Nonvenereal syphilis has apparently occurred in many forms and places, and one interpretation of this phenomenon is that venereal syphilis can revert to nonvenereal transmission. Others see it as a discrete disease with its own etiologic epidemiology. The most common and enduring form of the disease is called bejel; it occurs in the arid regions of North Africa, the Middle East, and the eastern Mediterranean, and seems to have antedated venereal syphilis as a disease entity by a considerable period of time. It is one of the endemic treponematoses caused by spirochetes, bacteria belonging to the genus Treponema. Other diseases in this group are yaws and pinta. Like yaws, bejel is essentially a disease of children, although those who escape the illness as children are likely to acquire it as adults, often from their own children. Its specific cause seems to be Treponema pallidum, the same agent as that of syphilis, although it may be a treponema intermediary between T. pallidum and Treponema pertenue, the agent of yaws. Although treponemal disease has been transferred experimentally to animals, humans appear to be the only natural reservoir.

Etiology, Epidemiology, and Clinical Manifestations

Because the treponemas that cause yaws, nonvenereal syphilis, pinta (an American disease), and syphilis are morphologically and serologically indistinguishable, it is believed that at least the Old World diseases may represent an evolutionary continuum running from south to north. Yaws, thought to be the oldest, spreads by skin-to-skin contact and flourishes in the hot and moist regions of Africa south of the Sahara where individuals have historically worn little clothing.