| Yaws | |
|---|---|
| Classification and external resources | |
Nodules on the elbow resulting from a Treponema pertenue bacterial infection. |
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| ICD-10 | A66 |
| ICD-9 | 102 |
Yaws (also frambesia tropica, thymosis, polypapilloma tropicum, pian or parangi, "Bouba," "Frambösie,"[1] and "Pian"[2]) is a tropical infection of the skin, 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).
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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,[3] 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.
The disease is transmitted by skin-to-skin contact with an infective lesion, with the bacterium entering through a pre-existing cut, bite or scratch. Within ninety days (but usually less than a month) of infection a painless but distinctive 'mother yaw' appears, which is a painless nodule which enlarges and becomes warty in appearance. Sometimes nearby 'daughter yaws' also appear simultaneously. This primary stage resolves completely within six months. The secondary stage occurs months to years later, and is characterised by widespread skin lesions of varying appearance, including 'crab yaws' on the palms and soles with desquamation. These secondary lesions frequently ulcerate (and are then highly infectious), but heal after six months or more. About ten percent of people then go on to develop tertiary disease within five to ten years (during which further secondary lesions may come and go), characterised by widespread bone, joint and soft tissue destruction, which may include extensive destruction of the bone and cartilage of the nose (rhinopharyngitis mutilans or 'gangosa').
Dark field microscopy of samples taken from early lesions (particularly ulcerative lesions) may show the responsible organism. Blood tests such as VDRL, Rapid Plasma Reagin (RPR) and TPHA will also be positive, but there are no current blood tests which distinguish among the four treponematoses.
Treatment is normally by a single dose of intramuscular penicillin, or by a course of penicillin, erythromycin or tetracycline tablets. Primary and secondary stage lesions may heal completely, but the destructive changes of tertiary yaws are largely irreversible.
The global prevalence of this disease and the other endemic trematoses, Bejel and Pinta, was reduced by the Global Control of Treponematoses (TCP) programme between 1952 and 1964 from about 50 million cases to about 2.5 million (a 95 percent reduction). However, following the cessation of this program these diseases remained at a low prevalence in parts of Asia, Africa and the Americas with sporadic outbreaks.
Yaws is a relatively easy disease to eradicate. Man is the only reservoir of infection. A single injection of long-acting penicillin or other beta lactam antibiotic cures the disease and is widely available; and the disease is highly localised making case tracing relatively easy.
Yaws is currently targeted by the South-East Asian Regional Office of the WHO for elimination from the remaining endemic countries in this region (India, Indonesia and East Timor) by 2010. So far, this appears to have met with some success, since no cases have been seen in India since 2004.[4][5]
Certification for disease free status requires an absence of the disease for at least 5 years. In 1996 there were 3,571 yaws cases in India; in 1997 after a serious elimination effort began the number of cases fell to 735. By 2003 the number of cases were 46. The last clinical case in India was reported in 2003 and the last latent case in 2006. On September 19th 2011 India will be able to apply for certification for the eradication of yaws.
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