Trichomoniasis

BySheldon R. Morris, MD, MPH, University of California San Diego
Reviewed/Revised Feb 2023
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Trichomoniasis is a sexually transmitted infection of the vagina or urethra that is caused by the protozoa Trichomonas vaginalis and that causes vaginal irritation and discharge and sometimes urinary symptoms.

  • Women may have a greenish yellow, frothy, fishy-smelling vaginal discharge with irritation and soreness in the genital area.

  • Men usually have no symptoms, but a few have a frothy discharge from the penis and mild pain or discomfort during urination.

  • Examination of a sample of the discharge under a microscope usually enables doctors to identify trichomoniasis.

  • Infected people and their sex partners are treated with antibiotics.

  • Using condoms during genital sex can help prevent passing trichomoniasis and other sexually transmitted infections (STIs) from one person to another.

(See also Overview of Sexually Transmitted Infections.)

Trichomonas vaginalis commonly causes an STI of the vagina in women and an STI of the urinary tract in men and women. Women are much more likely to develop symptoms. About 20% of women develop trichomoniasis of the vagina (trichomonas vaginitis) during their reproductive years.

People with trichomoniasis may also have gonorrhea or other STIs.

Symptoms of Trichomoniasis

In women, the infection usually starts with a greenish yellow, frothy, fishy-smelling discharge from the vagina. In some women, the discharge is slight. The genital area may be irritated and sore, and sexual intercourse may be painful. In severe cases, the genital area and surrounding skin may be inflamed, and the tissues around the vagina's opening (labia) may be swollen. Urination may be painful or frequent, as occurs in a bladder infection. Urinary and vaginal symptoms may occur alone or together.

Most men with trichomoniasis of the urethra (the tube carries urine from the bladder out of the body) have no or only mild symptoms, but they can still infect their sex partners. Some men have a frothy discharge from the penis, pain during urination, and an urge to urinate frequently.

Did You Know...

  • Most men with trichomoniasis have no symptoms, but they can still infect their sex partners.

Diagnosis of Trichomoniasis

  • Examination and sometimes culture of a sample of the discharge or urine

Doctors suspect trichomoniasis in the following people:

The organism is much more difficult to detect in men than in women.

In women, the diagnosis can usually be made quickly by examining a sample of the vaginal discharge with a microscope and identifying the organism. If results are unclear, the sample is cultured for several days.

In men, a sample of the discharge from the end of the penis (obtained in the morning, before urination) may be examined under a microscope and sent to the laboratory for culture. Alternatively, doctors sometimes do tests to identify the organism’s unique genetic material (DNA or RNA) using techniques that increase the amount of the bacteria's genetic material. These tests are called nucleic acid amplification tests (NAATS). These techniques make the organisms easier to detect.

Occasionally, microscopic examination of the urine detects Trichomonas, but identification is more likely if a urine culture is done.

Tests for other STIs are usually also done because people with trichomoniasis may also have gonorrhea or a chlamydia.

Treatment of Trichomoniasis

  • Simultaneous treatment of sex partners

expedited partner therapy).

vaginal yeast infections (vaginal candidiasis).

Infected people should abstain from sexual intercourse until the infection is cured, or they can infect their partners.

Prevention of Trichomoniasis

The following general measures can help prevent trichomoniasis (and other STIs):

  • Safer sex practices, including using a condom every time for oral, anal, or genital sex

  • Decreased risk of exposure to STIs by reducing the number of sex partners, not having high-risk sex partners (people with many sex partners or who do not practice safer sex), or practicing mutual monogamy or abstinence

  • Prompt diagnosis and treatment of the infection (to prevent spread to other people)

  • Identification of the sexual contacts of infected people, followed by counseling or treatment of these contacts

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