Yaws

Yaws

    Overview

    mapYaws is a poverty-related, infectious skin disease that affects mainly children below 15 years of age (with a peak between 6 and 10 years) in warm, rural, tropical areas in Africa, the Western Pacific Islands and Southeast Asia. About 75% of people affected by Yaws are children. It occurs in overcrowded communities, with limited access to basic amenities such as water and sanitation, and limited health care. It is said that “Yaws begins where the road ends”.

    Yaws mainly affects the skin but can also involve the bone and cartilage. Early detection and treatment can avoid gross disfigurement and disability which occur in about 10% of cases.

    As of 2022, Yaws is currently endemic in 15 countries worldwide, while 82 countries, areas and territories are considered previously endemic.

    The Yaws epidemiologic situation in 2022 in the Africa region is as follows:

    • 9 countries currently endemic (Group A): Benin, Cameroon, Central African Republic, Côte d’Ivoire, Ghana, Liberia, Congo, Democratic Rep. Congo, Togo
    • 26 countries previously endemic current status unknown (Group B)
    • 12 countries no previous history (Group C): Algeria, Botswana, Cabo Verde, Eritrea, Lesotho, Mauritania, Mauritius, Namibia, Sao Tome and Principe, Eswatini, Seychelles, South Africa.

    Symptoms

    The disease presents in three stages, the first and second of which can be treated. The third stage can involve changes to the bones in many parts of the body.

    • Primary Yaws (1-3 months from infection) is characterized by ulcers and papillomas.
    • In the secondary stage (3 months to 2 years of infection), symptoms include bone swelling and plantar keratosis.
    • Tertiary Yaws (up to 10 years after infection) is marked by cartilage destruction and bone malformations.

    Treatment

    Yaws can be cured by Azithromycin or benzathine penicillin:

    • Azithromycin (single oral dose) at 30 mg/kg (maximum 2 g) is the preferred treatment.
    • Benzathine penicillin (single intramuscular dose) 0.6 million units (children under 10 years of age) and 1.2 million units (persons over 10 years of age) may be used in case of failure of azithromycin treatment, or for patients who have a contraindication for azithromycin.

    The follow up should be done 4 weeks after antibiotic treatment. Complete clinical healing will be observed in over 95% of cases. Any individual with presumed treatment failure requires macrolide resistance testing and treatment with benzathine penicillin. Sometimes, exploring alternative diagnoses might be considered.

    Key facts

    • Yaws is a chronic disfiguring and debilitating childhood infectious disease.
    • Yaws affects skin, bone and cartilage
    • Yaws is currently endemic in 9 African countries
    • 50 -80% of the people affected are under 15 years of age
    • Peak occurrence is in children aged 6 – 10 years
    • A single dose of the antibiotic azithromycin can completely cure Yaws
    • Yaws is targeted for eradication by 2030
    • Mass treatment campaigns (also called total community treatment, TCT) and Total Targeted Treatment (TTT) are underway in affected populations
    Causative organism

    Yaws is caused by the bacterium Treponema pallidum subspecies pertenue, which is closely related genetically to T. pallidum subspecies pallidum, the causative agent of syphilis, bejel and pinta.

    Transmission

    Humans are currently believed to be the only reservoir. Transmission is from person to person.

    Diagnosis

    In the past, the disease was diagnosed through laboratory-based serological tests, but these tests cannot distinguish Yaws from syphilis. This means that careful clinical assessment of test results in Yaws-endemic areas is vital.

    Currently, some rapid point-of-care tests (syphilis Rapid Diagnostic Test (RDT) and Dual Path Platform (DPP) for Yaws can be used in the field.

    The RDT test is used to detect any syphilis infection in suspected persons with skin lesions, while DPP is used only in RDT-positive patients to confirm the diagnosis of Yaws.

    The polymerase chain reaction (PCR) test can also be used to confirm the diagnosis of Yaws by detecting the organisms in the skin lesions, and to test for antimicrobial resistance.

    Prevention

    There is no vaccine for Yaws. Health education and improvement in personal hygiene are essential components in reducing transmission of the disease. Contacts of Yaws patients should be treated.

    Eradication

    Yaws is targeted for global eradication by 2030 according to the Road map for neglected tropical diseases 2021–2030 and the Framework for the integrated control, elimination and eradication of tropical and vector-borne diseases in the African Region 2022–2030.

    Eradication requires certification that all countries are Yaws-free.

    The eradication approach consists of mass treatment (also called total community treatment, TCT) in which oral azithromycin (30 mg/kg, maximum 2 g) is administered to the entire population (minimum 90% coverage) in areas known as Yaws endemic.

    Three criteria for eradication of Yaws are:

    • absence of new serologically confirmed indigenous cases for 3 consecutive years;
    • absence of any case proven by PCR; and
    • absence of evidence of transmission for 3 continuous years measured with sero-surveys among children aged 1–5 years.
     

    Progress

    Some progress has been made to clarify progressively the epidemiological situation of Yaws and implement the Yaws eradication interventions in the African Region.

    • Three (Cameroon, Central African Republic, and Congo) out of nine known Yaws-endemic countries in the Africa region have been implementing total community treatment (TCT – treating the whole population) with azithromycin for Yaws eradication since 2020 after mapping. Target total treatment (TTT-treating clinical cases and contacts) has been implemented in the six other endemic countries with the support WHO, EMS,

    Organization of Coordination for the Control of Endemic Diseases in Central Africa, FAIRMED, Anesvad Foundation, Raoul Follereau Foundation and GLRA/DAHW

    • The strengthening of integrated surveillance systems, partnerships and country ownership are being promoted in the 26 previously endemic countries. These countries are encouraged to integrated Yaws in the NTD master plan.
    • Twelve countries with no history of Yaws (that are close to achieving NTDs road map targets) are encouraged and will be supported to prepare the dossier for review and certification of non-endemic status.
    WHO Response

    WHO's work on Yaws eradication involves:

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