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December 5, 2008
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Yaws

Medical Author: Charles Davis, MD, PhD
Medical Editor: Melissa Conrad Stöppler, MD

What is yaws? What are symptoms of yaws?

Yaws is a common chronic infectious disease that occurs mainly in warm humid regions such as the tropical areas of Africa, Asia, South and Central Americas, plus the Pacific Islands. The disease has many names (for example, pian, parangi, paru, frambesia tropica). Yaws usually features lesions that appear as bumps on the skin of the face, hands, feet, and genital area. The disease most often starts as a single lesion that becomes slightly elevated, develops a crust that is shed, leaving a base that resembles the texture of a raspberry or strawberry. This primary lesion is termed the mother yaw (also termed buba, buba madre, or primary frambesioma). Secondary lesions, termed daughter yaws, develop in about six to 16 weeks after the primary lesion. Almost all cases of yaws begin in children under 15 years of age, with the peak incidence in 6-10-year-old children. The incidence is about the same in males and females.

What causes yaws?

Yaws is caused by a particular bacterium called a spirochete (a spiral-shaped type of bacteria). The bacterium is scientifically referred to as Treponema pertenue. This organism is considered by some investigators to be a subspecies of T. pallidum, the organism that causes syphilis (a systemic sexually-transmitted disease). Other investigators consider it to be a closely related but separate species of Treponema. T. carateum, the cause of pinta (a skin infection with bluish-black spots), is also closely related to T. pertenue. The history of yaws is unclear; the first possible mention of the disease is considered to be in the Old Testament. D. Bruce and D. Nabarro discovered the spirochete causing yaws (T. pertenue) in 1905.

How does yaws begin and spread?

Yaws begins when T. pertenue penetrates the skin at a site where skin was scraped, cut, or otherwise compromised. In most cases, T. pertenue is transmitted from person to person. At the entrance site, a painless bump lesion, or bump, arises within two to eight weeks and grows. The initial lesion is referred to as the mother yaw. The lymph nodes in the area of the mother yaw are often swollen (regional lymphadenopathy). When the mother yaw heals, a light-colored scar remains.



Next: What are developmental stages in the course of yaws? »

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