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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
    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
    Métadonnées seulement
    Reservoir role of lizard Psammodromus algirus in transmission cycle of Borrelia burgdorferi sensu lato (Spirochaetaceae) in Tunisia
    (2006)
    Dsouli, Najla
    ;
    Younsi-Kabachii, Hend
    ;
    Postic, Danièle
    ;
    Nouira, Said
    ;
    Gern, Lise 
    ;
    Bouattour, Ali
    To investigate the reservoir role of the lizard Psammodromus algirus for the Lyme disease spirochete, 199 lizards were trapped from April to October 2003 in El Jouza, northwestern Tunisia. In this site, the infection rate of free-living Ixodes ricinus (L.) by Borrelia was evaluated by immunofluorescence as 34.6% for adult ticks and 12.5% for nymphs. Eighty percent of P. algirus (117/146) captured during this study were infested by I. ricinus, the predominant tick species collected from lizards. The intensity of tick infestation of this host by larvae and nymphs ranged from 0.14 to 7.07 and from 1.5 to 6.58, respectively. These immature stages of I. ricinus were found on lizards in spring and the beginning of summer, with a peak of intensity during June (10.16 immature ticks by lizard). Tissue cultures from lizards and xenodiagnosis with larval L ricinus were used to assess the infection and the ability, respectively, of infected lizards to transmit Borrelia to naive ticks. Seventeen percent of xenodiagnostic ticks (40/229) acquired B. lusitaniae while feeding on P. algirus. Therefore, we demonstrated the ability of the lizards to sustain Borrelia infection and to infect attached ticks, and we proved that P. algirus is a reservoir host competent to transmit B. lusitaniae.
  • Publication
    Métadonnées seulement
    Quantitative analysis of Borrelia burgdorferi gene expression in naturally (tick) infected mouse strains
    (2005)
    Lederer, Sharon
    ;
    Brenner, Christiane
    ;
    Stehle, Thomas
    ;
    Gern, Lise 
    ;
    Wallich, Reinhard
    ;
    Simon, Markus M
    Adaptation of Borrelia burgdorferi in the vector and vertebrate host is mediated by mechanisms that regulate differential expression of outer surface lipoproteins (Osps). In this study, real time PCR was applied to quantify tissue-specific expression of four linear plasmid (lp54)-encoded (ospA, zs7.a36, zs7.a66 zs7.a68) and one circular plasmid (cp26)-encoded (ospC) gene from B. burgdorferi sensu stricto, in a natural setting of tick-infected immunodeficient (C.B-17 SCID) and immunocompetent (BALB/c and AKR/OlaHsd) mice for up to 120 days post-infection (p.i.). Early during infection (day 30 p.i.) high numbers of spirochetes were found in the heart and joint, but not the ear and spleen tissues of disease-susceptible SCID mice. In disease-susceptible AKR mice spirochetes colonized the ear and joint tissues, but were undetectable in tissues of disease-resistant BALB/c mice. Later in infection (day 120 p.i.), spirochetes had expanded (similar to1,000-fold) in all SCID tissues tested but were undetectable in AKR and BALB/c mice. Of the five genes analyzed, only zs7.a36 transcripts were detected in various tissues of all infected mouse strains, though at differing levels, whereas ospC transcripts were only found in tissue specimens of SCID mice. Furthermore, gene expression of ospC and zs7.a36 appears to be differentially regulated in distinct organs of individual mice. In contrast, transcripts for ospA, zs7.a66, and zs7.a68 were not detected in any of the mouse strains, independent of their immune status and/or the severity of their infection/inflammatory responses. Late during infection (day 120 p.i.), transcription of zs7.a36 and ospC was down-regulated in the tissues of SCID mice despite expansion of spirochetes. This type of quantitative analysis may be helpful to further disclose principles of pathogenesis of Lyme borreliosis and to design strategies for its therapeutic treatment.
  • Publication
    Métadonnées seulement
    Detection and identification of Ehrlichia spp. in ticks collected in Tunisia and Morocco
    (2005)
    Sarih, M'Hammed
    ;
    M'Ghirbi, Youmna
    ;
    Bouattour, Ali
    ;
    Gern, Lise 
    ;
    Baranton, Guy
    ;
    Postic, Danièle
    A broad-range 16S rRNA gene PCR assay followed by partial sequencing of the 16S rRNA gene was used for the detection of members of the family Anaplasmataceae in ticks in North Africa. A total of 418 questing Ixodes ricinus ticks collected in Tunisia and Morocco, as well as 188 Rhipicephalus ticks from dogs and 52 Hyalomma ticks from bovines in Tunisia, were included in this study. Of 324 adult L ricinus ticks, 16.3% were positive for Ehrlichia spp., whereas only 3.4 and 2.8% of nymphs and larvae, respectively, were positive. A large heterogeneity was observed in the nucleotide sequences. Partial sequences identical to that of the agent of human granulocytic ehrlichiosis (HGE) were detected in L ricinus and Hyalomma detritum, whereas partial sequences identical to that of Anaplasma platys were detected in Rhipicephalus sanguineus. However, variants of Anaplasma, provisionally designated Anaplasma-like, were predominant in the L ricinus tick population in Maghreb. Otherwise, two variants of the genus Ehrlichia were detected in L ricinus and H. detritum. Surprisingly, a variant of Wolbachia pipientis was evidenced from L ricinus in Morocco. These results emphasized the potential risk of tick bites for human and animal populations in North Africa.
