Yaws (also frambesia tropica, thymosis, polypapilloma tropicum, pian or parangi, "Bouba," "Frambösie", and "Pian") is a tropical infection of theskin, bones and joints caused by the spirochete bacterium Treponema pallidum pertenue. Other treponemal diseases are bejel (Treponema pallidum endemicum), pinta (Treponema pallidum carateum), and syphilis (Treponema pallidum pallidum).
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. It is believed to have originated in tropical areas of Africa, and spread to other tropical areas of the world via immigration and slave trade.
Yaws is found in humid tropical regions in South America, Africa, Asia and Oceania. Mass treatment campaigns in the 1950s reduced the worldwide prevalence from 50-100 million to fewer than 2 million; however during the 1970s there were outbreaks in south-east Asia and there have been continued sporadic cases in South America. It is unclear how many people worldwide are infected at present.
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.
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.
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.
Treatment of yaws is simple and highly effective. Penicillin G benzathine given IM (intramuscularly) can cure the disease in the primary, secondary, and usually in the latent phase. Penicillin V can be given orally for about seven to 10 days, but this route is less reliable than direct injection. Anyone allergic to penicillin can be treated with another antibiotic, usually erythromycin, doxycycline, or tetracycline.
Tertiary yaws, which occurs in about 10% of untreated patients five to 10 years after initially getting the disease, is not contagious. The tertiary yaws patient is treated for the symptoms of the chronic conditions (altered or destroyed areas in bones, joints, cartilage, and soft tissues) that develop as a result of the infection. There is no vaccine for yaws.
Why is yaws a serious problem?
Yaws is a major public-health threat in the tropics. Tropical regions in Central and South America, Africa, Asia, and Oceania are all at continuing risk for yaws. A high percentage of children in such areas can be infected. Transmission of the disease is facilitated by overcrowding and poor hygiene, and yaws tends to be more prevalent in poor areas. In addition to making young children sick, approximately 10% of untreated children develop into young adults with deformities that are severely debilitating in the tertiary-yaws phase.
For example, some patients develop destructive ulcerations of the nasopharynx, palate and nose (termed gangosa), painful skeletal deformities, especially in the legs (termed saber shins), and other soft-tissue changes (gummas, inflammatory cell infiltration). See the second and third references in More Information section (listed below) for images of patients with yaws.
Yaws can be completely eradicated from an area by giving penicillin or another appropriate antibiotics to everyone in the population. This may, unfortunately, cost more than a poor country can afford. From 1950-1970, a worldwide effort to eradicate yaws was begun and made progress in reducing the approximately 50 million worldwide cases; after its end, yaws has seen a resurgence.
In the 1990s, attempts to eliminate yaws started again, with limited success as the effort is not worldwide or coordinated but done by individual countries. The WHO (World Health Organization) in 2007 reported about 2.5 million cases worldwide but freely admits their data is faulty, as most countries do not calculate the prevalence of yaws. WHO estimates that about 460,000 new cases of yaws occur each year.