BORRELIA-BURGDORFERI IN RODENTS (APODEMUS-FLAVICOLLIS AND A-SYLVATICUS) - DURATION AND ENHANCEMENT OF INFECTIVITY FOR IXODES-RICINUS TICKS

Ixodes ricinus is an important vector of Borrelia burgdorferi in Europ e, and small rodents (Apodemus flavicollis, A. sylvaticus and Clethrio nomys glareolus) are important sources for infecting ticks. In this st udy, we examined their reservoir role by studying the duration of thei r infectivity for ticks. A. flavicollis and A. sylvaticus mice capture d in nature were exposed to uninfected I. ricinus larvae at different times after their capture: 10 days, and 2, 7, 11, 14 and 40 months. Ti cks were examined for spirochaetes after moulting using direct immunof luorescence. All animals remained infective for ticks their life long but the efficiency of transmission from hosts to ticks varied from one individual to the other, presenting a three-fold variation (26.5% to 81.4%). Rodents continously exposed to successive infestations by larv al I. ricinus ticks over a period of one month showed an enhancement o f infectivity for larval ticks during this period.