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Murviel-lès-Montpellier, France

Cailly P.,French National Institute for Agricultural Research | Cailly P.,University of Nantes | Cailly P.,CIRAD - Agricultural Research for Development | Tran A.,CIRAD - Agricultural Research for Development | And 5 more authors.
Ecological Modelling | Year: 2012

As mosquitoes are vectors of major pathogens worldwide, the control of mosquito populations is one way to fight vector-borne diseases. The objectives of our study were to develop a tool to predict mosquito abundance over time, identify the main determinants of mosquito population dynamics, and assess mosquito control strategies. We developed a generic, mechanistic, climate-driven model of seasonal mosquito population dynamics that can be run over several years because it takes diapause into account. Both aquatic and adult stages are considered, resulting in 10 model compartments: eggs, larvae, and pupae for juveniles; emergent, nulliparous, and parous for adults, the latter two broken down into host-seeking, resting, and ovipositing adults. We then applied the model to Anopheles species of southern France, some of which (nulliparous adults) overwinter. We defined specific transition functions and parameter values for these species and this geographical area based on a literature review. Our model correctly predicted entomological field data. Control points in the model were related to mortality rates of adults, the sex-ratio at emergence, parameters related to development functions and the number of eggs laid by females. Lastly, we used our model to compare the efficiency of mosquito control strategies targeting larvae. We found that a larvicide spraying at regular time intervals acted as a preventive measure against mosquito emergence, and that such a strategy was more efficient than spraying only when the abundance of host-seeking females reached a given threshold. The proposed model can be applied easily to other mosquito species and geographic areas by adapting transition functions and parameter values. © 2011 Elsevier B.V. Source


Viennet E.,CIRAD - Agricultural Research for Development | Viennet E.,Australian National University | Garros C.,CIRAD - Agricultural Research for Development | Rakotoarivony I.,CIRAD - Agricultural Research for Development | And 11 more authors.
PLoS ONE | Year: 2012

Feeding success of free-living hematophagous insects depends on their ability to be active when hosts are available and to reach places where hosts are accessible. When the hematophagous insect is a vector of pathogens, determining the components of host-seeking behavior is of primary interest for the assessment of transmission risk. Our aim was to describe endo/exophagy and circadian host-seeking activity of Palaearctic Culicoides species, which are major biting pests and arbovirus vectors, using drop traps and suction traps baited with four sheep, as bluetongue virus hosts. Collections were carried out in the field, a largely-open stable and an enclosed stable during six collection periods of 24 hours in April/May, in late June and in September/October 2010 in western France. A total of 986 Culicoides belonging to 13 species, mainly C. brunnicans and C. obsoletus, was collected on animal baits. Culicoides brunnicans was clearly exophagic, whereas C. obsoletus was able to enter stables. Culicoides brunnicans exhibited a bimodal pattern of host-seeking activity with peaks just after sunrise and sunset. Culicoides obsoletus was active before sunset in spring and autumn and after sunset in summer, thus illustrating influence of other parameters than light, especially temperature. Description of host-seeking behaviors allowed us to discuss control strategies for transmission of Culicoides-borne pathogens, such as bluetongue virus. However, practical vector-control recommendations are difficult to provide because of the variation in the degree of endophagy and time of host-seeking activity. © 2012 Viennet et al. Source


Devillers J.,CTIS | Lagneau C.,EID Mediterranee | Lattes A.,University Paul Sabatier | Garrigues J.C.,University Paul Sabatier
SAR and QSAR in Environmental Research | Year: 2014

