Chlamydia (trachomatis, pneumoniae, psittacci, pecorum)

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What is Chlamydia?

There are three main species of chlamydia causing human infection - Chlamydia trachomatis, chlamydia pneumoniae (also known as Chlamydophila pneumoniae), and Chlamydia psittacci.

Chlamydia pneumonia and Chlamydia psittacci cause respiratory infections. Chlamydia trachomatis causes infections that can affect the eyes, urogenital area, or cause pneumonia in infants born to infected mothers depending on how the infection is transmitted. Trachoma is a nasty infection of the eyes that forms small granules along the conjunctiva (thin membrane covering the surface of the eye and inner surface of the eyelid). This can lead to ulceration, scarring and blindness.

Chlamydial trachomatis infection is one of the most common sexually transmitted infections (STIs) in the United States, UK and Australia. Chlamydial trachomatis is often included in the category of non-gonnococcal urethritis. A Chlamydia symptom is urethritis (inflammation of the urethra, the tube that carries urine from the bladder) that is not caused by Neisseria gonorrhoea.

Who gets Chlamydia?

Chlamydia organisms have a worldwide distribution.

C. trachomatis is now extremely common and the most common sexually transmitted infection in Australia. In particular men and women between 15 and 25 years of age are commonly affected. It is commonly assymptomatic so is easily passed on between sexual partners. There has been a steady rise in the incidence of Chlamydia trachomatis with a 76% increase between 1995 and 1999.

Men: Chlamydia is currently the most common STD in men. Young, sexually active men are at greatest risk. 20% of men with gonorrhoea will also have Chlamydia. Men suffer an anterior urethritis but approximately one quarter of men will have mild or no symptoms at all. 40% of non-gonococcal urethritis is due to Chlamydia.

Women In women the infection typically occurs in the endocervix and is very common with up to 5% of women affected. Women are much more commonly assymptomatic. Approximately 40% of women with gonorrhoea will have coexisting Chlamydial infection.

Children As Chlamydia trachomatis is sexually transmitted, it does not normally occur in children. However, infants can be acquire infections whilst in the womb of an infected mother. Infants get infections of the eyes, nose, throat or lungs. Neonatal conjunctivitis causes swelling, discharge and erythema and if not treated may lead to pneumonia. Chlamydia conjunctivitis occurs in approximately 25% of infants who have an infected mother. Infant pneumonia usually develops a few weeks after birth and occurs in 10-20% of infants exposed to the bug at birth.
Trachoma is common in the aboriginal population of Australia, being an important causative factor for corneal scarring and blindness.
There has been a steady rise in the incidence of Chlamydia trachomatis with a 76% increase between 1995 and 1999.
C pneumoniae and C psittacci are seen worldwide, being common causes of atypical pneumonia.

Predisposing Factors

Chlamydia trachomatis:
- For genito-urinary infection, unprotected sexual intercourse is the main cause of Chlamydia infection. Although patients with any sexually transmitted disease (STI) are at increased risk of co-infection with another STI, co-infection of chlamydia and gonorrhea is most common. If you are under 25, have changed your sexual partner in the last three months, do not use condoms or you or your partner has another sexually transmitted disease, you are a greatest risk of Chlamydia.
- Chlamydia trachomatis can be transmitted via the birth canal of an infected mother, and neonates exposed to chlamydia at birth may develop conjunctivitis (inflammation of the thin conjunctiva overlying the eyeball) 5-13 days later.
- Ocular infection (trachoma or adult inclusion conjunctivitis) is transmitted through contaminated hands, droplets, clothing, and flies.
Respiratory infection with Chlamydia pneumoniae is transmitted from person to person through infectious aerosols.
Chlamydia psittacci is carried by many species of birds (especially parrots) and can be transmitted to people in contact with the infected birds.

Progression

Chlamydia trachomatis can cause urethritis (inflammation of the urethra) in men. In women it causes cervicitis (inflammation of the cervix- the opening of the womb), urethritis or salpingitis (inflammation of the fallopian tubes which carry eggs from the ovaries). Reiter syndrome is a systemic syndrome affecting the eyes, joints and urethra and is frequently preceded by genital Chlamydia infection.
LGV is a type of genital infection in which there is a genital lesion, followed by inflammation and swelling of lymph nodes in the inguinal region and systemic signs, with chronic ulceration possibly as a sequelae.
Trachoma can lead to progressive inflammation of the conjunctiva on the eyelid, with scarring of the eyelid and inturning of the eyelashes - which can lead to corneal abrasions an potentially blindness.
Infant pneumonia and neonatal conjunctivitis normally occur 1 to 3 weeks after birth and are usually uncomplicated.
Chlamydia psittacci and Chlamydia pneumoniae are usually uncomplicated. However, Clamydia psittacci can cause a severe pneumonia with disease affecting several organ systems in epidemic cases.

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