Due to a form of 'herd protection', targeting trachoma treatment four times per year to children under 10 years old may be as effective as treating the entire population once per year – which is currently advised by WHO. These findings are published in an Article in this week's edition of The Lancet, written by Dr Thomas Lietman, FI Proctor Foundation and University of California, San Francisco, USA, and colleagues.
Trachoma, caused by chlamydial infection of the eye, can cause blindness if left untreated, and causes a huge health burden in poorer countries. The antibiotic azithromycin, taken orally, is used to treat this infection. Theoretically, elimination of infection is feasible if untreated individuals receive an indirect protective effect from living in repeatedly treated communities, which is similar to herd protection in vaccine programmes.
In this randomised trial, 24 population units in Amhara, Ethiopia, were randomised to distribution four-times per year of single dose azithromycin to children aged 1-10 years (12 units, 4764 children), or to delayed treatment until after the study (12 units, 6014 children). The researchers then compared the prevalence of ocular chlamydial infection in untreated individuals 11 years and older between baseline and 12 months in the treated units; and at 12 months between the treated and control units.
At 12 months, 637 children aged 1-10 years and 561 adults and children aged 11 years and older were analysed in the children-treated group, and 618 and 500, respectively, in the control group. The mean prevalence of infection in children under 10 years old decreased from 48% to 4% after four mass treatments. At 12 months, the mean prevalence of infection in the untreated age group (11 years and older) was 47% less than it had been 12 months earlier, and 35% less than in untreated communities.*
The authors conclude: "In this study, treatment of children decreased infection in untreated older children and adults, showing a form of herd protection from a mass antibiotic campaign. Treatment of children four times per year compared favourably with WHO's present recommendation of yearly mass treatment for all individuals in the community."
In an accompanying Comment, Professor Hugh R Taylor, Melbourne School of Population Health, University of Melbourne, Australia, says: "This study by Lietman and colleagues reinforces the importance of children as the main reservoir of infection in trachoma and the need to investigate further the best frequency of antibiotic treatment."
Dr Thomas Lietman, FI Proctor Foundation and University of California, San Francisco, USA T) +1 415 502 2662 E) tom.lietman@ucsf.edu
Professor Hugh R Taylor, Melbourne School of Population Health, University of Melbourne, Australia (travelling) T) +61 417 017037 E) h.taylor@unimelb.edu.au
For full Article and Comment, see: http://press.thelancet.com/trachomafinal.pdf
Notes to editors: *Comparing the treated cohort with untreated communities showed that the reduced infection prevalence was truly due to the treatment programme, and not a natural trend of trachoma infection declining.
Journal
The Lancet