Yaws is an infectious tropical disease caused by the spirochete (spiral shaped) bacterium known as Treponema pertenue. The disease presents in three stages of which the first and second are easily treated. The third, however, may involve complex changes to the bones in many parts of the body. The first stage is characterized by the appearance of small, painless bumps on the skin that group together and grow until they resemble a strawberry. The skin may break open, forming an ulcer. The second stage (usually starting several weeks or months after the first) presents with a crispy, crunchy rash that may cover arms, legs, buttocks and/or face. If the bottoms of the feet are involved, walking is painful and the stage is known as "crab yaws." Stage 3 yaws involves the long bones, joints, and/or skin. Yaws is very common in tropical areas of the world but it is not known in the United States. It is not a sexually transmitted disease. It occurs in children younger than 15 years of age.
Stage 1 yaws typically occurs in early childhood, with peak incidence at about six years of age. A single itchy, strawberry-like growth appears on the skin over which a thin yellow crust forms (papillomatous lesion). This growth, the “mother yaw”, appears at the spot where the organism entered the body (inoculation site), typically on the leg or foot.
Stage 2 yaws typically follows several weeks or months after the initial symptoms. Similar skin sores appear on the face, legs, arms, and/or around the rectum and genitals. These sores usually heal slowly and may recur. Lesions on the bottom of the feet may produce painful cracks and ulcerations (keratosis), resulting in an awkward “crab-like” walk or “crab yaws.”
At this stage, swollen glands (swollen lymph nodes) are not uncommon and the rash may develop a brown crust.
The symptoms of stage 3 yaws occur in only about 10% of the people who are infected and may follow a dormant period of several years. Painful ulcers or nodules may develop on the skin (cutaneous) and cause facial disfigurement. Painful, granular sores (gummatous lesions) may also develop on the bones, especially the long bones of the legs (tibia). Painful skin and bone nodules may impair joint function and mobility.
Stage 3 yaws may also produce different and distinct syndromes. One, known as goundou syndrome, is characterized by inflammation and swelling of the tissues surrounding the nose (paranasal swelling), as well as overgrowth of the bones in the same region of the face (hypertrophic osteitis). Another, known as gangosa syndrome (also known as rhinopharyngitis mutilans), is characterized by degenerative changes of the nose, throat (pharynx), and the roof of the mouth (hard palate).
Yaws is an infectious disease caused by a spiral-shaped bacterium (spirochete) known as Treponema pertenue. Yaws is usually transmitted by direct contact with the infected skin sores of affected individuals. In some cases, yaws may be transmitted through the bite of an infected insect.
Yaws is a common infectious disease among children living in the tropical areas of Africa, South and Central America, the West Indies, and the Far East. It is not known in the United States. Yaws affects males and females in equal numbers and is most common in children between the ages of six and 10.
The prevalence of yaws declined greatly following a mass treatment campaign with penicillin by the World Health Organization (WHO) in the 1950s and ’60s. However, there has been a resurgence of yaws in certain countries in Africa and Southeast Asia.
The diagnosis of stage 1 and stage 2 yaws is made by microscopic examination of tissue samples (darkfield examination) from the skin lesions of affected individuals. Stage 3 yaws may be diagnosed by specialized blood tests (i.e., VDRL and treponemal antibodies).
Stage 1 and 2 yaws is treated with antibiotics, especially with benzathine penicillin G. A single large dose of these medications usually heals the skin lesions and eliminates the organism. These antibiotic drugs may also be used to prevent this disease in family members and others who are in frequent contact with affected individuals. At the present time, there is no treatment for the destructive bone lesions or scars associated with stage 3 yaws.
Research on tropical diseases such as yaws is ongoing. For more information about these disorders, contact the World Health Organization (WHO) or Centers for Disease Control and Prevention (CDC) listed in the Resources section of this report.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. Government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
For information about clinical trials sponsored by private sources, contact:
Perine PL. Endemic Treponematoses. In: Fauci AS, Braunwald E, Isselbacher KJ, et al. Eds. Harrison’s Principles of Internal Medicine. 14th ed. McGraw-Hill Companies. New York, NY; 1998:1033-36.
Beers MH, Berkow R., eds. The Merck Manual, 17th ed. Whitehouse Station, NJ: Merck Research Laboratories; 1999:1185-86.
Berkow R., ed. The Merck Manual-Home Edition.2nd ed. Whitehouse Station, NJ: Merck Research Laboratories; 2003:1099.
Azimi P. Spirochetal Infections; Non Venereal Syphilitic Diseases. In: Behrman RE, Kliegman RM, Arvin AM. Eds. Nelson Textbook of Pediatrics. 15th ed. W.B. Saunder Company. Philadelphia, PA; 1996:856-57.
Antal GM, Lukehart SA, Meheus AZ. The endemic treponematoses. Microbes Infect. 2002;4:83-94.
Arteaga C, Gueguen GE, Richez P, et al. [Osteoarticular involvement in parasitic diseases: bone treponematosis]. J Radiol. 1998;79:1363-66.
Anselmi M, Moreira JM, Caicedo C, et al. Community participation eliminates yaws in Ecuador. Trop Med Int Health. 2003;8:634-38.
Scolnik D, Aronson L, Lovinsky R, et al. Efficacy of a targeted oral penicillin-based yaws control program amoung children living in rural South America. Clin Infect Dis. 2003;36:1232-38.
Wicher K, Wicher V, Abbruscato F, et al. Treponema pallidum subsp. pertenue displays pathogenic properties different from those of T. pallidum subsp. pallidum. Infect Immun. 2000;68:3219-25.
Koff AB, Rosen T. Nonveneral treponematoses: yaws, endemic syphilis, and pinta. J Am Acad Derm. 1993;29:4:83-94.
FROM THE INTERNET
Klein NC. Yaws. emedicine. Last updated: June 18, 2001. 11p.
Levine CL. Yaws. emedicine. Last updated: November 1, 2001. 10p.
Kotton C. Yaws. MEDLINEplus. Medical Encyclopedia. Update Date: 2/17/2003
Yaws. Aetna IntelliHealth. Last Updated: February 28, 2002. 3pp.
Hicks R. Yaws: Catching a raspberry. BBC1 Health. nd. 2pp.
Yaws. The 1911 Edition Encyclopedia. nd. 4pp.
Carson-DeWitt R. Yaws. healhAtoZ. Gale Encyclopedia of Medicine Ó2002. 3pp.