title: Prevalence of trachoma at sub-district level in ethiopia: determining when to stop mass azithromycin distribution.
abstract: BACKGROUND
  To eliminate blinding trachoma, the World Health Organization emphasizes implementing the SAFE strategy, which includes annual mass drug administration (MDA) with azithromycin to the whole population of endemic districts. Prevalence surveys to assess impact at the district level are recommended after at least 3 years of intervention. The decision to stop MDA is based on a prevalence of trachomatous inflammation follicular (TF) among children aged 1-9 years below 5% at the sub-district level, as determined by an additional round of surveys limited within districts where TF prevalence is below 10%. We conducted impact surveys powered to estimate prevalence simultaneously at the sub-district and district in two zones of Amhara, Ethiopia to determine whether MDA could be stopped.
  
  
  METHODS
  Seventy-two separate population-based, sub-district surveys were conducted in 25 districts. In each survey all residents from 10 randomly selected clusters were screened for clinical signs of trachoma. Data were weighted according to selection probabilities and adjusted for correlation due to clustering.
  
  
  RESULTS
  Overall, 89,735 residents were registered from 21,327 households of whom 72,452 people (80.7%) were examined. The prevalence of TF in children aged 1-9 years was below 5% in six sub-districts and two districts. Sub-district level prevalence of TF in children aged 1-9 years ranged from 0.9-76.9% and district-level from 0.9-67.0%. In only one district was the prevalence of trichiasis below 0.1%.
  
  
  CONCLUSIONS
  The experience from these zones in Ethiopia demonstrates that impact assessments designed to give a prevalence estimate of TF at sub-district level are possible, although the scale of the work was challenging. Given the assessed district-level prevalence of TF, sub-district-level surveys would have been warranted in only five districts. Interpretation was not as simple as stopping MDA in sub-districts below 5% given programmatic challenges of exempting sub-districts from a highly regarded program and the proximity of hyper-endemic sub-districts.
authors.affiliation: The Carter Center, Atlanta, Georgia, United States of America; Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: King
authors.affiliation: The Carter Center, Addis Ababa, Ethiopia.
authors.forename: Tesfaye
authors.initials: T
authors.lastname: Teferi
authors.affiliation: The Carter Center, Atlanta, Georgia, United States of America.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Cromwell
authors.affiliation: The Carter Center, Addis Ababa, Ethiopia.
authors.forename: Mulat
authors.initials: M
authors.lastname: Zerihun
authors.affiliation: The Carter Center, Atlanta, Georgia, United States of America; Department of Public Health and Primary Care, Institute of Public Health, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Jeremiah M
authors.initials: JM
authors.lastname: Ngondi
authors.affiliation: The Carter Center, Addis Ababa, Ethiopia.
authors.forename: Mesele
authors.initials: M
authors.lastname: Damte
authors.affiliation: The Carter Center, Addis Ababa, Ethiopia.
authors.forename: Frew
authors.initials: F
authors.lastname: Ayalew
authors.affiliation: The Carter Center, Addis Ababa, Ethiopia.
authors.forename: Zerihun
authors.initials: Z
authors.lastname: Tadesse
authors.affiliation: The Carter Center, Addis Ababa, Ethiopia.
authors.forename: Teshome
authors.initials: T
authors.lastname: Gebre
authors.affiliation: The Amhara National Regional State Health Bureau, Bahir Dar, Ethiopia.
authors.forename: Ayelign
authors.initials: A
authors.lastname: Mulualem
authors.affiliation: The Amhara National Regional State Health Bureau, Bahir Dar, Ethiopia.
authors.forename: Alemu
authors.initials: A
authors.lastname: Karie
authors.affiliation: The Carter Center, Addis Ababa, Ethiopia.
authors.forename: Berhanu
authors.initials: B
authors.lastname: Melak
authors.affiliation: The Carter Center, Addis Ababa, Ethiopia.
authors.forename: Mitku
authors.initials: M
authors.lastname: Adugna
authors.affiliation: The Carter Center, Addis Ababa, Ethiopia.
authors.forename: Demelash
authors.initials: D
authors.lastname: Gessesse
authors.affiliation: The Amhara National Regional State Health Bureau, Bahir Dar, Ethiopia.
authors.forename: Abebe
authors.initials: A
authors.lastname: Worku
authors.affiliation: The Carter Center, Addis Ababa, Ethiopia.
authors.forename: Tekola
authors.initials: T
authors.lastname: Endashaw
authors.affiliation: The Amhara National Regional State Health Bureau, Bahir Dar, Ethiopia.
authors.forename: Fisseha
authors.initials: F
authors.lastname: Admassu Ayele
authors.affiliation: Francis I. Proctor Foundation, University of California San Francisco, San Francisco, California, United States of America.
authors.forename: Nicole E
authors.initials: NE
authors.lastname: Stoller
authors.affiliation: The Carter Center, Atlanta, Georgia, United States of America.
authors.forename: Mary Rose A
authors.initials: MR
authors.lastname: King
authors.affiliation: The Carter Center, Atlanta, Georgia, United States of America.
authors.forename: Aryc W
authors.initials: AW
authors.lastname: Mosher
authors.affiliation: The Carter Center, Addis Ababa, Ethiopia.
authors.forename: Tesfaye
authors.initials: T
authors.lastname: Gebregzabher
authors.affiliation: The Carter Center, Addis Ababa, Ethiopia.
authors.forename: Geremew
authors.initials: G
authors.lastname: Haileysus
authors.affiliation: Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Odermatt
authors.affiliation: Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland.
authors.forename: Jürg
authors.initials: J
authors.lastname: Utzinger
authors.affiliation: The Carter Center, Atlanta, Georgia, United States of America.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Emerson
mesh_terms: D000900:Anti-Bacterial Agents / Q000600:supply & distribution* / Q000627:therapeutic use*; D017963:Azithromycin / Q000600:supply & distribution* / Q000627:therapeutic use*; D002675:Child, Preschool; D004358:Drug Therapy / Q000379:methods; D005002:Ethiopia / Q000453:epidemiology; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D015995:Prevalence; D014141:Trachoma / Q000188:drug therapy* / Q000453:epidemiology*
chemical_list: D000900:Anti-Bacterial Agents; D017963:Azithromycin