What is Yaws?

Yaws is endemic or non venereal (not a sexually transmitted disease) treponematosis, which is caused by close relatives of Treponema pallidum (etiological or causative agent of venereal syphilis) subspecies pallidum. Other endemic or non venereal treponematoses are pinta and endemic syphilis. The difference of these endemic or non venereal treponematoses from venereal syphilis, can be made by the mode of transmission (syphilis is a sexually transmitted disease or STD and other are non-sexually transmitted), age at which these are acquired, geographic distribution, and clinical manifestations. The endemic or non venereal treponematoses are generally seen in rural areas of developing countries and due to that, these diseases are not studied well and diagnosis or treatment of these infections may be very difficult in absence of any well conducted study or any guideline on diagnosis or treatment.

What is the causative agent of Yaws?

Yaws is caused by infection of Treponema pallidum subsp. Pertenue. The Treponema pallidum subsp. Pertenue has been studied very little. They are very similar to Treponema pallidum (the causative agent of syphilis) morphologically and there seem to be no antigenic differences among these organisms (that is why there is controversy, if they are really separate organisms or they are same).

What is the mode of transmission of Yaws?

Yaws is not spread by sexual contact. Yaws is spread by skin-to-skin contact (direct contact with infectious lesions) and generally occurs during early childhood (venereal syphilis occurs during adulthood). Children can acquire Yaws while playing or group sleeping with other children with Yaws. The risk of spread of Yaws is increased if there is disruption of the skin by insect bites or abrasions (small cut wound).

What is the epidemiology of Yaws?

Yaws is seen in many developing countries. It is estimated that at present the prevalence of Yaws and other endemic treponematoses to be more than 3 million infected cases with more than 400,000 new cases every year. Presently Yaws is present in Africa (West African countries of Ivory Coast, Ghana, Togo, Benin; the Central African Republic, Nigeria, and rural Democratic Republic of Congo formerly known as Zaire), Asia and the Pacific Islands (Papua New Guinea, East Timor, Vanuatu, Laos, Cambodia, and Indonesia) and in the Americas (Haiti and other Caribbean islands, Peru, Colombia, Ecuador, Brazil, Guyana, and Surinam).

What are the clinical manifestations of Yaws?

Yaws is also known as pian, framboesia, or bouba. Like other treponemal infections Yaws has clearly defined disease stages and the clinical stages of Yaws are localized primary lesion, disseminated secondary lesions, periods of latency, and sometimes late lesions. The primary lesion also known as “mother yaw” may be one or may be several. After 3–4 weeks of acquiring infection, the first lesion of Yaws begins as a papule, usually on an extremity (hand or leg), which then enlarges (particularly during moist warm weather) to become papillomatous or raspberry-like. The name "framboesia" is given to Yaws because of its “raspberry-like” primary lesion. Regional lymphadenopathy develops and the primary lesions heal generally in 6 months and during initial weeks of infection the dissemination of disease take place.

The primary lesion/lesions are followed by appearance of multiple disseminated secondary skin lesions (which may be several forms like macular, papular, or papillomatous). Secondary infection may occur in secondary skin lesions. If papillomatous lesion is present in the sole of feet (and painful), it results in a painful crablike gait ("crab yaws"). Nocturnal bone pain and polydactylitis are some other clinical manifestations which may sometimes occur. The early skin lesions (primary and secondary lesions) may persist for many months and are infectious (responsible for spread of infection). During initial five years of disease there may be cutaneous relapses (which are common).

The late manifestation of Yaws, can be termed as complications of Yaws (occurs in approximately 10% of patients) are generally serious and can involve skin, bone, and joints. Late Yaws generally manifests as gummas (which generally are extensive) of the skin and long bone, hyperkeratoses of the palms and soles, osteitis and periostitis. In late Yaws there may be destruction of nose, maxilla, palate, and pharynx and similar to the destructive lesions seen in leprosy is called gangosa.

How Yaws is diagnosed?

Diagnosis of Yaws and other endemic treponematoses is based on clinical manifestations (mainstay of diagnosis) and dark-field microscopy and serologic testing (if available, and generally they are not available where endemic treponematoses are seen generally, in rural areas of developing countries). The dark-field microscopy and serologic testing, (which are also used for diagnosis of all treponemal infections) are also positive in syphilis also and there is no test which can differentiate different treponemal infections (syphilis, Yaws, pinta, endemic syphilis etc.). In developed countries nonvenereal treponemal infections should be suspected if test for syphilis are positive and the patient migrated from an area where nonvenereal treponemal infections are endemic.

How Yaws is treated?

The drug of choice and recommended for treatment of Yaws is benzathine penicillin at the dose of 1.2 million units intramuscularly for adults and 600,000 units for children of less tha10 years of age. But unfortunately there are control trial studies of treatment of Yaws and other endemic treponematoses. Resistance to penicillin is reported but there is no documented evidence with definite proof, but there are reports of relapsing lesions of Yaws after treatment with penicillin. Tetracycline can be effective in treatment of Yaws. Other alternative drugs are doxycycline and erythromycin, but this is solely based on experience with treponemal venereal disease treatment. Side effects like Jarisch-Herxheimer reaction may occur after treatment of endemic treponematoses. There is generally decline in the titers of serological tests after treatment with penicillin, but the patient may not become seronegetive.

How Yaws can be prevented or controlled?

Unfortunately there has been no attempt to control or prevent the endemic treponematoses by public health decision-makers in any country. Penicillin therapy is inexpensive and effective for treatment and can be used for controlling the disease (Yaws). The control or prevention of Yaws and other endemic treponematoses has become more important in view of the spread of HIV in many developing countries, as HIV can impact the manifestations and transmission of the endemic treponematoses.

WHO (World Health Organization) undertook a mass eradication campaign of endemic treponematoses from 1952 to 1969 and more than 160 million people in Africa, Asia, and South America were examined for endemic treponemal infections. More than 50 million cases, contacts, and latent infections were identified and treated, which reduced the prevalence of active yaws from more than 20% to less than 1% in many areas.

India reported excellent success in controlling Yaws and reported no cases of Yaws after 2004. The campaign for eradication of Yaws in India was started in 1996 and in less than a decade the incidence was brought to zero.