title: Number of years of annual mass treatment with azithromycin needed to control trachoma in hyper-endemic communities in Tanzania.
abstract: BACKGROUND
  The World Health Organization recommends mass treatment as part of a trachoma control strategy. However, scant empirical data from hyperendemic communities exist on the number of rounds of treatment needed to reach a goal of <5% prevalence in children. We determined the prevalence of trachoma and infection with Chlamydia trachomatis in communities after 3-7 years of annual mass treatment in Tanzania.
  
  
  METHODS
  Seventy-one communities with trachoma and annual azithromycin coverage data were enrolled. A cross-sectional survey of ≥100 randomly selected children aged <5 years in each community was performed. Children were examined for clinical trachoma, and swab samples were taken for determination of ocular C. trachomatis infection.
  
  
  RESULTS
  After 3 years of mass treatment, the prevalence of trachoma decreased in a linear fashion with number of years of mass treatment, whereas decreased prevalences of C. trachomatis infection were related to the extent of the previous year's azithromycin coverage. Our model suggests that, for communities with baseline trachoma prevalence of 50% and annual treatment coverage of 75%, >7 years of annual mass treatment will be needed to reach a prevalence of trachoma of <5%.
  
  
  CONCLUSIONS
  Country programs in trachoma-endemic regions must realistically expect that several years of annual mass treatment may be necessary to eliminate trachoma.
authors.affiliation: Department of Opthalmology, Dana Center for Preventive Ophthalmology, Johns Hopkins Medical Institutions, Baltimore, MD, USA. shwest@jhmi.edu
authors.forename: Sheila K
authors.initials: SK
authors.lastname: West
authors.forename: Beatriz
authors.initials: B
authors.lastname: Munoz
authors.forename: Harran
authors.initials: H
authors.lastname: Mkocha
authors.forename: Charlotte A
authors.initials: CA
authors.lastname: Gaydos
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Quinn
mesh_terms: D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D017963:Azithromycin / Q000008:administration & dosage*; D002675:Child, Preschool; D002692:Chlamydia trachomatis / Q000302:isolation & purification; D003430:Cross-Sectional Studies; D004358:Drug Therapy / Q000379:methods*; D004363:Drug Utilization / Q000706:statistics & numerical data; D019353:Endemic Diseases; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D015995:Prevalence; D013636:Tanzania / Q000453:epidemiology; D013997:Time Factors; D014141:Trachoma / Q000188:drug therapy* / Q000453:epidemiology*; D016896:Treatment Outcome
chemical_list: D000900:Anti-Bacterial Agents; D017963:Azithromycin