Acetylcholinesterase (AChE) is an essential enzyme with an evolutionary conserved function: to terminate nerve signaling by rapid hydrolysis of the neurotransmitter acetylcholine. AChE is an important target for insecticides. Vector control by the use of insecticide-based interventions is today the main strategy for controlling mosquito-borne diseases that affect millions of people each year. However, the efficiency of many insecticides is challenged by resistant mosquito populations, lack of selectivity and off-target toxicity of currently used compounds. New selective and resistance-breaking insecticides are needed for an efficient vector control also in the future. In the work presented in this thesis, we have combined structural biology, biochemistry and medicinal chemistry to characterize mosquito AChEs and to develop selective and resistance-breaking inhibitors of this essential enzyme from two disease-transmitting mosquitoes.We have identified small but important structural and functional differences between AChE from mosquitoes and AChE from vertebrates. The significance of these differences was emphasized by a high throughput screening campaign, which made it evident that the evolutionary distant AChEs display significant differences in their molecular recognition. These findings were exploited in the design of new inhibitors. Rationally designed and developed thiourea- and phenoxyacetamide-based non-covalent inhibitors displayed high potency on both wild type and insecticide insensitive AChE from mosquitoes. The best inhibitors showed over 100-fold stronger inhibition of mosquito than human AChE, and proved insecticide potential as they killed both adult and larvae mosquitoes.We show that mosquito and human AChE have different molecular recognition and that non-covalent selective inhibition of AChE from mosquitoes is possible. We also demonstrate that inhibitors can combine selectivity with sub-micromolar potency for insecticide resistant AChE.

abstract: The role of climate change, as measured in terms of changes in the climatology of geophysical variables (such as temperature and rainfall), on the global distribution and burden of vector-borne diseases (VBDs) remains a subject of considerable debate. This dissertation attempts to contribute to this debate via the use of mathematical (compartmental) modeling and statistical data analysis. In particular, the objective is to find suitable values and/or ranges of the climate variables considered (typically temperature and rainfall) for maximum vector abundance and consequently, maximum transmission intensity of the disease(s) they cause. Motivated by the fact that understanding the dynamics of disease vector is crucial to understanding the transmission and control of the VBDs they cause, a novel weather-driven deterministic model for the population biology of the mosquito is formulated and rigorously analyzed. Numerical simulations, using relevant weather and entomological data for Anopheles mosquito (the vector for malaria), show that maximum mosquito abundance occurs when temperature and rainfall values lie in the range [20-25]C and [105-115] mm, respectively. The Anopheles mosquito ecology model is extended to incorporate human dynamics. The resulting weather-driven malaria transmission model, which includes many of the key aspects of malaria (such as disease transmission by asymptomatically-infectious humans, and enhanced malaria immunity due to repeated exposure), was rigorously analyzed. The model which also incorporates the effect of diurnal temperature range (DTR) on malaria transmission dynamics shows that increasing DTR shifts the peak temperature value for malaria transmission from 29C (when DTR is 0C) to about 25C (when DTR is 15C). Finally, the malaria model is adapted and used to study the transmission dynamics of chikungunya, dengue and Zika, three diseases co-circulating in the Americas caused by the same vector (Aedes aegypti). The resulting model, which is fitted using data from Mexico, is used to assess a few hypotheses (such as those associated with the possible impact the newly-released dengue vaccine will have on Zika) and the impact of variability in climate variables on the dynamics of the three diseases. Suitable temperature and rainfall ranges for the maximum transmission intensity of the three diseases are obtained. / Dissertation/Thesis / Doctoral Dissertation Applied Mathematics 2018

