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Key Features

  • Caused by Trichomonas vaginalis

  • Infects 3.7 million people each year in the United States

  • Has been associated with adverse pregnancy outcomes

  • Urethritis seen in 50% of males who have infection

  • Male partners of females with trichomoniasis have a 22% chance of contracting infection

  • Urethritis develops in half of males with infection

  • Rescreening for T vaginalis at 3 months following initial infection is recommended for women due to the high rate of reinfection

Clinical Findings

  • Symptomatic vaginitis with vaginal itching, a green-gray malodorous frothy discharge, and dysuria

  • Occasionally postcoital bleeding and dyspareunia may be present

  • Vulva may be erythematous

  • Cervix may be friable


  • Mixing the discharge with normal saline facilitates detection of the flagellated protozoan on microscopic examination (wet preparation); sensitivity is only 60–70%

  • Culture and nucleic acid amplification testing are available when the diagnosis is unclear

  • Two FDA-approved, point-of-care antigen-based detection assays for T vaginalis are available

    • However, false-positive results are problematic in populations with low disease prevalence

    • Both antigen assays are performed on vaginal secretions

    • Sensitivity is > 83% and a specificity is > 97%

  • Trichomonal urethritis frequently causes a positive urine leukocyte esterase test and white blood cells on urethral smear


  • Recommended regimens

    • Metronidazole, 2 g orally as a single dose or

    • Tinidazole, 2 g orally as single dose

  • Alternative regimen: metronidazole, 500 mg orally twice daily for 7 days

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