Trachoma, contagious infection of the eye caused by Chlamydia trachomatis, a bacteria related to the organism that causes psittacosis. Infection is spread by the bite of a host fly. Characterized by hard pustules or granular excrescences on the inner surface of the eyelids, inflammation of the membrane, and subsequent involvement of the cornea, trachoma is a major cause of blindness in some villages in northern Africa. It most commonly occurs among populations living under poor sanitary conditions.

 The disease begins after an incubation period of five to seven days with inflammation of the eye. Ensuing symptoms are considerable discharge of pus, swelling of the lids, tearing, and increased sensitivity to light. It goes on in a few weeks to chronic swelling, formation of blisters in the eye, and destruction and scarring of the cornea, which eventually causes blindness. In its early stages trachoma responds readily to the topical, and sometimes oral, administration of broad-spectrum antibiotics. In the 1950s the World Health Organization instituted a broad program for elimination of the disease.