Changements globaux, activités humaines et agents pathogènes (ré-) émergents transmis par les moustiques: diversité, écologie et contrôle des vecteurs potentiels

Worldwide, mosquitoes (Diptera: Culicidae) are known as potential vectors of pathogens that cause infectious diseases, affecting both humans and animals, such as malaria, dengue, chikungunya, West Nile fever and dirofilariasis. In terms of morbidity and mortality, mosquitoes are considered as the most dangerous animals confronting mankind. Indeed, over three billion people live at risk of becoming infected by a mosquito-borne disease. Focus on mosquitoes has greatly increased not only in the tropic areas but also in the Palearctic region like Europe and Mediterranean areas. Researches on re-emerging vector-borne diseases are become a major issue in human and animal health worldwide, both in the North and South hemisphere. The spread in space and time of these many vector-borne diseases is strongly influenced by environmental factors (landscape, location and abundance of hosts and vectors, etc.) and climate (temperature, humidity, etc.) that influence population dynamics of the vector and the reservoir hots of pathogens. The acquisition of bio-ecological and taxonomic knowledges of mosquitoes is nevertheless an essential step for the understanding, preventing and management of current risks of the (re)-emergence of mosquito-borne parasites and mainly the preparation and prevention against future threats. The absence of vaccine and treatments against most of mosquito-borne diseases implies efficient vector control strategies, which are up to date mainly based on the use of chemical insecticides. However, most vectors develop resistance against currently used products whereas new chemical compounds was limited firstly by financial costs in research and development, and secondly by the toxicity of derivatives to human population, biodiversity, and environment. The exploitation of new methods, such as the use of microbial communities (mainly bacteria or entomopathogenic fungi) for vector control, will be therefore a promoted strategy at the global level. This doctoral thesis focuses on five main objectives: (i) to inventory and identify mosquito fauna in the livestock areas and their surroundings, especially in the equestrian farms; (ii) to study the population genetic structure of the potential vector complex Cx. pipiens s.l.; iii) to study the phylogeny and the origin of exotic mosquito species (Ae. albopictus & Ae. koreicus) as well as the potential tracks of their introduction; (iv) to know the bioecology and spatiotemporal dynamic of potential vectors; and finally (v) to suggest a biocontrol tool that can prevent and fight the proliferation of mosquitoes especially potential vectors and those causing nuisance problems. Obtained results in this thesis allowed highlighting identification and record of new mosquito species in the studied areas. It also allowed updating the list of mosquito fauna in the two countries, Belgium (31 species including three invasive mosquitoes) and Algeria (53 species including four new records form this research: Culex brumpti, Coquillettidia richiardii, Cq. Buxtoni and Uranotaenia balfouri). The phylogenetic analyses (COI and ND4) performed during this thesis allowed to confirm that Aedes koreicus and Ae. japonicas complex constitute two distinct species. In addition, given the phylogenetic analyses (COI and ND5 genes) and information about the origin of used tires inspected during this study in Belgium, Ae. albopictus was very probably reintroduced from the United States. In both Belgium and Algeria, this work permitted identifying and confirming the presence of different molecular forms of the Cx. pipiens complex: Cx. pipiens form pipiens, Cx. pipiens f. molestus as well as their hybrid form. Medical and veterinary importance of identified mosquito species and the risk of (re-)emerging of mosquito-borne diseases in Belgium and Algeria are discussed. Finally, the endosymbiont bacteria Pseudomonas seemed to be an interesting candidate for paratransgenic bacteria in order to reduce and/or inhibit the transmission of pathogens by mosquito vectors

Livestock farms in Belgium shelter they the mosquitoes (Diptera, Culicidae) potentially vectors of arboviruses?

Although no major arbovirus which mosquitoes are responsible for its transmission has been recorded in Belgium in recent decades, environment and climate change, current and future, could favor the emergence of vector-borne diseases in the country, by inducing changes on Culicidae populations. This study aims to determine the potential importance of agricultural environments, and especially livestock farms, to welcome and favor the proliferation of certain species of mosquito responsible for transmission of arboviruses. A taxonomic inventory was conducted in 2008 (III, VI and X) and 2009 (V and IX) in ten cattle farms, and in 2010 (X) in ten stables located in Belgium. The harvest of mosquitoes is based on larval sampling at the level of 14 biotopes such as water troughs, used tires, abandoned utensils and temporary puddles or not. The morphotaxonomic study of larvae and genitalia has allowed to identify eight species in 18 study stations. These are Anopheles claviger Meigen, 1804 ; A. maculipennis s.l. Meigen, 1818 ; Culiseta annulata Schrank, 1776 ; Cs. morsitans Theobald, 1901 ; Culex modestus Ficalbi, 1889 ; Cx. torrentium Martini, 1925 ; Cx. territans Walker, 1856 and Cx. pipiens s.l. L., 1758. Of the 1843 individuals examined in 2009, Cx. pipiens s.l. represents 79.98% of the total harvest; however, Cx. modestus represents only 0.92%. Used tires form the most favorable habitat for larval development of Culicidae. Therefore, despite the low diversity of mosquito observed within the livestock environments, they represent a significant risk for the reproduction of some potential vectors of arboviruses. In addition, some larval habitats constitute very favorable sites for proliferation of mosquito, causing a real problem of nuisance for animals of farms

