What is Yaws?

Yaws is a chronic bacterial infection that primarily affects skin, bone, and cartilage. The disease is disfiguring and ultimately debilitating. However, yaws is considered to be in the late stages of global elimination.

Global Burden

Yaws

The global burden of yaws is largely unknown, since there is no official international system of notification about the disease’s prevalence. The majority of cases are believed to come from Southeast Asia, Oceania, and Sub-Saharan Africa. Indonesia and Timor-L’este are thought to experience the greatest number of cases, while India declared elimination of yaws in 2006.1

A massive WHO-sponsored eradication campaign in the 1950s brought the number of worldwide cases of yaws from upward of 50 million down to less than 2 million. But relaxed drug administration schedules in the 1970s led to the disease’s resurgence. The worldwide prevalence of the disease is unknown but is thought to be less than 1 million cases.2

Causative Agent

Yaws is caused by the spirochete bacterium Treponema pertenue, and a bacterium that is highly related to the bacterium that causes syphilis, a sexually transmitted infection. Yaws is spread by skin-to-skin contact between a lesion (called a ‘yaw’) on an infected person and an open cut or scrape on a second person where the bacteria enter the bloodstream.2

Pathogenesis

yaws

In the early stage of yaws, a nodule forms at the site of infection. This nodule (called a ‘mother yaw’) is full of infectious bacteria and persists for up to 6 months. Disseminated skin, bone, and cartilage lesions begin to appear when the infection is left untreated.2

In the later stage, which occurs years after primary infection, further skin lesions begin to appear. In a third stage that affects about 10% of infected individuals, widespread devastation of bone and cartilage can appear, characterized most frequently by the destruction of the nose, palate, and upper jaw, a distinctive condition called gangosa.3

Current Control Strategy

There are no specific preventive measures for yaws. Instead, the campaign to eliminate yaws is based on the interruption of transmission and early treatment of infected individual and their contacts. However, because yaws has an effective treatment, localized outbreaks, reliable clinical diagnosis, and no animal reservoirs, the WHO believes it is potentially eradicable.2

Existing Products

Drugs

The standard treatment for yaws is one dose of oral penicillin, which is highly effective at clearing the infection. It can also be treated with doxycycline and tetracycline in the case of allergies.2

Vaccines

There is no vaccine to prevent yaws.

Diagnostics

In the field, yaws is diagnosed based on clinical signs. It can also be diagnosed using microscopy or with the same blood test that is used for diagnosing syphilis, although differentiation between treponemal species remains a challenge.3

References

  1. WHO Regional Office for South-east Asia. “Eradicating Yaws: A regional priority”.
  2. WHO fact sheet (2007). “Yaws: a forgotten disease”.
  3. Meheus, Andre (2005). “Non-venereal treponematoses”Medicine 33(10).

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Drugs

There are no drugs in development for yaws due to the existence of highly effective and inexpensive antibiotics.

Vaccines

There are no vaccines in active development for yaws, but there is some interest in creating a vaccine for syphilis, which would likely cross-protect against the closely-related yaws. The development of a vaccine has been hindered by the paucity of effective vaccine targets on the treponemal outer membrane protein, and greater understanding of the body’s anti-syphilitic immunological mechanism is necessary.1

Diagnostics

There are no diagnostics in development for yaws, because most minimally trained clinical health workers can recognize and treat based on the clinical signs for yaws.

Get Involved

To learn how you can get involved in neglected disease drug, vaccine or diagnostic research and development, or to provide updates, changes, or corrections to the Global Health Primer website, please view our FAQs.

The tools available for the development of drugs, vaccines, and diagnostics for yaws are extremely limited. However, as this disease is near eradication at this time and new product development is not considered a priority, tools for this disease are not provided here.

References

Get Involved

To learn how you can get involved in neglected disease drug, vaccine or diagnostic research and development, or to provide updates, changes, or corrections to the Global Health Primer website, please view our FAQs.