Trachoma is a disease of the eye and the leading infectious cause of blindness worldwide. It is caused by an obligate intracellular bacterium called Chlamydia trachomatis. Infection is transmitted from person to person by direct or indirect transfer of ocular and nasal discharges of infected people; indirect transfer includes carriage on the body of species of flies. Preschool-age children harbour the principal reservoir of infection. Models suggest that an individual requires more than 150 lifetime infections to develop the blinding complications of trachoma.
Trachoma is endemic in some of the world’s poorest populations, who live in rural and remote areas and have highly inadequate access to water, sanitation and healthcare. Africa is the most affected continent, but it also has the most widespread control efforts. The disease is also found in Central and South America, Asia, Australia, and the Middle East. As of 2 January 2020, 13 countries had reported achieving elimination goals. In 2019 alone, 92 622 people received surgical treatment for advanced trachoma and 95.2 million were treated with antibiotics. Despite these successes, the disease remains a serious public health concern, with an estimated US$ 8 billion annual loss in productivity due to blindness and visual impairment.
Infection is associated with inflammatory changes in the conjunctiva known as “active trachoma”. An individual’s immune system can clear a single episode of infection, but in endemic communities, re-acquisition of the organism occurs frequently.
After years of repeated episodes of active trachoma, the inside of the eyelid can become so severely scarred (trachomatous conjunctival scarring) that it turns inwards and causes the eyelashes to rub against the eyeball (trachomatous trichiasis), resulting in constant pain and light intolerance; this and other alterations of the eye can lead to scarring of the cornea. Left untreated, this condition leads to the formation of irreversible opacities, with resulting visual impairment or blindness. The age at which this occurs depends on several factors including local transmission intensity. In very highly endemic communities, it can occur in childhood, though onset of visual impairment between the ages of 30 and 40 years is more typical.
Women are blinded up to four times as often as men, probably due to more frequent contact with infected children.
Individuals living in the poorest and most remote communities of Africa, Asia, Australia, the Middle East, Central and South America and the Pacific Islands are at risk.
Trachoma can be prevented by limiting environmental risk factors. These include inadequate hygiene, crowded households, inadequate access to water and inadequate access to and use of sanitation. Infections usually begin at an early age and grow less frequent and shorter in duration with increasing age. Infections are most often acquired through family and contact with others with active disease. Repeated infections cause the most serious symptoms of the disease.
Trachoma can be eliminated as a public health problem using the SAFE strategy, comprising:
- Surgery to treat trachomatous trichiasis, the blinding stage of the disease;
- Antibiotics to clear infection, particularly mass drug administration of the antibiotic azithromycin, which is donated by the manufacturer to national programmes through the International Trachoma Initiative;
- Facial cleanliness; and
- Environmental improvement, particularly better access to water and sanitation.
WHO adopted the SAFE strategy in 1993 and continues in its mandate to provide leadership and coordination of international efforts to eliminate trachoma as a public health problem.