Trichomoniasis

Organism

Trichomoniasis is caused by a motile, flagellated protozoan Trichomonas vaginalis, which infects the vagina, urethra and paraurethral glands and may less commonly infect the ectocervix, bladder, Bartholin's glands and prostate.

The incubation period is 4-28 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. Infectivity is low to moderate. Carriage in men is often self-limited although they may present with urethral discharge and/or dysuria.

Clinical presentation

Trichomoniasis causes an irritating discharge with associated vulvitis and vaginitis. The discharge is usually profuse, malodorous and often frothy. Vaginal pH is >4.5. Microscopic ulceration may be present on the cervix ('strawberry cervix'). Females may be asymptomatic, and males are usually (75%) asymptomatic. Chronic infection may be present with itch and dyspareunia (pain on sexual intercourse).

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.

Trichomoniasis is associated with premature rupture of membranes, low birth weight delivery and premature labour, as well as increased risk of HIV transmission. It can also be associated with other inflammatory conditions such as candidiasis and bacterial vaginosis.

Infected neonates can present with fever, respiratory problems, UTI, nasal discharge, and vaginal discharge. 

STI Atlas (external site)

Investigations

Detection of trichomoniasis can be difficult.

NAAT has superior sensitivity and specificity and can be used on vaginal swabs (SOLVS or posterior fornix) or FVU samples if available. 

Other tools include:

  • Vaginal pH >4.5
  • Immediate microscopic examination of wet prep vaginal sample for motile trichomonads if facilities are available. This method detects 50-60% of women with vaginal trichomoniasis and a smaller proportion of infection in men
  • Gram stain only detects up about 25% of infected females
  • Culture will detect a much larger proportion of women with vaginal trichomoniasis but is slow and generally not available. 
  • Immediate microscopic examination of a wet prep – if facilities are available. Sensitivity is about 50 to 70 per cent in experienced hands.
Treatment

Standard

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

        or

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

        or

  • metronidazole 400 mg orally, 12-hourly for 5-7 days.

Advise avoidance of alcohol with metronidazole for 24 hours afterwards and with tinidazole (72 hours afterwards). If there is relapse, the longer course of metronidazole may be required.

Women with co-existant BV should be offered the longer duration of treatment. 

Pregnancy

It is unclear whether treatment in pregnancy affects the risk of premature rupture of membranes and pre-term delivery, however symptomatic pregnant women should be tested and treated. Women at risk of, or with HIV, should be tested and treated in the first trimester. Routine testing is not recommended for other asymptomatic pregnant women. Metronidazole can be safely used in all stages of pregnancy. 

  • 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.

Vaginal treatment with metronidazole gel is not recommended as cure rates are less than 50%. 

Breastfeeding 

Breastfeeding women can be treated with a single 2mg dose of metronidazole. It is secreted in breast milk although doses infants receive are less then those used to treat infection in infants. A cautious approach is for mothers to express and discard their milk for 12-24 hours to allow excretion of the drug. 

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.

Follow up

Review the patient at one week to assess resolution of symptoms and to review contact tracing. NAAT test of cure can be done 2 weeks after treatment if the patient prefers. 

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.