Can we eliminate trachoma?

Trachoma is the leading cause of preventable blindness worldwide. Although it disappeared long ago from Western Europe and the United States, trachoma is still as endemic as ever in parts of Africa, the Middle East, Australia, and South East Asia. Ocular strains of Chlamydia trachomatis cause repeated episodes of conjunctivitis in children. In teenagers and adults, the disease progresses through a cascade of conjunctival scarring, entropion, trichiasis, and finally blinding corneal ulceration. Most cases of the infectious conjunctivitis are not apparent without flipping a child’s lids, so aVected children rarely receive appropriate treatment. Treatment with oral or prolonged topical antibiotics can eliminate chlamydia in the majority of cases, 5 but treated children will almost inevitably be reinfected unless infection in the rest of the community is addressed. Thus, trachoma can only be reduced significantly through an extensive public health campaign that targets whole communities. The World Health Organization (WHO), in conjunction with non-governmental organisations and national health services, recently began implementing a programme designed to eliminate blinding trachoma. The WHO’s GET 2020 programme (global elimination of trachoma by the year 2020) has adopted a comprehensive set of control measures for trachoma endemic areas summarised as the SAFE strategy (Surgery for entropion/ trichiasis, Antibiotics for infectious trachoma, Facial cleanliness to reduce transmission, and Environmental improvements such as access to clean water and control of disease-spreading flies). Antibiotics are a key component of this programme, and Pfizer Inc has already donated nearly a million doses of azithromycin to Morocco and Tanzania for trachoma control, and has committed at least a million more to Mali, Ghana, and Vietnam. The GET 2020 strategy has been carefully designed by a consortium of scientists and public health experts from around the world. Optimism is high, but the question remains—will it work? There are many reasons to think that the current elimination eVorts will be successful. Theoretically, it is possible to eliminate chlamydial infection from a community with repeat mass antibiotic administrations, even without a 100% eVective treatment and without complete coverage. This is because ocular chlamydial infection progresses so slowly through a community that if antibiotics are administered frequently enough (that is, annually in most locations), then infection will not be given a chance to return to its previous prevalence before the next treatment. Thus, infection should progressively decrease and eventually disappear stochastically. In fact, determining the proper “dosing regimen” for a community is somewhat analogous to determining the dose frequency of an antibiotic in an individual using pharmacokinetics. In some studies, infection appears to return to a community after mass antibiotic administration even more slowly than had been anticipated, further validating this approach (Osaki Holm S, Jha H, Bhatta R, et al. Azithromycin distribution strategies for trachoma, submitted for publication). Another encouraging sign is that in many areas trachoma appears to be disappearing in the absence of any specific control measures. Trachoma is a disease of the rural poor. As living conditions have improved over large areas of the world in the last century, trachoma has also disappeared. Also, since urban poor have never been aVected to the same degree as rural poor, then current trends of mass urban migrations should reduce trachoma (although perhaps at the expense of an increase in other diseases). Interestingly, studies in Nepal and other areas have suggested that as trachoma disappears, the prevalence of clinical signs (follicular conjunctivitis) may actually overestimate the prevalence of ocular chlamydial infections in a community. 12 Public health programmes that monitor trachoma prevalence are forced to rely on the clinical examination because laboratory tests are prohibitively expensive; thus, many areas which appear to have hypoendemic trachoma by clinical examination may have even less disease than we currently think. Perhaps most encouraging is that there may very well be a margin of error in eliminating active trachoma—we may not have to completely eradicate disease to prevent blindness due to trachoma. Ophthalmologists know that a single episode of genitally transmitted C trachomatis eye infection (adult inclusion conjunctivitis) will not typically lead to scarring. Similarly, investigators have long felt that less frequent or less severe episodes of trachoma in children do not typically lead to cicatricial disease—only repeated, severe disease leads to blindness. Trachoma is a disease where most morbidity can be eliminated even without Br J Ophthalmol 2001;85:385–387 385