• Sexually transmitted urogenital infection caused by a pear-shaped, parasitic protozoan
  • Causes vaginitis/urethritis in women, nongonococcal urethritis in men
  • Association with infertility in epidemiologic studies
  • In pregnancy, increases risk of preterm labor, preterm premature rupture of membranes, small for gestational age infant, and possibly stillbirth
  • Synonym(s): trich; trichomonal urethritis



  • The most common curable sexually transmitted infection (STI); in 2008, >275 million new cases worldwide, over half of curable STIs
  • Estimated 1.1 million new cases annually in United States
    • 10–25% of vaginal infections
    • In males, up to 17% of nongonococcal urethritis; French study shows decreasing prevalence in men since 2007.
  • Predominant age: middle-aged adults
    • Rare until onset of sexual activity
    • Common in postmenopausal women; age is not protective, and long-term carriage is common.

Pediatric Considerations

  • Rare in prepubertal children; diagnosis should raise concern of sexual abuse.
  • Neonatal infections occur most often in the lungs, also vaginal (1)


  • 2.1% in U.S. women aged 14 to 59 years
  • 0.5% of U.S. men aged 14 to 59 years
  • Racial disparity demonstrated
    • 9.6% of black women versus 0.8% of other women
    • 3.4% of black men versus 0.03% of other men

Etiology and Pathophysiology

  • Trichomonas vaginalis: pear-shaped, flagellated, parasitic protozoan
  • Grows best at 35–37°C in anaerobic conditions with pH 5.5 to 6.0
  • Divides by binary fission, does not have a cyst form so does not survive externally
  • STI, but nonsexual transmission possible because it can survive several hours in moist environment

No known genetic considerations

Risk Factors

  • Multiple sexual partners
  • Unprotected intercourse
  • Lower socioeconomic status
  • Other STIs
  • Untreated partner with previous infection
  • Use of douching or feminine powders
  • Hormonal contraception use does NOT increase risk.

General Prevention

  • Use of male or female condoms
  • Limiting sexual partners
  • Male circumcision may be protective.

Commonly Associated Conditions

  • Other STIs, including HIV, increases risk of STI (1)
  • Bacterial vaginosis (1)

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