STRAIN VARIATION OF LYME-DISEASE SPIROCHETES ISOLATED FROM IXODES-RICINUS TICKS AND RODENTS COLLECTED IN 2 ENDEMIC AREAS IN SWITZERLAND

The relationship among Lyme borreliosis, Borrelia genospecies, rodent reservoirs, and Ixodes ricinus L. ticks was studied in two endemic are as in Switzerland. Ear punch biopsies and sampling of internal organs were used to isolate Borrelia burgdorferi (Johnson, Schmid, Hyde, Stei gerwalt and Brenner) from small mammals, Apodemus sylvaticus L., A. fl avicollis Melchior, Clethrionomys glareolus Schreber. Spirochetes were isolated from ear tissue and spleen of the rodents. Isolates were hom ogeneous and belonged to typing group II identified as B. afzelii (Can ica, Nato, du Merle, Mazie, Baranton and Postic). Our data show that a specific association exists between B. afzelii and rodent reservoirs in European foci. Borreliae were also isolated from field-collected I. ricinus ticks from the same study areas. Proteinic and antigenic anal ysis indicated that more than one genospecies were present in the tick population. This suggests that other vertebrate hosts may serve as re servoirs of other Borrelia genospecies implicated with Lyme disease.