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Yaws (also Frambesia tropica, thymosis, polypapilloma tropicum or pian) is a tropical infection of the skin, bones and joints caused by the spirochete bacterium Treponema pertenue. Other treponematosis diseases are bejel (Treponema endemicum), pinta (Treponema carateum), and syphilis (Treponema pallidum). more...

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The disease is transmitted by skin contact with infected individuals, the spirochete entering through an existing cut or similar damage. Within ninety days (but usually less than a month) of infection a painless but distinctive 'mother yaw' ulcerous papule appears on the skin at the point of entry, it is often described as raspberry-like and is 10-50 mm in size. This lesion will persist for up to nine months and other secondary growths will appear on the body as the original one heals, there may also be inflammation of the fingers (dactylitis).

If untreated a secondary stage occurs after up to four months of latency, it is marked by more 'raspberry' growths but smaller and ulcerous - exuding a thin, highly infective fluid which attracts flies. These growths may also merge together into thick fissured plaques, which can occur on the feet and induce a distinctive gait. These secondary growths are irreversible but there can be relapsing lesions and asymptomatic periods.

In 10-20% of cases the disease can progress over a decade or more to a tertiary stage with destructive lesions of the skin and bones. Large subcutaneous nodules develop and grow before abscessing and ulcerating, these can become infected and may merge together forming serpiginous tracts. These tracts heal with keloid formation which can cause deformities, disabilities and limb contractures. The bone lesions caused are periostitis, osteitis, and osteomyelitis, damage to the tibia can lead to a condition known as sabre shins. In a very few cases a condition known as goundou is caused where growths on the nasal maxillae can result in extensive and severe damage to the nose and palate.

The largest group afflicted by Yaws are children aged 6 to 10 years in the Caribbean Islands, Latin America, West Africa, India, Oceania or Southeast Asia. There were World Health Organization funded campaigns against yaws from 1954 to 1963 which greatly reduced the incidence of the disease, although more recently numbers have risen again.

The disease is identified from blood tests or by a lesion sample through a darkfield examination under a microscope. Treatment is by a single dose of penicillin, erythromycin or tetracycline, recurrence or relapse is uncommon.

Examination of ancient remains has led to the suggestion that yaws has affected hominids for the last 1.5 million years. The current name is believed to be of Carib origin, "yaya" meaning sore; frambesia is a Modern Latin word inspired by the French word framboise ("raspberry").


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From Gale Encyclopedia of Medicine, 4/6/01 by Rosalyn S. Carson-DeWitt


Yaws is a chronic illness which first affects the skin, and then affects the bones.


Yaws tends to strike children, particularly between the ages of two and five. It is common in areas where poverty and overcrowding interfere with good hygiene practices. The most common locations are in rural areas throughout Africa, Southeast Asia, and in locations bordering the equator in the Americas.

Causes & symptoms

Yaws is caused by a spiral-shaped bacterium (spirochete) called Treponema pertenue. This bacterium belongs to the same family as the bacterium that causes syphilis.

Yaws is passed among people by direct skin contact. It requires some kind of a scratched or insect bitten area in order for the bacteria to actually settle in and cause infection. An injured spot on the leg is the most common part of the body through which the bacteria enter. Young children, who are constantly bumping themselves in play, who wear little clothing, who do not wash their hands often, and who may frequently put their hands in their mouths, are particularly susceptible.

The first symptom of yaws occurs three to four weeks after acquiring the bacteria. The area where the bacteria originally entered the skin becomes a noticeable bump (papule). The papule grows larger and develops a punched-out center (ulcer), covered with a yellow crust. Lymph nodes in the area may become swollen and tender. This first papule may take as long as six months to heal. Secondary soft, gummy growths then appear on the face, arms and legs, and buttocks. These soft, tumor-like masses may grow on the soles of the feet, causing the patient to walk in an odd and characteristic fashion on the sides of his or her feet (nicknamed "crab yaws"). More destructive tumors may then disrupt the bones of the face, the jaw, and the lower leg. Ulcers around the nose and on the face may be very mutilating.


Samples taken from the first papules may be examined using a technique called dark-field microscopy. This often allows the spirochetes to be identified. They may also be identified in fluid withdrawn from swollen lymph nodes. Various tests can also be run on blood samples to determine if an individual is producing antibodies (special immune cells) which are specifically made in response to the presence of these spirochetes.


A single penicillin injection in a muscle is sufficient to completely end the disease.


Without treatment, yaws is a terribly disfiguring chronic illness. With appropriate treatment, the progression of the disease can be completely halted.


For a time, the World Health Organization (WHO) was working to totally eradicate yaws, just as smallpox was successfully eradicated. This has not occurred, however. WHO continues to work to identify and respond to outbreaks quickly, in an effort to at least slow the spread of yaws.

Key Terms

A raised bump on the skin.
A punched-out, irritated pit on the skin.

Further Reading

For Your Information


  • Perine, Peter L. "Endemic Treponematoses." In Harrison's Principles of Internal Medicine, edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998.
  • Sherris, John C. and James J. Plorde. "Spirochetes." In Sherris Medical Microbiology: An Introduction to Infectious Diseases, edited by Kenneth J. Ryan. Norwalk, CT: Appleton and Lange, 1994.


  • Centers for Disease Control and Prevention. 1600 Clifton Road NE, Atlanta, GA 30333. (404) 332-4559.

Gale Encyclopedia of Medicine. Gale Research, 1999.

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