INFECTION OF FIELD-COLLECTED IXODES-RICINUS (ACARI, IXODIDAE) LARVAE WITH BORRELIA-BURGDORFERI IN SWITZERLAND

Free-living larvae from natural areas in five regions in Switzerland w ere collected to determine the infection rate of Ixodes ricinus L. lar vae by Borrelia burgdorferi Johnson. Larvae were examined for the spir ochetes using direct fluorescent antibody assay. Of 652 larvae examine d, spirochetes were detected in 20 (3.1%). No differences in infection rate among sites were detected. The low prevalence of B. burgdorferi in larvae, compared with higher infection rate in nymphs (12.8%) and a dults (14.5%), suggests that transovarial transmission is inefficient. These results suggest that I. ricinus can serve as a reservoir for B. burgdorferi in nature. Futher study is needed on the relative importa nce of ticks, compared with mammals and birds, as reservoirs for B. bu rgdorferi.