Trichomonas vaginalis diagnosis and management

Last updated: June 2013

Diagnosis

Trichomonas vaginalis is uncommon in Australian urban populations and is seen in Indigenous populations and oversees populations.

Asymptomatic carriage is common.

Testing is offered to the following groups:

• women with vaginal discharge
• men with urethritis who have failed standard therapy
• contacts of trichomonas
• those identified by history to have risk exposure.

Microscopy

Diagnosis is by detection of trichomonads (motile flagellated protozoans) on light microscopy of a wet preparation of vaginal secretions from the posterior fornix in women, or urethral swab in men.

Sensitivity of wet prep is only 60 to 70%, from vaginal swabs and 30% from male urethral swabs.

Nucleic Acid Amplification Test

Note: NAAT refers to Nucleic Acid Amplification Test, such as PCR

• Preferred test and most sensitive
• first-void urine samples males and females
• high vaginal swab in women.

Culture

Not routinely available.

Treatment

Standard therapy

Metronidazole 2 g orally as one dose (B2) 

OR

Tinidazole 2 g orally as one dose (B3).

Failing short course

For patients failing short course therapy despite concomitant partner therapy, or in HIV co-infection 

Metronidazole 400 mg orally 12 hourly for 7 days (B2).

Alcohol should not be consumed during treatment with metronidazole or tinidazole and for 24 and 72 hours respectively after treatment.

Occasionally metronidazole resistance can occur if suspected discuss with a Sexual Health Physician.

Trichomonas infection in pregnancy

T. vaginalis infection is associated with premature rupture of the membranes, preterm delivery and low birth weight. However, some trials have found that treatment of trichomoniasis with metronidazole in pregnancy may increase premature birth and low birth weight. Screening in pregnancy is not routinely recommended.

Treatment should be offered after consultation with treating obstetrician.

Patient education

The following points should be discussed:

• the nature of the infection
• the need for empiric treatment of sex partners
• men are usually asymptomatic
• abstinence from sex until the patient and regular partner are treated and cured. Sexual activity may resume when therapy has been completed and both patient and partner are without symptoms
• offer testing for other STIs.

Contact tracing

Although trichomoniasis is not a notifiable disease contacts should be tested and treated.

Follow up

One week after completion of therapy for the following:

• check that the regular sex partner has been treated (if applicable)
• check on compliance for multi-dose regimen
• evaluate symptoms and signs
• check reaction to medication
• enquire about sexual activity since treatment
• retest if symptoms remain or recur
• perform test of re-infection at 3 months.

Further information

For further information on diagnosis and management of trichomonas vaginalis contact Adelaide Sexual Health Centre.

Disclaimer

These guidelines are based on review of current literature, current recommendations of the United States Centers for Disease Control and Prevention, World Health Organization, the British Association for Sexual Health and HIV and local expert opinion.

They are written primarily for use by Adelaide Sexual Health Centre staff and some flexibility is required in applying them to certain private practice situations.