Question
Trichomonas vaginalis.
Answer
Trichomonas vaginalis: a flagellated, pear-shaped protozoan parasite, causing trichomoniasis, one of the most common non-viral sexually transmitted infections worldwide.
Morphology: exists only as a trophozoite (no cyst stage) — pear/oval shaped, approximately 10–20 μm, with four anterior flagella, an undulating membrane, and a prominent posterior axostyle.
Transmission: primarily sexual contact.
Clinical features: in women — frothy, malodorous, greenish-yellow vaginal discharge, vulvovaginal pruritus, and a “strawberry cervix” (punctate cervical haemorrhages) on examination; men are frequently asymptomatic carriers, occasionally presenting with mild urethritis.
Laboratory diagnosis:
- Wet mount microscopy — direct visualization of actively motile trophozoites in vaginal/urethral discharge (a rapid, classical bedside test, though only moderately sensitive).
- Culture (e.g., Diamond’s medium) — more sensitive than wet mount.
- NAAT (nucleic acid amplification test/PCR) — the most sensitive and specific modern method.
- Rapid antigen tests — point-of-care immunochromatographic assays.
Treatment: Metronidazole (or Tinidazole), with treatment of sexual partners recommended to prevent reinfection/further transmission.