Treponematosis (Endemic Syphilis, Yaws, and Pinta)

Treponematosis, also known as treponemiasis, traditionally refers to the group of nonvenereal diseases (including endemic syphilis [nonvenereal syphilis]) caused by Treponema species that are morphologically and serologically identical to each other and to Treponema pallidum subspecies pallidum, the cause of venereal syphilis. DNA from T pallidum subspecies pallidum is at least 99% homologous to that of T pallidum subspecies pertenue and T pallidum subspecies endemicum. ^[1] However, they differ in terms of clinical manifestations.

Treponema species typically associated with nonvenereal disease are transmitted among children living in tropical, subtropical, or warm arid climates, chiefly by direct contact. In humans, the pathogenic treponemes include T pallidum pallidum (syphilis), Treponema pallidum pertenue (yaws), Treponema pallidum endemicum (bejel or endemic syphilis), and Treponema carateum (pinta). ^{[2, 3, 4]} Recently, T pallidum endemicum (bejel) has been found in men who have sex with men in Japan, although transmission is believed to occur nonsexually. ^{[5, 6]}

Transmission of yaws and bejel typically occurs in children. Transmission typically occurs via direct skin-to-skin contact of lesions, which are infectious. Bejel is transmitted skin to skin but can also be transmitted mouth to mouth and on fomites (eg, via shared eating utensils or cups). Pinta is also transmitted by skin-to-skin contact and is more common in older children or teenagers.

Treponemes usually invade traumatized cutaneous or mucosal surfaces that come in contact with a draining open sore of the index case. A primary cutaneous lesion appears at the site of inoculation following an incubation period of a few weeks.The primary lesion could be a papule or an ulcer.  Treponema may be spread from this site either topically (by scratching) or hematogenously. These lesions often heal spontaneously. Treponematosis can remain latent or it may recur.

The secondary stage of any of these diseases follows the dissemination of the treponemes. It may begin while the primary lesion is still present or after a variable latent period. It may also resolve spontaneously, recur, or persist. The long-term effects of these infections include multiple cutaneous lesions and destruction of bones or cartilage.

The disease may then enter a clinically latent stage although still detectable with serologic tests. In a minority of cases there may be a tertiary stage characterized by deep tissue destruction including more severe bone and cartilage destruction. 

Frequency

United States

Although treponematosis does not occur in the United States, imported cases have been documented. It may be found in children immigrating from areas of endemicity, and the US Centers for Disease Control and Prevention (CDC) has recommended screening of all refugee children from endemic regions with a nontreponemal test at initial health screening. ^[7]

International

In 1997, the World Health Organization (WHO) estimated that 460,000 new cases of endemic treponematosis occurred worldwide. Currently, more than 2.5 million people may be infected. Currently, it is difficult to estimate disease burden owing to sporadic reporting and lack of data, which are reviewed in Global Health Observatory (GHO) data. ^[8]

Endemic syphilis (bejel) (T pallidum endemicum) is typically spread among children, most commonly in the Middle East and the southern regions of the Sahara Desert. In Europe, cases have been diagnosed in children who have moved from endemic areas. In one study, 12% of children younger than 5 years in Niger were seropositive. ^[9] High rates of seropositivity are also observed in Mali, Burkina Faso, and Senegal. Pinta (T carateum), which occurs in the Caribbean and in Central and South America, is more common in young adults.

Yaws (T pallidum pertenue) occurs mainly in equatorial regions and can be found in South America, Central America, the Caribbean, Africa, and Southeast Asia. It is associated with high humidity and rainfall. Fifty years ago, the WHO recognized that endemic treponematoses—yaws in particular—were a major cause of disfigurement and disability and a significant economic burden in poor countries.

In Haiti and the Dominican Republic, a pilot project was initiated to eradicate the disease with mass applications of penicillin. This project was so successful that it was extended to 46 other countries. Overall, the incidence of yaws was reduced to isolated foci of endemicity. As public health priorities changed and support for the eradication programs lapsed, the disease saw a resurgence in the 1970s and 1980s. The introduction of mass treatment has been necessary in some areas. In a WHO survey in 2012, ^[10] the status of yaws was unknown in many of the countries where it had previously been known to be endemic.

Now that an oral treatment has been recommended for first-line therapy, a new eradication campaign is underway by the WHO. ^[11]

Mortality/Morbidity

Untreated treponematosis may cause disfiguring cutaneous lesions and deformities of bone, cartilage (particularly the nose), and skin, potentially leading to significant disfigurement, pain, and disability. Affected children can become socially ostracized and often miss school. Thickening and cracking of the soles may make walking difficult. Treponematosis can extract a significant economic toll on already-disadvantaged populations. Fortunately, with penicillin or azithromycin therapy, cure rates of 95-97% are possible.

Race

Treponematosis has no reported racial predilection in terms of frequency or severity.

Sex

Treponematosis has no reported sexual predilection in terms of frequency or severity.

Age

Although individuals of any age can acquire treponematosis, endemic syphilis and yaws are more common in children younger than 10 years, whereas pinta is more common in young adults. Yaws most often infects children and peaks in those aged 2-10 years. Of new cases, 75% arise in children younger than 15 years. Congenital infections with the endemic treponemes are unusual because most primary infections occur in children. Primary treponematosis during pregnancy is rare.

For excellent patient education resources, visit eMedicineHealth's Sexual Health Center. Also, see eMedicineHealth's patient education article Syphilis.