Trachoma

**Definition:** A disease caused by an infection with the gram-negative bacteria Chlamydia trachomatis serovars A, B, and C. This disease is characterised by a roughening of the inner surfaces of the eyes, and inflammation that may lead to superficial vascularization of the cornea (pannus) and scarring of the conjunctiva. Long term effects include blindness or other visual impairments. Transmission is by direct or indirect contact with the eyes or nose of an infected individual.

**Long definition:** A chlamydial conjunctivitis of insidious or abrupt onset; the infection may persist for a few years if untreated, but the characteristic lifetime duration of active disease in hyperendemic areas is the result of frequent reinfection. The disease is characterized by the presence of lymphoid follicles and diffuse conjunctival inflammation (papillary hypertrophy), particularly on the tarsal conjunctiva lining the upper eyelid. The inflammation produces superficial vascularization of the cornea (pannus) and scarring of the conjunctiva, which increases with the severity and duration of the inflammatory disease.