Yaws - Causes, Treatment & When to See a Doctor

What is Yaws?

Yaws is a chronic, contagious skin disease caused by the bacterium Treponema pallidum subspecies pertenue. It belongs to the same family of spirochetes that cause syphilis, but unlike syphilis it is transmitted only through direct skin‑to‑skin contact, not sexually. Yaws primarily affects children living in warm, humid, rural areas of tropical Africa, Asia, the Pacific islands, and parts of the Caribbean. The disease progresses through several stages—primary, secondary, and late (tertiary)—each with its own characteristic skin lesions and systemic manifestations. If left untreated, yaws can cause severe disfigurement, bone destruction, and disability.

Common Causes (Differential Diagnosis)

While T. pallidum pertenue is the sole pathogen that causes yaws, clinicians often consider other conditions that can produce similar skin lesions or systemic signs. The most common differentials include:

• Treponemal infections: congenital syphilis, endemic syphilis (bejel), and adult syphilis.
• Non‑treponemal bacterial infections: cutaneous mycobacterioses (e.g., Buruli ulcer), leprosy.
• Fungal infections: chromoblastomycosis, sporotrichosis.
• Parasitic diseases: cutaneous leishmaniasis, tungiasis.
• Viral exanthems: molluscum contagiosum, verruca vulgaris (common warts).
• Auto‑immune skin disorders: psoriasis, lupus erythematosus.
• Contact dermatitis: irritant or allergic reactions to plants, chemicals, or animal exposure.
• Traumatic ulcerations: pressure sores or insect bites that become secondarily infected.
• Other treponemal diseases: pinta (caused by T. pallidum subsp. pinta).
• Neoplastic processes: cutaneous lymphoma or basal cell carcinoma (rare, but can mimic ulcerative lesions).

Associated Symptoms

Yaws manifests differently depending on the disease stage. Common accompanying signs and symptoms include:

• Fever, chills, and malaise during the early (primary) stage.
• Swollen, tender regional lymph nodes (especially in the neck, axillae, and groin).
• Characteristic “mother‑of‑pearl” papules or nodules that become ulcerated.
• Rash consisting of multiple, often painful, skin lesions that may spread to the trunk, limbs, and face.
• Bone pain, especially in the long bones, tibia, and ribs during the secondary stage.
• Joint swelling and arthritis‑like pain (known as “yaws arthritis”).
• Late (tertiary) disease may cause destructive bone lesions, gummatous (granulomatous) growths, and severe deformities.
• Loss of appetite and weight loss in chronic infection.

When to See a Doctor

Because yaws can lead to permanent disability, prompt medical attention is essential if you notice any of the following:

• Persistent or enlarging ulcerated skin lesions, especially on the legs, feet, or arms.
• Fever accompanied by a new rash or skin nodule.
• Swollen, painful lymph nodes near a skin lesion.
• Joint pain or swelling without a clear injury.
• Bone tenderness or unexplained pain in the legs, arms, or ribs.
• Any skin ulcer that does not heal within two weeks.
• Family or community members with similar lesions, suggesting an outbreak.

Diagnosis

Diagnosing yaws involves a combination of clinical evaluation, laboratory testing, and, when available, epidemiologic data.

Clinical Evaluation

• Detailed history focusing on recent skin contact, travel to endemic regions, and exposure to infected children.
• Physical examination of lesions (primary chancre, secondary papillomatous rash, or tertiary gummas).
• Assessment of lymphadenopathy and musculoskeletal involvement.

Laboratory Tests

• Serologic testing: Non‑treponemal tests (VDRL, RPR) are often positive; treponemal tests (TPPA, FTA‑ABS) confirm infection.
• Dark‑field microscopy: Direct visualization of spirochetes from a fresh ulcer exudate (requires expertise).
• PCR (polymerase chain reaction): Detects T. pallidum pertenue DNA; increasingly used in reference labs.
• Bone X‑ray or MRI: May reveal periosteal reaction or osteitis in late disease.

Epidemiologic Confirmation

In regions with active yaws eradication programs, a confirmed case in the community may support the diagnosis even when laboratory resources are limited.

Treatment Options

The eradication of yaws is achievable with a single dose of oral azithromycin, which is now the WHO‑recommended first‑line therapy. Alternative regimens are used when azithromycin is contraindicated.

Medical Treatment

• Azithromycin 30 mg/kg (maximum 2 g) single oral dose: 95‑% cure rate for early and late stages.
• Benzathine penicillin G 2.4 million units IM: Reserved for pregnant women, infants < 6 months, or azithromycin‑resistant cases.
• Doxycycline 100 mg PO twice daily for 14 days: Alternative for adults who cannot receive azithromycin.
• For tertiary disease with extensive bone involvement, prolonged courses of penicillin or azithromycin may be needed.

Supportive & Home Care

• Keep lesions clean with mild soap and water; apply sterile gauze to prevent secondary bacterial infection.
• Use analgesics such as acetaminophen or ibuprofen for fever and pain.
• Encourage adequate nutrition and hydration to support immune recovery.
• Educate caregivers on wound care and the importance of completing the full antibiotic course.

Prevention Tips

Because yaws spreads through direct skin contact, community‑level measures are most effective.

• Mass drug administration (MDA): Periodic community‑wide azithromycin distribution has dramatically reduced prevalence in endemic regions (WHO, 2023).
• Early case detection: Prompt treatment of any suspicious lesions halts transmission.
• Personal hygiene: Regular washing of hands and feet, especially after playing in soil or standing water.
• Protective clothing: Wearing shoes and long‑sleeved shirts reduces skin exposure to contaminated surfaces.
• Environmental control: Improving sanitation, drainage, and reducing standing water lowers the risk of skin maceration and subsequent infection.
• Health education: Community outreach teaching children and parents to avoid direct contact with ulcerated lesions.
• Vaccination research: Although no vaccine exists yet, ongoing trials aim to develop a treponemal vaccine; staying informed about advances can help future prevention.

Emergency Warning Signs

Key Take‑aways

Yaws is a treatable yet potentially disabling infection that thrives in underserved tropical settings. Early recognition, a single dose of azithromycin, and community‑wide prevention programs can eliminate both individual suffering and the broader public‑health threat. If you notice the characteristic painless ulcer or any of the associated symptoms, contact a health professional promptly—particularly in areas where yaws remains endemic.