The model predicted the seasonality, the altitudinal gradient, and the low populations’ activity taking place during the winter. Incorporating eco-climatic indices such as the Normalized Difference Vegetation Index into the model did not enhance its predictive power. In the second part, we quantified how Culicoides populations are spatially structured in the neighbourhood of farms, and demonstrated the unexpectedly high level of population found in forest. We also showed how four classes of land use could influence the relative abundances of Culicoides species in the agro-ecological landscapes of Belgium. Although in summer, BT vectors were abundant in each of the four classes investigated, their relative abundances varied strongly as a function of sex, species and environmental conditions, and we quantified these variations. Finally, we also presented a new method to quantify the interference between Onderstepoort light traps, and used it to measure their range of attraction for several of the most common BT vectors species in Northern Europe. The model developed on C. imicola in Italy provided enthusiastic perspectives regarding the regional-scale analyses of its distribution in time, although further improvements are nevertheless required in order to assess the broad scale ecology of BT vectors throughout Europe. Mapping the abundances of C. imicola in Sardinia high- lighted an important lack of reliability attributable to the many land use classes that are currently not sampled in the vector surveillance achieved across Europe. Together with the novelties presented in the second part and the recent findings establishing that BT could circulate among wild hosts in both epidemiological systems (i.e. in Southern and Northern Europe), we call for increasing epidemiological and entomo- logical studies at the interface between farms and the surrounding natural habitats. Last, depicting in time the landscape-scale findings for Northern Europe highlighted how dramatic could be the role played by intensive farming practices to maintain BT within the agro-ecological landscapes studied and to facilitate its circulation between them. Quantifying the amplitude of the risk of disease transmission linked to these practices would require a further complex modeling approach accounting simultaneously for the diel activity of hosts, mainly resulting from the farming activities, the diel activities of different vector species and the landscapes configuration found in contrasted agro-ecological systems.<p>Résumé :La fièvre catarrhale ovine (FCO), encore appelée maladie de la langue bleue, est une maladie infectieuse des ruminants transmise par la piqûre d’un vecteur de type moucheron appartenant au genre Culicoides (Diptera :Ceratopogonidae). L’ubiquité de ses vecteurs peut expliquer son succès d’installation à l’échelle globale. Par ailleurs, sa rapide expansion a été grandement facilitée par l’importante activité anthropique (élevage, transport, modification de l’habitat) et peut-être même par les changements climatiques globaux. La FCO a été récemment qualifiée de maladie infectieuse émergente en Europe du fait de (i) son récent établissement dans la région, bien au delà de son aire de répartition traditionnelle, (ii) de sa forte capacité de dispersion affectant chaque jour un nombre plus important d’hôtes et enfin (iii) de sa forte virulence. Après avoir détaillé les caractéristiques majeures des deux principaux foyers de FCO rencontrés en Europe depuis 1998, la présente thèse s’est plus particulièrement intéressée à l’étude de la distribution spatio-temporelle de ses principaux vecteurs dans le sud (partie 1) puis dans le nord (partie 2) de l’Europe, à différentes échelles. Dans la première partie, un modèle discret, spatialement et temporellement explicite, a été développé afin de mesurer l’influence de différents facteurs éco-climatiques sur la distribution de Culicoides imicola, principal vecteur de la FCO dans le Bassin Méditerranéen. Les profils mensuels de distribution rencontrés en Sardaigne durant 6 années consécutives ont ainsi pu être reconstitués, principalement sur base de la température. Une cartographie de l’abondance de C. imicola sur le territoire a permis de mettre à jour le manque d’information sur sa distribution en dehors des exploitations agricoles. Dans la deuxième partie du travail, nous nous sommes penchés sur la distribution spatiale des Culicoides tels qu’on peut les rencontrer au sein de différents paysages agro-écologiques de Belgique. Nous avons ainsi pu décrire la structure adoptée par les populations de Culicoides au voisinage des fermes ainsi que quantifier l’importante population présente dans les forêts avoisinantes. Nous avons par ailleurs montré l’influence de différentes catégories d’utilisation du sol sur l’abondance et la composition en espèces. Enfin, nous avons présenté une méthode permettant de quantifier l’interférence entre des pièges lumineux utilisés dans un même paysage pour échantillonner les populations, et l’avons utilisé afin de mesurer leur rayon d’attractivité sur les espèces vectrices les plus communément rencontrées dans le nord de l’Europe. En guise de conclusion générale et conjointement aux récentes découvertes de cas de FCO au sein de la faune sauvage européenne, nous appelons à réaliser un plus grand nombre d’études éco-épidémiologiques à l’interface entre exploitations agricoles et zones (semi-) naturelles avoisinantes. En outres, les résultats présentés dans la seconde partie ont été mis en relation avec le mode de fonctionnement journalier de nos exploitations agricoles. Nous avons ainsi pu déduire le rôle dramatique joué par les pratiques agricoles intensives dans le maintien du virus de la FCO au sein de nos paysages agro-écologiques, ainsi que dans sa circulation d’un paysage à l’autre. Un cadre de modélisation complexe permettant une analyse simultanée de l’activité nycthémérale des hôtes de la FCO et de ses vecteurs Culicoides en fonction de la configuration des paysages agro-écologiques est néanmoins requis afin de quantifier l’amplitude du risque de transmission de la FCO lié aux pratiques agricoles intensives. / Doctorat en Sciences agronomiques et ingénierie biologique / info:eu-repo/semantics/nonPublished

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