Vtp mutant is non-infectious to mice by tick bite.

a<p>No. of mice spirochetemic within 10 days post-infection.</p>b<p>No. of mice seropositive examined 3–4 months post-infection.</p>c<p>The lack of infection by the mutant compared to the wild-type and reconstituted strains is significantly different (Fisher’s Exact Test, <i>P</i> = 0.0001).