Demonstration of Treponema pallidum in axons of cutaneous nerves in experimental chancres of rabbits.

After cutaneous inoculation of viable Treponema pallidum subsp pallidum into the skin of chancre-immune or previously uninfected rabbits, organisms move from perivascular connective tissue to localize extracellularly in hair follicles, erector pili muscles, and cutaneous nerves. Large numbers of intact organisms can be seen within the perineurium using electron microscopy, and after extensive sampling a few organisms can be detected within the axon cytoplasm. These findings support the concept that T. pallidum may be able to pass along the nerve fibers to the central nervous system.