Elimination of lyme disease spirochetes from ticks feeding on domestic ruminants.

To determine whether and which spirochetes are cleared from Ixodes ricinus ticks during feeding on ruminants, ticks were removed from goats and cattle grazing on tick-infested pastures. Although about a quarter of ticks questing on the pasture were infected by spirochetes, no molted ticks that had previously engorged to repletion on ruminants harbored Lyme disease spirochetes. Borrelia miyamotoi spirochetes, however, appear not to be eliminated. Thus, the more subadult ticks are diverted from reservoir-competent hosts to zooprophylactic ruminants, the smaller the risk of infection by Lyme disease spirochetes is.