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Yaws

Overview

Yaws is a chronic bacterial infection caused by Treponema pertenue, a subspecies of Treponema pallidum (the causative organism of Syphilis). The disease occurs in warm humid regions, primarily in poorer communities. Areas affected include tropical forest areas of Africa, South East Asia, South and Central America and the Pacific islands. Yaws is an African word for berries which describes the appearance of the lesions which develop most commonly on the limbs. Yaws can affect the skin, bone and cartilage. When left untreated, it has been reported to cause deformities of the nose and leg bones resulting in chronic disfigurement and disability. Humans are the only reservoir for Treponema pertenue and infection is spread person-to-person via infected fluid of a lesion. Ecuador and India reported interruption of transmission in 2003 and now only 13 countries are currently endemic. Yaws most commonly affects children under 15 years old (75% of reported cases).

 

Signs and Symptoms

The incubation period of Yaws ranges from 9-90 days with an average of 21 days.

There are 2 stages of Yaws: early (infectious) and late (non-infectious)

Early Yaws presents with:

  • Initial papilloma developing at the site of entry of Treponema pertenue

       â€“ circular, solid swelling with no visible fluid

  • Papular skin lesions may ulcerate

  • Swollen lymph nodes near lesion location

  • Bone lesions and bone pain may occur

  • Periostitis

  • Dactylitis

Persists for 3-6 months followed by natural healing

 

Late Yaws presents after 5 years of initial infection with:

  • Disfigurement of nose and bones

  • Altered/destroyed areas of bones, joints and catilage

  • Thickening/cracking of the palms of the hand and soles of the feet

 

Causes

Yaws occurs where T.pertenue penetrates broken skin through direct person-to-person contact. Transmission occurs through non-sexual contact of fluid from a lesion to a minor injury on another individual. Initial lesions contain a high amount of T.pertenue.

 

At risk groups / risk factors

  • Peak incidence occurs in children aged 6-10 years old

  • Overcrowding

  • Poor hygiene

 

Diagnosis / microbiology testing

  • Clinical assessment

  • Serological testing – cannot distinguish Yaws from Syphilis

  • PCR technique used for definite diagnosis of Yaws and also to determine

      azithromycin resistance using swabs taken from Yaws lesions

 

Treatment

A single dose of antibiotic can be given for early infection:

  • Azithromycin 30mg/kg (single oral dose)

  • Benzathine benzylpenicillin 1.2 million units (adults) or 600,000 units (children) (single intramuscular dose).

  • Erythromycin, doxycycline or tetracycline is used where penicillin is not tolerated.

T.pallidum is highly sensitive to penicillin so a long-acting depot injection of benzathine benzylpenicillin is the standard therapy.

Although early stage lesions can heal completely, the destructive changes due to late Yaws is most often irreversible.

 

Vaccines / preventative measures

There is currently no vaccine for Yaws.

Prevention is based on the interruption of transmission using:

  • Early diagnosis

  • Treatment of individual cases

  • Mass, targeted treatment of affected populations or communities

  • Health education

  • Improvement in personal hygiene

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