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Gern, Lise

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Gern, Lise
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Ancien.ne collaborateur.trice
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https://libra.unine.ch/handle/123456789/303

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  • Publication
    Métadonnées seulement
  • Publication
    Accès libre
    Long term survey and control strategies of mosquitoes in southern Switzerland with focus on the invasive exotic species "Aedes albopictus"
    (2016)
    Flacio, Eleonora
    ;
    Gern, Lise 
    ;
    Betschart, Bruno 
    Les connaissances sur les moustiques présents au Tessin, un canton suisse situé au Sud des Alpes, étaient faibles jusqu’aux années 2000. Au début du siècle dernier, des recherches faunistiques ont été menées dans le cadre de la malaria et, plus tard, d’autres recherches ont été entreprises pour lutter contre les moustiques des marais qui gênaient les populations autour du lac Maggiore. Cependant, les connaissances sur la diversité des moustiques dans les principales zones humides ainsi que sur leur lieu d’origine et leur densité restaient insuffisantes pour lutter efficacement contre leur nuisance et les risques de transmission de pathogènes, comme par exemple le virus West Nile.
    Dans ce travail, nous avons approfondi les connaissances sur les moustiques indigènes ainsi que sur les moustiques exotiques, comme Aedes albopictus, le moustique tigre, qui se répandait dans les zones urbaines italiennes depuis les années 90. Les principales zones humides du Canton du Tessin ont été investiguées en utilisant différentes techniques de récolte. Ainsi, de nouvelles espèces de moustiques ont été découvertes: Ae. caspius, Ae. cataphylla, Culex martini, Cx. modestus, Coquillettidia buxtoniy and Cq. Richiardii. Les traitements de lutte qui étaient déjà utilisés sont apparus comme efficaces pour lutter contre les moustiques nuisibles pour la population. En 2000 un système de surveillance d’Ae. Albopictus a été mis en place. Ceci a permis de suivre l’activité et la diffusion du moustique depuis sa découverte en 2003 dans le Sud du canton et d’adopter des mesures coordonnées entre scientifiques, mairies et population. Ce système de surveillance s’est développé au cours du temps. Différentes stratégies ont été appliquées en fonction de la distribution du moustique sur le territoire. La participation de la population aux mesures de surveillance a été considérée comme fondamentale. Nous avons donc mis en place un système d’information ciblé pour la population lui permettant de participer activement à la surveillance. La présence du moustique a pu ainsi être maintenue à des niveaux raisonnables mais sa continuelle avancée dans le territoire n’a cependant pas pu être parée. Nous avons pu établir que le moustique s’est introduit au Tessin via le trafic autoroutier, puis s’est étendu à l’intérieur du canton grâce au trafic local. Le moustique est aujourd’hui bien établi dans le sud où les conditions météorologiques lui sont favorables. Au nord, et à plus de 400 m d’altitude, il n’apparaît que sporadiquement probablement en raison de conditions météorologiques moins favorables et d’un trafic routier moins intense.
    En surveillant Ae. Albopictus nous avons découvert d’autres espèces exotiques non encore décrites au Tessin ou en Suisse: Ae. cretinus, Ae. Koreicus et Ae. Japonicus, qui ont emprunté les mêmes voies d’introduction qu’Ae. Albopictus.
    Actuellement, le risque de transmission de maladies liées aux différentes espèces de moustiques répertoriées dans le canton peut être considéré comme faible et à ce jour, aucun cas de transmission locale de maladies n’a été relevé., Until 2000 in Canton Ticino, a Swiss region located South of the Alps, the knowledge on mosquito distribution was scarce. Some faunistic investigations related to malaria occurrence in the area were lead until the beginning of last century and others started at the end of that century to support control measures against wetland mosquitoes causing nuisance in residence areas close to lake Maggiore. A general evaluation on mosquito species was needed to assess the biodiversity in all main natural areas, and on the origin of nuisance to improve the control measures on mosquitoes. In addition the knowledge of the location and the densities of the different mosquito species would give an important tool to evaluate the risk of transmission of mosquito-borne pathogens, such as West Nile virus. Not only European native species needed investigations but also exotic species, like Aedes albopictus, which was rapidly spreading in the nearby Italian urban settlements since the 90’s. These exotic species are known as extremely bothersome and as potential vectors of several pathogens that could affect human and animal populations on the European territory.
    With a combination of several sampling techniques all main natural areas from Ticino were screened. New mosquito species for Ticino and/or Switzerland were discovered: Aedes caspius, Ae. cataphylla, Culex martini, Cx. modestus, Coquillettidia buxtoni and Cq. Richiardii. Control measures already undertaken showed their efficacy and risk of transmission of mosquito-borne pathogens was evaluated as very low. A surveillance system on Ae. Albopictus was set up in 2000. This permitted to follow up the mosquito activity and spread from its first discovery in 2003 in the South of Canton Ticino, and to adopt coordinated control measures involving scientists, municipalities and residents. This surveillance has developed through different strategies according to Ae. Albopictus presence in the territory. The public participation in measures to limit the mosquito presence represents a key tool of the surveillance strategy. This permitted to keep the mosquito presence at a reasonable level. Although the continuous spread in the region could not be avoided no local transmission of exotic diseases was recorded so far.
    Our data showed that the mosquito was introduced via the intense road traffic and then spread thanks to local traffic. Weather conditions allowed its establishment in the South. In the North and at altitudes above 400 m its presence is sporadic probably because of lower temperature and road traffic.
