Tropical infection of skin, bones, and joints caused by Treponema Pallidum spirochete.Encyclopedia Entry for Yaws :Yaws -Treponema pallidum var. pertenue (spirochete)Encyclopedia Entry for Yaws :Yaws. Yaws is an infection caused by a form of the Treponema pallidum bacteria. It is closely related to the bacterium that causes syphilis, but this form of the bacterium is not sexually transmitted. Yaws mainly affects children in rural, warm, tropical areas, such as, Africa, Western Pacific islands, and Southeast Asia. Yaws is transmitted by direct contact with the skin sores of infected people.About 2 to 4 weeks after infection, the person develops a sore called a 'mother yaw' where bacteria entered the skin. The sore may be tan or reddish and looks like a raspberry. It is most often painless, but does cause itching. The sores may last for months. More sores may appear shortly before or after the mother yaw heals. Scratching the sore can spread the bacteria from the mother yaw to uninfected skin. Eventually, the skin sores heal. Other symptoms include: Bone pain Scarring of the skin Swelling of the bones and fingers In the advanced stage, sores on the skin and bones can lead to severe disfigurement and disability. This occurs in up to 1 in 5 people who do not get antibiotic treatment.A sample from a skin sore is examined under a special type of microscope (darkfield examination). There is no blood test for yaws. However, the blood test for syphilis is often positive in people with yaws because the bacteria that cause these two conditions are closely related.Treatment involves a single dose of penicillin, or 3 weekly doses for later stage disease. It is rare for the disease to return. People who live in the same house with someone who is infected should be examined for yaws and treated if they are infected.If treated in its early stages, yaws can be cured. Skin lesions may take several months to heal. By its late stage, yaws may have already caused damage to the skin and bones. It may not be fully reversible, even with treatment.Yaws may damage the skin and bones. It can affect a person's appearance and ability to move. It can also cause deformities of the legs, nose, palate, and upper jaw.Contact your health care provider if: You or your child has sores on the skin or bone that don't go away. You have stayed in tropical areas where yaws is known to occur.Frambesia tropica.Hook EW. Nonsyphilitic treponematoses.