Yaws is a chronic bacterial infection caused by Treponema pallidum subspecies pertenue. This disease affects the skin, bones, and cartilage and is endemic in tropical regions of Asia, Africa, Latin America, and the western Pacific.
Yaws is mainly found in children who reside in endemic regions. Inoculation occurs when individuals are exposed to infected individuals  .
The following are the clinical stages:
The mother yaw, or primary lesion, forms at the contact site. This is usually a minor trauma on the skin, such as a cut, scratch, or bite on the lower extremities or buttocks. Specifically, the lesion appears as a non-tender, pruritic, reddish papule that grows in size and transforms into a papilloma. It contains central hypopigmentation and the healing process takes 3 to 6 months and is followed by the development of scars.
This phase lasts between 6 to 16 weeks.
Disseminated lesions of the skin and bones may form after a latency phase. The daughter yaws are commonly positioned close to the mouth and nose. They grow, ulcerate and produce an exudative fluid containing the organisms. Also, papules, macules and nodules may arise. Overall, secondary lesions may persist for weeks to months and may resolve without treatment. Scarring does not usually occur. This phase may also feature constitutional symptoms.
Complications include thickening of the skin, which manifests as painful hyperkeratotic plaques that form fissures. Consequently, these painful and uncomfortable skin manifestations make it difficult to walk and hence the patient develops a crablike gait referred to as crab yaws.
Bone sequelae include osteoperiostitis and fusiform swelling of the metatarsal and metacarpal joints.
This late stage occurs in 10% of infected patients. It presents with damage to the skin and bones after 5 to 15 years of latency. The nervous system and the eyes may also be affected. Furthermore, this phase is characterized by the formation of well-demarcated subcutaneous nodules, which go on to develop abscesses, necrosis and ulcerations.
Infection of the ulcers is typically followed by further destruction of the skin. If the ulcers coalesce, this results in the production of serpiginous channels that eventually heal with keloid formation. Consequently, these patients suffer from severe deformities and contractures.
One component of the patient assessment is the history of the individual which includes any contacts or exposures. Additionally, healthcare workers should consult the WHO clinical pictorial guide to help identify the infection. Further workup includes laboratory studies.
Serological tests are commonly used to confirm treponemal infection, however, they do do not differentiate yaws from syphilis. Hence, the clinician should correlate the clinical picture, the epidemiology, and the laboratory findings to arrive at the diagnosis.
The studies include: 1) rapid plasma reagent (RPR), 2) Venereal Disease Research Laboratory (VDRL), 3) fluorescent treponemal antibody absorption (FTA-ABS), 4) T. pallidum immobilization (TPI), and 5) T. pallidum hemagglutination assay (TPHA).
The RPR and VDRL tests are persistently reactive through all the stages. Specifically, they generate positive results as early as 2 to 3 weeks following the presentation of the mother lesion.
There two types of rapid tests that produce the point-of-care (POC) diagnosis . The rapid treponemal tests are widely utilized for the diagnosis of syphilis cases while the rapid dual treponemal and non-treponemal POC test distinguishes the antibodies of yaws from syphilis. It is used in various countries including Ghana, Papua New Guinea, Solomon Islands and Vanuatu to eliminate the disease.
Polymerase chain reaction (PCR)  is used to confirm the disease and also to identify resistance to azithromycin.
A biopsy of the lesions can be obtained for histopathologic analysis .
The therapy of this infection includes antibiotic treatment. One option is azithromycin, which is prescribed as a single oral dose at 30mg/kg. The maximum is 2 g. Additionally, the drug of choice is benzathine penicillin, which is administered intramuscularly as a single dose of 600, 000 units in children. This dose is doubled in adults. The lesions become non-contagious 24 hours after penicillin treatment. Furthermore, healing occurs within 1 to 2 weeks.
There are alternatives for penicillin-allergic patients such as tetracycline, erythromycin, or doxycycline . If benzathine penicillin is not available, then oral penicillin can be given for a duration of 7 to 10 days .
There are treatment guidelines depending on the epidemiologic profile. For example, in communities where more than half of the children are seropositive, then the entire population warrants treatment. When 10% to 50% are seropositive, then all children of ages 15 or under should be treated in addition to the affected individuals and their contacts. Finally, if below 10% of children are seropositive, then treatment is indicated for household members, contacts and infected individuals.
Approximately 10% of untreated patients suffer from disfigurement of the nose and legs in the late stage. This destruction phase results in disabilities that affect their quality of life. Furthermore, some patients will have neurologic and ophthalmologic manifestations.
