The mosquito Aedes (Stegomyia) albopictus (Skuse) (Diptera: Culicidae) is an invasive species which has colonized Southern Europe in the last two decades. As it is a competent vector for several arboviruses, its spread is of increasing public health concern, and there is a need for appropriate monitoring tools. In this paper, we have developed a modelling approach to predict mosquito abundance over time, and identify the main determinants of mosquito population dynamics. The model is temperature- and rainfall-driven, takes into account egg diapause during unfavourable periods, and was used to model the population dynamics of Ae. albopictus in the French Riviera since 2008. Entomological collections of egg stage from six locations in Nice conurbation were used for model validation. We performed a sensitivity analysis to identify the key parameters of the mosquito population dynamics. Results showed that the model correctly predicted entomological field data (Pearson r correlation coefficient values range from 0.73 to 0.93). The model’s main control points were related to adult’s mortality rates, the carrying capacity in pupae of the environment, and the beginning of the unfavourable period. The proposed model can be efficiently used as a tool to predict Ae. albopictus population dynamics, and to assess the efficiency of different control strategies.

Background and methodsThe 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.ResultsThe 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%.ConclusionsStructured 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.

To identify the mosquito species able to sustain the transmission of West Nile Virus (WNV) in the Camargue region (the main WNV focus of southern France), we assessed the vector competence of Culex modestus and Culex pipiens, the most abundant bird-feeders, and Aedes caspius, the most abundant mammophilic species occasionally found engorged with avian blood. Female mosquitoes were exposed to the infectious meal (10(10.3) plaque forming units (PFU)/mL) by membrane feeding, and hold at 26 degrees C. After the incubation period, disseminated infection was assessed by WNV detection using an indirect fluorescent antibody assay (IFA) on head squashes, and the transmission rate was assessed by the presence of WNV RNA in salivary secretions with a real-time reverse transcriptase-polymerase chain reaction (RT-PCR). After 14 incubation days, the disseminated infection and the transmission rates were 89.2% and 54.5% for Cx. modestus, 38.5% and 15.8% for Cx. pipiens, and 0.8% and 0 for Ae. caspius. Culex modestus was found to be an extremely efficient laboratory WNV vector and could thus be considered the main WNV vector in wetlands of the Camargue. Culex pipiens was a moderately efficient laboratory WNV vector, but in dry areas of the region it could play the main role in WNV transmission between birds and from birds to mammals. Aedes caspius was an inefficient vector of WNV in the laboratory, and despite its high densities, its role in WNV transmission may be minor in southern France.

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