Excerpt from Yaws

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Background

Yaws is the most prevalent infectious, nonvenereal, treponemal disease and is caused by Treponema pallidum subsp pertenue. The disease is transmitted by direct skin contact and usually affects children, with a peak incidence in those aged 6-10 years. Similar to syphilis, yaws can persist for years as a chronic, relapsing disease.

Yaws continues to be endemic along the tropical belt in areas characterized by hot temperatures, high humidity, and heavy rainfall. These conditions coupled with the persistence of poverty, poor sanitation, overcrowding, and lack of public health surveillance allow for disease perpetuation.

Pathophysiology

Cutaneous lesions characterize the primary and secondary stages. The tertiary stage may include involvement of skin, bones, and joints.

Frequency

International

In the early 1950s, the estimated number of active cases in areas of Africa, Asia, South America, Central America, and the Pacific Islands was 25-150 million. After the World Health Organization (WHO) supported mass treatment campaigns from 1954-1963, researchers observed a dramatic fall in the prevalence. Since then, however, cases of yaws rebounded because of the lack of public health surveillance and inadequate treatment facilities. Currently, researchers estimate that 100 million children are at risk of acquiring yaws.

Mortality/Morbidity

Unless treated, yaws can become a chronic, relapsing disease with skin, bone, and joint involvement. In 10% of cases, patients enter a late stage (tertiary stage) characterized by destructive cutaneous lesions and severely deforming bone and joint lesions. Neurologic and ophthalmologic involvement may also occur.

Sex

No sexual predilection exists.

Age

Children serve as the primary reservoir for yaws. It is most common in children younger than 15 years, with the peak incidence occurring between ages 6 and 10 years.

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