Antibiotics No Match for Blinding Eye Infection
Trachoma a major threat to sight in poorer countries, experts say
TUESDAY, Sept. 26, 2006 (HealthDay News) -- Antibiotics alone offer no effective treatment for trachoma, an infectious eye disease that is the second leading cause of blindness after cataract, a study indicates.
Some 600 million people worldwide are vulnerable to trachoma, and 146 million need treatment to preserve their sight, the World Health Organization estimates.
The new study, done in Vietnam, found that the benefits of antibiotic treatment were short-lived.
"This study found that when we treated children with the antibiotic azithromycin, the rate of infection and of the disease decreased, out to two years, but after two years of the last treatment, there was a rebound phenomenon, with the re-infection rate increasing," warned researcher Dr. Deborah Dean, a senior scientist at Children's Hospital Oakland Research Institute in California.
Her team reported the findings in the Sept. 27 issue of the Journal of the American Medical Association.
Trachoma is caused by the Chlamydia trachomatis bacterium, which can infect the eyes and genitals. While the disease is most common in children, over several decades of re-infection, the continuing inflammation can force the eyelids to invert. This forces the lashes to abrade the cornea and produces blinding scars.
The bacteria are spread by means of hand-to-eye contact and by flies that feed on cow dung and human waste in poor villages. In Africa and Asia, unclean conditions keep the bacteria rampant. Up to 25 percent of older people infected with the microbe eventually will go blind.
Antibiotic treatment is one part of a standard WHO health care strategy against trachoma. The three other parts are surgery to prevent eyelids from inverting, facial cleanliness and environmental improvements, such as provision of clean water.
In their study, the researchers tracked outcomes for more than 3,000 residents of three Vietnamese communities that got the WHO trachoma program for three years and compared it to outcomes of residents who only received surgery for the illness.
Surprisingly, they found that re-infection rates increased substantially in the communities that received the WHO's program and declined in the surgery-only communities.
The likely reason: Antibiotic treatment interrupts trachoma infection, the researchers said, but does not give the patient's immune system enough time to build an adequate defense against re-infection.
Other studies have shown that antibiotics can have benefits, however. In a trial done two years ago in Ethiopia, individuals received antibiotics after surgery to prevent eyelid curling.
"The antibiotic group had one-third fewer instances of eyelid curling," noted Emily West, an epidemiologist and assistant professor in the department of ophthalmology at Johns Hopkins Medical Institutes, in Baltimore. She was a member of that research team.
Current policy is for a medical team to visit a village once a year and distribute antibiotics to as many residents as possible, West said. "From 85 to 95 percent [of residents] have to be treated to make sure that the disease does not come back," she said.
However, Dean said, "it is unlikely that antibiotics alone will give that kind of control."
She noted that although trachoma may seem a distant menace to Americans, there was a time when it was a common condition for people living under frontier conditions. Better living standards have virtually banished the disease from this country, but it remains a menace to some American Indian tribes, Dean said.
"We have to think in terms of long-term strategy, and that is not going to be antibiotics alone," she said. "Local hygiene, including clean water, is a very important factor."
The ultimate solution would be a vaccine, Dean said. Antibiotics can treat a disease, but "no disease has ever been eliminated by antibiotics," Dean said. On the other hand, old menaces such as smallpox have effectively been eliminated by vaccines, she said.
Several groups, including one in Oakland, are working on trachoma vaccines, Dean said. She estimated the time-frame for the arrival of an effective vaccine at "5 to 10 years, if dreams come true."
To learn more about the fight against trachoma, visit the International Trachoma Initiative.