  • Publication
    Métadonnées seulement
    Characterization of Borrelia lusitaniae isolates collected in Tunisia and Morocco
    (2005)
    Younsi, Hend
    ;
    Sarih, M'Hammed
    ;
    Jouda, Fatima
    ;
    Godfroid, Edmond
    ;
    Gern, Lise 
    ;
    Bouattour, Ali
    ;
    Baranton, Guy
    ;
    Postic, Danièle
    Borrelia lusitaniae is a species within the complex Borrelia burgdorferi sensu lato and is infrequently isolated in Europe. In contrast, this species is by far the most predominant in North Africa and in Portugal. In this study, we analyzed the genetic diversity, at several loci, of a large population of isolates from free-living Ixodes ricinus ticks collected in Tunisia and Morocco. We found a moderate diversity of the whole genome by using pulsed-field gel electrophoresis as well as in the ospA gene sequences, compared to a high level of strain homogeneity in the small noncoding ribosomal spacer. In contrast, a high diversity of this locus has been previously reported for Portuguese isolates. We hypothesize that B. lusitaniae strains isolated in North Africa constitute a clone of Portuguese origin.
  • Publication
    Métadonnées seulement
    Ixodes ricinus density, and distribution and prevalence of Borrelia burgdorferi sensu lato infection along an altitudinal gradient
    (2004)
    Jouda, Fatima
    ;
    Perret, Jean-Luc
    ;
    Gern, Lise 
    In this study, we measured the phenology of Ixodes ricinus ticks and their infection with Borrelia burgdorferi sensu lato (sl) simultaneously along an altitudinal gradient to assess the impact of climate on the phenology of ticks and on their infection with B. burgdorferi sl. From 1999 to 2001, free-living I. ricinus ticks were collected monthly by flagging vegetation at three different altitudes (620, 740, and 900 in above sea level) on the slope of a mountain in Chaumont (Neuchatel, Switzerland). I. ricinus ticks were examined for the presence of B, burgdorferi sl by using direct fluorescent antibody assay and isolation of spirochetes. Borrelia species were characterized by polymerase chain reaction followed by restriction fragment-length polymorphism. Tick density and tick phenology varied with altitude. Although the peak tick density decreased and the onset of ticks was delayed with altitude, the phenology, vas much more stable among years at the highest altitudes than at the lowest. The prevalence of B. burgdorferi infection in nymphs and adults decreased with altitude. The prevalence of infection differed significantly among years, and it was significantly higher in adults (30%) than in nymphs (21%). B. burgdorferi infection in adults was positively related with adult density, but this was not observed for nymphs. Five B. burgdorferi sl genospecies were successfully : B. garinii, B. burgdorferi sensu stricto, B. afzelii, B. valaisiana, and B. lusitaniae. Mixed isolate infections were obtained from five of 140 infected ticks. The greatest diversity in Borrelia species was observed at the lowest altitude where all five Borrelia species were present, whereas at the two highest altitudes, B. lusitaniae was not observed.
  • Publication
    Métadonnées seulement
    First isolation of Borrelia burgdorferi sensu lato from Ixodes ricinus ticks in Morocco
    (2003)
    Sarih, M'Hammed
    ;
    Jouda, Fatima
    ;
    Gern, Lise 
    ;
    Postic, Danièle
    To determine the infection rate of Ixodes ricinus (I. ricinus) ticks with Borrelia burgdorferi sensu lato (B. burgdorferi sl) and to assess the frequency of the individual Borrelia species in this tick species, a total of 295 I. ricinus were collected in Taza region (Northeast of Morocco), from January to June 2002. The presence of B. burgdorferi A was determined by direct fluorescence antibody assay (DFA) and by PCR after culture. B. burgdorferi sl isolates were identified at the species level by restriction fragment length polymorphism. analysis of amplified products. The mean rate of I. ricinus infection with B. burgdorferi sl was 47.8%. Isolation attempts in BSK II medium resulted in 26 pure isolates. However, PCR performed on culture medium allowed to identify 82 Borrelia DNAs. B. lusitaniae has been identified from 76 out of 82 infected I. ricinus ticks (92.7%). Three ticks were infected by B. burgdorferi ss, and three other ticks were infected by B. garinii. This is the first report of the presence of B. burgdorferi A in Morocco and more specifically of B. burgdorferi ss in North Africa.
  • Publication
    Métadonnées seulement
    Coinoculation of Borrelia spp. with tick salivary gland lysate enhances spirochete load in mice and is tick species-specific
    (2002)
    Zeidner, Nordin S
    ;
    Schneider, Bradley S
    ;
    Nuncio, Maria S
    ;
    Gern, Lise 
    ;
    Piesman, Joseph
    C3H/HeN mice were inoculated with 10(6) spirochetes, either Borrelia burgdorferi strain N40 or the Portuguese strain of B. lusitaniae, PotiB2. Mice receiving spirochetes comoculated with salivary gland lysate (SGL) demonstrated significantly higher spirochete loads in target organs as measured by quantitative real-time polymerase chain reaction. This effect was tick dependent. in that Ixodes ricinus SGL specifically enhanced B. lusitaniae load, whereas I. scapidaris SGL specifically increased B. burgdorferi N40 load, but did not significantly affect the dissemination of B. lusitaniae. Protein profile analysis indicated at least 5 major protein differences between I. scapiularis and I. ricinus SGL, which can possibly account for this specific tick-spirochete interaction.