Biology subjects

Laroche, L.

Publications and source records attributed to Laroche, L..

3 recordsLinked to original sources

bioRxiv2024

Sand flies and Toscana virus: intra-vector infection dynamics and impact on Phlebotomus perniciosus life-history traits

Toscana virus (TOSV) is a leading cause of summer viral meningitis in central Italy and south of France, and can cause severe neurological cases. Within the Mediterranean basin, it is transmitted by hematophagous sand flies belonging to the Phlebotomus genus. Despite the identification of the primary TOSV vectors, the viruss developmental cycle in vector species remains largely unknown. Limited research has been conducted on transmission dynamics and the vectorial competence and capacity of the principal TOSV vector, Phlebotomus perniciosus. In this context, we investigated the intra-vector TOSV infection dynamics in Ph. perniciosus, as well as its impact on the vectors life history traits. Female sand flies were experimentally infected with TOSV though an artificial blood meal. Systemic dissemination of the virus was observed approximately three days post-infection, potentially resulting in a shorter extrinsic incubation period. Moreover, the study revealed a longer hatching time for eggs laid by infected females. This research not only confirmed the vector competence of Ph. perniciosus but also provided the first insight into TOSVs developmental cycle and its impact on the vector. These findings prompt further exploration of TOSV transmission dynamics, raise new hypotheses on the virus transmission and highlight the importance of follow-up studies. Author summaryToscana virus (TOSV) is a reemerging sandfly-borne virus causing neuroinvasive infections in humans. This virus is endemic in the Mediterranean basin, with a potential risk of introduction in northern Europe and Asia. Despite decades of research, few studies have focused on the development cycle of TOSV in sand flies and the dynamics of transmission. Here, we provide a comprehensive study of the intra-vector dynamics of TOSV infection and its impact on both vector biology and transmission. Through experimental infections of the major vector Phlebotomus perniciosus, we not only confirmed vector competence but also provided the first insight into the TOSV developmental cycle in the vector by estimating the extrinsic incubation period at six days. Our study reveals an impact of TOSV infection on vector hatching time leading to a delayed emergence of infected sand flies, with a potential impact on transmission. Our findings encourage further exploration of transmission dynamics, raise new hypotheses on alternative transmission pathways, and emphasize the importance of follow-up studies.

microbiology↗

bioRxiv2023

Establishment and maintenance of two sand fly colonies (Phlebotomus perniciosus and Phlebotomus papatasi) to implement experimental infections

Sand flies are vectors of Leishmania and Phlebovirus, pathogens responsible for public health concerns in numerous countries. Sand fly colonies are essential for research on vector-pathogen interactions. Methods for establishing and maintaining sand fly colonies have been well described in the literature. However, very few colonies of these considerable vectors currently exist. In order to encourage the creation of new colonies, we provide a timeline for researchers who want to implement colonies of Phlebotomus perniciosus and Phlebotomus papatasi. In this study, we set up colonies of both species to test and optimize their breeding conditions. For Ph. perniciosus, we reached a stable production of 800 individuals per week, one year after the start of the colony. For Ph. papatasi, a stable production of 400 individuals per week was reached 11 months after establishing the colony. Moreover, we have successfully conducted experiments within a year of establishing the colonies. In conclusion, our data on these two species showed that colonies could be established without difficulty with 1000-1500 eggs. It is possible to reach a stable weekly production of 800 individuals one year after starting the colony. We also describe colony settings and breeding recommendations to facilitate this procedure for other laboratories.

ecology↗

bioRxiv2018

Higher-order discrimination learning by honey bees in a virtual environment

Non-elemental learning constitutes a cognitive challenge because, contrary to elemental learning forms, it does not rely on simple associations, as events to be learned are usually ambiguous in terms of reinforcement outcome. Negative patterning constitutes a paradigmatic case of non-elemental learning, as subjects have to learn that single elements A and B are reinforced while their conjunctive representation AB is not reinforced (A+, B+ vs. AB-). Solving this problem requires treating the compound AB as being different from the linear sum of its components in order to overcome stimulus ambiguity (A+/A- and B+/B-). The honey bee is the only insect capable of mastering negative patterning as shown by numerous studies restricted mainly to the olfactory domain. Here we studied the capacity of bees to solve a negative patterning discrimination in the visual domain and used to this end a virtual reality (VR) environment in which a tethered bee walking stationary on a treadmill faces visual stimuli projected on a semicircular screen. Stimuli are updated by the bees movements, thus creating an immersive environment. Bees were trained to discriminate single-colored gratings rewarded with sucrose solution (blue, green; A+, B+) from a non-rewarded composite grating (blue-green, AB-). Bees learned this discrimination in the VR environment and inhibited to this end linear processing of the composite grating, which otherwise is treated as the sum of its components. Our results show for the first time mastering of a non-linear visual discrimination in a VR environment by honey bees, thus highlighting the value of VR for the study of cognition in insects.

animal behavior and cognition↗