Understanding Trichomonas vaginalis
Trichomonas vaginalis is a flagellated protozoan parasite and the causative agent of trichomoniasis, the most common non-viral sexually transmitted infection worldwide. In the United States, an estimated 2–3 million cases occur annually. Despite its prevalence, trichomoniasis is underrecognized because most infections produce no symptoms — particularly in men.
Transmission occurs primarily through genital-to-genital sexual contact. Unlike many other STIs, trichomoniasis can also persist asymptomatically in the lower genitourinary tract for months or years. This underscores the importance of testing rather than relying on symptoms alone.
your board-certified provider, provides thorough evaluation and evidence-based treatment per the CDC 2021 STI Treatment Guidelines in a non-judgmental, clinically rigorous manner.
Symptoms by Sex
Symptoms in Women
- • Frothy, yellow-green vaginal discharge — the most characteristic finding
- • Vaginal itching, burning, or irritation
- • Dyspareunia (discomfort during intercourse)
- • Dysuria (burning with urination)
- • "Strawberry cervix" (colpitis macularis) — visible on clinical exam in ~2% of cases
Up to 70% of women are asymptomatic at the time of diagnosis.
Symptoms in Men
- • Urethral discharge (often mild or transient)
- • Dysuria or urethral irritation
- • Discomfort after ejaculation
The majority of men with trichomoniasis have no symptoms at all. Spontaneous clearance occurs in some untreated men, but transmission continues during this period.
CDC 2021 Treatment Guidelines
The CDC 2021 STI Treatment Guidelines updated the preferred treatment for trichomoniasis, particularly for women. Treatment differs by sex:
Metronidazole 500 mg
Twice daily (BID) for 7 days
The 7-day regimen is now preferred over single-dose for women, based on superior cure rates in clinical trials (cure rate ~95% vs ~85% for single-dose).
Metronidazole 2 g
Single oral dose
Single-dose therapy maintains excellent efficacy in men and supports adherence.
Important: Alcohol Interaction with Metronidazole
Metronidazole causes a disulfiram-like reaction with alcohol, producing nausea, vomiting, flushing, and tachycardia. Avoid all alcohol during treatment and for at least 72 hours (3 days) after completing your last dose. This includes alcohol in mouthwashes and some liquid medications.
Alternative Regimen (Metronidazole Allergy or Intolerance)
Tinidazole 2 g single oral dose (or 1 g daily x5 days) is the preferred alternative for patients who cannot tolerate metronidazole. It has comparable efficacy and a somewhat lower frequency of GI side effects. The alcohol interaction also applies to tinidazole — avoid for 72 hours after the last dose.
Partner Treatment & Recurrence
Partner treatment is essential — without it, reinfection rates are very high. All sexual partners from the past 60 days should be notified and treated. Patients and partners should abstain from sexual activity until both have completed treatment and are asymptomatic.
Recurrent trichomoniasis is common and most often caused by reinfection from an untreated partner rather than treatment failure. True metronidazole resistance exists but is uncommon. If infection persists or recurs despite completed treatment and partner treatment, your provider can coordinate re-testing and consider alternative regimens such as tinidazole or high-dose metronidazole.
Test of cure is not recommended for asymptomatic patients treated with the standard regimen. Retesting at 3 months is recommended for all patients due to high rates of reinfection.