Molecular detection of six high importance endosymbiotic bacteria in Belgian wild-caught mosquitoes

Introduction Several disease vectors presented a resistance to various pesticides currently used. One of an alternative solution was to use endosymbiotic bacteria because their probably interactive effects with their host. According to the introduction risks of mosquito born disease and their dispersion, we propose to investigate the prevalence of six endosymbiontic bacteria in wild-caught Culicidae in Belgium. Methods Eleven species of Belgian fields mosquitoes (Culex pipiens s.l., Cx. torrentium, Cx. hortensis, Anopheles claviger, An. maculipennis s.l., An. plumbeus, Culiseta annulata, Ochlerotatus geniculatus, Oc. dorsalis, Aedes albopictus and Coquillettidia richiardii) were used for the screening of six genera endosymbiotic bacteria (Wolbachia sp., Commamonas sp., Delftia sp., Pseudomonas sp., Acinetobacter sp. and Asaia sp.) according to their possible impact in mosquito biology. PCR was done for the screening and positives bands were sequenced and deposited in GenBank. Results Total of 144 larvae and 32 adults were used. Wolbachia, Pseudomonas, Acinetobacter and Asaia were found in mosquitoes with different proportions, according to stages (adults, larvae) with a predominance of Pseudomonas in all species, as far as Acinetobacter and Asaia also have a high prevalence. Commamonas and Delftia were absent from all species tested, either in larvae and in adults. Discussion Choice of endosymbiotic bacteria studied here was allowing of their importance in literature. For Pseudomonas, it showed that this bacteria could produced ovipositon attractants for mosquito. Acinetobacter was suggested efficient in transmission and maintenance within host populations. Asaia was capable of efficiently crossing body barriers and colonizing different organs. Wolbachia was currently the most studied bacteria which plays an important role in the genetic manipulation of the host. Present advances in understanding the mosquito–microbiota relationships may have a great impact in a better understanding of some traits of mosquito biology and in the development of innovative mosquito-borne disease-control strategies.Contribution à l’étude des endosymbiotes des Culicidae de Belgique : rôles dans la transmission virale et cible pour le contrôle des moustique

Moustiques (Diptera : Culicidae) de la région du M’Zab-Ghardaïa, Algérie : biodiversité et importance médico-vétérinaire

De nombreuses espèces de moustiques sont susceptibles de jouer un rôle dans la transmission de divers agents pathogènes responsables des maladies infectieuses humaines et animales. D'autres, outre leur rôle vecteur, sont un véritable fléau par les piqûres douloureuses qu’ils occasionnent et, constituent de ce fait un grand problème de nuisance. L'identification précise et la connaissance de la biodiversité fonctionnelle des vecteurs est un pas essentiel pour la compréhension du risque de (ré)-émergence et la dynamiques des maladies vectorielles. Le présent travail est une étude rétrospective des inventaires des Culicidae réalisés sur le terrain dans la région du M’Zab (Ghardaïa, Algérie) durant les années allant de 2008 à 2012. Les résultats de l’étude morphotaxonomique des Culicidae inventoriés ont montré la présence de dix espèces réparties en cinq genres (Culex, Culiseta, Ochlerotatus, Anopheles et Uranotaenia). Un aperçu sur le rôle vectoriel des espèces signalées dans la région et leur importance au niveau de la santé médicale et vétérinaire sont présentés à partir des données bibliographiques. Les espèces potentiellement vectrices d’arbovirus (Virus de Nile occidentale et Virus de la Vallée du Rift) et de protozoaires (Plasmodium spp) qui peuvent causer des problèmes épidémiologique au niveau de la région du M’Zab sont Cx. pipiens sl L., 1758, Cx. theileri Theobald, 1903, Ochlerotatus caspius Pallas, 1771, Anopheles sergentii Theobald, 1907, An. dthali Patton, 1905 et An. multicolor Cambouliu, 1902