YAWS Disease

Yaws is a chronic infectious disease caused by the bacterium Treponema pallidum pertenue, a subspecies of the organism that causes syphilis. Unlike syphilis, which is sexually transmitted, yaws spreads primarily through direct skin-to-skin contact, usually among children living in warm, humid, tropical regions with poor hygiene and sanitation.
The disease affects mainly the skin, bones, and cartilage, leading to painful lesions and deformities if left untreated. Though debilitating, yaws is curable with antibiotics and has been the focus of several global eradication campaigns led by the World Health Organization (WHO).

Historical Background

Yaws has been recognised for centuries and was once widespread across Africa, Southeast Asia, Latin America, and the Pacific Islands. The first major control effort was launched by the WHO and UNICEF in 1952, which dramatically reduced global cases by mass treatment campaigns using benzathine penicillin.
However, after the success of initial eradication efforts, surveillance weakened, and the disease re-emerged in some endemic areas. In 2012, the WHO relaunched the Yaws Eradication Programme with a renewed global strategy using single-dose oral antibiotics, making eradication both feasible and cost-effective.

Causative Agent

• Bacterium: Treponema pallidum pertenue, a spiral-shaped (spirochete) bacterium closely related to T. pallidum pallidum, which causes venereal syphilis.
• Mode of Transmission:
  • Direct skin contact with an infected lesion or exudate.
  • Usually occurs among children under 15 years, especially between 6–10 years of age.
  • Transmission is facilitated by humid conditions, overcrowding, and poor hygiene.
• Reservoir: Humans are the only known reservoir of infection.

The bacterium does not survive long outside the human body, so transmission occurs through non-sexual, person-to-person contact, often within families or close communities.

Geographical Distribution

Yaws is confined mainly to tropical and subtropical regions, especially in:

• West and Central Africa – Ghana, Cameroon, Democratic Republic of Congo.
• South and Southeast Asia – India, Indonesia, Timor-Leste.
• Pacific Islands – Papua New Guinea, Solomon Islands, Vanuatu.

The disease typically occurs in remote, rural areas with limited access to healthcare and sanitation facilities.

Stages and Symptoms

Yaws progresses through several clinical stages if untreated.
1. Primary Stage (Initial Lesion):

• Begins 3–4 weeks after infection as a small papule (bump) at the site of entry.
• The lesion enlarges, becomes ulcerative, and develops a yellow crust — known as the “mother yaw”.
• It is highly infectious and often accompanied by local swelling of lymph nodes.
• The lesion usually heals spontaneously within 3–6 months, but bacteria remain in the body.

2. Secondary Stage:

• Occurs weeks to months later as the bacteria spread through the bloodstream.
• Multiple skin lesions (papillomatous or ulcerative) appear on the face, arms, legs, and buttocks.
• Bone and joint pain, especially in the legs, may occur.
• In children, periostitis (inflammation of bone tissue) can cause painful swelling of long bones and bowing of the legs.
• These lesions are also infectious.

3. Latent Stage:

• Follows secondary lesions; the patient shows no visible symptoms.
• The infection may remain dormant for years but can still progress internally.

4. Tertiary Stage (Late Stage):

• Develops in about 10% of untreated cases after 5–10 years.
• Causes chronic ulcers, disfigurement of the nose, face, or bones (gummatous lesions), and permanent disability.
• The late stage is non-infectious but leads to severe social and physical consequences.

Diagnosis

Diagnosis is based on clinical examination and laboratory tests.
1. Clinical Diagnosis:

• Characteristic appearance of skin lesions in endemic areas is often sufficient for preliminary diagnosis.

2. Serological Tests:

• Non-treponemal tests such as VDRL (Venereal Disease Research Laboratory) and RPR (Rapid Plasma Reagin) detect antibodies produced in response to treponemal infection.
• Confirmatory treponemal tests like TPHA (Treponema Pallidum Hemagglutination Assay) or FTA-ABS (Fluorescent Treponemal Antibody Absorption Test) confirm infection.
• Modern rapid diagnostic tests (RDTs) can differentiate between active and past infections and are suitable for field use.

Treatment

Yaws is completely curable with antibiotics.
Recommended Treatments:

• Single oral dose of Azithromycin (30 mg/kg, up to 2 g in adults) – the drug of choice recommended by WHO since 2012.
• Benzathine Penicillin (1.2 million units for adults; 0.6 million for children) – effective alternative where oral azithromycin is unavailable.

Treatment not only cures the individual but also interrupts community transmission, making mass drug administration (MDA) an effective eradication strategy.

Prevention and Control

1. Mass Treatment Campaigns:

• The Morges Strategy (2012) recommends Total Community Treatment (TCT) using single-dose azithromycin to all individuals in endemic areas, followed by Total Targeted Treatment (TTT) for new or residual cases.

2. Early Detection and Treatment:

• Surveillance for early symptoms and prompt treatment of identified cases.

3. Health Education:

• Promoting hygiene, reducing skin contact with infectious lesions, and improving sanitation.

4. Strengthening Primary Health Services:

• Training health workers and ensuring regular drug supply to endemic areas.

5. Environmental Improvements:

• Enhancing living conditions, providing safe water, and controlling overcrowding.

Global Eradication Efforts

The World Health Organization (WHO) aims to achieve global eradication of yaws by 2030.
Strategies include:

• Nationwide mapping of endemic regions.
• Implementing mass azithromycin treatment campaigns.
• Strengthening community-based surveillance.
• Integrating yaws control with other neglected tropical disease (NTD) programmes.