Yaws Ulcers - Causes, Treatment & When to See a Doctor

What is Yaws Ulcers?

Yaws is a contagious tropical infection caused by the bacterium Treponema pallidum pertenue. It primarily affects the skin, bone, and soft tissue of children living in warm‑climate, low‑resource regions of Africa, Asia, and the Pacific. The disease progresses through several stages, and the most recognizable manifestation of the secondary stage is the development of painful, raised skin lesions that evolve into characteristic “yaws ulcers.”

These ulcers begin as painless, raised papules that later break down, forming shallow, bleeding sores with a raised, inflamed border. When left untreated, they may heal spontaneously, leaving darkened scars, or they can recur and lead to deeper tissue damage, bone loss, and disfigurement.

Common Causes

While the term “yaws ulcer” specifically refers to the ulcerative lesions caused by T. pallidum pertenue, several other infectious and non‑infectious conditions can produce similar ulcerative skin lesions. Understanding these helps clinicians avoid misdiagnosis.

• Yaws infection (Treponema pallidum pertenue) – the primary cause.
• Bejel (endemic syphilis) – caused by the same species group (T. pallidum) but transmitted via non‑sexual contact.
• Ulcero‑granulomatous cutaneous leishmaniasis – a protozoan infection common in similar endemic areas.
• Buruli ulcer (Mycobacterium ulcerans) – a necrotizing skin infection that can mimic yaws lesions.
• Traumatic ulceration – repeated friction or injury in children playing barefoot.
• Fungal infections (e.g., sporotrichosis) – produce ulcerative nodules along lymphatic vessels.
• Necrotizing bacterial infections (e.g., Streptococcus pyogenes) – can cause rapid ulcer formation.
• Autoimmune ulcerative disorders (e.g., pyoderma gangrenosum) – rare but can be mistaken for yaws.
• Viral ulcerations (e.g., herpes simplex virus) – generally smaller but sometimes confused.
• Skin cancers (e.g., basal cell carcinoma) – in older individuals; appearance may overlap.

Associated Symptoms

Yaws ulcers seldom appear in isolation. The disease’s natural history often includes the following accompanying signs:

• Primary papule – a painless, raised bump that appears 1–2 weeks after infection.
• Rash – multiple, moist, raised lesions on the trunk, limbs, or face.
• Fever and malaise – low‑grade fever is common during the secondary stage.
• Joint pain (arthralgia) – especially in the knees, ankles, and wrists.
• Bone pain or swelling – chronic infection can involve the periosteum, causing osteitis.
• Hyperpigmented “gummas” – scar‑like nodules that may develop months to years later.
• Enlarged lymph nodes – usually painless and located near ulcer sites.
• Generalized fatigue – due to chronic inflammation.

When to See a Doctor

Because yaws can be cured with a single dose of antibiotics, early medical evaluation is crucial. Seek professional care if you notice any of the following:

• Development of a painless papule that later becomes an ulcer.
• Multiple ulcerative lesions that are spreading or recurring.
• Ulcers that bleed easily, ooze pus, or become increasingly painful.
• Fever, joint pain, or swelling in addition to skin lesions.
• Any ulcer that does not begin to heal within 2 weeks of appearance.
• Signs of secondary infection (redness spreading, heat, increased pain, foul odor).
• History of travel or residence in yaws‑endemic regions, especially in children.

Diagnosis

Accurate diagnosis relies on a combination of clinical assessment, laboratory testing, and sometimes imaging.

1. Clinical Examination

Physicians look for the classic “yaws ulcer” – a shallow, pink‑red ulcer with a raised, indurated border and a central necrotic area. The distribution (typically on the limbs, especially the ankles and knees) helps differentiate it from other ulcers.

2. Serologic Tests

• Rapid plasma reagin (RPR) or Venereal Disease Research Laboratory (VDRL) test – non‑treponemal assays that detect antibodies produced in response to infection.
• Treponemal tests (e.g., TPPA, FTA‑ABS) – confirmatory tests that differentiate yaws from other treponemal diseases.

Because yaws is caused by a non‑syphilis treponeme, titers are usually lower than in venereal syphilis, but the pattern of reactivity aids diagnosis.

3. Molecular Methods

Polymerase chain reaction (PCR) from ulcer swabs can directly detect T. pallidum pertenue DNA. While not always available in low‑resource settings, PCR offers the highest specificity.

4. Histopathology (Rare)

Biopsy of an ulcer edge may show a dense infiltrate of plasma cells and endothelial proliferation, typical of treponemal infection.

5. Imaging (for late disease)

In chronic cases with bone involvement, X‑ray or MRI can reveal periosteal reaction, osteitis, or joint destruction.

Treatment Options

Yaws is remarkably responsive to a single dose of an appropriate antibiotic. Prompt treatment stops transmission, prevents complications, and eliminates ulcers.

Medical Treatment

• Azithromycin (single oral dose of 30 mg/kg, max 2 g) – WHO‑recommended first‑line therapy due to easy administration and low side‑effect profile (Mayo Clinic, 2023).
• Benzathine penicillin G (intramuscular, 1.2 million units for children, 2.4 million units for adults) – an alternative for patients with azithromycin contraindications or in areas where resistance is suspected (CDC, 2022).
• Repeat dosing is rarely needed, but a second dose may be given 2–4 weeks later if serology does not decline.

Management of Ulcer Care

• Wound cleaning – gentle irrigation with sterile saline twice daily.
• Topical antiseptics – povidone‑iodine or chlorhexidine applied after cleaning.
• Dressings – non‑adhesive, breathable dressings to protect from secondary bacterial infection.
• Pain control – acetaminophen or ibuprofen as needed.
• Monitoring – check for signs of infection (increasing redness, swelling, pus).

Home Care & Supportive Measures

• Maintain good nutrition (protein‑rich foods) to promote wound healing.
• Encourage hydration and adequate rest.
• Keep the affected limbs clean and avoid scratching or picking at the ulcers.
• Educate caregivers about the importance of completing the antibiotic course.

Prevention Tips

Yaws is transmitted through direct skin‑to‑skin contact with infectious lesions, most often among children playing barefoot or sharing clothing. Community‑level strategies have dramatically reduced incidence worldwide, and the following measures help sustain those gains.

• Mass‑drug administration (MDA) – single‑dose azithromycin given to all children < 15 years in endemic districts (WHO, 2021).
• Early case detection – training teachers and community health workers to recognize characteristic lesions.
• Personal hygiene – regular washing of hands and feet; keep skin clean and dry.
• Footwear – encourage wearing shoes or sandals, especially during outdoor play.
• Separate ulcerated clothing – wash clothes and bedding in hot water, avoid sharing blankets.
• Environmental sanitation – reduce open defecation and stagnant water that attract biting insects, as insects can facilitate skin abrasions.
• Vaccination research – while no vaccine is currently licensed, ongoing trials may offer future protection (NIH, 2022).

Emergency Warning Signs

Key Take‑aways

Yaws ulcers are a treatable manifestation of a tropical treponemal infection that predominantly affects children in resource‑limited settings. Early recognition, a single dose of azithromycin, and proper wound care lead to rapid cure and halt transmission. Community‑wide prevention programs, good personal hygiene, and prompt medical evaluation of suspicious lesions remain the cornerstone of control and eventual eradication.