Trichomoniasis is caused by a motile, flagellated protozoan Trichomonas vaginalis, which infects the vagina, urethra and paraurethral glands.

The incubation period is 4-20 days, average of 7 days. However many people are symptom free carriers for years. The period of communicability is for the duration of persistent infection which  may be for years. Contact infectivity is low to moderate.

Clinical presentation

The condition causes an irritating discharge with associated vulvitis and vaginitis. The discharge is usually profuse, and often frothy. Vaginal pH is >4.5. Microscopic ulceration is often present on the cervix. Females may be asymptomatic, and males are usually asymptomatic.

Unlike other STIs, there is also a higher prevalence in older women in areas where trichomonas infection is prevalent and women can remain infected for some years if not treated.

It is now documented that trichomoniasis is associated with premature rupture of membranes and premature labour, as well as increased risk of HIV transmission. It can also be associated with other inflammatory conditions such as candidiasis.


Trichomoniasis can be difficult to demonstrate.

  • Vaginal pH >4.5
  • Gram stain only picks up about 25 per cent of infected females
  • Immediate microscopic examination of a wet prep – if facilities are available. Sensitivity is about 50 to 70 per cent in experienced hands.

Additional cases can be picked up by Pap smears. More sensitive technologies such as culture and NAAT may be useful where available.



  • Metronidazole 2 g orally, as a single dose


  • tinidazole 2 g orally, as a single dose with food


  • metronidazole 400 mg orally, 12-hourly for 5 days.

Advise avoidance of alcohol with either metronidazole or tinidazole treatment and for 24 hours thereafter. If there is relapse, the longer course of metronidazole may be required.


  • Metronidazole 2 g orally, as a single dose (category B2)
  • Metronidazole 400 mg orally, 12-hourly for 5 days (category B2). Metronidazole can be used in the first trimester of pregnancy where the benefits outweigh the potential risks.
  • Clotrimazole 1 per cent vaginal cream can be used for 6 days (category A), but cure is less likely.
  • Medicines in pregnancy.

Related links

Management of partners
Trichomoniasis is always an STI and male partner(s) should also be treated. Making the diagnosis of trichomoniasis in an asymptomatic male is difficult if no NAAT is available. Therefore, male partners should be checked for other STIs and given empirical treatment with single dose metronidazole or tinidazole when they attend. Consider when infection may have occurred.
Review the patient at one week to assess resolution of symptoms and to review contact tracing.
Public health issues

This is not a notifiable disease.

Always test for other STIs.

If a child is diagnosed with an STI, issues of sexual abuse and/or sexual assault should be considered.