Secondary lesions usually heal in about 6 months, but relapses may occur later, when yaws usually becomes latent. The cardiovascular and CNS complications of tertiary syphilis are not usually seen in tertiary yaws. Diagnosis Dark-field microscopic examination of exudate from lesions reveals organisms with the characteristic morphology and rotational motion of pathogenic treponemes. In addition to active cases of yaws, incubating cases and latent disease provide reservoirs of infection. Thus, control of yaws and other nonvenereal treponematoses requires mass treatment complemented by improvements in hygiene.
Endemic syphilis is prevalent in arid areas of the Middle East and Africa.
It is usually acquired in childhood. Spread occurs by direct contact and by use of contaminated utensils for eating and drinking. The causative organism can penetrate intact mucous membranes, but entrance is facilitated by labial, oral, or mucosal lesions. After proliferation at the site of primary inoculation, bloodstream dissemination sometimes causes a secondary stage of illness and a subsequent latent phase. The incubation period is about 3 weeks, but primary lesions are encountered infrequently.