Biology subjects

Lacour, G.

Publications and source records attributed to Lacour, G..

6 recordsLinked to original sources

bioRxiv2026

Early-warning surveillance of West Nile and Usutu viruses in water and mosquito excreta using digital PCR

1.West Nile virus (WNV) and Usutu virus (USUV) are mosquito-borne pathogens maintained in bird-mosquito cycles and increasingly cause human and equine disease in temperate regions. As most infections are asymptomatic, surveillance based on clinical and veterinary reports provides delayed signals for vector control and equine vaccination strategies. We implemented, in 2024 and 2025, an operational environmental surveillance strategy combining molecular xenomonitoring of adult mosquito excreta with water sampling from wetlands and mosquito breeding sites, coupled to a standardized multiplex reverse transcription digital PCR workflow. Viral detection was performed using a multiplex digital PCR assay with characterized limits of blank, detection, and quantification, and low-level positives were confirmed by Sanger sequencing. This multi-matrix approach detected WNV RNA in southern France as early as 1 July 2024, 40 days before the first human case and 67 days before the first equine alert, and on 9 April 2025, a full 19 weeks ahead of the first human case that year. USUV RNA was similarly detected from 5 July 2024 and 22 April 2025, providing actionable early warnings to guide targeted vector control and preparedness. Across both years, WNV and USUV were detected 29 and 8 times among 396 samples in 2024, and 90 and 14 times among 815 samples in 2025, revealing previously unrecognized, cryptic virus circulation. These results demonstrate that integrating environmental surveillance provides a sensitive, proactive framework for the early detection of emerging Culex-borne arboviruses, offering precious lead time for public one-health strategies.

ecology↗

bioRxiv2025

Temperature is the key weather determinant of Aedes albopictus seasonal activity in southern France

The presence and the activity of Aedes albopictus are a growing concern for nuisance and public health in Europe. Vector control operators, public health officers, and communities look for weather-based decision support systems to inform mosquito management policies. Despite an increasing number of entomological and modelling studies, our incomplete understanding of mosquito population response to weather drivers in natural conditions restricts the development of sound vector management policies. Here, we aim to clarify the role of weather conditions on Ae. albopictus presence and abundance in four sites in southwestern France. We rely on ovitrap longitudinal records collected on a 1-2 weeks basis and weather time series over 2023 and 2024 to model oviposition activity. Our analysis combines a mechanistic model from literature and a new machine learning model fitted on cross-correlated lagged weather predictors. Both models satisfactorily reproduce the observed oviposition dynamics, correctly predicting the onset and the end of the activity - periods that existing models have often inadequately captured. Temperature plays a major role in triggering the presence of Ae. albopictus, explaining the interannual variation of oviposition in all sites, especially in spring and autumn. In fact, warm springs and autumns extend the periods in which Ae. albopictus life-history traits (fertility, development, survival) approach their thermal optima. In summer, a more prominent role of rain and humidity emerges among secondary drivers of oviposition intensity. This work contributes to the development of operational weather-driven forecasting tools for Ae. albopictus activity to support vector control operations in different biogeographical contexts.

ecology↗

bioRxiv2025

Aedes albopictus is rapidly invading its climatic niche in France: wider implications for biting nuisance and arbovirus control in Western Europe

The Asian tiger mosquito, Aedes albopictus, is a competent vector of arboviruses, such as dengue. After its introduction into southern Europe, this invasive species has been rapidly spreading as well as causing autochthonous cases of arboviral diseases. Both Ae. albopictus presence and potential to transmit arboviruses are facilitated at warm temperatures, hence global warming is expected to affect their presence in temperate regions. We use a climate- and environmental-driven mechanistic modelling framework to investigate the impact of recent climate change on Ae. albopictus range expansion and its potential to transmit dengue in Western Europe. We simulate climatic suitability, adult density and dengue transmission risk which we compare with a large ensemble of entomological and epidemiological observations over the past 20 years. Most importantly, we analyze a novel spatiotemporal dataset of colonized municipalities in metropolitan France to estimate the spread rate of Ae. albopictus and compare it with model predictions. Lastly, we analyze the sensitivity of entomological and epidemiological risk to changes in temperature, rainfall and human density. Distribution of simulated mosquito populations and dengue transmission risk satisfactorily match entomological and dengue observations for Western Europe (AUC = 0.90 and 0.75 respectively). While lowlands in southern Europe were already climatically suitable for hosting Ae. albopictus around 2010, Western France, together with large populated cities, such as London, Zagreb and Vienna, have become suitable recently. Importantly, the accelerating colonization of Ae. albopictus in France may be approaching the limit of its theoretical climatic niche; future expansion will depend on the climate-driven enlargement of suitable areas. Area at risk of dengue transmission has recently expanded from the Mediterranean coasts over northern Spain and Western France. The sensitivity analysis suggests that climate change may expose medium-sized cities to the highest epidemiological risk; this finding is consistent with recently reported dengue outbreaks in Europe.

