title: Effect of a single mass antibiotic distribution on the prevalence of infectious trachoma.
abstract: BACKGROUND
  The World Health Organization recommends mass antibiotic distributions in its strategy to eliminate blinding trachoma as a public health concern. Some hypothesize that a single distribution is sufficient to control the ocular strains of chlamydia that cause trachoma. Others believe infection will inevitably return and periodic treatments or other measures are essential.
  
  
  OBJECTIVE
  To determine whether ocular chlamydial infection returns to the community up to 24 months after a single mass antibiotic distribution in a hyperendemic region of Ethiopia.
  
  
  METHODS
  Longitudinal cohort study conducted March 2003 to March 2005 in the Gurage Zone of Ethiopia. Eight randomly selected villages were assessed for ocular chlamydial infection. Fifteen untreated villages were randomly chosen at 12 months to allow assessment of a secular trend.
  
  
  METHODS
  A single dose of oral azithromycin was offered to all residents of the 8 selected villages who were aged 1 year or older.
  
  
  METHODS
  Prevalence of ocular chlamydial infection in all children aged 1 to 5 years from each intervention village prior to treatment and 2, 6, 12, 18, and 24 months after mass antibiotic treatment, and also in untreated villages enrolled at 12 months.
  
  
  RESULTS
  Five hundred fifteen children were examined for ocular chlamydial infection at baseline. For the follow-up examinations, the mean participation rate was 83%. The mean prevalence of infection in children aged 1 to 5 years decreased from 43.5% (95% confidence interval [CI], 35.0%-52.0%) to 5.1% (95% CI, 1.1%-9.2%) after treatment. On average, infection returned gradually over 24 months to 11.3% (95% CI, 4.5%-18.1%; P = .001). In 7 of 8 villages, infection was higher at 24 months than at 2 months. In the remaining village, no infection could be identified at any point after treatment. Villages enrolled at 12 months had significantly fewer infections than those enrolled 12 months earlier, suggesting a secular trend (P<.001).
  
  
  CONCLUSIONS
  Ocular chlamydial infection was not eliminated in children aged 1 to 5 years after a single mass azithromycin distribution; it slowly returned over 24 months, although not to baseline levels. Repeated treatments or other effective measures will be necessary for elimination.
authors.affiliation: F. I. Proctor Foundation, University of California, San Francisco, CA 94143-0412, USA.
authors.forename: Jaya D
authors.initials: JD
authors.lastname: Chidambaram
authors.forename: Wondu
authors.initials: W
authors.lastname: Alemayehu
authors.forename: Muluken
authors.initials: M
authors.lastname: Melese
authors.forename: Takele
authors.initials: T
authors.lastname: Lakew
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Yi
authors.forename: Jenafir
authors.initials: J
authors.lastname: House
authors.forename: Vicky
authors.initials: V
authors.lastname: Cevallos
authors.forename: Zhaoxia
authors.initials: Z
authors.lastname: Zhou
authors.forename: Kathryn
authors.initials: K
authors.lastname: Maxey
authors.forename: David C
authors.initials: DC
authors.lastname: Lee
authors.forename: Brett L
authors.initials: BL
authors.lastname: Shapiro
authors.forename: Muthiah
authors.initials: M
authors.lastname: Srinivasan
authors.forename: Travis
authors.initials: T
authors.lastname: Porco
authors.forename: John P
authors.initials: JP
authors.lastname: Whitcher
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Gaynor
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Lietman
mesh_terms: D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D019072:Antibiotic Prophylaxis; D017963:Azithromycin / Q000627:therapeutic use*; D002675:Child, Preschool; D003140:Communicable Disease Control; D005002:Ethiopia; D006801:Humans; D007223:Infant; D008137:Longitudinal Studies; D015995:Prevalence; D014141:Trachoma / Q000453:epidemiology / Q000517:prevention & control*; D016896:Treatment Outcome
chemical_list: D000900:Anti-Bacterial Agents; D017963:Azithromycin