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Gern, Lise
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Gern, Lise
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- PublicationAccès libreAssessment of intraspecific mtDNA variability of European Ixodes ricinus sensu stricto (Acari: Ixodidae)The Ixodes ricinus complex is composed of 14 species distributed worldwide. Some members of this complex are involved in the transmission of a number of diseases to animals and humans, in particular Lyme borreliosis, tick-borne encephalitis, ehrlichiosis and babesiosis. While the phylogenetic relationships between species of the I. ricinus complex have been investigated in the past, still little is known about the genetic structure within the species I. ricinus sensu stricto. We have investigated the intraspecific variability among 26 I. ricinus s.s. ticks collected in various European countries, including Switzerland, Italy, Austria, Denmark, Sweden, and Finland by using five mitochondrial gene fragments corresponding to the control region, 12S rDNA, cytb, COI, and COII. The five genes considered here showed a low genetic variability (1.6–5%). Our results based on both statistical parsimony (applied to the COI + COII + cytb + 12S + CR data set, for a total of 3423 bp) and maximum parsimony (applied to the COI + COII + cytb + 12S data set, for a total of 2980 bp) did not provide any evidence for a correlation between the identified haplotypes and their geographic origin. Thus, the European I. ricinus s.s. ticks do not seem to show any phylogeography structure.
- PublicationMétadonnées seulementPresence of potentially pathogenic Babesia sp for human in Ixodes ricinus in Switzerland(2006)
; Piffaretti, Jean-ClaudeWe have designed and performed a new PCR method based on the 18S rRNA in order to individuate the presence and the identity of Babesia parasites. Out of H 59 Ixodes ricinus (Acari: Ixodidae) ticks collected in four areas of Switzerland, nine were found to contain Babesia DNA. Sequencing of the short amplicon obtained (411 452 bp) allowed the identification of three human pathogenic species: Babesia microti, B. divergens, for the first time in Switzerland, Babesia sp. EU1. We also report coinfections with B. sp. EU1-Borrelia burgdoferi sensu stricto and Babesia sp. EU1-B. afzelii. - PublicationMétadonnées seulementDiversity of the population of Tick-borne encephalitis virus infecting Ixodes ricinus ticks in an endemic area of central Switzerland (Canton Bern)(2006)
; Piffaretti, Jean-ClaudeTick-borne encephalitis virus (TBEV), a member of the genus Flavivirus, has a positive-strand RNA genome containing a single open reading frame flanked by non-coding regions (NCRs). Ixodes ricinus ticks (n = 307) were collected from vegetation in a natural TBEV focus in Belp, Switzerland. The presence and identity of the virus were determined by nested RT-PCR followed by sequencing of the 5'-terminal region that comprises the 5' NCR and the capsid-encoding region (C). The presence of the western European TBEV subtype (W-TBEV) genome was detected in 14.3% of the ticks. Nucleotide sequence analysis revealed a high variability of 55.5%. In particular, four DNA fragments (CS 'A', CS 'B', the folding-stem structure and the start codon) showed substantial heterogeneity, which has the potential of compromising replication, translation and packaging of the viral genome. This variability may reflect a viral strategy to select the fittest RNA molecule to produce a viral infection in the different vertebrate hosts that may be encountered by the ticks. It may also indicate a possible ancient introduction of TBEV to the Belp site. In addition, it may contribute to explaining the annual low incidence of tick-borne encephalitis in the natural focus of Belp, despite the high prevalence of TBEV genomes in ticks. - PublicationAccès libreDiversity within Borrelia burgdorferi sensu lato genospecies in Switzerland by recA gene sequence(2004)
; Piffaretti, Jean-ClaudeA total of 874 Ixodes ricinus ticks were collected in Switzerland to investigate the genetic diversity of the Borrelia population. We integrated to the RT-PCR method the DNA sequence analysis of a 162-bp fragment of the recA gene. Five genospecies were detected: Borrelia afzelii, Borrelia burgdorferi s.s., Borrelia garinii, Borrelia valaisiana, and Borrelia lusitaniae. A heterogeneous distribution was observed within the B. burgdorferi s.l. genospecies. The most prevalent and diverse genospecies found in Switzerland was Borrelia afzelii, which might suggest a rapid evolution of this genospecies.