Human arboviral diseases have emerged or re-emerged in numerous countries worldwide due to a number of factors including the lack of progress in vaccine development, lack of drugs, insecticide resistance in mosquitoes, climate changes, societal behaviours, and economical constraints. Thus, Aedes aegypti is the main vector of the yellow fever and dengue fever flaviviruses and is also responsible for several recent outbreaks of the chikungunya alphavirus. As for the other mosquito species, the A. aegypti control relies heavily on the use of insecticides. However, because of increasing resistance to the different families of insecticides, reduction of Aedes populations is becoming increasingly difficult. Despite the unquestionable utility of insecticides in fighting mosquito populations, there are very few new insecticides developed and commercialized for vector control. This is because the high cost of the discovery of an insecticide is not counterbalanced by the ‘low profitability’ of the vector control market. Fortunately, the use of quantitative structure–activity relationship (QSAR) modelling allows the reduction of time and cost in the discovery of new chemical structures potentially active against mosquitoes. In this context, the goal of the present study was to review all the existing QSAR models on A. aegypti. The homology and pharmacophore models were also reviewed. Specific attention was paid to show the variety of targets investigated in Aedes in relation to the physiology and ecology of the mosquito as well as the diversity of the chemical structures which have been proposed, encompassing man-made and natural substances. © 2014 The Author(s). Published by Taylor & Francis. Source


Mathieu B.,University of Strasbourg | Cetre-Sossah C.,CIRAD - Agricultural Research for Development | Garros C.,CIRAD - Agricultural Research for Development | Chavernac D.,CIRAD - Agricultural Research for Development | And 7 more authors.
Parasites and Vectors | Year: 2012

Background and methods: The appearance of bluetongue virus (BTV) in 2006 within northern Europe exposed a lack of expertise and resources available across this region to enable the accurate morphological identification of species of Culicoides Latreille biting midges, some of which are the major vectors of this pathogen. This work aims to organise extant Culicoides taxonomic knowledge into a database and to produce an interactive identification key for females of Culicoides in the Western Palaearctic (IIKC: Interactive identification key for Culicoides). We then validated IIKC using a trial carried out by six entomologists based in this region with variable degrees of experience in identifying Culicoides. Results: The current version of the key includes 98 Culicoides species with 10 morphological variants, 61 descriptors and 837 pictures and schemes. Validation was carried out by six entomologists as a blind trial with two users allocated to three classes of expertise (beginner, intermediate and advanced). Slides were identified using a median of seven steps and seven minutes and user confidence in the identification varied from 60% for failed identifications to a maximum of 80% for successful ones. By user class, the beginner group successfully identified 44.6% of slides, the intermediate 56.8% and the advanced 74.3%. Conclusions: Structured as a multi-entry key, IIKC is a powerful database for the morphological identification of female Culicoides from the Western Palaearctic region. First developed for use as an interactive identification key, it was revealed to be a powerful back-up tool for training new taxonomists and to maintain expertise level. The development of tools for arthropod involvement in pathogen transmission will allow clearer insights into the ecology and dynamics of Culicoides and in turn assist in understanding arbovirus epidemiology. © 2012 Mathieu et al.; licensee BioMed Central Ltd. Source


Roche B.,UMIIRD | Leger L.,IRD Montpellier | L'Ambert G.,EID Mediterranee | Lacour G.,EID Mediterranee | And 5 more authors.
PLoS ONE | Year: 2015

Invasion of new territories by insect vector species that can transmit pathogens is one of the most important threats for human health. The spread of the mosquito Aedes albopictus in Europe is emblematic, because of its major role in the emergence and transmission of arbo-viruses such as dengue or chikungunya. Here, we modeled the spread of this mosquito species in France through a statistical framework taking advantage of a long-term surveillance dataset going back to the first observation of Ae. albopictus in the Metropolitan area. After validating the model, we show that human activities are especially important for mosquito dispersion while land use is a major factor for mosquito establishment. More importantly, we show that Ae. albopictus invasion is accelerating through time in this area, resulting in a geographic range extending further and further year after year. We also show that sporadic "jump" of Ae. albopictus in a new location far from the colonized area did not succeed in starting a new invasion front so far. Finally, we discuss on a potential adaptation to cooler climate and the risk of invasion into Northern latitudes. Copyright: © 2015 Roche et al. Source

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