Vignette d'image

Gern, Lise

Nom
Gern, Lise
Affiliation principale
Fonction
Ancien.ne collaborateur.trice
Identifiants
https://libra.unine.ch/handle/123456789/303

Résultat de la recherche

Filtres

8
8
8
Réinitialiser les filtres

Paramètres

Voici les éléments 1 - 8 sur 8
  • 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
    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
    Transmission of Borrelia garinii OspA serotype 4 to BALB/c mice by Ixodes ricinus ticks collected in the field
    (2001)
    Hu, Chang Min
    ;
    Wilske, Bettina
    ;
    Fingerle, Volker
    ;
    Lobet, Yves
    ;
    Gern, Lise 
    In Europe, Borrelia garinii OspA serotype 4 has been isolated from the cerebrospinal fluid of patients but, up to now, has never been identified among culture isolates from Ixodes ricinus ticks. This information raises the question of whether OspA serotype 4 is transmitted by I. ricinus in nature. In the present study, L ricinus nymphs collected in an area of endemicity in southern Germany were allowed to feed on mice. Cultivation of ear biopsy specimens showed that six of seven B. garinii-infected mice were infected by OspA serotype 4. In contrast, very few B. garinii OspA serotype 4 organisms were isolated directly from the ticks which infected the mice; most isolates were B. afzelii. The infected mice transmitted mainly OspA serotype 4 to xenodiagnostic ticks, preferentially in combination with B. afzelii.
  • Publication
    Métadonnées seulement
    Transmission of Borrelia afzelii from Apodemus mice and Clethrionomys voles to Ixodes ricinus ticks: differential transmission pattern and overwintering maintenance
    (1999)
    Humair, Pierre-François
    ;
    Rais, Olivier 
    ;
    Gern, Lise 
    This study deals with the ecology of Lyme borreliosis in Europe. The relationships between Borrelia burgdorferi sensu lato spirochetes, Clethrionomys and Apodemus rodent reservoirs and the Ixodes ricinus tick vector were investigated during 16 consecutive months in an enzootic area in Switzerland. Cultivation of ear skin biopsies was used to isolate spirochetes from C. glareolus, A. sylvaticus, A. flavicollis and Glis glis. Borrelia infection was more frequently observed in Clethrionomys than in Apodemus. Tick xenodiagnosis was used to determine the infectivity of rodents. The infection rate in licks fed on Clethrionomys was higher than that in licks fed on Apodemus, but Apodemus yielded more infected ticks than Clethrionomys because of a better tick moulting success. Xenodiagnostic ticks were placed into BSK medium to obtain isolates. Isolates from rodents and rodent-feeding ticks were all identified as B. afzelii. The follow-up of the infectivity status of repeatedly recaptured rodents clearly demonstrated that these hosts remained infective for ticks during winter till the following spring. Comparing C. glareolus and A. sylvaticus, each rodent species showed different host infection, different host infectivity and contributed differently to the moulting success of feeding ticks. These factors influence differentially the pattern of transmission of B. afzelii from Clethrionomys voles and Apodemus mice to I. ricinus ticks.
  • Publication
    Métadonnées seulement
    An avian reservoir (Turdus merula) of the Lyme borreliosis spirochetes
    (1998)
    Humair, Pierre-François
    ;
    Postic, Danièle
    ;
    Wallich, Reinhard
    ;
    Gern, Lise 
    The reservoir competence of passerine birds for the Lyme borreliosis spirochetes was studied in an enzootic focus in Switzerland. Skin aspirates and skin biopsies were used to isolate Borrelia spirochetes from Turdus species. B. burgdorferi sensu late was isolated and/or PCR-detected in BSK medium containing skin biopsy or skin aspirate from 5 blackbirds (T. merula) and one song thrush (T. philomelos). Seven isolates were obtained from 3 different blackbirds. Either B. garinii or Borrelia from the genomic group VS116 was found in bird skin samples. Mixed infection occurred in 2 cases. Tick xenodiagnosis was used to determine whether blackbirds transmitted Borrelia to ticks. Five xenodiagnoses were performed on 3 different blackbirds. Borrelia DNA was detected in BSK medium inoculated with xenodiagnostic ticks from all the passerines tested. Isolates cultured from xenodiagnostic ticks were obtained from 2 blackbirds. Isolates belonged to group VS116 (n = 10) and to B. garinii (n = 1). Our study has shown that Turdus sp. are infected by B. garinii and by Borrelia from group VS116 and that blackbirds are implicated as reservoirs for these 2 genomic groups of Borrelia, as they transmit living borreliae to ticks. An association seems to exist between birds and Borrelia VS116, and to a lesser extent, B. garinii, similar to the association existing between small rodents and B. afzelii. Our observations emphasize the fact that different enzootic cycles maintain Lyme borreliosis spirochetes in nature.
