Trichomoniasis

Overview

Trichomoniasis is a sexually transmitted infection (STI) of the genital tract caused by the protozoan Trichomonas vaginalis. Women are the main carriers of the disease; men who are infected men are usually asymptomatic.

It is a preventable and curable STI. However, reinfection appears to be common.

Disease epidemiology

T. vaginalis is the most common non-viral STI. Globally, there were an estimated 156 million new cases of T. vaginalis infection among people aged 15 to 49 years old in 2020 (73.7 million in females, 82.6 million in males). Approximately one-third of new infections occur in the African region, followed by Regions of the Americas.

Pathogen

Trichomonas vaginalis

Transmission

T. vaginalis is most often transmitted through vaginal, anal, or oral intercourse with an infected individual.

Incubation period: 5 to 28 days.

Infectious period: Unknown but is presumed to last until treatment is completed. If untreated, it may persist for months or years.

Clinical features

Vaginal trichomoniasis may be asymptomatic in up to 50% of the cases or cause abnormal vaginal discharge (the classical frothy yellow-green discharge occurs in 10% to 30% of the cases), vulval itching, dysuria, or offensive odour. Other signs include vulvitis, vaginitis and 2% of patients have strawberry cervix. Up to 50% of men with T. vaginalis are asymptomatic and usually present as sexual partners of infected women. Some male patients may have symptoms of urethritis and rarely balanoposthitis.

If untreated, T. vaginalis infection in pregnant women is associated with adverse pregnancy outcomes, particularly premature rupture of membranes, preterm delivery, and delivery of a low birthweight infant. T. vaginalis infection at delivery may predispose to maternal postpartum sepsis.

Risk factors

Risk factors include:

• Unprotected sex with an infected person

• Having multiple sex partners

• Inconsistent condom use if the relationship is not monogamous

• History or current presence of other STIs

• A previous episode of trichomoniasis

Diagnosis

Tests for diagnosis include:

• Nucleic acid-based amplification testing (NAAT), which offers the highest sensitivity for the detection of T. vaginalis and should be the test of choice where available.

• Culture has a sensitivity of 75%–96% compared to microscopy and can detect T. vaginalis in men.

• Wet-mount microscopy can also be used but this is not a sensitive test in men.

• Point-of-care test e.g. OSOM Trichomonas Rapid Test (Genzyme Diagnostics, USA) has demonstrated a high sensitivity and specificity.

• Trichomonads are sometimes reported on cervical cytology (sensitivity of about 60%–80%) but there is a high false-positive rate of about 30%. Use of liquid-based PAP smear testing has shown enhanced sensitivity. The diagnosis should still be confirmed by direct microscopy of vaginal secretions or culture.

All women should be screened for other STIs and HIV.

Treatment and management

Both symptomatic and asymptomatic patients should be treated.

Recommended regimens for T. vaginalis in adults:

• Metronidazole 400mg–500mg orally 2 times a day, for 7 days

• Metronidazole 2g orally single dose

• Tinidazole 2g orally single dose

Pregnancy considerations:

T. vaginalis infection has been associated with adverse pregnancy outcomes; all infected pregnant women should be treated. Metronidazole in pregnancy has not been shown to be teratogenic or mutagenic and can be used during all stages of pregnancy or breastfeeding. Imidazole and metronidazole pessaries may be used to provide symptomatic relief, but oral metronidazole is needed for eradication of infection.

Metronidazole is secreted in breast milk and may affect its taste. Avoid high doses of breastfeeding or if using a single dose of metronidazole; breastfeeding should be discontinued for 12 to 24 hours to reduce infant exposure.

Persistent symptoms:

Patients with persistent symptoms treated with either regimen should be retreated with:

• Metronidazole 400mg orally 2 times a day, for 7 days.

If treatment failure or reinfection occurs, (excluding non-compliance), treat with:

• Metronidazole 2g orally daily for 5 to 7 days.

Failure after the third regimen should prompt antibiotic resistance testing.

Follow-up:

• Follow-up is unnecessary for asymptomatic patients.

Refer to the Department of Sexually Transmitted Infections Control (DSC) website for more information on alternative regimens.

Precaution, prevention, and control

Prevention of T. vaginalis:

• Inform current or recent sexual partners if a diagnosis of T. vaginalis has been confirmed

• Avoid sexual intercourse until treatment is completed

• Not having sex

• Consistent and correct use of condoms when engaging in sexual activity

• Limit the number of sex partners

• Get tested for STIs regularly

Management of sexual contacts:

Sex partners within four weeks prior to presentation of symptoms (or last sexual partner if more than four weeks) should be treated on epidemiological grounds and screened for other STIs. They should be advised to abstain from intercourse until they and their sex partners have been adequately treated and any symptoms have resolved. There is evidence to suggest that patient-delivered partner therapy might have a role in partner management for trichomoniasis.

Notification

Trichomoniasis is not a notifiable disease. Please refer to the Infectious Disease Notification for more information. 

Resources

Refer to the DSC website for more information on Trichomoniasis.