RELATIONSHIP BETWEEN BORRELIA-BURGDORFERI SENSU LATO SPECIES, RED SQUIRRELS (SCIURUS-VULGARIS) AND IXODES-RICINUS IN ENZOOTIC AREAS IN SWITZERLAND

The infection and reservoir status of red squirrels (Sciurus vulgaris) for Borrelia burgdorferi sensu late were studied in Switzerland. B. b urgdorferi sensu late was isolated from 15 skin samples from 4/6 dead red squirrels, victims of road traffic. Isolates were identified using restriction fragment length polymorphism (RFLP): B. burgdorferi sensu stricto was present in 14 culture tubes containing skin samples and B . afzelii in two other tubes. A mixed infection was revealed in one ca se. A total of 227 ticks attached to squirrels were cultivated in BSKI I medium and 90 isolates were obtained. Genotypic identification by RF LP showed that B. afzelii (59%) and B. burgdorferi sensu stricto (46%) dominated in ticks feeding on red squirrels. Data collected from one particular animal, highly infested with Ixodes ricinus and harbouring numerous Borrelia-infected Ixodes ricinus ticks, showed that transmiss ion of B. burgdorferi sensu late occurred from S. vulgaris to feeding ticks. More precisely, B. burgdorferi sensu stricto and B. afzelii wer e mainly transmitted from S. vulgaris to ticks. The present data empha sized the results obtained previously from small rodents and birds in Japan and in Switzerland, showing the occurrence of specific associati ons between host species and Borrelia genospecies. (C) 1998 Elsevier S cience B.V. All rights reserved.