Treating entire communities with the oral antibiotic azithromycin might effectively control an infection that causes widespread eye disease in developing countries, according to a new study.
The eye disease is trachoma, one of the world's leading causes of preventable blindness. Research results show oral treatment to be markedly better in reducing the number of infections than topical therapy, which uses an ointment form of the antibiotic tetracycline. Public health programs historically used the topical ointment for treatment and control of trachoma.
"We have known for decades that we had the antibiotics to successfully treat this disease when cases developed, but we didn't seem to have the right drug delivery method to control the bug over time. Now we know that we do, and we are very excited at the promise of these results," said Julius Schachter, PhD, professor of laboratory medicine at the University of California San Francisco and lead investigator of the study.
"Although azithromycin costs more than tetracycline ointment, the expense may be offset by the higher costs of distributing and administering multiple doses of the ointment," added Schachter, who also is director of the UCSF Chlamydia Research Laboratory at San Francisco General Hospital Medical Center. Study findings are reported in the August 21st issue of the British medical journal, The Lancet.
Researchers compared the effect of the two antibiotic regimens on infection rates in villages located in trachoma endemic areas where transmission of infection is high. The villages were in the African countries of Egypt, The Gambia, and Tanzania.
Previous studies have shown that topical antibiotics reduced the severity of disease and infection levels for the short-term, but they did not control trachoma levels over the long-term.
Trachoma occurs when the bacterium Chlamydia trachomatis infects the inner eyelid. The disease persists in staggering numbers in developing countries because of lack of medical attention, poor personal hygiene, and environmental conditions.
On a global scale, 600 million people live in trachoma endemic areas, and an estimated 150 million--mostly children--have the disease. The eye infection is transmitted easily from person to person by hand-to-eye contact, possibly aided by flies that are attracted to the sticky discharge from diseased eyes.
Infection usually begins in childhood, and without proper treatment, scarring occurs. After repeated episodes, the scarring causes the eyelid to contract and turn inward. With every blink, the eyelashes damage the cornea, eventually leading to blindness. Total blindness often occurs in mid-life and, in endemic communities, 25 percent of individuals in the 50-60 year old age group may be blinded.
Since the 1950s, the standard treatment for trachoma has been daily application of tetracycline ointment in the inflamed eye for six weeks. In the current study, the research team compared this standard topical regimen with three doses of oral azithromycin at one-week intervals. Results showed infection rates after one year decreased from 60 to 90 percent with azithromycin, which was greater than the decrease seen after tetracycline treatment.
The authors conclude that the effective reduction of chlamydial infection combined with the ease of administration makes azithromycin an important component of current public health programs for long-term control of trachoma. The steps in this strategy, known as SAFE, include: surgery for advanced disease, antibiotics to treat and prevent infections, face washing and good personal hygiene, and environmental improvements, such as better access to clean water and sanitation and health education.
According to Schachter, use of azithromycin in the SAFE strategy would provide substantial benefit to people in endemic areas by reducing infection.
"A goal for this study was to assess control of trachoma through treatment of entire communities. In practice, the advantage of oral azithromycin will be even greater than these study results show because of the good compliance that can be achieved with this administration method," Schachter said.
In addition to the eye, Chlamydia trachomatis can infect the nose, throat, genital tract, and rectum. In the United States, other strains of chlamydia cause the common sexually transmitted disease of the same name.
The National Institutes of Allergy and Infectious Disease, Pfizer Labs, The Edna McConnell Clark Foundation, and Abbott Laboratories supported the study. Co-authors of the Lancet paper are Chandler R. Dawson, MD, Francis I. Proctor Foundation, UCSF; Sheila K. West, PhD, and Susan Vitale, MD, Wilmer Eye Institute; Linda Bobo, PhD, Johns Hopkins University; David Mabey, FRCP, Robin Baily, MRCP, and Denise Mabey, MD, London School of Hygiene and Tropical Medicine; Thomas C. Quinn, MD, Johns Hopkins and NIAID; Ahmed Sheta, MD, and Sunny Sallam, MD, Alexandria University, Egypt; Harran Mkocha, BS, Central Eye Health Foundation, Tanzania; and Hannah Faal, MD, Ministry of Health, The Gambia.
Journal
The Lancet