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Trachoma: Chlamydial Eye Infection – Causes, Progression, and Treatment

Trachoma is a chronic keratoconjunctivitis caused by Chlamydia trachomatis serovars A, B, Ba, C. It is the leading infectious cause of blindness globally.

Pathogenesis (WHO Grading)

  1. TF (Trachomatous Inflammation – Follicular): ≥5 follicles on upper tarsal conjunctiva. Active disease, contagious.
  2. TI (Trachomatous Inflammation – Intense): Pronounced inflammatory thickening, obscuring >½ tarsal vessels.
  3. TS (Trachomatous Scarring): White bands/lines in tarsal conjunctiva.
  4. TT (Trachomatous Trichiasis): ≥1 eyelash touches globe; corneal abrasion risk.
  5. CO (Corneal Opacity): Central opacity blurring vision; end-stage blindness.

Transmission

  • Direct contact (hands, fomites – towels, clothing).
  • Flies (Musca sorbens) – mechanical vectors.
  • Risk factors: poor hygiene, water scarcity, crowding, young children (reservoir).

Treatment

  • Azithromycin 20 mg/kg single dose (max 1 g) – preferred; mass drug administration (MDA) in endemic areas.
  • Alternative: Tetracycline 1% eye ointment BID × 6 weeks (less effective, adherence issues).
  • Trichiasis surgery (bilamellar tarsal rotation) for TT.
  • Corneal transplant for CO (limited access in endemic regions).

WHO SAFE Strategy

  • Surgery for trichiasis.
  • Antibiotics (azithromycin MDA).
  • Facial cleanliness.
  • Environmental improvement (water, sanitation, fly control).

Global Status

  • Endemic in 44 countries (mostly Africa, some Asia, Americas, Middle East).
  • 13 countries validated elimination (2023).
  • Target: Global elimination as public health problem by 2030.

Early antibiotic treatment prevents scarring and blindness. Community-wide SAFE implementation is curative at population level.

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