Trichomonas Vaginalis

Medicine > Infection

Background knowledge 🧠

Definition

Trichomonas vaginalis is a protozoan parasite that causes trichomoniasis, a sexually transmitted infection (STI).
It primarily affects the urogenital tract.
Most common in women but can also affect men.

Epidemiology

Worldwide, trichomoniasis is one of the most common non-viral STIs.
More prevalent in sexually active women aged 16-35 years.
Higher prevalence in resource-limited settings.
UK prevalence: Approximately 0.2% among women in reproductive age.
Increased risk in individuals with multiple sexual partners.

Aetiology and Pathophysiology

Caused by the anaerobic protozoan Trichomonas vaginalis.
Transmission primarily through sexual contact.
In women, infects the vagina, urethra, and paraurethral glands.
In men, primarily affects the urethra, but may also infect the prostate.
Disruption of vaginal flora (e.g., reduction of Lactobacillus) may increase susceptibility.
Can survive in the genital tract for months to years if untreated.

Clinical Features 🌡️

Symptoms

In women: Frothy, yellow-green vaginal discharge with an unpleasant odour.
Vaginal itching and irritation.
Dysuria and urinary frequency.
Symptoms may worsen during menstruation.
In men: Often asymptomatic but can include urethral discharge and dysuria.
Up to 50% of women and 90% of men may be asymptomatic.

Signs

Erythema and oedema of the vulva and vagina.
Strawberry cervix (punctate hemorrhages on the cervix) in approximately 2% of cases.
Vaginal pH typically >4.5.
Thin, frothy discharge visible on speculum examination.
May have associated cervicitis.

Investigations 🧪

Tests

Microscopy of vaginal or urethral swab showing motile trichomonads (flagellated protozoa).
Culture: Sensitivity approaches 95% but results may take 3-7 days.
NAAT (Nucleic Acid Amplification Test) is the gold standard due to high sensitivity and specificity.
Wet mount microscopy may be done in clinics but has lower sensitivity.
Consider screening for other STIs, such as Chlamydia and Gonorrhea.

Management 🥼

Management

First-line treatment: Metronidazole 400-500 mg orally twice daily for 5-7 days.
Alternative: Single dose of 2g metronidazole (increased side effects).
Treat sexual partners simultaneously to prevent reinfection.
Advise abstaining from sexual activity until treatment completion and symptoms resolve.
Pregnancy: Metronidazole is considered safe but discuss risks/benefits.
Consider alternative antibiotics if metronidazole is contraindicated.
Re-test in 3 months for recurrent infections.

Complications

Increased risk of HIV transmission and acquisition.
Pelvic inflammatory disease (PID) in women.
In pregnant women: Preterm birth, low birth weight, and postpartum endometritis.
Prostatitis and urethritis in men.
Potential for long-term genitourinary complications if untreated.

Prognosis

Excellent with appropriate treatment.
High cure rates with metronidazole therapy.
Risk of recurrence if sexual partners are not treated.
Reinfection is common due to poor partner compliance or reinfection.
Routine follow-up recommended to ensure clearance.

Key Points

Trichomoniasis is a common and treatable STI caused by Trichomonas vaginalis.
Symptomatic women often present with frothy, malodorous discharge.
Men are frequently asymptomatic but can contribute to transmission.
NAAT is the preferred diagnostic method due to high sensitivity.
Metronidazole is the treatment of choice; sexual partners must be treated to prevent reinfection.
Complications include increased risk of HIV transmission and adverse pregnancy outcomes.
Routine follow-up is essential to ensure treatment efficacy and prevent recurrence.

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