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

Abstract

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