Yaws

Yaws is an infectious tropical disease caused by the spirochete (spiral shaped) bacterium known as Treponema pertenue. Yaws is a chronic contagious non-venereal disease.

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Areas affected

Yaws is the most common of all and occurs primarily in the warm, humid and tropical areas of Africa, Central and South America, the Caribbean, Indian peninsula and the equatorial islands of South-East Asia.

Effects of Yaws

Yaws is not a fatal disease, but causes disabilities and visible deformities of the face and extremities contributing to stigma and discrimination. It affects the skin, bone and cartilage; if left untreated it can lead to deformities of the nose and bones of the leg. However, the disease can be cured and prevented by a single dose of antibiotics.

Symptoms of Yaws

There are two basic stages of yaws: early (infectious) and late (non-infectious).

In early yaws, an initial papilloma (a circular, solid swelling on the skin, with no visible fluid) develops at the site of entry of the bacterium. This papilloma is full of organisms and may persist for 3–6 months followed by natural healing. Nocturnal bone pain and bone lesions may also occur in the early stage. These primary skin lesions (Early Yaws) usually occur in children and adolescents in endemic areas.

Juxta-articular nodules on the elbow resulting from a Treponema pertenue bacterial infection

Late yaws appears after 5 years of the initial infection and is characterized by disfigurement of the nose and bones, and thickening and cracking of the palms of the hand and soles of the feet. These complications on the soles of the feet make it difficult for patients to walk. Late yaws are non-infectious but may make a person disabled.

Cause of Yaws

Yaws is caused by Treponema pertenue which closely resembles to T.pallidium. It is a slender spirochete that is serologically indistinguishable from the spirochete T.pallidium which causes syphilis. The agents found in the epidermis of the lesions, lymph glands, spleen and bone marrow. The organism rapidly dies outside the tissues.

Reservoir of infection- Man is the only known reservoir of yaws. Clinical lesions relapse 2-3 times or more during the first 5 years of infections and serve as source for new infections. The most latent cases are found in clusters centered around an infectious case. There are frequent relapses in latent cases

Dactylitis caused by osteoperiostitis due to yaws

Transmission-Yaws is transmitted through direct (person-to-person), non-sexual contact with the fluid from the lesion of an infected person to an uninfected persons through minor injuries. Most lesions occur on the limbs. The initial lesion of yaws is filled with the bacteria. The incubation period is 9–90 days (average 21 days).

About 75% of people affected are children under 15 years old (peak incidence occurs in children aged 6–10 years). Males and females are equally affected.

Overcrowding, poor hygiene and poor socioeconomic conditions favours the spread of the yaws.

Diagnosis of Yaws

Yaws simulates the lesions of scabies, impetigo, skin tuberculosis, tinea versicolor, tropical ulcer, leprosy and psoriasis. It may also accompany these diseases. Penicillin treatment is very useful in differential diagnosis because of miraculous relief seen in yaws but not in other skin diseases.

Most latent and incubating cases are found in clusters around an infectious case and can usually be diagnosed by epidemiological tracing.

Serology

Yaws treatment

Standard laboratory-based tests-

Serological tests are widely used to diagnose treponemal infections (e.g. syphilis and yaws). Serological tests cannot distinguish yaws from syphilis and its interpretation on adults in yaws endemic areas (disease constantly present in a particular region) need careful clinico-epidemiological assessment.

Commonly used tests are Venereal Disease Research Laboratory (VDRL) test and the rapid plasma reagin (RPR) test which are inexpensive, rapid and simple to perform. It takes time for sero-positivity to appear after the onset of disease and hence, initial (mother) case may be sero-negative.

Rapid point-of-care tests (medical testing at or near the site of patient care)-Rapid tests allow the point-of-care diagnosis and treatment of patients. There are 2 types of rapid tests:

Rapid treponemal tests are widely used in the diagnosis of syphilis; however, these tests cannot distinguish between present active yaws and past infections. Therefore, its use alone could lead to overtreatment of patients and over-reporting of cases.

New rapid dual (non-treponemal and treponemal) point-of-care syphilis test allows simultaneous yet separate detection of both antibodies. It is now being used in yaws eradication efforts.

Polymerase chain reaction (PCR)- Genomic analysis using polymerase chain reaction (PCR) can be used to definitely confirm yaws, and this test will be very useful in the last phase of the eradication programme. The PCR technique can also be used to determine azithromycin resistance from swabs taken from yaws lesions.

Scars of yaws lesions

Treatment of Yaws

Two antibiotics are recommended for the treatment of Yaws by WHO. Anyone allergic to penicillin can be treated with another antibiotic, usually erythromycin, doxycycline, or tetracycline. Azithromycin (in a single oral dose of 30 mg/kg or the maximum 2 g) is the choice that the World Health Organization (WHO) recommends because of the ease of administration. Yaws can be cured with a single dose oral of azithromycin.

Complications of Yaws

About 10% of affected people develop deformities of the legs and nose after 5 years if not received treatment. The disease and its complications lead to school absenteeism and prevent adults from farming activities. It also leads to scarring of the areas affected even after treatment.

Prevention of Yaws

There is no vaccine for yaws. Prevention is based on the interruption of transmission through early diagnosis and treatment of individual cases and mass or targeted treatment of affected populations or communities. Health education and improvement in personal hygiene are essential components of prevention.

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