  • Publication
    Métadonnées seulement
    Relationship between Borrelia burgdorferi sensu lato species, red squirrels (Sciurus vulgaris) and Ixodes ricinus in enzootic areas in Switzerland
    (1998)
    Humair, Pierre-François
    ;
    Gern, Lise 
    The infection and reservoir status of red squirrels (Sciurus vulgaris) for Borrelia burgdorferi sensu late were studied in Switzerland. B. burgdorferi sensu late was isolated from 15 skin samples from 4/6 dead red squirrels, victims of road traffic. Isolates were identified using restriction fragment length polymorphism (RFLP): B. burgdorferi sensu stricto was present in 14 culture tubes containing skin samples and B. afzelii in two other tubes. A mixed infection was revealed in one case. A total of 227 ticks attached to squirrels were cultivated in BSKII medium and 90 isolates were obtained. Genotypic identification by RFLP showed that B. afzelii (59%) and B. burgdorferi sensu stricto (46%) dominated in ticks feeding on red squirrels. Data collected from one particular animal, highly infested with Ixodes ricinus and harbouring numerous Borrelia-infected Ixodes ricinus ticks, showed that transmission of B. burgdorferi sensu late occurred from S. vulgaris to feeding ticks. More precisely, B. burgdorferi sensu stricto and B. afzelii were mainly transmitted from S. vulgaris to ticks. The present data emphasized the results obtained previously from small rodents and birds in Japan and in Switzerland, showing the occurrence of specific associations between host species and Borrelia genospecies. (C) 1998 Elsevier Science B.V. All rights reserved.
  • Publication
    Métadonnées seulement
    Immunization with a polyvalent OspA vaccine protects mice against Ixodes ricinus tick bites infected by Borrelia burgdorferi ss, Borrelia garinii and Borrelia afzelii
    (1997)
    Gern, Lise 
    ;
    Hu, Chang Min
    ;
    Voet, Pierre
    ;
    Hauser, Pierre
    ;
    Lobet, Yves
    Sequence variability of the outer surface protein (Osp) A among Borrelia burgdorferi sl species suggests that a monovalent OspA vaccine may not protect against the various Borrelia present in Eurasia. Here, we confirmed that a monovalent recombinant OspA (rOspA) vaccine noes not protect mice against Ixodes ricinus mediated infection with B. burgdorferi ss, Borrelia garinii and Borrelia afzelii. However when mice were vaccinated with a cocktail of various rOspA from these three species, they were protected, and all challenge ricks that fed on them were cleared of their spirochetes. These results showed that a multiple OspA antigens vaccine, compatible with human use, was very efficient at protecting mice against B. burgdorferi ss, B. garinii and B. afzelii. (C) 1997 Elsevier Science Ltd.
  • Publication
    Métadonnées seulement
    Apodemus sp. rodents, reservoir hosts for Borrelia afzelii in an endemic area in Switzerland
    (1997)
    Hu, Chang Min
    ;
    Humair, Pierre-François
    ;
    Wallich, Reinhard
    ;
    Gern, Lise 
    Borrelia burgdorferi is maintained in nature in transmission cycles alternatively involving ticks and reservoir hosts. Small rodents like Apodemus mice and Clethrionomys voles are the primary reservoir of Lyme disease in Europe. In this study, we analyzed by SDS-PAGE and Western blot 20 borrelial isolates from xenodiagnostic ticks fed on four Apodemus sp. mice captured in the Staatswald forest (Switzerland). All isolates but one showed a homogeneous protein pattern expressing an outer surface protein, (Osp) A of 32 kDa and an OspB of 35 kDa and reacted with monoclonal antibody (mAb) I 17.3 specific for B. afzelii. One isolate expressed an OspA of 32.5 kDa and an OspB of 35 kDa and did not react with species-specific mAbs I 17.3, D6 and H3TS, but was shown to belong to B., afzelii by Southern blot analysis. The possibility exists that non-cultivatable borreliae are present in xenodiagnostic ticks. However, our results clearly show that Apodemus sp. are reservoir hosts for B. afzelii, since this genospecies is transmitted from Apodemus sp. to feeding larval ticks.