INFECTION-RATE OF IXODES-RICINUS TICKS WITH BORRELIA-AFZELII, BORRELIA-GARINII, AND BORRELIA-BURGDORFERI SENSU-STRICTO IN SLOVENIA

In spring 1993, Ixodes ricinus ticks were collected from six regions o f Slovenia to determine their overall rate of infection with Borrelia burgdorferi sensu late and to assess the frequency of individual speci es in these tick populations. Ticks were dissected and midgut tissue i noculated into modified Barbour-Stoenner-Kelly (BSK II) medium. Borrel ia isolates were differentiated into separate species using species-sp ecific polymerase chain reaction (PCR) primers and by large restrictio n fragment pattern (LRFP) analysis. Infected ticks were found in all s ix regions surveyed, Spirochaetes were isolated from 69 of 363 ticks ( 19 %): the isolation rate from adult female ticks was 35 % (23/66 tick s cultured), from adult male ticks 22 % (20/91), and from nymphal tick s 13 % (26/206). Determination of the species of 60 isolates revealed that 32 were Borrelia afzelii (53 %), 20 were Borrelia garinii (33 %), and 8 were Borrelia burgdorferi sensu stricto (13 %). In the Ljubljan a region Borrelia afzelii and Borrelia garinii predominated (43 % and 40 %, respectively), whereas Borrelia burgdorferi sensu stricto consti tuted only 17 % of isolates. In three other regions of the country Bor relia afzelii was isolated exclusively, although the number of isolate s investigated was small. This study demonstrates the presence of all three European species of Borrelia burgdorferi sensu late within the S lovenian tick population and also within a geographic area of less tha n 100 m(2).