Yaws eradication

What is yaws?

The disease

Yaws is a poverty-related chronic skin disease that affects mainly children below 15 years of age (with a peak between 6 and 10 years).

It is caused by the bacterium - is a Treponema pallidumm subspecies pertenue and transmitted by skin contact. Yaws mainly affects the skin, but can also involve the bone and cartilage. The organism that causes yaws is closely related to the one that causes syphilis. Early detection and treatment can avoid gross disfigurement and disability which occur in about 10% of cases.

Yaws occurs in overcrowded communities, with limited access to basic amenities, such as water and sanitation, as well as health care.

Diagnosis

Traditionally, laboratory-based serological tests such as Treponema pallidum particle agglutination (TPPA) and rapid plasma reagin (RPR) are widely used to diagnose treponemal infections (for example, syphilis and yaws). These tests cannot distinguish yaws from syphilis however, and the interpretation of results from these tests in adults who live in yaws endemic areas needs careful clinical assessment because of syphillis.

Rapid point-of-care tests that can be used in the field are widely available.
However, most of them are treponemal-based and cannot distinguish between past and current infection. Recently dual treponemal and nontreponemal rapid tests have become available, thus simplifying diagnosis in the field. These tests are able to detect both present and past infections to guide treatment of people with active infection.

Rapid point-of-care tests used in the field

Polymerase chain reaction (PCR) can be used to definitively confirm yaws by detecting the organisms in the skin lesions. It can also be used to monitor azithromycin resistance and this test will be very useful in the last phase of the eradication programme.

Treatment

Either of 2 antibiotics – azithromycin or benzathine penicillin – may be used to treat yaws:

  • Azithromycin (single oral dose) at 30 mg/kg (maximum 2 gm) is the preferred choice in the WHO "Yaws Eradication Strategy" (the Morges Strategy) because of the ease of administration and logistical consideration in large-scale treatment campaigns.
  • Benzathine penicillin (single intramuscular dose) at 1.2 million units (adults) and 600 000 units (children). For patients allergic to penicillin and azithromycin, doxycycline 100mg (1 tab) orally, b.d. twice daily for 7 days may be used.
Before-after treatment with antibiotics