Yaws

Overview
Yaws (also Pétasse 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), syphilis (Treponema pallidum), and Lyme Disease (Borrelia burgdorferi)

Epidemiology
The disease is transmitted by skin contact with infected individuals or eye gnats, 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' ulcer appears. 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 tropical areas of the Americas, Africa, Asia or Oceania. 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 Pétasse ("raspberry").

Occurrence
Yaws was nearly eradicated by a worldwide treatment program in the 1950s, which reduced the number of sufferers of yaws from an estimated 50 million to nearly zero. However, the World Health Organization reported in January 2007 that yaws is on the rise again, with roughly a half a million sufferers, mostly in poor, rural areas.