ecology↗

bioRxiv2023

Multiplexed amplicon sequencing reveals the heterogeneous spatial distribution of pyrethroid resistance mutations in Aedes albopictus mosquito populations in Southern France.

The risk of mosquito-borne diseases transmission is moving fast toward temperate climates with the colonization and proliferation of the Asian tiger mosquito vector Aedes albopictus and the rapid and mass transport of passengers returning from tropical regions where the viruses are endemic. The prevention of major Aedes-borne viruses heavily relies on the use of insecticides for vector control, mainly pyrethroids In Europe. High-throughput molecular assays can provide a cost-effective surrogate to phenotypic insecticide resistance assays when mutations have been previously linked to a resistance phenotype. Here, we screened for the spatial distribution of kdr mutations at a large scale using a two-step approach based on multiplexed amplicon sequencing and an unprecedented collection of field-derived mosquitoes in South of France. We identified the presence of the V1016G allele in 14 sites. The V1016G allele was predominantly found in South-East France close to the Italian border with two additional isolated sites close to Bordeaux and Marmande. All mosquitoes were heterozygous for this mutation and should not be phenotypically resistant to pyrethroid insecticide. Four other mutations were identified in our targeted genomic sequence: I1532T, M1006L, M1586L, M995L. Sequencing a section of maternally inherited mitochondrial genome confirmed that the spread of Ae. albopictus in France originated from founders with haplogroup A1. These findings contribute to the broader understanding of resistance dynamics in Europe and can inform targeted approaches to mitigate the impact of resistance on vector control.

genetics↗

bioRxiv2021

dynamAedes: a unified modelling framework for invasive Aedes mosquitoes

O_LIMosquito species belonging to the genus Aedes have attracted the interest of scientists and public health officers for their invasive species traits and efficient capacity of transmitting viruses affecting humans. Some of these species were brought outside their native range by human activities such as trade and tourism, and colonised new regions thanks to a unique combination of eco-physiological traits. C_LIO_LIConsidering mosquito physiological and behavioural traits to understand and predict the spatial and temporal population dynamics is thus a crucial step to develop strategies to mitigate the local densities of invasive Aedes populations. C_LIO_LIHere, we synthesised the life cycle of four invasive Aedes species (Ae. aegypti, Ae. albopictus, Ae. japonicus and Ae. koreicus) in a single multi-scale stochastic modelling framework which we coded in the R package dynamAedes. We designed a stage-based and time-discrete stochastic model driven by temperature, photo-period and inter-specific larval competition that can be applied to three different spatial scales: punctual, local and regional. These spatial scales consider different degrees of spatial complexity and data availability, by accounting for both active and passive dispersal of mosquito species as well as for the heterogeneity of the input temperature data. C_LIO_LIOur overarching aim was to provide a flexible, open-source and user-friendly tool rooted in the most updated knowledge on species biology which could be applied to the management of invasive Aedes populations as well as for more theoretical ecological inquiries. C_LI

ecology↗

bioRxiv2020

Variation in pyrethroid resistance phenotypes in Anopheles darlingi from residual malaria transmission area: warning on suspected resistance built-up in French Guiana.

Anopheles darlingi is the major vector of malaria in South America. In French Guiana, malaria transmission occurs inland and along the rivers with a particular reemergence in the lower Oyapock area. Control against malaria vector is performed using deltamethrin indoor residual spraying and long lasting impregnated bednets. For four years, the level of resistance to pyrethroids was monitored using CDC bottle tests in An. darlingi populations. Resistance built-up was suspected in a mosquito population in malaria endemic area but did not sustained, supposably due to the reintroduction of susceptible alleles. No mutation on the insecticide target genes was found, metabolic resistance is then suspected.

zoology↗