50: Trachoma

Classification: ICD-9 076.1; ICD-10 A71

Syndromes and synonyms: Chronic follicular conjunctivitis.

Agent: Repeated re-infection with Chlamydia trachomatis serovars A, B, Ba, and C, an obligate intracellular bacterium. The genital serovars D to K can infect the conjunctiva, but generally do not lead to blindness as they cause self-limited infections that typically do not recur.

Reservoir: Humans.

Vector: Flies contribute to the spread of ocular serovars of C. trachomatis.

Transmission: Repeated direct contact with infected secretions from infected individual (mainly from eye or nose); also by hands and fomites (shared clothes, towels or bedlinen). Flies also play a role in the transmission. High risk of infection in close contacts of infected individuals.

Incubation Period: 5 to 12 days for conjunctivitis; years to decades for trichiasis and eventually corneal damage and blindness. Repeated re-infection over many years is required for deposition of sufficient conjunctival scar to lead to the blinding complications; host genetic factors are probably also important.

Clinical findings:

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