Untreated patients may have relapses even after 5 to 15 years. During these relapses, the infection targets the skin, bones, and joints.
Six decades ago, yaws was found in all tropical areas and Africa demonstrated the highest prevalence according to reports by the World Health Organization (WHO) in the 1990s. India announced the eradication of the infection in 2006.
Yaws occurs in tropical forest regions in Africa, Asia, Latin America and the Pacific. Specifically, it is observed in impoverished and overpopulated communities in hot and humid areas.
In 2010, the WHO highlighted that yaws is still common in poor communities and populations. Moreover, it is endemic in Indonesia, Timor-Leste, Papua New Guinea, the Solomon Islands, as well as the African countries of Cameroon, Central Africa Republic, Congo, the Democratic Republic of the Congo, Ghana, Sierra Leone, and others as well.
Approximately three quarters of infected individuals are younger than 15 years of age and especially in the ages of 6 to 10. In fact, it is believed that there are 34 million people at risk for infection, in which 23 million are less than 15 years of age and the remaining are between 16 and 24 years old.
With regards to gender, there is no preference.
This infection is transmitted when minor skin cuts or abrasions on an unaffected person come into contact with fluid from skin lesions of affected patients. Furthermore, yaws is seen frequently on the extremities.
The incubation period ranges from 9 to 90 days. T. pallidum pertenue enters the subcutaneous lymphatic system and disseminates throughout the body. Yaws occurs in two stages: infectious and non-infectious.
This is the early phase, in which the lesion appears as a papilloma that marks the entry site of the organism. This circular, swollen lesion is filled with the spirochetes. Due to hematogenous dissemination, lesions can present everywhere. They typically remain for 3 to 6 months and heal spontaneously. Early yaws may be associated with bone pain and lesions.
The late stage occurs 5 years after the primary infection. The main features are deformities of the nose and bones, as well as thickening of the palms and soles. Due to the latter, patients experience difficulty when walking.
The key preventative strategies for yaws is health education and implementation of good hygiene.
Note that measures are being undertaken to eradicate the disease, especially through early diagnosis and prompt treatment of active cases. Furthermore, there is targeteted therapy of communities and populations.
Yaws is the most common infection in the group referred to as endemic treponematoses, which also includes bejel and pinta. The agent responsible for yaws is Treponema pallidum subspecies pertenue, which is transmitted through skin-to-skin contact in individuals typically less than 15 years of age. Furthermore, the disease is frequently observed in poor, unsanitary conditions in tropical areas with hot and humid climates, as well as frequent rainfalls .
This infection typically presents as a skin lesion that may disseminate if left untreated. In advanced disease states, yaws affects the skin, bones, and joints; untreated patients may develop physical handicaps and disfigurement . Overall, yaws is a chronic disease that may relapse   .
Diagnosis is based on a full evaluation including the patient's history and any exposures or contact risks. There are various serologic tests, although certain techniques may not differentiate between yaws and syphilis. Therefore, the diagnosis is determined through assessment of the clinical findings, epidemiology of yaws, and positive laboratory testing.
The ultimate therapeutic goal is to eradicate yaws, which can be accomplished with early diagnosis and treatment. Other preventative measures include education and practicing good hygiene.
Yaws is a long-term bacterial infection involving the skin, bones, and joints. The bacterium responsible for this disease is called Treponema pallidum pertenue, which is in the same family as the bacteria that causes syphilis. However, yaws is not transmitted sexually. It is transmitted when a scratch, abrasion, or bite comes into contact with a lesion or fluid from a lesion of an affected patient.
This disease primarily infects children under 15 years old in impoverished and overcrowded hot and humid tropical regions in Asia, Africa, Latin America, and the Western Pacific islands.
Approximately 2 to 4 weeks after infection, the patient develops a skin lesion known as "mother yaw" typically on the leg. It may be itchy and, if scratched, the infection may spread to other sites of the body.
The healthcare worker will assess the history and any possible exposures to the disease such as household members, classmates, etc. Also, the healthcare worker will examine and evaluate the lesion. Finally, there are blood tests that will help the medical team to make the diagnosis.
The treatment for this infection is penicillin. Additionally, the clinician will determine who else will need treatment including all exposures (household members, classmates, etc). Early diagnosis and treatment are necessary to finally eliminate this disease.
One of the key ways to prevent this disease is through health education and practicing good hygiene.