Tick-borne Borrelia infection in Sweden

Abstract

Spirochetes were cultivated from 17% of 114 Ixodes ricinus ticks in the Stockholm area. Three strains of these spirochetes were selected for studies by electron microscopy. These three strains had definite morphological similarities to spirochetes of the genus Borrelia, as judged by the number of flagella, absence of cytoplasmic tubules, and dimensions. The three strains were not identical, but seemed to consist of two different kinds of cells, one with eight and one with eleven flagella. The three strains were also shown to react with a monoclonal antibody that reacts with Lyme disease spirochetes (Borrelia burgdorferi), but not with strains of other Borreliae, Treponemes, or Leptospiras. These results indicate the possibility of transmission of Borrelia spirochetes from ticks to humans in Sweden. The antibody response to one of the spirochetal strains isolated from Swedish I. ricinus was studied in 37 patients with the typical clinical picture of erythema chronicum migrans (ECM), in 45 patients with chronic meningitis (CMe) cured by high-dose intravenous penicillin, in 298 patients with post-infectious arthritis, and in controls. The antibody response was estimated by indirect immunofluorescence assay (IFA) enzyme-linked immunosorbent assay (ELISA). The antibody levels differed significantly between patients with CMe and healthy individuals (p less than 0.001), both with respect to serum antibody levels and CSF-antibody levels. The antibody levels also differed significantly between patients with ECM and healthy controls as measured by ELISA (p less than 0.05), whereas the difference was not significant as measured by IFA. Five of 298 patients with post-infectious arthritis had higher titers than any of the controls, and two of these five patients had titers higher than any patient with CMe or ECM. These results indicate spirochetal aetiology of ECM, and in some patents with CMe or postinfectious arthritis. As a diagnostic test for ECM, both IFA and ELISA were of limited value, since only 5/37 (14%) ECM patients were positive by IFA, and 14/37 (38%) by ELISA. Regarding patients with CMe, 23/45 (51%) were seropositive by IFA and 30/45 (67%) by ELISA. However, measurement of CSF-antibodies were found to be a more sensitive method than measurement of serum antibodies both by IFA and ELISA, since 38/45 (84%) CMe patients were positive by IFA, and 41/45 (91%) by ELISA. In addition, estimation of CSF antibodies was also found to be a more specific method than estimation of serum antibodies.(ABSTRACT TRUNCATED AT 400 WORDS)