Chlamydia: why a symptomless infection is the most dangerous

What is chlamydia and why does it deserve particular attention?

Chlamydia is the most common bacterial sexually transmitted infection, caused by Chlamydia trachomatis. According to WHO data, more than 129 million new cases of chlamydial infection are recorded worldwide each year, and the true number is considerably higher because so many people carry it without symptoms. In Ukraine chlamydia is consistently the most common bacterial STI, affecting mainly young people aged 15–29. The main danger of chlamydia is that it is silent: up to 70% of infected women and up to 50% of men have no complaints at all and continue to spread the infection unknowingly. Untreated, Chlamydia trachomatis causes ascending inflammation — in women endometritis, salpingitis and pelviperitonitis, which lead to tubal infertility, ectopic pregnancy and chronic pelvic pain. In men untreated chlamydia causes epididymitis, prostatitis and a potential reduction in fertility. Besides the urogenital forms, chlamydial infection can affect the rectum, the throat and the conjunctiva. Reactive arthritis (Reiter's syndrome) is an extragenital complication that develops in 1–3% of those infected and comprises a triad: urethritis, conjunctivitis and arthritis.

Clinical features and forms of chlamydial infection

Chlamydia has a varied clinical picture that depends on the site of infection and the patient's sex:

• Urogenital chlamydia in women: the incubation period is 7–21 days. Where symptoms do appear, women report mucopurulent vaginal discharge, bleeding between periods, dysuria, lower abdominal pain and pain during intercourse. Examination reveals erosion and swelling of the cervix (chlamydial cervicitis). Untreated, the infection spreads to the endometrium and the fallopian tubes, causing pelvic inflammatory disease (PID) in 10–40% of untreated women. Scarring of the tubes is the leading cause of tubal infertility.
• Urogenital chlamydia in men: presents as urethritis — mucopurulent urethral discharge, itching and burning on urination, discomfort in the perineum. Untreated, the infection can cause epididymitis — pain and swelling of the epididymis, which in severe cases leads to obstructive azoospermia and infertility. Chlamydial prostatitis is characterised by chronic pelvic pain and disturbance of urination.
• Extragenital forms: anorectal chlamydia is often symptomless and may present as proctitis (pain, mucopurulent rectal discharge, tenesmus); pharyngeal chlamydia is usually symptomless and rarely causes a sore throat; chlamydial conjunctivitis may be unilateral or bilateral, with purulent discharge and swelling of the eyelids. Lymphogranuloma venereum (LGV) is an invasive form caused by serovars L1–L3 that produces deep ulcers and lymphadenopathy.
• Complications: Fitz-Hugh–Curtis syndrome (perihepatitis) — acute inflammation of the liver capsule with pain in the right upper abdomen, mimicking cholecystitis or pleurisy. Reactive arthritis (Reiter's syndrome) — asymmetrical involvement of the large joints, developing 1–6 weeks after infection. Chlamydial infection during pregnancy increases the risk of premature labour, premature rupture of the membranes, and neonatal conjunctivitis and pneumonia in the baby.

Modern methods of diagnosis

Diagnosis rests mainly on laboratory testing, since the clinical picture is often absent or non-specific. Nucleic acid amplification testing (NAAT) is the gold standard: it detects Chlamydia trachomatis DNA or RNA in samples from the urethra, cervical canal, vagina, rectum and throat, and in a first-catch urine sample, with a sensitivity of 95–99% and specificity above 99%. Self-collected vaginal samples have a sensitivity comparable to clinician-collected ones, which makes screening more accessible. Culture (in McCoy cell culture) has high specificity but low sensitivity (50–70%); it retains value for determining antibiotic sensitivity where resistance is suspected and in forensic cases. Serology (IgG, IgA and IgM to C. trachomatis by ELISA or microimmunofluorescence) is of limited value in diagnosing uncomplicated urogenital chlamydia, but is useful in diagnosing LGV, reactive arthritis, tubal infertility and neonatal pneumonia. Screening recommendations: annual screening of all sexually active women under 25 and of older women with risk factors (a new partner, multiple partners, a history of STI). Men are tested if they have symptoms or as contacts.

Treatment: current protocols and recommendations

Treatment of uncomplicated urogenital chlamydia is effective and straightforward when the infection is found in time. The first-choice drug is doxycycline 100 mg twice a day for 7 days: recent meta-analyses have confirmed its advantage over azithromycin, particularly in rectal infection (effectiveness 97% against 82%). The alternative regimen is azithromycin 1 g as a single dose, which remains an option where doxycycline cannot be taken (pregnancy, intolerance). For pregnant women: azithromycin 1 g as a single dose, or amoxicillin 500 mg three times a day for 7 days. In complicated chlamydia (PID, epididymitis): doxycycline 100 mg twice a day for 14 days combined with ceftriaxone 500 mg intramuscularly as a single dose. Treatment of LGV: doxycycline 100 mg twice a day for 21 days. Treating the sexual partner at the same time is essential, even if they have no symptoms and whatever their test results. A test of cure by NAAT is recommended 4 weeks after treatment ends. Repeat screening 3 months after treatment is advised to exclude re-infection, which occurs in 10–20% of cases.

Prevention and protecting reproductive health

Prevention rests on three strategies: primary prevention, screening and treatment of contacts. Barrier contraception — consistent and correct use of condoms reduces the risk of transmission by 60–90%. Screening programmes are the most effective population-level tool: countries with systematic screening (Sweden, the United Kingdom, Australia) have achieved reductions of 30–50% in the prevalence of chlamydia and in the rate of PID. In Ukraine annual screening of sexually active women under 25 is recommended. Treating sexual partners: all partners from the past 60 days (or the most recent partner, if contact was earlier) should be tested and treated. Expedited partner therapy (EPT) — providing a prescription for the partner without a personal visit — is recommended by CDC and is being introduced in many countries. Information and counselling: explaining the nature of the infection, the need to abstain from sexual contact during the 7 days of treatment, and the importance of a test of cure and repeat screening. There is no vaccine against chlamydia at present, but several candidate vaccines are in phase I–II clinical trials, which gives grounds for cautious optimism.

When to seek help immediately

See a dermatovenerologist, gynaecologist or urologist for any unusual discharge from the genital tract, painful urination, lower abdominal pain or discomfort in the perineum — even if the symptoms are minimal, chlamydia can progress silently. An urgent examination is needed after unprotected sex with a new partner, or if a partner reports a positive STI test. Testing is essential for sexually active women under 25 even in the complete absence of complaints, because symptomless chlamydia is the most common cause of tubal infertility in young women. Seek help immediately for acute lower abdominal pain with fever — this may indicate PID, which requires hospital treatment. Pregnant women should be screened for chlamydia at the first antenatal visit and again in the third trimester if risk factors are present. Remember: chlamydia is completely curable when found in time, but every day of delay increases the risk of irreversible harm to reproductive health.