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Gern, Lise

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Gern, Lise
Affiliation principale
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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
    Identification of host bloodmeal source and Borrelia burgdorferi sensu lato in field-collected Ixodes ricinus ticks in Chaumont (Switzerland)
    (2007)
    Cadenas, Francisca Moran
    ;
    Rais, Olivier 
    ;
    Humair, Pierre-François
    ;
    Douet, Véronique 
    ;
    Moret, Jacqueline
    ;
    Gern, Lise 
    To evaluate the importance of vertebrate species as tick hosts and as reservoir hosts in two endemic areas for Lyme borreliosis in Switzerland, we applied molecular methods for the analysis of bloodmeal source and Borrelia infection in questing Ixodes ricinus L. ticks. In total, 1,326 questing ticks were simultaneously analyzed for Borrelia and for blood meal remnants by using reverse line blot. An overall infection prevalence of 19.0% was recorded for Borrelia sp., with similar rates in both sites. Using a newly developed method for the analysis of bloodmeal targeting the 12S rDNA mitochondrial gene, identification of host DNA from field-collected ticks was possible in 43.6% of cases. Success of host identification at the genus and species level reached 72%. In one site, host identification success reached its maximum in spring (93% in May), decreasing in summer (20% in July) and rising in autumn (73% in October). In the other site, identification rate in ticks remained low from April to July and increased in autumn reaching 68% in October and November. The most prevalent identified host DNA was artiodactyls in both sites. Red squirrel DNA was significantly more frequently detected in ticks collected in one site, whereas insectivore DNA was more frequent in ticks in the other site. DNA from more than one vertebrate host was detected in 19.5% of nymphs and 18.9% of adults. Host DNA was identified in 48.4% of the Borrelia infected ticks. Although DNA from all Borrelia species was found in at least some ticks with DNA from mammals and some ticks with DNA from birds, our results confirm a general association of B. afzelii and B. burgdorferi sensu stricto with rodents, and B. valaisiana and B. garinii with birds.
  • Publication
    Métadonnées seulement
    Phenology of Ixodes ricinus and infection with Borrelia burgdorferi sensu lato along a North- and South-facing altitudinal gradient on Chaumont Mountain, Switzerland
    (2007)
    Cadenas, Francisca Moran
    ;
    Rais, Olivier 
    ;
    Jouda, Fatima
    ;
    Douet, Véronique 
    ;
    Humair, Pierre-François
    ;
    Moret, Jacqueline
    ;
    Gern, Lise 
    Questing Ixodes ricinus L. ticks were collected monthly from 2003 to 2005 on the north- and south-facing slopes of Chaumont Mountain in Neuchatel, Switzerland, at altitudes varying from 620 to 1,070 in. On the south-facing slope, questing tick density was higher than on the north-facing slope, and it decreased with altitude. Density tended to increase with altitude on the north-facing slope. Saturation deficit values higher than 10 mmHg and lasting for >2 mo were often recorded on the south-facing slope, explaining seasonal patterns of questing tick activity. The overall prevalence of Borrelia burgdorferi sensu lato was 22.4%, and prevalence differed according to exposure and among years. No difference was noticed between nymphs and adults. Four Borrelia species were identified. Mixed infections were detected in 52 ticks, B. garinii and B. valaisiana (n = 21) and B. afzelii and B. burgdorferi s.s. (n = 20) were the most frequent associations observed. The density of infected ticks varied from 3.6 to 78.7 infected nymphs per 1 00 m(2) and from 0.6 to 16.9 infected adults per 100 m(2), both slopes combined. The study on the south-facing slope was a follow-up of a previous study carried out at the same location during 1999-2001. Comparison of climatic data between the two periods showed a marked increase in saturation deficit. Substantial differences in density and phenology of ticks also were observed. At high elevations, ticks were significantly more abundant during the current study. This can be explained by rising temperatures recorded during summer at altitude, reaching values similar to those registered in the first study beneath. At the lowest altitude, adults were significantly less abundant, probably due to long-lasting high saturation deficits that impaired nymphal survival. The density of Borrelia-infected ticks was higher than in the previous study.
  • Publication
    Métadonnées seulement
    Molecular identification of bloodmeal source in Ixodes ricinus ticks using 12S rDNA as a genetic marker
    (2007)
    Humair, Pierre-François
    ;
    Douet, Véronique 
    ;
    Cadenas, Francisca Moran
    ;
    Schouls, Leo M
    ;
    Van de Pol, Ingrid
    ;
    Gern, Lise 
    We developed an efficient molecular method for the identification of the bloodmeal sources in the tick Ixodes ricinus (L.), the European vector of the agents of Lyme borreliosis and tick-borne encephalitis. A approximate to 145-bp orthologous fragment of the vertebrate mitochondrial 12S rDNA was used as a molecular marker to discriminate host vertebrate species. The method consists of a single run polymerase chain reaction amplification of the 12S rDNA molecular marker by using nondegenerate primers followed by a reverse line blot hybridization assay by using specific oligonucleotide probes. The palette of probes allowed us to distinguish major groups of host vertebrates (e.g., mammals, small rodents, artiodactyls, birds, lizards) and to identify the bloodmeal sources at the genus or species level. External primers were designed and used to sequence the 12S rDNA molecular marker of a broad range of known or potential host vertebrate species (n = 60), including mammal (n = 28), bird (n = 31), and reptile (n = 1) species. The use of this technique coupled with known methods for identification of tick-borne pathogens (e.g., Borrelia burgdorferi sensu lato) allowed us to determine the source of infective bloodmeal and to identify reservoir species. The present method was successfully used to identify the source of bloodmeals in all feeding I. ricinus ticks and in half of questing field-collected L ricinus ticks. Moreover, the bloodmeal source was identified in 65% of ticks infected with B. burgdorferi sensu lato. Further development of this technique may be envisaged for the detection of other vector-borne patbogens and their reservoir hosts.
