Yaws is a chronic contagious non-venereal disease which belongs to a group of chronic bacterial infections (endemic treponematoses, nonvenereal spirochetal diseases) that is caused by treponemes.
Yaws is the most common of all and occurs basically in the hot, humid and tropical areas of Africa, Central and South America, the Caribbean, Indian peninsula and the equatorial islands of South-East Asia.
Generally yaws is caused by Treponema pallidum subspecies pertenue. Yaws is not a fatal disease, but it causes disabilities and visible deformities of the face and extremities further contributing to stigma and discrimination.
It affects the skin, bone and cartilage if left untreated it can lead to disorders of the nose and bones of the leg. However, the disease can be cured and prevented by a single dose of antibiotics.
Causes 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 on an infectious case. There are frequent relapses in latent cases
Transmission - Yaws is transferred via direct (person-to-person), non-sexual contact with the fluid from the lesion of an infected person to an uninfected persons via 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 from yaws are children under 15 years old (peak incidence occurs in children aged 6–10 years). Males and females are equally affected.
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.
Symptoms of Yaws
There are two basic stages of yaws: early (infectious) and late (non-infectious).
In the starting phase of yaws, an initial papilloma (a circular, solid swelling on the skin, with no visible fluid) is developed 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.
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.