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A total of 825 adult ticks (727 Ixodes ricinus, 72 Dermacentor marginatus and 26 Haemaphysalis punctata) was collected from vegetation in Valais (Switzerland) in 1987 to 1992. They were examined for the presence of Borrelia burgdorferi sensu lato, the etiologic agent of Lyme borreliosis. B. burgdorferi sensu lato was detected by indirect immunofluorescence assay, dark field microscopy and/or culture in 221 out of 727 I. ricinus (30.4%) and none in the other two species. From these 221 infected ticks we obtained 50 isolates. Indirect immunofluorescence assay and culture were used for all ticks but dark field examination has also been performed and compared to the two above mentioned methods for 231 I. ricinus. Indirect immunofluorescence assay and culture were used for all ticks but dark field examination has also been performed and compared to the two above mentioned methods for 231 I. ricinus. Indirect immunofluorescence was found the most efficient method for the detection of Borrelia in ticks with 54 positive out of 231, followed by dark field examination with 35 positive and culture with 12 isolates. We found no site free of Borrelia where I. ricinus is present. The rate of infection varied from 9.7 to 47.5%, as detected by the addition of the three methods. Typing of the 50 isolates revealed also a nonhomogeneous distribution of the Borrelia species. Based on the electrophoretic mobility of the OspA and B and immunostaining with species specific monoclonal antibodies (H3TS for B. burgdorferi sensu stricto, D6 for B. garinii and J8.3 for B. afzelii) 4 groups could be observed. Half of the isolates (n = 26) were typed as B. burgdorferi sensu stricto, 19 as B. garinii, 3 as B. afzelii and 2 as group VS116. This forth group formed of two isolates from one location is genetically distinct from the 3 former species described in Europe so far. The Borreliae of this group are unreactive with any of the three monoclonal antibodies used.

Isolation of Borrelia burgdorferi from the CSF is relatively rare. The present report describes the first three isolations in Switzerland. Clinically, our first observation confirmed the frequent association of B. burgdorferi with peripheral facial paresis in children. The other two cases illustrate the variety of symptoms in neuro-borreliosis. In the first case the culture was positive after 6 weeks. The results of serologic tests (indirect immunofluorescence and ELISA) for detection of antibodies against B. burgdorferi were negative or non-significant in this child's serum. On the other hand, specific antibodies (IgG) were detected in the serum by western blot. Culture of the second CSF already showed Borrelia growth after 10 days. Immunofluorescence revealed high antibody titers (1/256) against B. burgdorferi in this patient's serum. IgG showed a weakly positive reaction in western blot. The reliability of this result was confirmed by isolation of Borrelia. In neither of the two CSF could intrathecal synthesis of specific antibodies be demonstrated. In the third case, however, immunofluorescence showed IgG antibody titers of 1/128 in the CSF and 1/512 in serum. Intrathecal synthesis of specific antibodies was demonstrated with an index of 13.4 (norm2). Western blot confirmed the specificity of the reactions observed with the serum and CSF IgG. Culture of CSF produced significant growth of Borrelia within 7 days. Protein profile and reactions with poly- and monoclonal antibodies confirmed that the three strains belonged to B. burgdorferi.(ABSTRACT TRUNCATED AT 250 WORDS)

Fifty Borellia burgdorferi strains isolated from humans and ticks in Europe and the United States were analyzed by multilocus enzyme electrophoresis. Eleven genetic loci were characterized on the basis of the electrophoretic mobilities of their products. Ten loci were polymorphic. The average number of alleles per locus was 5.9, with a mean genetic diversity of 0.673 among electrophoretic types (ETs). The strains were grouped into 35 ETs constituting three main divisions (I, II, and III) separated at a genetic distance greater than 0.75. Divisions I, II, and III contained 13, 6, and 16 ETs, respectively. These findings, together with previous data from DNA hybridization and restriction enzyme analysis of rRNA genes, suggest that divisions I, II, and III may represent three distinct genomic species. All three divisions contained human clinical ETs. However, in division I, which includes the ET of the type strain of B. burgdorferi, the human pathogenic ETs constituted a single clone. The ETs of division I were from west-central Europe and the United States, whereas divisions II and III contained ETs from west-central and northern Europe but not from the United States. Finally, our data show that the genetic structure of B. burgdorferi populations is clonal.