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Microbiology · Other clinically important bacteria

Non-venereal treponemes (yaws, bejel and pinta) !

  • Bacterium
  • Does not Gram-stain
  • For completeness

Relatives of the syphilis agent spread by skin contact among children in poor tropical areas: yaws, bejel and pinta.

Updated 2026-11-01

Also called: frambesia, carate

At a glance

Gram
Does not Gram-stain
Shape
Spirochaete
Family
Treponemataceae
Stain
Not seen on Gram stain; dark-field microscopy of lesions

Morphology

  • Thin spirochaetes identical to Treponema pallidum under the microscope
  • Yaws: T. pallidum subspecies pertenue; bejel: subspecies endemicum; pinta: Treponema carateum
  • Cannot be grown on artificial media

Transmission

  • Direct skin contact with lesions, helped by small wounds
  • Bejel: also mouth to mouth and through shared utensils
  • Not sexually transmitted and not passed from mother to fetus

Reservoir: Humans

Isolation precautions

What the care team adds to standard precautions.

  • Standard

Virulence factors

  • Few surface proteins, which hampers the immune response
  • Chronic lesions that destroy skin, bone and cartilage if untreated (yaws, bejel)
  • Pinta stays confined to the skin

Diseases it causes

Clinical picture

  • Yaws: a papule that grows like a raspberry and ulcerates; later multiple lesions, pain and deformity of long bones and fingers
  • Bejel: mouth and skin lesions, periostitis and destruction of nose and palate
  • Pinta: skin patches that turn from bluish to depigmented, resembling vitiligo

Diagnosis

  • Clinical and epidemiological diagnosis
  • Syphilis serology (treponemal and non-treponemal) is positive and does not tell them apart
  • PCR to confirm yaws and to monitor azithromycin resistance

Treatment

Macrolides (single-dose azithromycin, the first choice in yaws) or benzathine penicillin. WHO uses community-wide mass treatment with azithromycin to eradicate yaws.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

Prevention

  • Treating the whole community and all contacts
  • Hygiene, water and soap
  • Active case finding among children

Test yourself

Think of the answer, then tap the question to see it.

What causes pinta?

Treponema carateum.

Why does a positive VDRL in a child from a yaws-endemic area not confirm syphilis?

Non-venereal treponemes give the same positive serology; they are told apart by the clinical picture and epidemiology.

Which antibiotic does WHO use for mass treatment of yaws?

Single-dose azithromycin.

How does the spread of yaws differ from that of syphilis?

Yaws spreads by skin contact with lesions, mostly among children; it is not sexual and does not pass to the fetus.

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Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: Yaws (WHO, 2024); Bejel, Pinta, and Yaws - Infectious Disease - MSD Manual Professional Edition (MSD Manual Professional Edition, 2025).

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Representative model, for educational purposes only.