Describe trichomoniasis — its aetiology, clinical features and management.

Definition

Trichomoniasis is a sexually transmitted infection of the vagina caused by Trichomonas vaginalis, a flagellated motile protozoan.

Clinical Features

A profuse, frothy, greenish-yellow, offensive vaginal discharge with vulval itching and soreness, dysuria and dyspareunia; on examination a "strawberry" cervix (punctate haemorrhages) may be seen, and the vaginal pH is raised (> 4.5).

Diagnosis

Wet-mount microscopy of the discharge shows the motile, flagellated trichomonads; culture and NAAT are more sensitive. A positive amine (whiff) test may coexist.

Treatment

• Metronidazole (single 2 g dose or a 7-day course) — oral, since the infection is vaginal and urethral.
• Treat the sexual partner simultaneously (it is an STI) and advise abstinence until both are cured; screen for other sexually transmitted infections.

Complications

Trichomoniasis is associated with preterm labour and low birth weight in pregnancy, an increased risk of acquiring and transmitting HIV and other sexually transmitted infections, and ascending infection/PID; the "strawberry cervix" reflects the intense inflammation.

Organism and Transmission

*Trichomonas vaginalis* is an anaerobic flagellated protozoan transmitted almost exclusively sexually; it infects the vagina, urethra and paraurethral glands, with an incubation period of about 4–28 days.

Note on Treatment

The patient is advised to avoid alcohol while taking metronidazole (a disulfiram-like reaction); metronidazole is also used (with caution) in pregnancy.

A Note on WHY Trichomoniasis Is an Sti — and the Partner Must Be Treated

A useful and frequently-neglected point is understanding why treating the woman alone for trichomoniasis guarantees her reinfection. Unlike candidiasis (an overgrowth of a commensal) and bacterial vaginosis (a disturbance of the normal flora), trichomoniasis is a true sexually transmitted infection caused by a flagellated protozoan, Trichomonas vaginalis, which is acquired from a sexual partner. The crucial fact is that the male partner is usually asymptomatic — he harbours the organism in the urethra and prostate without complaint, and therefore neither seeks nor is offered treatment. If only the woman is treated, she is promptly reinfected at the next intercourse (the so-called 'ping-pong' infection), and the cycle repeats indefinitely, generating apparent 'treatment failure' that is really reinfection. Hence the rules: treat the woman and all sexual partners simultaneously with oral metronidazole, advise abstinence (or condoms) until both have completed treatment, and — since it is an STI — screen for other sexually transmitted infections, including HIV. Two further points: topical treatment is inadequate (the organism also colonises the urethra and Skene's glands, so systemic treatment is required); and in pregnancy trichomoniasis is associated with preterm birth and low birth weight.

Treat the partner simultaneously to prevent reinfection.

• Trichomoniasis: a true STI caused by Trichomonas vaginalis (a flagellated protozoan) — profuse, frothy, greenish-yellow, offensive discharge with pruritus and dyspareunia.
• Signs: vaginal pH >4.5, a 'strawberry cervix' (punctate haemorrhages); diagnosis by motile trichomonads on a saline wet mount.
• Treat the partner — he is usually asymptomatic; treating the woman alone leads to 'ping-pong' reinfection.
• Treatment: oral metronidazole (2 g single dose or 400 mg twice daily for 7 days) for the woman and all partners; topical treatment is inadequate.
• As an STI, screen for other infections including HIV; in pregnancy it is associated with preterm birth and low birth weight.