A rationale for continuing mass antibiotic distributions for trachoma.
BACKGROUND
The World Health Organization recommends periodic mass antibiotic distributions to reduce the ocular strains of chlamydia that cause trachoma, the world's leading cause of infectious blindness. Their stated goal is to control infection, not to completely eliminate it. A single mass distribution can dramatically reduce the prevalence of infection. However, if infection is not eliminated in every individual in the community, it may gradually return back into the community, so often repeated treatments are necessary. Since public health groups are reluctant to distribute antibiotics indefinitely, we are still in need of a proven long-term rationale. Here we use mathematical models to demonstrate that repeated antibiotic distributions can eliminate infection in a reasonable time period.


METHODS
We fit parameters of a stochastic epidemiological transmission model to data collected before and 6 months after a mass antibiotic distribution in a region of Ethiopia that is one of the most severely affected areas in the world. We validate the model by comparing our predicted results to Ethiopian data which was collected biannually for two years past the initial mass antibiotic distribution. We use the model to simulate the effect of different treatment programs in terms of local elimination of infection.


RESULTS
Simulations show that the average prevalence of infection across all villages progressively decreases after each treatment, as long as the frequency and coverage of antibiotics are high enough. Infection can be eliminated in more villages with each round of treatment. However, in the communities where infection is not eliminated, it returns to the same average level, forming the same stationary distribution. This phenomenon is also seen in subsequent epidemiological data from Ethiopia. Simulations suggest that a biannual treatment plan implemented for 5 years will lead to elimination in 95% of all villages.


CONCLUSIONS
Local elimination from a community is theoretically possible, even in the most severely infected communities. However, elimination from larger areas may require repeated biannual treatments and prevention of re-introduction from outside to treated areas.
Ray
Kathryn J
KJ
Francis I, Proctor Foundation, University of California, San Francisco, CA, USA. kathrynjray@gmail.com
Porco
Travis C
TC
Hong
Kevin C
KC
Lee
David C
DC
Alemayehu
Wondu
W
Melese
Muluken
M
Lakew
Takele
T
Yi
Elizabeth
E
House
Jenafir
J
Chidambaram
Jaya D
JD
Whitcher
John P
JP
Gaynor
Bruce D
BD
Lietman
Thomas M
TM
D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D019072:Antibiotic Prophylaxis; D017963:Azithromycin / Q000008:administration & dosage*; D002648:Child; D002675:Child, Preschool; D002692:Chlamydia trachomatis / Q000302:isolation & purification; D003141:Communicable Diseases / Q000188:drug therapy*; D003906:Developing Countries; D004334:Drug Administration Schedule; D019353:Endemic Diseases / Q000517:prevention & control*; D005002:Ethiopia / Q000453:epidemiology; D006801:Humans; D007223:Infant; D008875:Middle Aged; D008962:Models, Theoretical; D015995:Prevalence; D012424:Rural Population; D013997:Time Factors; D014141:Trachoma / Q000188:drug therapy / Q000517:prevention & control*; D016896:Treatment Outcome
D000900:Anti-Bacterial Agents; D017963:Azithromycin