Genital chlamydial infection is the most common treatable, notifiable infection throughout much of the world, including Australia and New Zealand.

Both men and women may be affected by infection with chlamydia, but young women bear the brunt of this infection, which may result in serious reproductive health sequelae.

Local epidemiology

Chlamydia continues to hold the lamentable title of most commonly notified infection in Australia. In 2011, 80 807 notifications of this sexually transmissible infection (STI) were made to the National Notifiable Diseases Surveillance System (NNDSS), almost twice as many notifications as received in 2005.¹ The NNDSS monitors chlamydia through passive surveillance of cases reported to health departments by doctors or laboratories.

Passive surveillance, however, does not allow us to determine if chlamydia notifications are rising simply because more people are being tested. In fact, a recent analysis of the Australian Collaboration for Chlamydia Enhanced Sentinel Surveillance (ACCESS) concluded that there has been a modest increase in prevalence and much of the sharp increase in notification data in recent years is most likely due to increased testing.² Regardless of the reason, current rates of chlamydia are cause for concern. It is thought that four- to six-times as many chlamydia infections occur as are notified – notifications just represent the tip of the infection iceberg.

There are significant gaps in our knowledge of the natural history and pathogenesis of chlamydia infection. The exact duration of an untreated infection is not known, though it is thought to be in the order of months to years – this can make it very difficult to determine when a person acquired their infection and makes counselling of couples particularly tricky! It is likely the clinical manifestations of chlamydia are due to a combination of tissue damage from chlamydial replication and host inflammatory response.

Chlamydia trachomatis preferentially infects the columnar or transitional epithelium of the urethra, with spread to the epididymis; the endocervix, with spread to the endometrium, fallopian tube and peritoneum; and the rectum. Most of the time chlamydia is an asymptomatic infection. In men, it may cause a urethritis (typically dysuria and a mild to moderate whitish or clear urethral discharge) and epididymitis. In women, it may cause a cervicitis (mucopurulent discharge and an oedematous, congested cervix that may bleed on contact), urethritis, bartholinitis, salpingitis and perihepatitis (Fitz-Hugh-Curtis syndrome). If left untreated, infection in women may cause inflammation and scarring and lead to well-known reproductive sequelae: pelvic inflammatory disease, tubal factor infertility and ectopic pregnancy. Reactive arthritis can been associated with Chlamydia trachomatis infection.

Chlamydia in pregnancy

Adverse pregnancy outcomes have been associated with chlamydia infection, including premature rupture of membranes, preterm delivery and low birth weight. At least 60–70 per cent of exposed infants acquire chlamydial infection, which may result in neonatal conjunctivitis and pneumonia. Screening and treatment of pregnant women is the most effective way to prevent transmission and disease in the newborn.

Testing

Nucleic acid amplification tests (NAATs), such as polymerase chain reaction (PCR), remain the gold standard for diagnosis of Chlamydia trachomatis, owing to their high sensitivity and specificity. PCR testing allows sampling by first catch urine (FCU) in both men and women. It is not necessary to ask the patient to hold their urine prior to obtaining a FCU sample; in fact doing so may result in a lost opportunity if they fail to return for testing. Self-collected vaginal or rectal swabs are also possible, with sensitivity no less than that of practitioner-collected cervical swabs. This simple and efficient method of testing has improved the acceptability of screening to patients and has allowed chlamydia testing to be rolled out in a variety of clinical and non-clinical settings.

Treatment

Chlamydia is easily treated with a single one-gram dose of azithromycin. The National Management Guidelines for Sexually Transmissible Infections³ also recommend doxycycline 100mg twice daily for seven days as an alternative first-line regimen. Single dose antibiotics, such as azithromycin, are preferred in the management of STIs due to improved compliance. Single dose azithromycin is both safe and effective in pregnant women.

Chlamydia control has long been blessed with an absence of drug resistance. Recent evidence, however, points to a possible increase in azithromycin treatment failures in both men and women, at levels of greater than five per cent.⁴ While treatment failure is an uncommon scenario, it could perhaps be kept in mind for recurrent infection, once re-infection has been excluded.

Prevention

Single dose antibiotic treatment, partner testing and treatment, contact tracing; screening and health education form the foundation of chlamydia control strategies.

Infection with chlamydia does not result in adequate immunity to prevent re-infection. Repeat infections are common and may result in higher rates of sequelae. All women with a positive test for chlamydia should be asked to return for repeat screening in three months. Re-screening too soon may result in a false positive result as the DNA of dead bacteria continue to be detected by PCR for three weeks or more after treatment. Innovative ways to encourage people to return for follow up screening have been trialled, including SMS reminders, posting testing kits to the patient’s home and offering payments of some kind.

To prevent re-infection of the index case, and ongoing spread within the community, sexual partners should be tested and presumptively treated with azithromycin. Most people feel comfortable to notify their sexual partners themselves, though some may require assistance. The Australasian Contact Tracing Manual⁵ provides guidance on the process of contact tracing and specifies that sexual partners for the previous six months be notified. Local sexual health clinics and public health units may assist in the process of contact tracing, and the ‘Let Them Know’ website can also send messages to sexual contacts of people with a range of STIs.

Education is always an important part of prevention and a positive chlamydia diagnosis provides a great opportunity to discuss safer sex behaviour, including consistent condom use.

Conclusion

Chlamydia is an important sexually transmissible pathogen in Australia that can cause serious reproductive health sequelae. Chlamydia control should be a manageable goal: it’s easy to test for and easy to treat. Yet it eludes us. Every effort is required to continue to increase testing in high-risk populations. As chlamydia is often asymptomatic, people may not present specifically for testing. Screening for chlamydia may need to be opportunistic and should be offered to all women under the age of 29, in particular those that have had unprotected sex, recently changed partners or are attending as part of antenatal screening.