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Resume Ochlerotatus caspius et Oc. detritus, deux especes de moustiques frequemment rencontrees en Tunisie, font l’objet de traitements insecticides en vue de limiter leur nuisance. Cependant, la portee de ces traitements demeure limitee compte tenu des grandes etendues de leurs biotopes larvaires et du caractere synchrone de leurs eclosions. Le but de cette etude vise a caracteriser, a travers des analyses multivariees (AFC, CHA), la niche ecologique de chaque espece afin de definir des plans d’intervention plus adaptes. Nos resultats montrent que les abondances larvaires d’Oc. caspius et Oc. detritus sont principalement correlees au couvert vegetal et a la salinite des gites larvaires. En effet, Oc. detritus se developpe abondamment dans les milieux fortement sales domines par Sarcocornia fruticosa, alors qu’Oc. caspius est associe a une vegetation plus diversifiee supportant une salinite moindre dominee par Juncus maritimus, et developpant une litiere vegetale plus abondante.

Summary. -Effect of the water quality on the expression of the biotic potential of Culex pipiens Linnaeus in the area of Ben Arous (South of Tunis). An inventory of breeding sites of mosquitoes, drawn up in the area of Ben Arous, allowed the selection of three types of breeding places : floody cave, drainage ditche, floody stone-pit. These sites were followed for one year and a half and their physico-chemical (temperature, pH, salinity, organic polluants, phosphate and nitrogen compounds) and biological (mosquitoes and associated fauna) parameters were studied. These sites, characterized with their content of polluant elements, have a greet influence on their associated fauna. In fact, the clear water of the stone-pit allowed the development of many taxa. This diversity was reduced in polluted water where Culex pipiens was only associated either with Chironomidae or Syrphidae. Concerning the quantitative aspect of C. pipiens, we have demonstrated that this mosquito responds favorably to increased amount of organic matter in the water with a ratio of 1 to 216 according to the degree of the water pollution., Résumé. -Un inventaire des biotopes larvaires des moustiques dans la région de Ben Arous nous a permis de choisir trois types de gîtes représentatifs : vide sanitaire, fossé de drainage et une ancienne carrière inondée. Ces gîtes ont été suivis pendant un an et demi et leurs caractéristiques physico-chimiques (température, pH, salinité, polluants organiques, composés azotés et phosphatés) et biologiques (moustiques et faune annexe) ont été analysées. Caractérisés par leurs teneurs différentes en éléments polluants, ces biotopes larvaires ont une influence considérable sur la faune qui leur est associée. En effet, l'eau de l'ancienne carrière, relativement propre, permet le développement de nombreux taxons. Lorsque l'eau est eutrophisée (cas du vide sanitaire et du fossé de drainage), nous avons remarqué un appauvrissement très prononcé de la faune se limitant aux larves de Culex pipiens associées aux larves de Chironomidae dans le premier gîte et de Syrphidae dans le second gîte. Concernant l'aspect quantitatif de C. pipiens, nous avons mis en relief le fait que ce moustique répond positivement à une augmentation de la teneur de l'eau en matière organique avec un rythme de multiplication variant dans un rapport de 1 à 216 selon le degré de pollution de l'eau., Krida Ghazi, Rhaiem Adel, Bouattour Ali. Effet de la qualité des eaux sur l'expression du potentiel biotique de Culex pipiens Linné dans la région de Ben Arous (banlieue sud de Tunis). In: Bulletin de la Société entomologique de France, volume 102 (2), juin 1997. pp. 143-150.

Le moustique Culex pipiens a ete implique dans la transmission du virus West Nile en Tunisie. Les caracteristiques bioecologiques de l’espece ainsi que certains facteurs environnementaux ont favorise l’emergence de ce virus dans une region jusqu’alors indemne. Ce scenario fait craindre l’emergence d’autres arbovirus dont le virus de la fievre de la vallee du Rift (FVR) qui affecte principalement les petits ruminants. La proximite de pays ou circule le virus de la FVR avec lesquels la Tunisie entretient le commerce d’animaux n’est pas sans risque. Pour mesurer le risque potentiel d’introduction du virus de la FVR en Tunisie, differents aspects ont ete etudies : la competence vectorielle des populations de Cx. pipiens et leur niveau de differenciation genetique. Nous avons mis en evidence une competence vectorielle faible vis-a-vis du virus de la FVR et une differenciation forte entre populations temoignant d’une faible capacite de dispersion de l’espece. Ainsi, nous concluons que meme si le virus de la FVR etait introduit, l’amplification virale dans le vecteur Cx. pipiens, tout en etant possible, ne serait pas associee a une dissemination du virus par l’intermediaire du moustique. Toutefois, le caractere emergent du virus de la FVR et la presence d’autres especes potentiellement vectrices (e.g. Ochlerotatus caspius) doivent imposer le maintien et meme le renforcement des surveillances zoosanitaire et entomologique afin de limiter le risque d’introduction et de circulation du virus de la FVR en Tunisie.

