Trachoma Still Leading Cause of Blindness in Developing World

Trachoma* remains the leading infectious cause of blindness in the developing world, affecting more than 40 million people, reports UNC epidemiologist James Cook in this week's NEJM. Three million are visually impaired because of this entirely treatable disease, and 500 million remain at risk. Current endemic areas include much of Africa, southeast Asia, Australia, and Brazil.

An initiative to eradicate the disease, the Alliance for the Global Elimination of Blinding Trachoma by the Year 2020, has been established by WHO, and the associated World Health Assembly supports the use of single-dose azithromycin (20 mg/kg for children; 1g/kg for adults) for secondary prevention. Consequently Pfizer, which manufactures azithromycin under the trade name Zithromax, has donated the drug for the eradication initiative and, with the Edna McConnell Clark Foundation, has created the International Trachoma Initiative. (Gasp. A pharma company's doing something commendable.)

The efforts of the WHO initiative and others have been at least partly successful, according to Cook. The estimated number of infected individuals worldwide dropped from 100 million in 1996 to 43 million this year. Fifteen countries have national control programs, and approximately 74 million people have been treated through initiatives since 1998. Trachoma has evidently been eliminated in Morocco. (Cook writes that WHO is currently defining trachoma-elimination criteria.)

Success has also been achieved in Tanzania, according to correspondence in the same issue of the NEJM. UK investigators write that 1 or 2 rounds of mass treatment with azithromycin may be sufficient to eliminate trachoma in areas where infection levels are moderate, such as in Tanzania. (WHO currently recommends 3 annual treatments in areas with moderate infection levels.)

Despite the promising outlook, Cook raises a number of concerns with respect to trachoma-eradication programs, including the possible emergence of bacterial resistance with mass treatment. However, he believes that the eradication of trachoma-related blindness is entirely possible by 2020. 

*Chronic keratoconjunctivitis due to infection with serovars A, B, Ba, or C of Chlamydia trachomatis.

Image of trachomatous conjunctival scarring from WHO trachoma grading cards.