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100 THIRD WHO REPORT ON NEGLECTED TROPICAL DISEASES
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4.6 Endemic treponematoses
Introduction
Endemic treponematoses, comprising yaws, endemic syphilis (bejel) and pinta, result
from infection with bacteria of the genus Treponema (1). Yaws is the most widespread
of the three diseases. Mass treatment campaigns led by WHO and UNICEF during 1952–1964
reduced the prevalence of treponematoses from 50 million to 2.5 million (2,3). Progress was
not sustained, however, and endemic treponematoses resurged in the 1970s, prompting the
World Health Assembly to adopt resolution WHA31.58 in 1978 for their control (Annex 1a).
Yaws is not a fatal disease. Nonetheless, there are social, economic, humanitarian and ethical
considerations that justify the intensification of efforts to eradicate it.
Children aged 2–14 years are those worst affected and serve as the main reservoir of infection
for yaws and endemic syphilis. For yaws, cases peak among those aged 2–10 years (4). For pinta,
the age range is 10–30 years. Yaws affects boys more often than girls; there is no difference
between males and females in the numbers affected by endemic syphilis and pinta. In its late
stages, yaws can cause disfiguring, crippling disabilities and deformities that prevent children
from going to school and adults from doing physical labour. Ulcers that become infected may
lead to severe secondary bacterial infection, including tetanus. Long-term complications of
yaws (arising 5 or more years after the onset of infection) occur in 10% of untreated cases,
causing disfigurement of the face and legs.
Diagnosis is often made on a clinical basis, but recent reports show that ulcers caused by
Haemophilus ducreyi coexist in areas endemic for yaws and may be a confounder in yaws
diagnosis (5). A new rapid dual non-treponemal and treponemal point-of-care syphilis test
has been evaluated against the standard serological tests in yaws (6). The results are promising
(sensitivity 95% and specificity 97%); the rapid test can therefore be used in yaws eradication
efforts. Molecular techniques such as polymerase chain reaction can also be used to confirm
yaws and monitor resistance to available treatment (7,8). Effective and inexpensive treatment
is available against the treponematoses, which can now be accomplished with a single oral dose
of azithromycin or, in instances where azithromycin is not available or appropriate, a single
injection of long-acting benzathine benzylpenicillin.