Les MVs sont un problème majeur de santé publique. L'émergence des MVs nécessite de nouveaux outils pour la surveillance de ces maladies. Ce projet s’intéresse aux deux familles de vecteurs: Ixodidae (R. sanguineus, D. reticulatus et I. ricinus) et Anophèles (An. gambiae s.l. et An. funestus). Une revue synthétise les données actuelles des MTTs et leur vectors, avant de présenter des méthodes de surveillance de ces maladies. La partie expérimentale s'est concentré sur l'élaboration de méthodes pour la sélection des utiles protéines salivaires pour l'évaluation du contact hôte-vecteur. Pour Ixodidae, la stratégie antigénique utilisée a permis d’identifier des protéines salivaires antigéniques communes et spécifiques d’espèce de ces tiques. Ces protéines pourraient servir pour l’évaluation de l’exposition de l’hôte aux Ixodidae. Pour Anophèles, la stratégie candidate utilisée a révélé une protéine salivaire antigénique d’Anopheles (f-5’nuc) pouvant être marqueur prometteur distinguant l'exposition aux Anophèles au niveau de l'espèce. Pour conforter ces résultats, l’établissement d’une relation entre la cinétique des réponses d'anticorps de l’hôte contre ces candidats salivaires, la faune Culicidienne et la variation de densité des populations de moustiques est en cours. Ce projet a souligné que tous les deux vectors peuvent induire une réponse immunitaire chez leur hôte contre des protéines salivaires antigéniques injectées. Il a permis également d’identifier des protéines salivaires permettant la discrimination de l'exposition d'hôte aux vecteurs au niveau du genre ou de l’espèce, offrant de nouvelles stratégies pour la surveillance des MVs. / Vector-borne diseases (VBD) are a major health problem worldwide. The emergence of VBD requires novel monitoring tools. The present project focused on two vector families: Ixodidae (R. sanguineus, D. reticulatus and I. ricinus) and Anopheles (An. gambiae s.l. and An. funestus). A review updates the repartition of TBD, their vectors in Europe, prior to present the different tools for monitoring of TBD transmission. The experimental part focused on establishing methods for selection of useful vector salivary proteins for host-vector contact assessment. Concerning Ixodidae, the studied antigenic strategy successfully identified the shared and discriminant tick salivary antigenic proteins. These identified proteins could be an useful tool to measure host exposition to Ixodidae bites. Concerning Anopheles, the studied candidate strategy revealed an salivary antigenic protein ( f-5’nuc) that could be a promising antigenic marker to distinguish malaria vector exposure at the species level. To comfort these results, the relationship between the kinetic host antibody response against anopheline salivary candidates and the Anopheles fauna population and density variations is under progress. The present work underlined that both two studied vector families following blood meal can elicit a host antibody response against injected vector salivary antigenic proteins. This project proposed for the first time some vector salivary proteins allowing discriminating host exposure to vector bites from genus to species level, opening new strategies for VBD monitoring at the individual and population levels.

Background Dengue is a significant problem of international health concern. According to the World Health Organization in 2012, globally, dengue is “the most important mosquito borne viral disease” with incidence 30 higher than it had been 50 years ago. While most of the burden of disease associated with dengue is located in areas with a tropical and sub-tropical climate, increasing evidence suggests temperate areas are also at risk. Considering the recent introduction of relevant mosquito vectors into Southern Europe, and increasing numbers of imported dengue via travelers, Europe and other temperate areas may be increasingly at risk for dengue emergence, establishment and local transmission in the foreseeable future. Methods Recent dengue emergence in Madeira and reemergence in Tokyo underline the hypothesis that passenger air-travel can be an important conduit for the importation of vector-borne disease leading to emergence in naïve areas climatically suitable for dengue transmission, including parts of Europe. Combining information on travel with virus genetic similarity was useful in discerning likely pathways of for the importation of infections. Generalizing information learned from outbreaks in Tokyo and Madeira with global epidemic intelligence, global travel networks, and climate change projections, leads to more refined understanding of the magnitude of dengue infectious imported into temperate areas and these virus introduction events’ potential implications for seeding epidemics in the 21st century. Results While compared to total travel, imported dengue events and epidemics of dengue outside the tropics are rare, our combined evidence and modeled estimations suggest strongly that epidemic dengue emergence in temperate areas is possible and will continue to increase. We found that global change dynamics including warming temperatures in the much of the northern hemisphere and increasing passenger interconnectivity between areas endemic for dengue and dengue free areas are key mechanisms partly explaining these unprecedented epidemiological transitions. Conclusion While we calibrated our models on information known about dengue, many elements of the methods and conclusions may increase understanding of the potentially global implications for imported infections of other climate-sensitive infectious diseases’ that may have similar parameters. During 2016 and the years to come, techniques developed in this doctoral research will contribute to models used in risk analysis for vector-borne diseases of interest, including the increasing important potential for imported Chikungunya and Zika viruses into a variety of unexposed areas.

Bed bugs (Hemiptera:Cimicidae) are a common, hematophagous ectoparasite of humans and other animals, and are experiencing an international resurgence. Cimicids have been implicated in the transmission many disease agents, including various Bartonella species, however disease transmission has not yet been confirmed. Bartonella spp. are transmitted by a variety of arthropods, including fleas, lice and sand flies, and it is speculated that bed bugs may also serve as a potential vector. In this study, we used an artificial membrane to feed two groups of adult Cimex lectularius rabbit blood, either infected or uninfected with Bartonella henselae. After two weeks, the presence of Bartonella henselae was assessed via PCR, and salivary glands from infected and uninfected bed bugs were dissected and processed for transmission electron microscopy. We were unable to visually identify Bartonella henselae in the images, and therefore unable to confirm the role of bed bugs in B. henselae transmission.

No description available.

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