Feasibility of eliminating ocular Chlamydia trachomatis with repeat mass antibiotic treatments.
BACKGROUND
Mass antibiotic administrations for ocular chlamydial infection play a key role in the World Health Organization's trachoma control program. Mathematical models suggest that it is possible to eliminate trachoma locally with repeat mass treatment, depending on the coverage level of the population, frequency of mass treatments, and rate that infection returns into a community after each mass treatment. Precise estimates of this latter parameter have never been reported.


OBJECTIVE
To determine the rate at which chlamydial infection returns to a population after mass treatment and to estimate the treatment frequency required for elimination of ocular chlamydia from a community.


METHODS
Longitudinal cohort study of 24 randomly selected villages from the Gurage Zone in Ethiopia conducted February 2003 to October 2003. A total of 1332 children aged 1 to 5 years were monitored for prevalence of ocular chlamydial infection pretreatment and 2 and 6 months posttreatment.


METHODS
All individuals older than 1 year were eligible for single-dose oral azithromycin treatment. Pregnant women were offered tetracycline eye ointment.


METHODS
Prevalence of ocular chlamydial infection, measured by polymerase chain reaction, in children aged 1 to 5 years, in each of 24 villages at each time point was used to estimate the rate of return of infection and the treatment frequency necessary for elimination.


RESULTS
The prevalence of infection was 56.3% pretreatment (95% confidence interval [CI], 47.5%-65.1%), 6.7% 2 months posttreatment (95% CI, 4.2%-9.2%), and 11.0% 6 months posttreatment (95% CI, 7.3%-14.7%). Infection returned after treatment at an exponential rate of 12.3% per month (95% CI, 4.6%-19.9% per month). The minimum treatment frequency necessary for elimination was calculated to be once every 11.6 months (95% CI, 7.2-30.9 months), given a coverage level of 80%. Thus, biannual treatment, already being performed in some areas, was estimated to be more than frequent enough to eventually eliminate infection.


CONCLUSIONS
The rate at which ocular chlamydial infection returns to a community after mass treatment suggests that elimination of infection in a hyperendemic area is feasible with biannual mass antibiotic administrations and attainable coverage levels.
ORBIS International, Addis Ababa, Ethiopia.
Muluken
M
Melese
Jaya Devi
JD
Chidambaram
Wondu
W
Alemayehu
David Chung
DC
Lee
Elizabeth H
EH
Yi
Vicky
V
Cevallos
Zhaoxia
Z
Zhou
Cathy
C
Donnellan
Michael
M
Saidel
John P
JP
Whitcher
Bruce D
BD
Gaynor
Thomas M
TM
Lietman
D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D019072:Antibiotic Prophylaxis; D017963:Azithromycin / Q000008:administration & dosage*; D002675:Child, Preschool; D002692:Chlamydia trachomatis / Q000302:isolation & purification; D003235:Conjunctivitis, Inclusion / Q000188:drug therapy / Q000453:epidemiology / Q000517:prevention & control*; D003906:Developing Countries; D005002:Ethiopia / Q000453:epidemiology; D006801:Humans; D007223:Infant; D008137:Longitudinal Studies
D000900:Anti-Bacterial Agents; D017963:Azithromycin