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What is trichomoniasis?

  • Trichomoniasis is a sexually transmitted infection (or sexually-transmitted disease, STD).
  • It is caused by a protozoan (a microscopic parasite), usually found in the vagina and urethral tissues.
  • Although this condition is most often treated in women, trichomoniasis infection in men can also occur (and often has no symptoms).

Trichomoniasis Causes

Trichomoniasis is caused by Trichomonas vaginalis, a flagellated motile protozoan.

  • Approximately 174 million people worldwide are infected with this parasite each year, making it the most common curable sexually transmitted infection worldwide. In the U.S., it is estimated that about 3.7 million people have the infection. Only about 30% of these people will have any symptoms.
  • The average size of a trichomonad is 15 mm (they are not visible with the naked eye).
  • Reproduction of the parasites occurs every 8 to 12 hours.
  • Trichomonas vaginalis was isolated in 14% to 60% of male partners of infected women and in 67% to 100% of female partners of infected men. It is unclear why women are infected more often than men. One possibility is that prostatic fluid contains zinc and other substances that may be harmful to trichomonads.
Last Reviewed 11/20/2017
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Vaginal Infection Symptoms

Trichomoniasis Causes

Trichomoniasis causes a frothy vaginal discharge that may be yellow-green or gray, itching and irritation of the genitals, burning with urination (sometimes confused with a urinary tract infection), discomfort during intercourse, and a foul smell. Because trichomoniasis is a sexually-transmitted disease, symptoms may appear within 4-20 days after exposure. Men rarely have symptoms, but if they do, they may have a thin, whitish discharge from the penis and painful or difficult urination.

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Trichomoniasis is a sexually transmitted infection caused by the protozoa Trichomonas vaginalis.

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