Laboratory Evaluation of Flight Capacities of Aedes japonicus (Diptera: Culicidae) Using a Flight Mill Device.

Dispersion expands the distribution of invasive species and as such, it is a key factor of the colonization process. Aedes japonicus japonicus (Theobald, 1901) is an invasive species of mosquito and a vector of various viruses. It was detected in the northeast of France in 2014. The population of this species can expand its distribution by several kilometers per year. However, though flight capacities play an active part in the dispersion of Ae. japonicus, they remain unknown for this species. In this study, we investigated the flight capacities of Ae. japonicus in a laboratory setting using the flight mill technique. We evaluated the influence of age on flight. We recorded videos of individual flights with a camera mounted on Raspberry Pi. We extracted data on distance, duration, and speed of flight using the Toxtrac and Boris software. Our analysis showed a median flight distance of 438 m with a maximum of 11,466 m. Strong flyers, which represented 10% of the females tested, flew more than 6,115 m during 4 h and 28 min at a speed of 1.7 km per h. As suspected, Ae. japonicus is a stronger flyer than the other invasive species Aedes albopictus (Skuse, 1894) (Diptera: Culicidae). To our knowledge, this is the first flight mill study conducted on Ae. japonicus and therefore the first evaluation of its flight capacity. In the future, the flight propensity of Ae. japonicus determined in this study can be included as a parameter to model the colonization process of this invasive vector species.

Update on tick-borne pathogens detection methods within ticks.

Ticks are known vectors of various pathogens, including bacteria, parasites and viruses, that impact both animal and human health. Improving knowledge of the distribution of tick-borne pathogens, combined with their early detection in ticks, are essential steps to fight against tick-borne diseases and mitigate their impacts. Here we give an overview of what are the common methods of pathogen detection in tick samples, including recent developments concerning how to handle tick samples, get access to tick-borne pathogens by chemical or physical disruption of the ticks, and methods used for the RNA/DNA extraction steps. Furthermore, we discuss promising tools that are developed for other sample types such as serum or blood to detect tick-borne pathogens, and those that could be used in the future for tick samples.

Diapause characterisation and seasonality of Aedes japonicus japonicus (Diptera, Culicidae) in the northeast of France.

The invasive mosquito Aedes japonicus japonicus (Theobald, 1901) settled in 2013 in the Alsace region, in the northeast of France. In this temperate area, some mosquito species use diapause to survive cold winter temperatures and thereby foster settlement and dispersal. This study reports diapause and its seasonality in a field population of Ae. japonicus in the northeast of France. For two years, eggs were collected from May to the beginning of November. They were most abundant in summer and became sparse in late October. Diapause eggs were determined by the presence of a fully developed embryo in unhatched eggs after repeated immersions. Our study showed effective diapause of Ae. japonicus in this part of France. At the start of the egg-laying period (week 20), we found up to 10% of eggs under diapause, and this rate reached 100% in October. The 50% cut-off of diapause incidence was determined by the end of summer, leading to an average calculated maternal critical photoperiod of 13 h 23 min. Interestingly, diapause was shown to occur in part of the eggs even at the earliest period of the two seasons, i.e. in May of each year. Even though we observed that the size of eggs was positively correlated with diapause incidence, morphology cannot be used as the unique predictive indicator of diapause status due to overlapping measurements between diapausing and non-diapausing eggs. This study provides new knowledge on diapause characterisation and invasive traits of Ae. japonicus.

TITLE: Caractérisation de la diapause et saisonnalité d'Aedes japonicus japonicus (Diptera, Culicidae) dans le nord-est de la France. ABSTRACT: Aedes japonicus japonicus (Theobald, 1901), un moustique invasif, s'est installé en 2013, en Alsace, dans le nord-est de la France. Dans une telle région tempérée, certaines espèces de moustiques ont recours à la diapause pour survivre aux températures froides de l'hiver, ce qui favorise donc l'établissement et la dispersion de ces espèces. Cette étude montre le phénomène de diapause et la saisonnalité d'une population sauvage d'Ae. japonicus dans le nord-est de la France. Pendant deux ans, les œufs ont été collectés de mai à début novembre. Ils étaient plus abondants durant l'été et plus rarement présents en octobre. Les œufs diapausants ont été déterminés par la présence d'un embryon entièrement développé dans les oeufs non éclos après des immersions répétées. Notre étude a mis en évidence une diapause effective d'Ae. japonicus dans le nord-est de la France. Au début de la période de ponte (semaine 20), jusqu'à 10 % des œufs a été trouvé à l'état de diapause et ce taux atteint 100 % en octobre. Un taux de 50 % de diapause a été atteint à la fin de l'été, amenant à une photopériode critique maternelle calculée de 13 heures 23 minutes en moyenne. De façon intéressante, il a été montré que la diapause se produisait chez une partie des œufs, et ce même dès le début des deux saisons, en mai de chaque année. Bien que nous ayons observé que les mesures des œufs étaient positivement corrélées avec le taux de diapause, la morphologie des œufs seule ne peut pas être utilisée comme unique indicateur de prédiction du statut de diapause, à cause d'un chevauchement des mesures entre les œufs diapausants et non diapausants. Cette étude offre de nouvelles connaissances sur les caractéristiques de la diapause et sur les traits d'invasion d'Ae. japonicus.

Wing Morphometrics of Aedes Mosquitoes from North-Eastern France.

BACKGROUND: In the context of the increasing circulation of arboviruses, a simple, fast and reliable identification method for mosquitoes is needed. Geometric morphometrics have proven useful for mosquito classification and have been used around the world on known vectors such as Aedes albopictus. Morphometrics applied on French indigenous mosquitoes would prove useful in the case of autochthonous outbreaks of arboviral diseases. METHODS: We applied geometric morphometric analysis on six indigenous and invasive species of the Aedes genus in order to evaluate its efficiency for mosquito classification. RESULTS: Six species of Aedes mosquitoes (Ae. albopictus, Ae. cantans, Ae. cinereus, Ae. sticticus, Ae. japonicus and Ae. rusticus) were successfully differentiated with Canonical Variate Analysis of the Procrustes dataset of superimposed coordinates of 18 wing landmarks. CONCLUSIONS: Geometric morphometrics are effective tools for the rapid, inexpensive and reliable classification of at least six species of the Aedes genus in France.