    The Ae. Albopictus survey permitted to discover additional exotic species new in Canton Ticino and / or Switzerland, which were probably also introduced via road traffic: Ae. cretinus, Ae. Koreicus and Ae. Japonicas.
  • Publication
    Accès libre
    Cross-immunity and community structure of a multiple-strain pathogen in the tick vector
    (2015-11)
    Durand, Jonas 
    ;
    Jacquet, Maxime 
    ;
    Paillard, Lye 
    ;
    Rais, Olivier 
    ;
    Gern, Lise 
    ;
    Voordouw, Maarten 
    Many vector-borne pathogens consist of multiple strains that circulate in both the vertebrate host and the arthropod vector. Characterization of the community of pathogen strains in the arthropod vector is therefore important for understanding the epidemiology of mixed vector-borne infections. Borrelia afzelii and B. garinii are two species of tick-borne bacteria that cause Lyme disease in humans. These two sympatric pathogens use the same tick, Ixodes ricinus, but are adapted to different classes of vertebrate hosts. Both Borrelia species consist of multiple strains that are classified using the highly polymorphic ospC gene. Vertebrate cross-immunity against the OspC antigen is predicted to structure the community of multiple-strain Borrelia pathogens. Borrelia isolates were cultured from field-collected I. ricinus ticks over a period spanning 11 years. The Borrelia species of each isolate was identified using a reverse line blot (RLB) assay. Deep sequencing was used to characterize the ospC communities of 190 B. afzelii isolates and 193 B. garinii isolates. Infections with multiple ospC strains were common in ticks, but vertebrate cross-immunity did not influence the strain structure in the tick vector. The pattern of genetic variation at the ospC locus suggested that vertebrate cross-immunity exerts strong selection against intermediately divergent ospC alleles. Deep sequencing found that more than 50% of our isolates contained exotic ospC alleles derived from other Borrelia species. Two alternative explanations for these exotic ospC alleles are cryptic coinfections that were not detected by the RLB assay or horizontal transfer of the ospC gene between Borrelia species.
  • Publication
    Métadonnées seulement
    Genetic variation in transmission success of the Lyme borreliosis pathogen Borrelia afzelii
    (2015)
    Tonetti, Nicolas 
    ;
    Voordouw, Maarten 
    ;
    Durand, Jonas 
    ;
    Monnier, Séverine
    ;
    Gern, Lise 
    The vector-to-host and host-to-vector transmission steps are the two critical events that define the life cycle of any vector-borne pathogen. We expect negative genetic correlations between these two transmission phenotypes, if parasite genotypes specialized at invading the vector are less effective at infecting the vertebrate host and vice versa. We used the tick-borne bacterium Borrelia afzelii, a causative agent of Lyme borreliosis in Europe, to test whether genetic trade-offs exist between tick-to-host, systemic (host-to-tick), and a third mode of co-feeding (tick-to-tick) transmission. We worked with six strains of B. afzelii that were differentiated according to their ospC gene. We compared the three components of transmission among the B. afzelii strains using laboratory rodents as the vertebrate host and a laboratory colony of Ixodes ricinus as the tick vector. We used next generation matrix models to combine these transmission components into a single estimate of the reproductive number (R0) for each B. afzelii strain. We also tested whether these strain-specific estimates of R0 were correlated with the strain-specific frequencies in the field. We found significant genetic variation in the three transmission components among the B. afzelii strains. This is the first study to document genetic variation in co-feeding transmission for any tick-borne pathogen. We found no evidence of trade-offs as the three pairwise correlations of the transmission rates were all positive. The R0 values from our laboratory study explained 45% of the variation in the frequencies of the B. afzelii ospC strains in the field. Our study suggests that laboratory estimates of pathogen fitness can predict the distribution of pathogen strains in nature.
  • Publication
    Métadonnées seulement
    Tick-borne pathogens in ticks collected from breeding and migratory birds in Switzerland
    (2014-11-17)
    Lommano, Elena 
    ;
    Dvorak, Charles
    ;
    Vallotton, Laurent
    ;
    Jenni, Lukas
    ;
    Gern, Lise 
  • Publication
    Métadonnées seulement
    Protozoan and bacterial pathogens in tick salivary glands in wild and domestic animal environments in South Africa
    (2014)
    Berggoetz, M
    ;
    Schmid, M
    ;
    Ston, D
    ;
    Wyss, V
    ;
    Chevillon, Christophe
    ;
    Pretorius, A-M
    ;
    Gern, Lise 
  • Publication
    Métadonnées seulement
    Tick-borne pathogens in the blood of wild and domestic ungulates in South Africa: interplay of game and livestock
    (2014)
    Berggoetz, M
    ;
    Schmid, M
    ;
    Ston, D
    ;
    Wyss, V
    ;
    Chevillon, Christophe
    ;
    Pretorius, A-M
    ;
    Gern, Lise 
  • Publication
    Métadonnées seulement
  • Publication
    Métadonnées seulement
    Borrelia burgdorferi genospecies detection by RLB hybridization in Ixodes cinus ticks from different sites of North-Eastern Poland
    (2014)
    Dunaj, Justyna
    ;
    Zajkowska, JM
    ;
    Kondrusik, M
    ;
    Gern, Lise 
    ;
    Rais, Olivier 
    ;
    Moniuszko, Anna
    ;
    Pancewicz, Slawomir
    ;
    Swierzbi?ska, R