International audience; Rift Valley fever virus continues to cause large outbreaks of acute and febrile illness among humans and domestic animals in Africa. The high pathogenicity of the virus is mainly due to the non-structural protein derived from the S segment NSs, which was shown to inhibit the type I interferon expression at the transcriptional level and to suppress host cell RNA synthesis. Clone 13, a naturally attenuated clone containing a deletion of 70% in NSs, is a promising vaccine candidate as it has no pathogenicity for mice and is highly immunogenic leading to long-lasting immunity. If Clone 13 succeeds in inducing a transient viremia in inoculated animals, is a mosquito vector able to replicate Clone 13 and is the vector affected by viral infection? In this work, we orally infected two mosquito species, Aedes vexans and Culex pipiens quinquefasciatus, with the avirulent Clone 13. We showed that the mosquito Ae. vexans better replicated the avirulent Clone 13 than Cx. p. quinquefasciatus. Moreover, infection with Clone 13 did not cause any important changes in mosquito's life-history traits compared to noninfected females. Nevertheless, it is likely that Clone 13 would not be efficiently transmitted by mosquito vectors.

International audience; We evaluated the ability of three mosquito species (Aedes caspius, Aedes detritus, Culex pipiens), collected in southern France and Tunisia, and of different laboratory-established colonies (Aedes aegypti, Aedes albopictus, Aedes vexans, Anopheles gambiae, Culex pipiens, Culex quinquefasciatus) to disseminate two strains of Rift Valley fever virus (RVFV), the virulent ZH548 and the avirulent Clone 13. After feeding on an infectious blood meal at 10(8.5) plaque-forming units/mL, females were maintained at 30 degrees C for 14 days. Surviving females were tested for the presence of virus on head squashes. Disseminated infection rate corresponds to the number of females with disseminated infection among surviving females. Among field-collected mosquitoes, Cx. pipiens was the most susceptible species with disseminated infection rates ranging from 3.9% to 9.1% for French strains and up to 14.7% for Tunisian strains. Among laboratory-established colonies, Ae. aegypti from Tahiti exhibited the highest disseminated infection rates: 90% when infected with ZH548 and 72.6% with Clone 13. The presence of competent Cx. pipiens in southern France and Tunisia indicates the potential for RVFV epizootics to occur if the virus was introduced into countries of the Mediterranean basin.

Compared morphological characteristics of the four larval stages of Culex (Culex) pipiens Linnaeus from Tunisia (Diptera, Culicidae). The study of compared morphological characteristics of the four larval stages of Culex pipiens, collected in the south of Tunis, allowed us to precise these characteristics. The frontal seta, antennal seta (inserted at the third level of the antenna), subsiphonal seta (seta 1-VIII), ano-siphonal seta (seta 3-VIII), as well as the ventral brush (seta 4-X) of the anal segment play an important role in distinguishing these stages. It is the same for the number of spines on the siphonal pecten. In addition, the number and the arrangement of the scales' segment VIII represent reliable criteria to distinguish these four larval stages., L'étude de la morphologie comparée des quatre stades larvaires de Culex pipiens échantillonné dans le sud de Tunis nous a permis de préciser leurs caractères morphologiques. Les soies frontales, la soie antennaire (insérée à la hauteur du tiers moyen de l'antenne), subsiphonale, ano-siphonale ainsi que les soies de la brosse ventrale du segment anal jouent un rôle important dans la distinction de ces stades. Il en est de même pour le nombre de dents portées par le peigne siphonique. Le nombre et la disposition des écailles qui ornent le VIIIe segment abdominal sont également des critères fiables pour distinguer les quatre stades., Krida Ghazi, Rhaiem Adel, Jarraya A., Bouattour Ali. Morphologie comparée des quatre stades larvaires de Culex (Culex) pipiens Linné récolté en Tunisie (Diptera, Culicidae). In: Bulletin de la Société entomologique de France, volume 103 (1), mars 1998. pp. 5-10.

International audience; Culex pipiens pipiens is a common mosquito found in North Africa and is the primary vector of Bancroftian filariasis in Egypt. Experimental infections with C. p. pipiens have demonstrated that this species supports Brugia pahangi development (parasitic yield 6.3%). In addition, the genetic variation among C. p. pipiens populations from Ben Arrous (in the suburb of Tunis) estimated from isoenzyme polymorphism of five neutral genes (Pgm, Gpi, Hk1, Got-1, and Got-2) was slight (Fst = +0.083). C. p. pipiens from Tunis seems to consist of a homogeneous population that is susceptible to Brugia infection.

International audience; West Nile fever (WNF) and Rift Valley fever (RVF) are emerging diseases causing epidemics outside their natural range of distribution. West Nile virus (WNV) circulates widely and harmlessly in the old world among birds as amplifying hosts, and horses and humans as accidental dead-end hosts. Rift Valley fever virus (RVFV) re-emerges periodically in Africa causing massive outbreaks. In the Maghreb, eco-climatic and entomologic conditions are favourable for WNV and RVFV emergence. Both viruses are transmitted by mosquitoes belonging to the Culex pipiens complex. We evaluated the ability of different populations of Cx. pipiens from North Africa to transmit WNV and the avirulent RVFV Clone 13 strain. Mosquitoes collected in Algeria, Morocco, and Tunisia during the summer 2010 were experimentally infected with WNV and RVFV Clone 13 strain at titers of 107.8 and 108.5 plaque forming units/mL, respectively. Disseminated infection and transmission rates were estimated 14-21 days following the exposure to the infectious blood-meal. We show that 14 days after exposure to WNV, all mosquito st developed a high disseminated infection and were able to excrete infectious saliva. However, only 69.2% of mosquito strains developed a disseminated infection with RVFV Clone 13 strain, and among them, 77.8% were able to deliver virus through saliva. Thus, Cx. pipiens from the Maghreb are efficient experimental vectors to transmit WNV and to a lesser extent, RVFV Clone 13 strain. The epidemiologic importance of our findings should be considered in the light of other parameters related to mosquito ecology and biology.