Endemic Treponematoses at a Glance
- Pinta, yaws, and endemic syphilis (bejel) are nonvenereal infections usually acquired by skin-to-skin-contact.
- They are caused by Treponema pallidum subspecies or closely related treponemes.
- They are mostly endemic in rural areas within tropical and subtropical regions of selected countries.
- Like venereal syphilis, these infections are clinically characterized by three successive stages separated by periods of latency.
- Although not fatal, they are disfiguring and disabling.
- Penicillin therapy is highly effective for both the cutaneous and systemic lesions.
The endemic, or nonvenereal, treponematoses are infections caused by bacteria that are closely related to Treponema pallidum pallidum, the etiologic agent of venereal syphilis. These include Treponema carateum (pinta), Treponema pallidum pertenue (yaws), and Treponema pallidum endemicum (bejel or endemic syphilis). The diseases are distinguished from venereal syphilis by mode of transmission, age of acquisition, geographic distribution, and clinical features. Unlike syphilis, they are transmitted mostly among children living in tropical and subtropical climates, chiefly by casual contact rather than sexual contact, and congenital infection is unusual. As many as 2.5 million persons are believed to be infected with nonvenereal treponematoses. However, a significant proportion of infected persons remain asymptomatic. Like venereal syphilis, the diseases progress through successive clinical early (primary and secondary) and late stages usually separated by periods of latency.1
Without treatment, patients remain potentially infectious indefinitely, although the skin lesions may become inconspicuous or subclinical. Patients do not develop lifelong immune resistance. Cross-immunity is absent in the early stages of endemic syphilis, yaws, and pinta but is variable in late stages. Notably, patients with late pinta are resistant to syphilis, but those with yaws or syphilis at any stage are susceptible to pinta. The level of cross-protection may be proportional to the severity of the initial infection.1 Untreated treponematoses are nonfatal but may cause cutaneous lesions and deformities of the bone and cartilage. This potentially leads to significant disfigurement, pain, disability, and social isolation, thus incurring a significant economic burden on already disadvantaged populations.
The different treponemal species causing venereal and nonvenereal treponematoses are morphologically and serologically identical and induce comparable histopathological changes. This reflects the high antigenic relatedness among these organisms and justifies the long-standing controversy about the origin of these diseases. Some authors had even claimed that the morphologically identical treponemes represent the same organism causing different clinical manifestations under different climatic conditions.2 Over the past two decades, evidence from molecular studies has accumulated supporting the argument for species specificity. Molecular data have allowed the elucidation of genetic features differentiating T. pallidum pallidum from the nonvenereal treponemes.3–7 It was not until recently that Centurion et al identified subspecies-specific genetic signatures in the trp gene family that allow differentiation among the T. pallidum subspecies.8
Epidemiology and Etiology
Pinta is an ancient disease that was first described in the sixteenth century in Amerindians.9 The ...