Infection: Trichmonas; TV; Trichomoniasis; Trichmonas vaginalis infection

Brief description:
  • A type of protozoa that cases vaginal and urethral infection.
  • In NZ, unlike other STIs, Trichomonas is more common in women aged >25. It is also more commonly seen in those of Maori or Pacific ethnicity, and in areas of social deprivation.
  • Up to 50% of women and the majority of men will be asymptomatic.
  • Vaginal discharge is the commonest symptom, which may be malodourous and frothy. Also causes vulvovaginal itch, vulval dermatitis and post-coital bleeding.
Did you know?

Infection can persist for years in women if untreated.

Who should I test?
  • Test women with vaginal discharge or other vaginal and vulval symptoms.
  • Not a recommended test for men with urethritis – reserved for persistent cases.
  • It can take up to 2 weeks to test positive if infection occurs relating to specific sexual event.
  • Male sexual contacts should be treated empirically rather than tested.
Test of choice:

Request Trichomonas NAAT

NAAT/PCR on a low vaginal swab (self- or clinician-collected; chlamydia and gonorrhoea testing should be done also, and can be shared on same swab).

  • A specific kit is usually required for NAAT testing e.g. the Aptima swabs/urine kit.
  • Excellent sensitivity – a negative teston a well-collected sample makes the diagnosis very unlikely
  • Excellent specificity – a positive testin an at risk person makes the diagnosis highly likely
  • First void urine may also be used in women, but has lower sensitivity.

If testing in a male is required discuss with the clinical microbiologist first.

Tests to avoid/specialist tests:
  • Culture on a high vaginal swab is an acceptable alternative if NAAT/PCR is not available, however it is less sensitive and slower.
  • Wet prep microscopy is no longer recommended due to limited sensitivity.
Other considerations:
  • Co-infection with other STIs is common.
  • Test of cure is not required if symptoms resolve.
  • If symptoms persist, or there are other exposures, don’t retest within 4 weeks of treatment, as the test may remain positive due to residual dead organisms.