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Sexual Health

Trichomoniasis

Trichomoniasis is a sexually transmitted infection caused by Trichomonas vaginalis; it is often asymptomatic, but may cause vaginitis or urethritis, and diagnosis requires appropriate laboratory testing followed by systemic treatment and partner management.

In a nutshell

Trichomoniasis is a sexually transmitted protozoal infection that may be asymptomatic. Women may have frothy yellow-green discharge, vulvovaginal irritation and dysuria; men may have urethral symptoms or no symptoms. NAAT is the most sensitive test, and treatment is an oral nitroimidazole plus partner management.

Classic presentation

A woman with vulvovaginal irritation and frothy yellow-green discharge; a strawberry cervix is a classic but uncommon sign. The male partner may be asymptomatic.

Key points

  • Trichomonas vaginalis is sexually transmitted and infection is often asymptomatic, especially in men.
  • NAAT is the most sensitive commonly available test; a negative wet mount does not exclude infection.
  • Treat with systemic oral metronidazole and manage current and recent partners through sexual health services.
  • Offer a full STI screen including HIV and assess for pregnancy, PID, testicular disease or systemic illness.
  • Persistent or recurrent symptoms require checking adherence and re-exposure before specialist treatment-failure management.

First-line investigation

NAAT using the locally validated vaginal, penile-meatal, urethral or urine specimen, alongside examination and a full STI screen where indicated.

Management

Assess severity, pregnancy and alternative diagnoses

  • Check for fever, pelvic pain, PID, testicular disease, systemic illness, pregnancy and other STI features before treating as uncomplicated trichomoniasis.1,2

Confirm with an appropriate test and treat systemically

  • Use a locally validated NAAT where available and treat confirmed infection with oral metronidazole; do not rely on a negative wet mount or use vaginal gel alone.1,3

Adapt the pathway for pregnancy and breastfeeding

  • Treat symptomatic pregnancy promptly using the BASHH pregnancy regimen and verify current BNF advice for individual pregnancy, breastfeeding, allergy and interaction questions.1,3

Treat partners and screen for coinfection

  • Offer a full STI screen including HIV, arrange partner notification, and treat current partners and partners from the preceding 4 weeks regardless of their result.1,2

Re-test only when symptoms or recurrence justify it

  • Check adherence and re-exposure first; if symptoms persist or recur, use NAAT at the appropriate interval and refer to sexual health for treatment failure or true nitroimidazole allergy.1

Exam traps

  • The strawberry cervix is classic but uncommon; its absence does not exclude trichomoniasis.
  • A negative wet mount does not exclude infection because sensitivity is limited, especially in men.
  • Vaginal metronidazole gel alone is inadequate; treatment requires systemic therapy.
  • Treat current and recent partners even if they have no symptoms or their test is negative, following sexual-health guidance.
  • Do not label pelvic pain, fever or testicular disease as uncomplicated trichomoniasis; assess for PID, another STI or another diagnosis.

Illustrations

Trichomonas vaginalis on stained microscopyA May-Grünwald–Giemsa-stained micrograph of Trichomonas vaginalis showing its pear-shaped body and flagellar structures.Dr Graham Beards, Wikimedia Commons · CC-BY-SA-4.0

Key sources

  1. BASHH, UK national guideline on the management of Trichomonas vaginalis, 2021 (Latest located dedicated UK guideline for diagnosis, treatment, pregnancy, partner management, treatment failure and follow-up. The BASHH guideline page indicates review planning in 2026; no replacement or addendum was located at the access date.)Published 14 Jun 2022
  2. NHS, Trichomoniasis (Current NHS information on symptoms, testing, metronidazole treatment, partner treatment, abstinence and complications)Published 16 Jul 2025
  3. BNF, Metronidazole (Current UK prescribing cross-check for metronidazole contraindications, interactions, pregnancy and breastfeeding advice; detailed BNF access is restricted in this environment.)
  4. NHS Ayrshire & Arran Medicines, Trichomonas vaginalis (UK antimicrobial pathway cross-check for oral metronidazole, pregnancy or breastfeeding cautions, STI screening, partner treatment and abstinence; local policy must be followed.)

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.