ACCELERATED INFECTIVITY OF TICK-TRANSMITTED LYME-DISEASE SPIROCHETES TO VECTOR TICKS

We determined whether the span of infectivity of Lyme disease spiroche tes (Borrelia burgdorferi) to vector ticks varies with the mode of inf ection in laboratory mice. Noninfected larval deer ticks were permitte d to feed on two strains of spirochete-infected mice that had been nat urally (via tick bite) and parenterally (via needle injection) infecte d with B. burgdorferi 2, 4, or 8 weeks earlier, and engorged ticks wer e dissected and examined for spirochetes by direct immunofluorescence microscopy. After initial infection, spirochetal infectivity to ticks was less efficient in needle-infected mice than in mice infected via t ick bites. Tick-transmitted spirochetes develop more rapidly from the skin of infected mice and do not induce a strong antispirochete antibo dy response during the early stage of infection.