BORRELIA-BURGDORFERI SENSU LATE IN TICKS (ACARI, IXODIDAE) FROM 2 DIFFERENT FOCI IN SPAIN

The prevalence of Borrelia burgdorferi sensu lato in several tick spec ies was studied over a 2 year period in two ecologically different are as in Spain. One area was an endemic area for Lyme disease, with a num ber of autochthonous human cases and supported large populations of Ix odes ricinus on cattle and birds; the second area was characterized by the absence of I. ricinus together with the presence of foxes and the ir associated tick species. While I. ricinus was the main vector of B. burgdoreri in the endemic area (with a mean prevalence of 14% in adul ts and 51% in nymphs), adults of both Ixodes canisuga and Ixodes hexag onus had high rates of B. burgdorferi prevalence (30 and 28%, respecti vely) in the zone where I. ricinus was absent. Immatures of Ixodes fro ntalis were found to be carriers of the spirochete only in those zones where I. ricinus is present, suggesting evidence for reservoir compet ence in a tick-bird cycle.