Prevalence of antibodies to Borrelia burgdorferi in Danish rodents.

Six rodent species from six Danish localities were examined for antibodies to Borrelia burgdorferi by immunofluorescence assay (IFA). A total of 1097 specimens were tested using a serum titre of 1:8. The wild mice Apodemus sylvaticus and A. flavicollis had high prevalences of B. burgdorferi antibodies of 42.1% and 27.9% respectively, but the vole Microtus agrestis also showed an exceptionally high prevalence of 32.7%. Clethrionomys glareolus had a low average prevalence of 17.4%. The lowest and highest prevalences of rodents seropositive for B. burgdorferi of 6.5% and 100% were found for Micromys minutus and Mus musculus respectively. Twice as many of the Microtidae voles (M. agrestis and C. glareolus) as of the family Muridae were caught, and in Denmark the actual number of seropositive Microtidae was 1.6 times higher than for Muridae. The results indicate that in Denmark the family Microtidae species plays an important role as an animal reservoir host for B. burgdorferi. The prevalence of antibodies against B. burgdorferi varied from locality to locality, but seropositive rodents were found at all localities examined, indicating that the spirochete was widely present in Denmark.