Yaws is a neglected tropical disease

Karachi: Yaws is a neglected tropical disease that affects the skin, bone and cartilage. The disease is caused by a bacterium from the same group of organisms that cause venereal syphilis; however, the transmission of yaws is not sexually-related. Yaws can be eradicated as humans are the only reservoir. A recent finding has shown that that a single, oral dose of the antibiotic azithromycin can completely cure yaws, opening up prospects for large-scale treatment of affected populations.

According to a WHO report, Yaws forms part of a group of chronic bacterial infections caused by treponemes which include endemic syphilis and pinta, and are commonly known as endemic treponematoses. Yaws is the most common of these infections.

The disease is found primarily in poor communities in warm, humid and tropical forest areas of Africa, Asia, Latin America and the Pacific.

Yaws is also known as framboesia (German or Dutch) and pian (French) and affects the skin, bone and cartilage. It is caused by T pallidum subspecies pertenue. This organism belongs to the same group of bacteria that cause venereal syphilis.

Yaws is transmitted through direct (person-to-person) non-sexual contact with the fluid from the lesion of an infected person. Most lesions occur on the limbs. The initial lesion of yaws is teemed with the bacteria. Contact with this fluid, especially among children who play together and sustain minor injuries, leads to transmission of infection. The incubation period is 9–90 days (average 21 days).

About 75% of people affected are children under 15 years old (peak incidence occurs in children aged 6–10 years). Males and females are equally affected.

Overcrowding and poor socio-economic conditions facilitate the spread of the yaws. Without treatment, infection can lead to chronic disfigurement and disability.

Scope of the problem

The eradication campaigns of 1952-1964 targeted 46 countries. Since 1990, formal reporting of yaws to WHO stopped due to the discontinuation of yaws eradication programmes in many countries. Only a few countries kept yaws as part of their public health agenda.

A review of historic documents from the 1950s shows that at least 90 countries within the tropical belt 20 degrees north and south of the equator, were endemic for yaws. However, only 12 are known to be currently endemic for yaws, while 2 countries, Ecuador and India, which claim to have interrupted transmission in 2003, need to be verified. Furthermore, WHO also plans to assess the status of yaws in 76 previously endemic countries.

Reporting of yaws is not mandatory so the available data, published in a recent edition of the Weekly Epidemiological Record are only indications of the global distribution of the disease.

There are two basic stages of yaws: early (infectious) and late (non-infectious). In early yaws, an initial papilloma (a circular, solid, swelling on the skin, with no visible fluid) develops at the site of entry of the bacterium. This papilloma is full of the organisms and may persist for 3–6 months followed by natural healing. Bone pain and bone lesions may also occur in the early stage.

Late yaws appears after five years of the initial infection and is characterized by disfigurement of the nose and bones, and thickening and cracking of the palms of the hand and the soles of the feet. These complications on the soles of the feet make it difficult for patients to walk.

In the field, diagnosis is primarily based on clinical and epidemiological findings. WHO has recently published a clinical pictorial guide to help health and community health workers identify the disease.

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