VECTOR COMPETENCE OF IXODES-SCAPULARIS AND IXODES-RICINUS (ACARI, IXODIDAE) FOR 3 GENOSPECIES OF BORRELIA-BURGDORFERI

The vector competence of 2 tick species, Ixodes ricinus (L.) and Ixode s scapularis Say, was determined and compared for 3 genospecies of Bor relia burgdorferi. The 3 genospecies of B. burgdorferi used in the fol lowing experiments were Borrelia burgdorferi sensu stricto (B-31 and B -31.D1 clone), Borrelia afzelii (strain Pgau.C3), and Borrelia garinii (strain VS286 and VSBP). Spirochetes from all 5 strains were inoculat ed intradermally into outbred mice; larval ticks of both species were subsequently fed on those mice and replete larvae were assayed for inf ection by culture in BSK-H media every 7 d for 4 wk. Infection frequen cies in I. scapularis exposed to the 5 strains were as follows: B-31 ( 90%), B-31.D1 (83%), Pgau.C3 (87%), VS286 (10%), and VSBP (5%). The co mparable infection frequencies for I. ricinus were B-31 (3%), B-31.D1 (3%), Pgau.C3 (90%), VS286 (5%), and VSBP (3%). Resultant nymphal I. s capularis successfully transmitted B-31, B-31.D1, Pgau.C3, and VS286 t o outbred mice. I. ricinus nymphs transmitted Pgau.C3 and VS286. Both species failed to transmit strain VSBP.