From the Greek trepo (rotate, turn) and ne¯ma (thread), Treponema is a genus of gram-negative, anaerobic or microaerophilic bacteria. They are spiral-shaped and have flagella, which extend from motors at the pole, producing undulating movement through fluids, enabling tissue invasion and dissemination (Figure). In 1905, microbiologist Fritz Richard Schaudinn and dermatologist Paul Erich Hoffmann described Treponema pallidum subsp. pallidum as Spirochaeta pallida from a fresh human vulvar lesion.

Treponema spp. can invade the epidermis and oral, intestinal, and genital mucosa of humans and animals. They cause human diseases, such as syphilis, yaws, pinta, and bejel, and animal diseases, such as digital dermatitis. T. phagedenis, T. pedis, and T. medium infect mainly cattle. T. paraluiscuniculi can cause syphilis in rabbits.

Most Treponema spp. are not cultivable, except for T. palllidum subsp. pallidum and T. phagedenis. T. pallidum subsp. pallidum causative syphilis is a reemerging disease in industrialized countries. Digital dermatitis, a polytreponemal disease, is considered to be the major infectious claw disease in cattle worldwide.