Epidemiology - Chlamydia trachomatis

Epidemiology

C. trachomatis is distributed worldwide.

◗ Geographical distribution

LGV caused by C. trachomatis is highly prevalent in Asia, Africa, and South America. The disease occurs sporadically in Europe, Australia, and North America. LGV is responsible for 10% of genital ulcer disease in developing countries. Genital chlamy-diasis and gonorrhea caused by Neisseria gonorrhoeae may often coexist. These two pathogens are the most common causes of epididymitis in sexually active adult men. Trachoma is world-wide in distribution and nearly 500 million people are infected worldwide. The infection is endemic in the Middle East, Africa, Far East, and India. The condition is responsible for blindness in 7–9 million patients. Trachoma is particularly prevalent in these countries because of overcrowding, poor sanitation, and poor personal hygiene. All these factors facilitate transmission of infection. Moreover, C. trachomatis is the common cause of infant pneumonia worldwide.

◗ Habitat

C. trachomatis is a strict human pathogen. It is found inthe conjunctiva and genitourinary tract in an infected host. C. trachomatis also inhabits the respiratory and gastrointestinaltracts of humans.

◗ Reservoir, source, and transmission of infection

Humans are the only natural host of C. trachomatis and thus are only significant reservoir of infections. Ocular discharges from infected cases are the common source of eye infection for tra-choma. Occasionally, respiratory discharges and human feces can be a source of infection.

Trachoma is transmitted by eye-to-eye contact through (a) droplets, (b) contaminated hands, and (c) contaminated clothings. All these methods facilitate transmission of ocu-lar discharges from the eyes of infected children to those of normal children. Trachoma is also transmitted by inoculation of respiratory droplets or by ingestion of food and water con-taminated with human feces. Genital discharges are the source of infection for adult inclusion conjunctivitis. Adult inclusion conjunctivitis is usually transmitted by orogenital contact and also by autoinoculation. Although rare, eye–hand transmis-sion has been reported for adult inclusion conjunctivitis.

Inclusion conjunctivitis in the newborns is acquired by the infants born vaginally from mothers who are infected with C. trachomatis. C. trachomatis eye infection occurs in approxi-mately 25% of infants whose mothers’ genital tract is infected with C. trachomatis.

Infected genital discharge is also the source of infection for pneumonia of the newborn. Pneumonia develops in 10–20% of infants during their birth through an infected birth canal. Chlamydial genital infections are usually caused by vaginal, anal, and oral sexual contact.