  • Publication
    Métadonnées seulement
    Prevalence of Borrelia burgdorferi sensu lato in ticks collected from migratory birds in Switzerland
    (2006)
    Poupon, Marie-Angèle
    ;
    Lommano, Elena 
    ;
    Humair, Pierre-François
    ;
    Douet, Véronique 
    ;
    Rais, Olivier 
    ;
    Schaad, Michael
    ;
    Jenni, Lukas
    ;
    Gern, Lise 
    The prevalence of ticks infected by Borrelia burgdorferi sensu lato on birds during their migrations was studied in Switzerland. A total of 1,270 birds captured at two sites were examined for tick infestation. Ixodes ricinus was the dominant tick species. Prevalences of tick infestation were 6% and 18.2% for birds migrating northward and southward, respectively. Borrelia valaisiana was the species detected most frequently in ticks, followed by Borrelia garinii and Borrelia lusitaniae. Among birds infested by infected ticks, 23% (6/26) were infested by B. lusitaniae-infected larvae. Migratory birds appear to be reservoir hosts for B. lusitaniae.
  • Publication
    Accès libre
    Prevalence of Borrelia burgdorferi Sensu Lato in Ticks Collected from Migratory Birds in Switzerland
    (2006)
    Poupon, Marie-Angèle
    ;
    Lommano, Elena 
    ;
    Humair, Pierre-François
    ;
    Douet, Véronique 
    ;
    Rais, Olivier 
    ;
    Schaad, Michael
    ;
    Jenni, Lukas
    ;
    Gern, Lise 
    The prevalence of ticks infected by Borrelia burgdorferi sensu lato on birds during their migrations was studied in Switzerland. A total of 1,270 birds captured at two sites were examined for tick infestation. Ixodes ricinus was the dominant tick species. Prevalences of tick infestation were 6% and 18.2% for birds migrating northward and southward, respectively. Borrelia valaisiana was the species detected most frequently in ticks, followed by Borrelia garinii and Borrelia lusitaniae. Among birds infested by infected ticks, 23% (6/26) were infested by B. lusitaniae-infected larvae. Migratory birds appear to be reservoir hosts for B. lusitaniae.
  • Publication
    Métadonnées seulement
    PCR-reverse line blot typing method underscores the genomic heterogeneity of Borrelia valaisiana species and suggests its potential involvement in Lyme disease
    (2003)
    Godfroid, Edmond
    ;
    Hu, Chang Min
    ;
    Humair, Pierre-François
    ;
    Bollen, Alex
    ;
    Gern, Lise 
    Detection of the Borrelia burgdorferi sensu lato complex in biological samples is currently done by conventional immunological and molecular biological methods. To improve on the accuracy of these methods and to simplify the procedure for testing large numbers of samples, a solid-phase sandwich hybridization system readily applicable to the detection of PCR products has been designed. This colorimetric detection system relies on the use of polybiotinylated detection probes and of specific capture oligonucleotides covalently linked at allocated positions on nylon membrane strips. From a phylogenetic analysis on a great number of ospA gene sequences, we have designed and synthesized a set of PCR primers specific to the five Borrelia burgdorferi sensu lato genospecies present in Europe and a subset of probes (capture and detection probes) specific to these five genospecies (B. burgdorferi sensu stricto, B. garinii, B. afzelii, B. valaisiana, and B. lusitaniae). This combined PCR hybridization system was evaluated with a large number of various B. burgdorferi isolates and clinical specimens. These analyses clearly showed that the system could be used as a typing method to distinguish five genospecies belonging to the B. burgdorferi sensu lato complex. In addition, the study showed that B. valaisiana strains might be more heterologous than suspected up to now and clustered into three genomic groups.
  • Publication
    Métadonnées seulement
    Apodemus species mice are reservoir hosts of Borrelia garinii OspA serotype 4 in Switzerland
    (2002)
    Hügli, Delphine
    ;
    Hu, Chang Min
    ;
    Humair, Pierre-François
    ;
    Wilske, Bettina
    ;
    Gern, Lise 
    Among Borrelia burgdorferi sensu lato isolates, seven outer surface protein A (OspA) serotypes have been described: serotypes 1 and 2 correspond to B. burgdorferi sensu stricto and Borrelia afzelii, respectively, and serotypes 3 to 7 correspond to Borrelia garinii. In Europe, serotype 4 has never been isolated from Ixodes ricinus ticks until recently, although this serotype has been frequently isolated from cerebrospinal fluid from patients. In Europe, B. afzelii and B. burgdorferi sensu stricto were found associated with rodents and B. garinii was found associated with birds. In this study, the reservoir role of Apodemus mice for B. garinii OspA serotype 4 was demonstrated by xenodiagnosis. Apodemus mice are the first identified reservoir hosts for B. garinii OspA serotype 4.
  • Publication
    Métadonnées seulement
    Ecology of Borrelia burgdorfesi sensu lato in Europe
    (: CABI International, 2002)
    Gern, Lise 
    ;
    Humair, Pierre-François
    ;
    Gray, Jeremy
    ;
    Kahl, Olaf
    ;
    Lane, Robert S
    ;
    Stanek, Gerold
  • Publication
    Accès libre
    Ecology of Borrelia burgdorferi sensu lato in Europe
    (2002)
    Gern, Lise 
    ;
    Humair, Pierre-François
  • Publication
    Métadonnées seulement
    The wild hidden face of Lyme borreliosis in Europe
    (2000)
    Humair, Pierre-François
    ;
    Gern, Lise