The endemic, or nonvenereal, treponematoses are bacterial infections caused by close relatives of Treponema pallidum subspecies pallidum, the etiologic agent of venereal syphilis (Chap. 169). Yaws, pinta, and endemic syphilis are traditionally distinguished from venereal syphilis by mode of transmission, age of acquisition, geographic distribution, and clinical features. These infections are limited to rural areas of developing nations and are seen in developed countries only among recent immigrants from endemic regions. Our “knowledge” about the endemic treponematoses is based on observations by health care workers who have visited endemic areas; virtually no well-designed studies of the natural history, diagnosis, or treatment of these infections have been conducted. The treponemal infections are compared and contrasted in Table 170-1.
Table 170-1 Comparison of the Treponemes and Associated Diseases
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Table 170-1 Comparison of the Treponemes and Associated Diseases
|Feature||Venereal Syphilis||Yaws||Endemic Syphilis||Pinta|
|Organism||T. pallidum subsp. pallidum||T. pallidum subsp. pertenue||T. pallidum subsp. endemicum||T. carateum|
|Modes of transmission||Sexual, transplacental||Skin-to-skin||Household contacts: mouth-to-mouth or via shared drinking/ eating utensils||Skin-to-skin|
|Usual age of acquisition||Adulthood or in utero||Early childhood||Early childhood||Late childhood|
|Primary lesion||Cutaneous ulcer (chancre)||Papilloma, often ulcerative||Rarely seen||Nonulcerating papule with satellites, pruritic|
|Location||Genital, oral, anal||Extremities||Oral||Extremities, face|
|Secondary lesions||Mucocutaneous lesions; condylomata lata||Cutaneous papulosquamous lesions; osteoperiostitis||Florid mucocutaneous lesions (mucous patch, split papule, condyloma latum); osteoperiostitis||Pintides, pigmented, pruritic|
|Late complications||Gummas, cardiovascular and CNS involvementa||Destructive gummas of skin, bone, cartilage||Destructive gummas of skin, bone, cartilage||Nondestructive, dyschromic, achromic macules|
The endemic treponematoses are chronic diseases transmitted by direct contact during childhood and, like syphilis, can cause severe late manifestations years after initial infection. In a World Health Organization (WHO)–sponsored mass eradication campaign from 1952 to 1969, more than 160 million people in Africa, Asia, and South America were examined for treponemal infections, and more than 50 million cases, contacts, and latent infections were treated. This campaign reduced the prevalence of active yaws from >20% to <1% in many areas. In recent decades, lack of focused surveillance and diversion of resources have resulted in documented resurgence of these infections in some regions. The estimated geographic distribution of the endemic treponematoses in the 1990s is shown in Fig. 170-1. The most recent WHO estimate (1997) suggested that there are 460,000 new cases per year and a prevalence of 2.5 million infected persons; during the subsequent decade, an increased incidence was documented in some countries. Areas of resurgent yaws morbidity include West Africa (Ivory Coast, Ghana, Togo, Benin), the Central African Republic, Nigeria, and rural Democratic Republic of Congo. The prevalence of endemic syphilis is estimated to be >10% in some regions of Ghana, Mali, Niger, Burkina Faso, and Senegal. In Asia and the Pacific Islands, reports suggest active outbreaks of yaws in Indonesia, Papua New Guinea, East Timor, Vanuatu, Laos, and Kampuchea. India actively renewed its focus on yaws eradication in 1996 and has reported no new cases since 2003. In the Americas, foci of yaws are thought to persist in Haiti and other Caribbean islands, Peru, Colombia, Ecuador, Brazil, Guyana, and Surinam. Pinta is limited to Central America and northern South America, where it is found rarely and only in remote villages. Evidence of yaws-like disease and seroreactivity in wild gorillas and baboons in Africa has led to speculation that there may be an animal reservoir for yaws, although strains recently obtained from humans and nonhuman primates have not been subjected to molecular comparison. A single strain isolated from a baboon in 1966 contains several identified genetic differences from available yaws isolates from humans.
The etiologic agents of the endemic treponematoses are T. pallidum subspecies pertenue (yaws), T. pallidum subspecies endemicum (endemic syphilis), and T. carateum (pinta). These little-studied organisms are morphologically identical to T. pallidum subspecies pallidum, and no definitive antigenic differences among them have been identified to date. A controversy has existed about whether the pathogenic treponemes are truly different organisms. Three of the four organisms are classified as subspecies of T. pallidum; the fourth (T. carateum) remains a separate species simply because no organisms have been available for genetic studies. A number of genetic loci distinguish the agents of venereal and nonvenereal treponemal infections, and molecular signatures (assessed by polymerase chain reaction amplification of tpr genes and restriction digestion) can differentiate the individual agents of venereal syphilis, yaws, and bejel. Whether these genetic differences are related to the distinct clinical courses of these diseases has not been determined.
All of the treponemal infections are chronic and are characterized by defined disease stages, with a localized primary lesion, disseminated secondary lesions, periods of latency, and possible late lesions. Primary and secondary stages are more frequently overlapping in yaws and endemic syphilis than in venereal syphilis, and the late manifestations of pinta are very mild relative to the destructive lesions of the other treponematoses. The current preference is to divide the clinical course of the endemic treponematoses into “early” and “late” stages.
The major clinical distinctions made between venereal syphilis and the nonvenereal infections are the apparent lack of congenital transmission and of central nervous system (CNS) involvement in the nonvenereal infections. It is not known whether these distinctions are entirely accurate. Because of the high degree of genetic relatedness among the organisms, there is little biological reason to think that T. pallidum subspecies endemicum and T. pallidum subspecies pertenue would be unable to cross the blood-brain barrier or to invade the placenta. These organisms are like T. pallidum subspecies pallidum in that they can disseminate from the site of primary infection and can ...