A recent article in The Journal of the American Medical
Association reports that when preschool children in villages
in Ethiopia took the antibiotic azithromycin twice per year instead of
once per year, the number of children with eye infections caused by the
contagious eye disease trachoma was significantly reduced. The study
was conducted by Muluken Melese of Orbis International, Addis Ababa,
Ethiopia and colleagues.
Trachoma is the an infectious eye disease that is the leading cause of
the world’s preventable blindness. It is caused by the a chlamydia
bacterium.
Trachoma is common in poor, dry areas like rural sub-Saharan Africa,
but it has been eradicated from Western Europe and the United
States. “The World Health Organization has launched a program
to control trachoma, relying in large part on annual repeated mass
azithromycin administrations. Program administrators anticipate that
the treatments will reduce the prevalence of the ocular strains of
chlamydia that cause trachoma to a level low enough that resulting
blindness will be no longer be a major public health concern. However,
local elimination of ocular chlamydia may be obtainable,” according to
the authors of the study..
The elimination of trachoma is possible, according to some mathematical
models. However, it may require recurrent treatment in areas where
people are at a greater risk of becoming infected. It is regarded that
elimination is a particularly important goal – if antibotics are
discontinued and communities lose some their immunity, there is a
concern that infection may return.
The researchers focused on the Gurage Zone in Ethiopia – 16 rural
villages with a high prevalence of trachoma. They analyzed the results
of azithromycin given once and twice per year to all residents age 1
year or older from March 2003 to April 2005. About 91% of the 16,403
eligible individuals received their scheduled treatment.
One major result of the study showed a 6-fold decrease in infections of
preschool children from eight villages who received two annual
treatments compared to one, from 42.6% to 6.8% by 24 months. When the
treatment was administered four times in the other eight villages,
infections were reduced in preschool children by a factor of 35, from
31.6% to 0.9% by 24 months.
The researchers report that at 24 months, 0.9 percent of children were
infected in the biannually treated villages compared to 6.8 percent of
children in the annually treated villages – a significant difference.
At 24 months, 75% of preschool children did not show any infection
after receiving biannual treatment compared to 12.5% of the residents
receiving annual treatments. There was also an association between
having no infection identified at 24 months and being in the biannual
treatment group.
“Biannual coverage of a large portion of the community may be necessary
to eliminate infection from a severely affected community or at least
to do so in a timely manner. Although programs may be reluctant to
devote their scarce resources to more frequent treatment, this may be
more cost-effective in the long term. Local elimination of the ocular
strains of chlamydia from villages is a feasible goal but may require
biannual distributions in hyperendemic areas. The results of this study
confirm models that suggest treatments will need to be given for more
than the 2 years to predictably achieve elimination in more than 95
percent of villages. Whether elimination from a larger area is possible
will depend on the frequency of community-to-community
transmission,” conclude the researchers.
An editorial by David Mabey and Anthony W. Solomon of the London School
of Hygiene & Tropical Medicine, London maintains that the
research performed by Melese and colleagues is valuable for the
treatment of trachoma.
They write:
“Treating entire regions twice yearly could help ensure that gains made
from frequent antibiotic use are not eroded by reintroduction of
infection from outside the treated area but will significantly increase
the cost of antibiotics and of their distribution. Finally, studies to
examine whether more frequent azithromycin use will result in the
emergence of macrolide-resistant strains of C. trachomatis or other
important pathogens are urgently required, for such an outcome would
more than offset any gain derived from biannual treatment. In the
meantime, the findings of Melese et al represent an important
contribution to understanding how blinding trachoma can be reduced and
hopefully eliminated.”
Comparison of Annual and Biannual Mass Antibiotic
Administration for Elimination of Infectious Trachoma
Muluken Melese, Wondu Alemayehu, Takele Lakew, Elizabeth Yi, Jenafir
House, Jaya D. Chidambaram, Zhaoxia Zhou, Vicky
Cevallos, Kathryn Ray, Kevin Cyrus Hong, Travis C. Porco,
Isabella Phan, Ali Zaidi, Bruce D. Gaynor, John P. Whitcher, Thomas M.
Lietman
JAMA. (2008). Vol. 299 No. 7: pp. 778-784
Click
Here to View Abstract
Mass Antibiotic Administration for Eradication of Ocular
Chlamydia trachomatis
David Mabey and Anthony W. Solomon
JAMA. (2008). Vol. 299 No. 7: pp. 819-820
Click
Here to View Abstract
: Peter M Crosta